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Endocrinology, doi:10.1210/en.2007-0189
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Endocrinology Vol. 148, No. 6 2854-2862
Copyright © 2007 by The Endocrine Society

Direct Evidence that Stimulation of Neuropeptide Y Y5 Receptor Activates Hypothalamo-Pituitary-Adrenal Axis in Conscious Rats via both Corticotropin-Releasing Factor- and Arginine Vasopressin-Dependent Pathway

Nobukazu Kakui and Koichi Kitamura

Pharmaceutical Research Center, Meiji Seika Kaisha Ltd., Kohoku-ku, Yokohama 222-8567, Japan

Address all correspondence and requests for reprints to: Nobukazu Kakui, Ph.D., Pharmaceutical Research Center, Meiji Seika Kaisha Ltd., 760 Moro-oka-cho, Kohoku-ku, Yokohama 222-8567, Japan. E-mail: nobukazu_kakui{at}meiji.co.jp.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
An abundance of data suggests a crucial role of neuropeptide Y (NPY) as an activator of the hypothamamo-pituitary-adrenal (HPA) axis. However, there is quite limited evidence regarding receptors that mediate this response. Here, we address the possibility that Y5 receptor subtype may be responsible for NPY-induced activation of HPA axis. For this purpose, the effects of an intracerebroventricular injection of Y5-selective agonist, [cPP1–7, NPY19–23, Ala31, Aib32, Gln34]-human pancreatic polypeptide (hPP), on circulating ACTH and corticosterone in conscious rats were evaluated. Central injection of hPP (100 pmol) produced significant increases in plasma ACTH and corticosterone compared with artificial cerebrospinal fluid, and previous treatment with a novel Y5-selective antagonist, FMS586 [3-(9-isopropyl-6,7,8,9-tetrahydro-5H-carbazol-3-yl)-1-methyl-1-(2-pyridin-4-yl-ethyl)-urea hydrochloride] (25 mg/kg, po), completely blocked these alterations. Pretreatment with corticotropin-releasing factor (CRF) receptor antagonist (astressin, 10–50 µg/rat, iv) or arginine vasopressin (AVP) receptor antagonist ([deamino-Pen1, O-Me-Tyr2, Arg8] vasopressin; 3–30 µg/rat, iv) differentially suppressed these increases by 70–80 or 40–50%, respectively. The combined treatment showed no additive effect of these antagonists. Furthermore, an exogenous AVP (0.3 µg/rat, iv)-induced HPA activation was fully inhibited by astressin, suggesting a convergent pathway of AVP receptor signals onto CRF neurons. Central injection of hPP also evoked marked up-regulation of mRNA expression for CRF and AVP in the hypothalamus, which, likewise, were completely reversed by FMS586. Our observations provide the first evidence that selective stimulation of Y5 receptor provokes activation of the HPA axis and its downstream pathway is chiefly composed of both CRF (primary regulator) and AVP (subordinate to the former) with distinct relative contribution.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
ACTIVATION OF THE hypothalamo-pituitary-adrenal (HPA) axis is a fundamental adaptive process in mammals. This process is triggered by fasting-induced glucopenia (1) or neuropeptides involved in appetite stimulation (2, 3), resulting in glucocorticoid secretion as a compensatory response to reduced glucose availability. Neuropeptide Y (NPY) has been considered to exert a critical role for the homeostatic regulation of this system (4, 5, 6, 7). An acute injection of NPY into the paraventricular nucleus (PVN) produces increases in circulating ACTH and corticosterone (CORT) in both conscious and anesthetized rats (4, 5, 7). Chronic infusion of this peptide into the cerebral ventricle in normal rats also causes hypercorticosteronemia (8). The secretion of ACTH from the anterior pituitary gland is principally under the regulation of the two hypothalamic hormones corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) (9). Electron microscopic study confirmed the existence of synapses between NPY-containing neurons (and the dendrites) and cell bodies of CRF-immunoreactive neurons in the parvocellular subnuclei of the PVN (10). NPY dose dependently stimulates CRF secretion from rat hypothalamus explants (11). In vivo studies provided evidence that central administration of NPY stimulates CRF immunoreactivity in median eminence (12) and enhances the mRNA expression of CRF in the hypothalamus (13). Similar findings have been reported as for the interaction of NPY and AVP. An injection of NPY into the PVN (14) or supraoptic nucleus (SON) (15) in rats increased plasma levels of AVP. Double-labeling immunohistochemical studies demonstrated that fibers containing NPY-like immunoreactivity form a close association with AVP-immunoreactive perikarya in the SON (15).

The NPY receptor(s) that mediates activation of HPA axis remain(s) to be determined. Until now, five different subtypes, Y1, Y2, Y4, Y5, and Y6, have been cloned from several species (16). Previous report investigating the in vivo ACTH-releasing activity of various NPY analog peptides suggested that the profile satisfying the requirements of such activity is unlikely to be that of Y1–Y4 and Y6 receptors and also does not completely coincide with that of Y5 subtype, a well-known feeding receptor (17). The latter interpretation was derived from the inability of the active fragment peptide ([D-Trp32]NPY), a relatively low-affinity Y5 receptor ligand with possible antagonistic property (17), to induce feeding behavior. Meanwhile, Y5-mediated negative control of gonadotropic axis (18) and thyrotropic axis (19) has been demonstrated, which suggests extensive potential of this receptor for the regulation of pituitary hormone secretion. Thus, there needs additional precise investigation for the involvement of Y5 receptor in the regulation of HPA axis.

In the current study, we explored the effect of central injection of the Y5-selective agonist [cPP1–7, NPY19–23, AL31, Aib32, Gln34]-human pancreatic polypeptide (hPP) (20) and of peripheral injection of the novel Y5-selective antagonist FMS586 [3-(9-isopropyl-6,7,8,9-tetrahydro-5H-carbazol-3-yl)-1-methyl-1-(2-pyridin-4-yl-ethyl)-urea hydrochloride] (21) on ACTH and CORT secretion in conscious rat. Next, in terms of the relative importance between two major ACTH secretagogues (CRF and AVP), we examined the effect of each peptide antagonist (alone or in combination) on the hPP-induced HPA axis activation and also mutual interaction of these secretagogues in an exogenous agonist vs. antagonist competition format. Finally, we evaluated hPP-induced changes in mRNA expression for CRF and AVP in microdissected hypothalamus.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Animals
Male Fisher 344 rats (7 wk) were purchased from Charles River Japan (Atsugi, Japan). They were housed individually on a 12-h light, 12-h dark (lights on, 0700–1900 h) schedule in a temperature- and humidity-controlled room and, 1–2 wk later, were used for the following experiments. They were provided with the standard laboratory chow and water ad libitum, unless otherwise stated. Animal care was performed according to the protocols reviewed by the Ethical Committee for Animal Experiment in Meiji Seika Pharmaceutical Research Center.

Reagents
FMS586 was synthesized at Ashigara Research Laboratories of Fuji Photo Film (Kanagawa, Japan) (21). Human/rat CRF and AVP were obtained from Peptide Institute Inc. (Osaka, Japan). hPP was from Nacalai Tesque (Kyoto, Japan). Astressin, [deamino-Pen1, O-Me-Tyr2, Arg8] vasopressin (dPTyVP), CORT, and aprotinin were from Sigma (St. Louis, MO). All of the other chemicals used were of analytical grade.

Surgical procedures
Implantation of icv cannula.
Rats were anesthetized with pentobarbital (50 mg/kg, ip) and implanted with a permanent 25-gauge stainless steel guide cannula (Eicom, Kyoto, Japan). The stereotaxic coordinates were –0.8 mm posterior to the bregma, 1.5 mm lateral to the midline, and 3.5 mm ventral from the skull surface (21). Rats were allowed to recover for more than 7 d until the next surgery.

Implantation of femoral vein catheter.
Under the same anesthetic, the left femoral vein was isolated and cannulated with a silicone tubing (inner diameter, 0.5 mm; outer diameter, 1.0 mm) connected to a micro-silicone tubing (inner diameter, 0.4 mm; outer diameter, 0.5 mm; 5 cm of this portion in the femoral vein). The tubing was secured, and the thicker side was passed under the skin, externalized through an incision made between the shoulder blades, and passed through the protective spring anchored to a swivel at the top of a metabolic cage. The rats were placed in a jacket and allowed to move freely inside the cages. The catheter was daily rinsed with saline containing diluted heparin (50 U/ml). After several days of recovery period, rats were accustomed to handling on a daily basis. In the following experiments, systemic administration of some compounds and blood sampling were conducted in common via this single route in each rat.

Animal experiments
All experiments were performed between 1000 and 1500 h. Two hours before the start of the experiments, rats were deprived of food. Their body weight ranged from approximately 240 to 260 g during the following series of experiments.

Study 1.
The purpose of this experiment was to examine the activation of HPA axis in response to central administration of the Y5-selective agonist hPP and to evaluate the antagonistic effect of FMS586 to such stimulation. The doses of the agonist (100 pmol, icv) and the antagonist (25 mg/kg, po) were shown to be valid for substantial activation and sufficient inhibition of Y5 receptor function (21). Rats were randomly divided into four groups and orally given either FMS586 or its vehicle (0.1 mN HCl as an acidity-matched control). One hour later, they were icv injected with either hPP or artificial cerebrospinal fluid (aCSF). Blood samples were collected 60 min before and 0, 30, 60, and 120 min after the icv injection.

Study 2.
The purpose of this experiment was to investigate the relative contribution of CRF and AVP signals as a downstream pathway of hypothalamic Y5 receptor activation. Rats were iv injected with astressin (CRF antagonist; 10, 30, or 50 µg/rat) (22), dPTyVP (AVP V1a/b antagonist; 3, 10, or 30 µg/rat) (23), or vehicle (saline) and, 30 min later, were icv injected with either hPP or aCSF. In a combined treatment study, both of these antagonists (10, 30, or 50 µg/rat astressin plus 10 µg/rat dPTyVP) were iv injected as a mixture. The rats in control group were iv injected with vehicle and then icv injected with aCSF. Blood samples were collected 30 min after the icv injection.

Study 3.
The purpose of this experiment was to pharmacologically clarify the mutual relationship of CRF and AVP and to decide the role of which peptide was more dominant than the other as an ACTH secretagogue. In the first subset of experiments, dose-finding studies were planned for acute iv injection with CRF (1 or 2 µg/rat) or AVP (0.3 or 0.6 µg/rat). From ACTH and CORT responses at 30 min after the injections, the minimal effective doses were determined to be 1 µg/rat for CRF and 0.3 µg/rat for AVP, respectively. In the second subset of experiments, rats were iv injected with astressin (30 or 50 µg/rat), dPTyVP (10 µg/rat), or vehicle (saline) and, 30 min later, were iv injected with CRF (1 µg/rat). In the third subset of experiments, rats were iv injected with astressin (50 µg/rat), dPTyVP (10 or 30 µg/rat), or vehicle (saline) and, 30 min later, were iv injected with AVP (0.3 µg/rat). The rats receiving two iv injections with saline were used as a control. Blood samples were collected 30 min after the second iv injection.

All of the blood samples in studies 1–3 were withdrawn via indwelling catheter from undisturbed conscious rats and immediately replaced with an equivalent volume of apyrogenic saline containing diluted heparin (50 U/ml). These blood samples were drawn into chilled tubes containing 1 mM EDTA and 30 µg/ml aprotinin (each at final concentration), centrifuged, and stored at –80 C until analysis.

Study 4.
In this experiment, rats receiving icv cannulation surgery were used for microdissection of hypothalamus and subsequent RT-PCR assay for CRF and AVP mRNA expression. Four groups of rats were treated with vehicle (po) plus aCSF (icv), vehicle (po) plus hPP (100 pmol, icv), FMS586 (25 mg/kg, po) plus aCSF (icv), or FMS586 (25 mg/kg, po) plus hPP (100 pmol, icv), respectively, as described in experiment 1. Four hours after the icv injection, the rats were killed. The whole brain was immediately removed and kept in ice-cold PBS for 30 min. The hypothalamus, bordered rostrocaudally in a 1-mm slice from the optic chiasm of 3-mm width, laterally by the optic tract, and dorsoventrally by the apex of the third ventricle, was then microdissected, placed into 500 µl of RNA stabilization reagent (RNAlater; Qiagen, Valencia, CA), and stored at 4 C for more than 24 h.

RT-PCR analysis
CRF and AVP mRNA levels in the hypothalamic tissues were quantified using RT-PCR. Total hypothalamic RNA was isolated with the RNeasy Mini kit (Qiagen) following the protocol of the manufacturer. Quantification and purity of RNA were assessed by the ratio of UV absorbance at 260 to 280 nm, and RNA samples with a ratio above 1.6 were used for additional analysis. A constant amount of RNA (0.5 µg) from individual animals was converted to cDNA with the Omniscript Reverse Transcription kit (Qiagen). On completion of RT, 2 µl of the cDNA mixture was added to separate PCR mixtures containing 100 pmol of CRF (forward, 5'-GAAGAGAAAGGGGAAAGGCAAAGA-3'; reverse, 5'-GCCGTGAGGGGCGTGGAGTT-3'), AVP (forward, 5'-CCTCACCTC TGCCTGCTACTT-3'; reverse, 5'-GGGGGCGATGGCTCAGTAGAC-3'), or glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (forward, 5'-TGCTGAGTATGTCGTGGAGTCT-3'; reverse, 5'-AATGGGAGTTGC TGTTGAAGTC-3') oligonucleotide primers, 2 mM MgCl2, Taq buffer, and 2.5 U of Taq DNA Polymerase (Toyobo Co. Ltd., Osaka, Japan) in a total volume of 20 µl. The PCR protocol used 35 cycles of amplification, and each cycle included denaturation at 94 C for 30 sec, annealing at 62 C for 30 sec (CRF) or at 58 C for 30 sec (AVP), and primer extension at 72 C for 1 min. The PCR products (403 bp for CRF and 440 bp for AVP) were separated on a 2% agarose gel and visualized with ethidium bromide, and the band intensities were quantified using the Scion (Frederick, MD) Image software.

Hormone analysis
Plasma was analyzed for CORT and ACTH levels by reverse-phase HPLC/UV system and RIA, respectively. For CORT assay, plasma was extracted in 2 vol of ice-cold acetonitrile (vortexing for 30 sec) and centrifuged at 10,000 rpm for 10 min at 4 C. The supernatants were diluted in distilled water (supernatant/water at 3:2) and injected onto the HPLC system consisting of an LC-6A pump (Shimadzu, Kyoto, Japan) equipped with a UV detector (SPD-6AV; Shimadzu) set at 250 nm, an ODS column (Inertsil ODS-2, 4.6 x 250 mm, 5 µm; GL Sciences, Tokyo, Japan), and a Rheodyne 7725i injector with a 100-µl loop. The mobile phase was 33% (vol/vol) acetonitrile. Separation of CORT was performed isocratically at room temperature and at a flow rate of 1.0 ml/min. In this analytical condition, CORT was eluted at 15 min. The detection limit was 100 pg (signal/noise ratio at 3:1). The intraassay and interassay coefficients of variation were less than 5%.

ACTH levels were determined with a commercially available RIA kit (ACTH IRMA; Mitsubishi Kagaku Iatron, Tokyo, Japan). The intraassay and interassay coefficients of variation were 7–12%.

Statistics
All results were represented as mean ± SEM. Statistical significance of the differences among multiple groups was tested using one-way ANOVA, followed by Dunnett’s multiple comparison test. A two-tailed Student’s t test was used to evaluate the difference between two experimental groups. Values associated with a P value of <0.05 were considered significant.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Study 1: effect of hPP (icv) and/or FMS586 (po) on the release of ACTH and CORT
Central injection of hPP (100 pmol) produced significant increases in plasma ACTH (Fig. 1AGo) and CORT (Fig. 1BGo) levels compared with the aCSF-treated group. ACTH levels peaked at 30 min (512.0 ± 61.2 pg/ml, P < 0.01 vs. 127.3 ± 30.6 pg/ml in aCSF group) and thereafter gradually decreased until 120 min. The novel Y5-selective antagonist FMS586, by itself, showed no significant changes in ACTH levels but clearly suppressed the agonist-induced releases (114.9 ± 21.1 pg/ml at 30 min, P < 0.001 vs. vehicle-hPP group). A quite similar tendency was observed in plasma CORT responses. An hPP-dependent initial increase (505.1 ± 52.7 ng/ml at 30 min, P < 0.001 vs. 104.5 ± 32.0 ng/ml in vehicle group) was significantly inhibited by the treatment with FMS586 (227.1 ± 29.8 ng/ml, P < 0.01). FMS586 alone did not significantly modify the time course pattern of CORT compared with the vehicle group.


Figure 1
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  		FIG. 1. Effect of Y5-selective agonist (hPP, 100 pmol, icv) and/or Y5-selective antagonist (FMS586, 25 mg/kg, po) on plasma ACTH (A) and CORT (B) levels in conscious male Fisher rats. FMS586 or vehicle (Veh) was given 60 min before icv injection of hPP or aCSF. At the indicated intervals, plasma was sampled and analyzed for ACTH and CORT. Data are represented as mean ± SEM (n = 5–6). ##, P < 0.01; ###, P < 0.001; **, P < 0.01; ***, P < 0.001, significantly different from the values in vehicle-aCSF group and vehicle-hPP group, respectively.

 
Study 2: effect of previous treatment with CRF and/or AVP antagonist on hPP (icv)-induced increases in plasma ACTH and CORT
From the time course analysis of hPP-induced activation of HPA axis (Fig. 1Go, A and B), we chose the blood sampling time at 30 min after hPP injection in studies 2 and 3. Pretreatment with the CRF receptor antagonist astressin significantly inhibited hPP-induced hypersecretion of ACTH (Fig. 2AGo) and CORT (Fig. 2BGo). The maximal inhibition rate was 77.7% (at 50 µg/rat, P < 0.001 vs. hPP-vehicle group) and 70.2% (at 50 µg/rat, P < 0.01 vs. hPP-vehicle group) for ACTH and CORT, respectively. dPTyVP, an AVP antagonist, was partially effective for the suppression of hPP-induced increases in ACTH (Fig. 3AGo) and CORT (Fig. 3BGo). The maximal inhibition rate was 51.4% (at 10 µg/rat, P < 0.05 vs. hPP-vehicle group) and 41.3% (at 10 µg/rat, P < 0.05 vs. hPP-vehicle group) for ACTH and CORT, respectively. In the next experiment, the possibility that the combined effect of each receptor blockade might be additive or synergistic was tested. The hPP-induced hypersecretion of ACTH and CORT was substantially inhibited by combined administration of astressin (10, 30, or 50 µg/rat) and dPTyVP (10 µg/rat) (Fig. 4Go, A and B). The treatment with dPTyVP (10 µg/rat) potentiated the effect of a low dose (10 µg/rat) of astressin approximately to the levels found in the single treatment with dPTyVP, but the maximal inhibition in the treatment with middle to high doses of astressin plus dPTyVP was almost the same as observed in the treatment with astressin alone. These data obviously indicate no additive effects of astressin and dPTyVP.


Figure 2
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  		FIG. 2. Substantial inhibition by CRF antagonist astressin (10, 30, or 50 µg/rat, iv) of hPP-induced activation of HPA axis (A, ACTH; B, CORT) in conscious male Fisher rats. Astressin was injected 30 min before icv injection of hPP. Plasma was withdrawn at 30 min after hPP. Data are represented as mean ± SEM (n = 5–6). ##, P < 0.01; ###, P < 0.001; *, P < 0.05; **, P < 0.01; ***, P < 0.001, significantly different from the values in aCSF group and hPP-vehicle group, respectively.

 

Figure 3
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  		FIG. 3. Modest inhibition by AVP antagonist dPTyVP (3, 10, or 30 µg/rat, iv) of hPP-induced activation of HPA axis (A, ACTH; B, CORT) in conscious male Fisher rats. dPTyVP was injected 30 min before icv injection of hPP. Plasma was withdrawn at 30 min after hPP. Data are represented as mean ± SEM (n = 5–6). ###, P < 0.001; *, P < 0.05, significantly different from the values in aCSF group and hPP-vehicle group, respectively.

 

Figure 4
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  		FIG. 4. Effect of combined administration of astressin (Ast; 10, 30, or 50 µg/rat, iv) and dPTyVP (10 µg/rat, iv) on hPP-induced activation of HPA axis (A, ACTH; B, CORT) in conscious male Fisher rats. Both antagonists were simultaneously injected 30 min before icv injection of hPP. Plasma was withdrawn at 30 min after hPP. Data are represented as mean ± SEM (n = 4–5). ###, P < 0.001; *, P < 0.05; **, P < 0.01; ***, P < 0.001, significantly different from the values in aCSF group and hPP-vehicle group, respectively.

 
Study 3: effect of CRF or AVP antagonist on CRF- or AVP-induced increases in plasma ACTH and CORT
Next, we aimed to investigate the interaction between CRF and AVP and to make clear which peptide is more dominant as an ACTH secretagogue. An iv injection of CRF dose dependently increased the plasma ACTH (712.8 ± 102.8 pg/ml at 1 µg/rat, P < 0.05 and 1257.8 ± 173.8 pg/ml at 2 µg/rat, P < 0.001 vs. 168.0 ± 29.4 pg/ml in saline group) and CORT (572.4 ± 22.0 ng/ml at 1 µg/rat, P < 0.001 and 681.2 ± 45.4 ng/ml at 2 µg/rat, P < 0.001 vs. 175.5 ± 50.7 ng/ml in saline group). The increases evoked by 1 µg/rat CRF were dose-dependently inhibited by pretreatment with astressin (30 or 50 µg/rat) but not with dPTyVP (10 µg/rat) (Fig. 5Go, A and B). An iv injection of AVP also significantly stimulated the secretion of ACTH (332.4 ± 54.8 pg/ml at 0.3 µg/rat, P < 0.05 and 588.2 ± 74.1 pg/ml at 0.6 µg/rat, P < 0.001 vs. 86.5 ± 16.0 pg/ml in saline group) and CORT (511.5 ± 42.5 ng/ml at 0.3 µg/rat, P < 0.001 and 541.0 ± 84.7 ng/ml at 0.6 µg/rat, P < 0.001 vs. 61.7 ± 17.8 ng/ml in saline group). Interestingly, not only dPTyVP (10 or 30 µg/rat) but also astressin (50 µg/rat) almost completely suppressed AVP (0.3 µg/rat)-induced increases in ACTH (Fig. 6AGo) and CORT (Fig. 6BGo). The results from studies 2 and 3 strongly suggest that the AVP pathway eventually leads to CRF receptor-mediated signals that may regulate ACTH secretion from the pituitary corticotroph cells.


Figure 5
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  		FIG. 5. Specific inhibition by astressin (30 or 50 µg/rat, iv) of CRF (1 µg/rat, iv)-induced activation of HPA axis (A, ACTH; B, CORT) in conscious male Fisher rats. Astressin or dPTyVP (10 µg/rat, iv) was injected 30 min before the injection of CRF. Plasma was withdrawn at 30 min after CRF. Data are represented as mean ± SEM (n = 5–8). #, P < 0.05; ###, P < 0.001; **, P < 0.01, significantly different from the values in saline group and CRF-vehicle group, respectively.

 

Figure 6
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  		FIG. 6. Complete inhibition by either dPTyVP (10 or 30 µg/rat, iv) or astressin (50 µg/rat, iv) of AVP (0.3 µg/rat, iv)-induced activation of HPA axis (A, ACTH; B, CORT) in conscious male Fisher rats. Astressin or dPTyVP was injected 30 min before the injection of AVP. Plasma was withdrawn at 30 min after AVP. Data are represented as mean ± SEM (n = 4–5). #, P < 0.05; ###, P < 0.001; *, P < 0.05; **, P < 0.01; ***, P < 0.001, significantly different from the values in saline group and AVP-vehicle group, respectively.

 
Study 4: effect of hPP (icv) and/or FMS586 (po) on the hypothalamic CRF and AVP mRNA expression
We again focused on the intrahypothalamic events triggered by Y5 receptor activation. An injection of hPP (100 pmol, icv) significantly induced mRNA expression of both CRF [0.97 ± 0.08 (arbitrary units standardized to GAPDH mRNA levels), P < 0.001 vs. 0.26 ± 0.03 in vehicle-aCSF group) and AVP (1.09 ± 0.04, P < 0.001 vs. 0.51 ± 0.07 in vehicle-aCSF group) (Fig. 7GoA–C). These increases were almost completely inhibited by pretreatment with FMS586 (CRF, 0.43 ± 0.14, P < 0.01 vs. vehicle-hPP group; AVP, 0.57 ± 0.08, P < 0.01 vs. vehicle-hPP group), whereas FMS586 per se did not modify the mRNA expression levels for CRF (0.42 ± 0.13, P = 0.270) and AVP (0.64 ± 0.14, P = 0.422) (Fig. 7GoA–C). These results are consistent with the data of studies 1 and 2 and strongly support the hypothesis that the downstream pathway of hypothalamic Y5 stimulation involves the release of both of these ACTH secretagogues possibly via a direct synaptic interaction within the hypothalamic neural networks.


Figure 7
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  		FIG. 7. Effect of hPP and/or FMS586 on mRNA expression for CRF, AVP, or GAPDH in the hypothalamus assessed by RT-PCR. FMS586 or vehicle (Veh) was orally given 60 min before icv injection of hPP or aCSF. Four hours after the icv injection, the rats were killed, and the hypothalamic tissues were dissected and processed for RT-PCR assays. The GAPDH mRNA was evaluated as an internal standard in all samples. The representative data of RT-PCR assays were displayed (n = 3) (A). The relative values of CRF (B) and AVP (C) corrected against GAPDH intensities were presented as arbitrary units from all of the hypothalamic samples used (n = 6–8). Data are represented as mean ± SEM. ###, P < 0.001; **, P < 0.01, significantly different from the values in vehicle-aCSF group and vehicle-hPP group, respectively.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Here we have shown that central administration of Y5-specific agonist evokes an acute activation of HPA axis in undisturbed conscious rats as established previously with the natural ligand NPY (4, 5, 6, 7), and this response is blocked almost completely by previous treatment with the Y5-selective antagonist. Although such activation is sensitive to the blockade of both CRF and AVP receptor, the downstream signaling pathway from hypothalamic Y5 stimulation appears to converge on CRF receptor. Also, our findings regarding the Y5 agonist-induced mRNA expression for both peptides are highly indicative of the underlying neuronal networks between Y5 receptor and each peptide within the hypothalamus.

The Y5 agonist hPP (100 pmol, icv) markedly increased plasma ACTH and CORT, and pretreatment with FMS586 (25 mg/kg, po) was almost sufficient to prevent the agonist-induced HPA activation (Fig. 1Go, A and B). We reported previously that the same dosing of hPP induces hyperphagic response in satiated rats (21). In that study, the minimal effective dose of FMS586 was shown to be 25 mg/kg (po). Thus, the dynamic changes in plasma HPA parameters obtained here are quite likely to be mediated via central Y5 receptor. Considering that all of the hormonal evaluations were conducted under transient food deprivation, it is evident that these changes are independent of orexigenic activity, which Y5 receptor essentially possesses.

The reduced responsiveness of hPP-induced HPA axis activation was observed by pretreatment with either astressin (Fig. 2Go, A and B) or dPTyVP (Fig. 3Go, A and B). The maximal inhibition rates calculated from these data (70–80% for astressin, 40–50% for dPTyVP) definitely indicate that CRF dominantly mediates ACTH-secreting signals in the downstream cascade of central Y5 activation. A lesser degree of inhibition shown in the treatment with dPTyVP might reflect the involvement of not only AVP but also oxytocin released into the hypophysial portal circulation, provided that dPTyVP is also an antagonist of oxytocin receptor (24), and this hormone may function as a hypophysiotropic factor (25). Surprisingly, we found no differences between the treatment with astressin alone and astressin plus dPTyVP in the maximal suppression of hPP-induced increases in ACTH and CORT (Fig. 4Go, A and B). The lack of additive effect of astressin and dPTyVP was by far beyond our expectation from the viewpoint of a well-known "synergistic" interaction of CRF and AVP in the regulation of ACTH release (26, 27, 28, 29). Therefore, we next planned to clarify the mutual relationship and relative dominance of these secretagogues by pharmacological approaches. Exogenous CRF (1 µg/rat)-induced increases in ACTH and CORT were suppressed by pretreatment with astressin but not with dPTyVP (Fig. 5Go, A and B). Meanwhile, astressin as well as dPTyVP clearly inhibited exogenous AVP (0.3 µg/rat)-induced increases in these parameters (Fig. 6Go, A and B). Here, we confirmed that these phenomena are not derived from pharmacological artifacts, because astressin at 0.1–10 µM does not bind to the human recombinant AVP V1b receptor (data from MDS Pharma, Taipei, Taiwan), which shows a high degree of sequence similarity (91.3%) to the rat counterparts. These facts, together with no additive effect of both antagonists, imply that the AVP pathway probably converges on CRF receptor-mediated signals in the PVN-pituitary neurosecretory networks.

Although the underlying mechanisms for the interaction of CRF and AVP remain unclear, we can raise some possibilities at each of the hypothalamic and pituitary levels. The simplest interpretation is an assumption that there exists a direct AVPergic innervation of subpopulations of CRF-containing nerve terminals in the external zone of median eminence. This notion appears to well explain our data but is not fully compatible with already established evidence that AVP alone directly acts on pituitary corticotropes and enables these cells to release ACTH (30, 31, 32). According to a previous study, the degree of coexistence of CRF and AVP in the same neurosecretory vesicles approximates to 50% of CRF axons in the external zone of median eminence (33), suggesting that differential activation of these heterogeneous subpopulations might lead to a quite complicated pattern of their secretion and subsequent stimulation of corticotropes. Thus, one would expect much higher orders of complexity in this local regulatory system. Future experiments designed to analyze the secretion of these peptides at the hypophysial portal levels would help us to test the above hypothesis. Otherwise, the possible interaction might reside within the pituitary cells. It is generally accepted that the initial intracellular messengers involved in CRF- and AVP-induced ACTH release are distinct. CRF mainly activates the cAMP-protein kinase A pathway (34, 35), whereas AVP acts through the phosphoinositidase-protein kinase C in the ACTH-secreting cells (36, 37). Accordingly, we suppose that an acute treatment with astressin instantly suppresses the basal activity of CRF receptor and its downstream signal cascade, which might subsequently lead to indirect inactivation of AVP receptor signals. However, there is no molecular evidence regarding these biological processes in our study. Therefore, a full understanding of the detailed mechanisms awaits additional investigation that would be focused on the molecular biochemistry of the pituitary corticotropes.

The evaluation of mRNA expression for CRF and AVP in the total hypothalamus strongly supported our plasma data. Central injection of the Y5 agonist potently enhanced both CRF and AVP mRNA expressions compared with aCSF treatment, and pretreatment with FMS586 significantly blocked the increases (Fig. 7GoA–C). Y5 receptors have been identified in the PVN and SON (38, 39), the regions highly implicated in the regulation of pituitary hormonal secretion (40, 41). The above findings prove that neurosecretory stimuli primed by hPP initiate the neuroendocrine cascade at the hypothalamic level by provoking the release of CRF and AVP into the hypophysial portal blood and thereby trigger the gene expression of these peptides to replenish depleted stores. Consistent with this notion is a histochemical analysis in which colocalization of Y5 immunoreactivity and either CRF or AVP immunoreactivity in the same neuron of PVN or SON is quantitatively demonstrated (42). However, the wiring diagram for the relationship of Y5 receptor and these two peptides remains to be further investigated by the additional neuroanatomical studies.

Much study is needed to understand the role of Y5 receptor in the regulation of pituitary hormone secretion under physiological and pathophysiological conditions such as obesity and metabolic syndrome. Recent studies explicitly indicated the involvement of Y5 receptor in a negative control of both gonadotropic axis (18) and thyrotropic axis (19) in satiated normal rats. Meanwhile, during starvation, up-regulation of orexigenic substance such as NPY in the hypothalamus (43, 44) and concomitant decreases in circulating levels of gonadotropin (45) or TSH (46) occur probably for the sake of energy conservation. Also, the concept that a chronic central infusion of NPY leads to obesity and metabolic abnormalities in association with hypogonadism (47, 48) or hypothyroidism (49) is now well established. Thus, a presumption can be made that Y5 receptor, as a key mediator, receives the signals of endogenously released NPY and induces above-mentioned changes for the facilitation of energy storage and, in some pathological situations, obesity-related metabolic syndrome.

Closely similar to such neuroendocrine regulation of gonadotropic and thyrotropic axes by NPY, HPA axis, the main pathway in the present study, is also under the control of NPY at the levels of PVN. Numerous studies have demonstrated an important association between hypothalamic NPY and circulating CORT in the pathophysiology of obesity and its related metabolic diseases. A chronic infusion of exogenous NPY induces major abnormalities such as marked hyperphagia, increased body weight gain, hyperinsulinemia, insulin resistance, and hypercorticosteronemia, all of which are found in animal models of spontaneous obesity (8, 50). These effects disappear in adrenalectomized rats (51). This suggested that the combined presence of NPY and CORT is essential for an evolution toward obesity with its hormonal and metabolic alterations. Furthermore, glucocorticoids induce an obesity syndrome by acting centrally and not peripherally, accompanied with the up-regulation of NPY in the hypothalamus (52). Indeed, glucocorticoid receptors are found on NPY-containing neurons in the arcuate nucleus (53). Here, as suggested from the above findings, of particular importance should be the positive feedback relationship between these two substances. Namely, activation of NPY neurons in response to some physiological stimuli causes hypersecretion of CORT, which, in turn, prompts de novo synthesis and release of NPY in the arcuate nucleus-PVN pathway, the so-called "vicious circle" of events ultimately leading to the metabolic diseases (54). Moreover, from the facet of blood glucose homeostasis, critical roles of this neuropeptide and the adrenal glucocorticoid have been suggested. Insulin-induced hypoglycemia rapidly stimulates the release of CORT (activation of HPA axis), and this acute stress response is significantly inhibited by an immunoneutralization of hypothalamic NPY (55). We believe that our observation of Y5-specific stimulation of HPA axis sheds a novel light on all of these previous data, which verify a homeostatic role of NPY as a neuroendocrine and metabolic regulator. Undoubtedly, there remains the issue of relative importance of other receptor subtypes such as Y1 or Y2. However, future experiments using highly selective ligands as in the present study might resolve this question.

Although FMS586, on its own, was ineffective in altering basal ACTH and CORT release, it fully suppressed hPP-induced increases in these parameters (Fig. 1Go, A and B). The pharmacological profile with high brain penetrability and selectivity of this novel Y5 antagonist as a feeding suppressant has been introduced recently (21). Taking into account the possible physiological significance of NPY-Y5 pathway in the regulation of HPA axis, considerable attention may have to be paid not only to anorectic but also glucocorticoid-suppressing property of Y5 antagonists in any efficacy studies that will evaluate antiobesity or antidiabetic actions.

To conclude, the present study shows that the Y5 receptor subtype is involved in the activation of HPA axis mediated by NPY. Pharmacological and biochemical analyses of the downstream pathway located in the PVN-pituitary network indicate that CRF receptor-mediated signal is a major determinant of ACTH secretion, and the other contributor, AVP, whose signals appear to converge on CRF receptor, also functions as a relatively minor ACTH secretagogue.


   Footnotes
 
First Published Online March 15, 2007

Abbreviations: aCSF, Artificial cerebrospinal fluid; AVP, arginine vasopressin; CORT, corticosterone; CRF, corticotropin releasing factor; dPTyVP, [deamino-Pen1, O-Me-Tyr2, Arg8] vasopressin; FMS586, 3-(9-isopropyl- 6,7,8,9-tetrahydro-5H-carbazol-3-yl)-1-methyl-1-(2-pyridin-4-yl-ethyl)-urea hydrochloride; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HPA, hypothamamo-pituitary-adrenal; hPP, [cPP1–7, NPY19–23, Ala31, Aib32, Gln34]-human pancreatic polypeptide; NPY, neuropeptide Y; SON, supraoptic nucleus; PVN, paraventricular nucleus.

The authors have nothing to disclose.

Received February 8, 2007.

Accepted for publication March 8, 2007.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Goldstein DS, Garty M, Bagdy G, Szemeredi K, Sternberg EM, Listwak S, Pacak K, Deka-Starosta A, Hoffman A, Chang PC, Stull R, Gold PW, Kopin IJ 1993 Role of CRH in glucopenia-induced adrenomedullary activation in rats. J Neuroendocrinol 5:475–486[CrossRef][Medline]
  2. Jaszberenyi M, Bujdoso E, Telegdy G 2001 The role of neuropeptide Y in orexin-induced hypothalamic-pituitary-adrenal activation. J Neuroendocrinol 13:438–441[CrossRef][Medline]
  3. Russell SH, Small CJ, Dakin CL, Abbott CR, Morgan DG, Ghatei MA, Bloom SR 2001 The central effects of orexin-A in the hypothalamic-pituitary-adrenal axis in vivo and in vitro in male rats. J Neuroendocrinol 13:561–566[CrossRef][Medline]
  4. Wahlestedt C, Skagerberg G, Ekman R, Heilig M, Sundler F, Hakanson R 1987 Neuropeptide Y (NPY) in the area of the hypothalamic paraventricular nucleus activates the pituitary-adrenocortical axis in the rat. Brain Res 417:33–38[CrossRef][Medline]
  5. Harfstrand A, Eneroth P, Agnati L, Fuxe K 1987 Further studies on the effects of central administration of neuropeptide Y on neuroendocrine function in the male rat: relationship to hypothalamic catecholamines. Regul Pept 17:167–179[CrossRef][Medline]
  6. Inoue T, Inui A, Okita M, Sakatani N, Oya M, Morioka H, Mizuno N, Oimomi M, Baba S 1989 Effect of neuropeptide Y on the hypothalamic-pituitary-adrenal axis in the dog. Life Sci 44:1043–1051[CrossRef][Medline]
  7. Hanson ES, Dallman MF 1995 Neuropeptide Y (NPY) may integrate responses of hypothalamic feeding systems and the hypothalamo-pituitary-adrenal axis. J Neuroendocrinol 7:273–279[CrossRef][Medline]
  8. Zarjevski N, Cusin I, Vettor R, Rohner-Jeanrenaud F, Jeanrenaud B 1993 Chronic intracerebroventricular neuropeptide-Y administration to normal rats mimics hormonal and metabolic changes of obesity. Endocrinology 133:1753–1758[Abstract/Free Full Text]
  9. Antoni FA 1986 Hypothalamic control of adrenocorticotropin secretion: advances since the discovery of 41-residue corticotropin-releasing factor. Endocr Rev 7:351–378[Abstract/Free Full Text]
  10. Liposits Z, Sievers L, Paull WK 1988 Neuropeptide-Y and ACTH-immunoreactive innervation of corticotropin releasing factor (CRF)-synthesizing neurons in the hypothalamus of the rat. An immunocytochemical analysis at the light and electron microscopic levels. Histochemistry 88:227–234[CrossRef][Medline]
  11. Tsagarakis S, Rees LH, Besser GM, Grossman A 1989 Neuropeptide-Y stimulates CRF-41 release from rat hypothalami in vitro. Brain Res 502:167–170[CrossRef][Medline]
  12. Haas DA, George SR 1987 Neuropeptide Y administration acutely increases hypothalamic corticotropin-releasing factor immunoreactivity: lack of effect in other rat brain regions. Life Sci 41:2725–2731[CrossRef][Medline]
  13. Suda T, Tozawa F, Iwai I, Sato Y, Sumitomo T, Nakano Y, Yamada M, Demura H 1993 Neuropeptide Y increases the corticotropin-releasing factor messenger ribonucleic acid level in the rat hypothalamus. Brain Res Mol Brain Res 18:311–315[Medline]
  14. Leibowitz SF, Sladek C, Spencer L, Tempel D 1988 Neuropeptide Y, epinephrine and norepinephrine in the paraventricular nucleus: stimulation of feeding and the release of corticosterone, vasopressin and glucose. Brain Res Bull 21:905–912[CrossRef][Medline]
  15. Willoughby JO, Blessing WW 1987 Neuropeptide Y injected into the supraoptic nucleus causes secretion of vasopressin in the unanesthetized rat. Neurosci Lett 75:17–22[CrossRef][Medline]
  16. Blomqvist AG, Herzog H 1997 Y-receptor subtypes—how many more? Trends Neurosci 20:294–298[CrossRef][Medline]
  17. Small CJ, Morgan DG, Meeran K, Heath MM, Gunn I, Edwards CM, Gardiner J, Taylor GM, Hurley JD, Rossi M, Goldstone AP, O’Shea D, Smith DM, Ghatei MA, Bloom SR 1997 Peptide analogue studies of the hypothalamic neuropeptide Y receptor mediating pituitary adrenocorticotrophic hormone release. Proc Natl Acad Sci USA 94:11686–11691[Abstract/Free Full Text]
  18. Raposinho PD, Broqua P, Pierroz DD, Hayward A, Dumont Y, Quirion R, Junien JL, Aubert ML 1999 Evidence that the inhibition of luteinizing hormone secretion exerted by central administration of neuropeptide Y (NPY) in the rat is predominantly mediated by the NPY-Y5 receptor subtype. Endocrinology 140:4046–4055[Abstract/Free Full Text]
  19. Fekete C, Sarkar S, Rand WM, Harney JW, Emerson CH, Bianco AC, Beck-Sickinger A, Lechan RM 2002 Neuropeptide Y1 and Y5 receptors mediate the effects of neuropeptide Y on the hypothalamic-pituitary-thyroid axis. Endocrinology 143:4513–4519[Abstract/Free Full Text]
  20. Cabrele C, Langer M, Bader R, Wieland HA, Doods HN, Zerbe O, Beck-Sickinger AG 2000 The first selective agonist for the neuropeptide YY5 receptor increases food intake in rats. J Biol Chem 275:36043–36048[Abstract/Free Full Text]
  21. Kakui N, Tanaka J, Tabata Y, Asai K, Masuda N, Miyara T, Nakatani Y, Ohsawa F, Nishikawa N, Sugai M, Suzuki M, Aoki K, Kitaguchi H 2006 Pharmacological characterization and feeding-suppressive property of FMS586 [3-(5,6,7,8-tetrahydro-9-isopropyl-carbazol-3-yl)-1-methyl-1-(2-pyridin-4- yl-ethyl)-urea hydrochloride], a novel, selective, and orally active antagonist for neuropeptide Y Y5 receptor. J Pharmacol Exp Ther 317:562–570[Abstract/Free Full Text]
  22. Gulyas J, Rivier C, Perrin M, Koerber SC, Sutton S, Corrigan A, Lahrichi SL, Craig AG, Vale W, Rivier J 1995 Potent, structurally constrained agonists and competitive antagonists of corticotropin-releasing factor. Proc Natl Acad Sci USA 92:10575–10579[Abstract/Free Full Text]
  23. Heinemann A, Horina G, Stauber RE, Pertl C, Holzer P, Peskar BA 1998 Lack of effect of a selective vasopressin V1A receptor antagonist SR 49,059, on potentiation by vasopressin of adrenoceptor-mediated pressor responses in the rat mesenteric arterial bed. Br J Pharmacol 125:1120–1127[CrossRef][Medline]
  24. Bankowski K, Manning M, Haldar J, Sawyer WH 1978 Design of potent antagonists of the vasopressor response to arginine-vasopressin. J Med Chem 21:850–853[CrossRef][Medline]
  25. Link H, Dayanithi G, Fohr KJ, Gratzl M 1992 Oxytocin at physiological concentrations evokes adrenocorticotropin (ACTH) release from corticotrophs by increasing intracellular free calcium mobilized mainly from intracellular stores. Oxytocin displays synergistic or additive effects on ACTH-releasing factor or arginine vasopressin-induced ACTH secretion, respectively. Endocrinology 130:2183–2191[Abstract/Free Full Text]
  26. Gillies GE, Linton EA, Lowry PJ 1982 Corticotropin releasing activity of the new CRF is potentiated several times by vasopressin. Nature 299:355–357[CrossRef][Medline]
  27. Childs GV, Burke JA 1987 Use of the reverse hemolytic plaque assay to study the regulation of anterior lobe adrenocorticotropin (ACTH) secretion by ACTH-releasing factor, arginine vasopressin, angiotensin II, and glucocorticoids. Endocrinology 120:439–444[Abstract/Free Full Text]
  28. Rivier C, Vale W 1983 Interaction of corticotropin-releasing factor and arginine vasopressin on adrenocorticotropin secretion in vivo. Endocrinology 113:939–942[Abstract/Free Full Text]
  29. Aguilera G, Rabadan-Diehl C 2000 Vasopressinergic regulation of the hypothalamic-pituitary-adrenal axis: implications for stress adaptation. Regul Pept 96:23–29[CrossRef][Medline]
  30. Nicholson SA, Adrian TE, Gillham B, Jones MT, Bloom SR 1984 Effect of hypothalamic neuropeptides on corticotrophin release from quarters of rat anterior pituitary gland in vitro. J Endocrinol 100:219–226[Abstract/Free Full Text]
  31. Murakami K, Hashimoto K, Ota Z 1984 Interaction of synthetic ovine corticotropin releasing factor and arginine vasopressin on in vitro ACTH release by the anterior pituitary of rats. Neuroendocrinology 39:49–53[Medline]
  32. Knepel W, Homolka L, Vlaskovska M, Nutto D 1984 Stimulation of adrenocorticotropin/beta-endorphin release by synthetic ovine corticotropin-releasing factor in vitro. Enhancement by various vasopressin analogs. Neuroendocrinology 38:344–350[Medline]
  33. Whitnall MH, Smyth D, Gainer H 1987 Vasopressin coexists in half of the corticotropin-releasing factor axons present in the external zone of the median eminence in normal rats. Neuroendocrinology 45:420–424[Medline]
  34. Giguere V, Labrie F, Cote J, Coy DH, Sueiras-Diaz J, Schally AV 1982 Stimulation of cyclic AMP accumulation and corticotropin release by synthetic ovine corticotropin-releasing factor in rat anterior pituitary cells: site of glucocorticoid action. Proc Natl Acad Sci USA 79:3466–3469[Abstract/Free Full Text]
  35. Aguilera G, Harwood JP, Wilson JX, Morell J, Brown JH, Catt KJ 1983 Mechanisms of action of corticotropin-releasing factor and other regulators of corticotropin release in rat pituitary cells. J Biol Chem 258:8039–8045[Abstract/Free Full Text]
  36. Raymond V, Leung PC, Veilleux R, Labrie F 1985 Vasopressin rapidly stimulates phosphatidic acid-phosphatidylinositol turnover in rat anterior pituitary cells. FEBS Lett 182:196–200[CrossRef][Medline]
  37. Bilezikjian LM, Woodgett JR, Hunter T, Vale WW 1987 Phorbol ester-induced down-regulation of protein kinase C abolishes vasopressin-mediated responses in rat anterior pituitary cells. Mol Endocrinol 1:555–560[Abstract/Free Full Text]
  38. Durkin MM, Walker MW, Smith KE, Gustafson EL, Gerald C, Branchek TA 2000 Expression of a novel neuropeptide Y receptor subtype involved in food intake: an in situ hybridization study of Y5 mRNA distribution in rat brain. Exp Neurol 165:90–100[CrossRef][Medline]
  39. Nichol KA, Morey A, Couzens MH, Shine J, Herzog H, Cunningham AM 1999 Conservation of expression of neuropeptide Y5 receptor between human and rat hypothalamus and limbic regions suggests an integral role in central neuroendocrine control. J Neurosci 19:10295–10304[Abstract/Free Full Text]
  40. Makara GB, Stark E, Karteszi M, Palkovits M, Rappay G 1981 Effects of paraventricular lesions on stimulated ACTH release and CRF in stalk-median eminence of the rat. Am J Physiol 240:E441–E446
  41. Neumann ID, Torner L, Toschi N, Veenema AH 2006 Oxytocin actions within the supraoptic and paraventricular nuclei: differential effects on peripheral and intranuclear vasopressin release. Am J Physiol Regul Integr Comp Physiol 291:R29–R36
  42. Campbell RE, ffrench-Mullen JM, Cowley MA, Smith MS, Grove KL 2001 Hypothalamic circuitry of neuropeptide Y regulation of neuroendocrine function and food intake via the Y5 receptor subtype. Neuroendocrinology 74:106–119[CrossRef][Medline]
  43. Bertile F, Oudart H, Criscuolo F, Maho YL, Raclot T 2003 Hypothalamic gene expression in long-term fasted rats: relationship with body fat. Biochem Biophys Res Commun 303:1106–1113[CrossRef][Medline]
  44. Swart I, Overton JM, Houpt TA 2001 The effect of food deprivation and experimental diabetes on orexin and NPY mRNA levels. Peptides 22:2175–2179[CrossRef][Medline]
  45. Bergendahl M, Huhtaniemi I 1994 The time since castration influences the effects of short-term starvation on gonadotrophin secretion in male rats. J Endocrinol 143:209–219[Abstract/Free Full Text]
  46. van Haasteren GA, Linkels E, van Toor H, Klootwijk W, Kaptein E, de Jong FH, Reymond MJ, Visser TJ, de Greef WJ 1996 Effects of long-term food reduction on the hypothalamus-pituitary-thyroid axis in male and female rats. J Endocrinol 150:169–178[Abstract/Free Full Text]
  47. Pierroz DD, Catzeflis C, Aebi AC, Rivier JE, Aubert ML 1996 Chronic administration of neuropeptide Y into the lateral ventricle inhibits both the pituitary-testicular axis and growth hormone and insulin-like growth factor I secretion in intact adult male rats. Endocrinology 137:3–12[Abstract]
  48. Raposinho PD, Pierroz DD, Broqua P, White RB, Pedrazzini T, Aubert ML 2001 Chronic administration of neuropeptide Y into the lateral ventricle of C57BL/6J male mice produces an obesity syndrome including hyperphagia, hyperleptinemia, insulin resistance, and hypogonadism. Mol Cell Endocrinol 185:195–204[CrossRef][Medline]
  49. Fekete C, Kelly J, Mihaly E, Sarkar S, Rand WM, Legradi G, Emerson CH, Lechan RM 2001 Neuropeptide Y has a central inhibitory action on the hypothalamic-pituitary-thyroid axis. Endocrinology 142:2606–2613[Abstract/Free Full Text]
  50. Zarjevski N, Cusin I, Vettor R, Rohner-Jeanrenaud F, Jeanrenaud B 1994 Intracerebroventricular administration of neuropeptide Y to normal rats has divergent effects on glucose utilization by adipose tissue and skeletal muscle. Diabetes 43:764–769[Abstract]
  51. Sainsbury A, Cusin I, Rohner-Jeanrenaud F, Jeanrenaud B 1997 Adrenalectomy prevents the obesity syndrome produced by chronic central neuropeptide Y infusion in normal rats. Diabetes 46:209–214[Abstract]
  52. Zakrzewska KE, Cusin I, Stricker-Krongrad A, Boss O, Ricquier D, Jeanrenaud B, Rohner-Jeanrenaud F 1999 Induction of obesity and hyperleptinemia by central glucocorticoid infusion in the rat. Diabetes 48:365–370[Abstract]
  53. Hisano S, Kagotani Y, Tsuruo Y, Daikoku S, Chihara K, Whitnall MH 1988 Localization of glucocorticoid receptor in neuropeptide Y-containing neurons in the arcuate nucleus of the rat hypothalamus. Neurosci Lett 95:13–18[CrossRef][Medline]
  54. Krysiak R, Obuchowicz E, Herman ZS 1999 Interactions between the neuropeptide Y system and the hypothalamic-pituitary-adrenal axis. Eur J Endocrinol 140:130–136[Abstract]
  55. Inui A, Inoue T, Nakajima M, Okita M, Sakatani N, Okimura Y, Chihara K, Baba S 1990 Brain neuropeptide Y in the control of adrenocorticotropic hormone secretion in the dog. Brain Res 510:211–215[CrossRef][Medline]



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