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Endocrinology, doi:10.1210/en.2006-0753
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Endocrinology Vol. 147, No. 10 4723-4729
Copyright © 2006 by The Endocrine Society

Prolactin-Releasing Peptide Mediates Cholecystokinin-Induced Satiety in Mice

David A. Bechtold and Simon M. Luckman

Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom

Address all correspondence and requests for reprints to: Dr. Simon Luckman, Faculty of Life Sciences, University of Manchester, 1.124 Stopford Building, Oxford Road, Manchester M13 9PT, United Kingdom. E-mail: simon.luckman{at}manchester.ac.uk.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
We have shown previously that prolactin-releasing peptide (PrRP) plays a role in the regulation of feeding and energy expenditure in rats. We hypothesize that PrRP may have a physiological action through its putative receptor, GPR10, to mediate the central anorexigenic effects of peripheral satiety factors. Here we examine the effects of PrRP and cholecystokinin (CCK) on feeding in mice, including PrRP receptor gene knockout animals (GPR10–/–). Intracerebroventricular administration of PrRP (1–4 nmol) inhibited feeding in C57B6/J mice under both fast-induced and nocturnal feeding conditions. In contrast to the observations made in wild-type mice, neither PrRP nor CCK reduced food intake in GRP10–/– mice. The reduction in feeding and the release of corticosterone induced by systemic injection of the stressor lipopolysaccharide was similar in both GPR10+/+ and GPR10–/– mice. These findings suggest that PrRP, acting through GPR10, is involved in regulating food intake and may be a key intermediary in the central satiating actions of CCK.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
PROLACTIN-RELEASING PEPTIDE (PrRP) is the peptide ligand for the G protein-coupled receptor, GPR10 (1). Although originally named for its ability to stimulate prolactin release from rat pituitary cells in culture (1), PrRP is unlikely to function as a true mediator of prolactin release in vivo (2, 3, 4, 5). However, PrRP has been shown to stimulate the secretion of a number of hypothalamic-pituitary hormones, including oxytocin and ACTH (6, 7, 8), and has been implicated in central stress responses, nociception, cardiovascular regulation, and energy homeostasis (9, 10).

Although PrRP may mediate some of the effects of stress (11), including a reduction in food intake, a number of observations by our group and others suggest that PrRP may be involved in the homeostatic regulation of feeding and energy balance. For example, PrRP mRNA in the brain is down-regulated in states of negative energy balance (fasting and lactation) (12), and central administration of PrRP decreases feeding and body weight gain in rats without supporting a conditioned taste aversion or disrupting the normal behavioral satiety sequence (12, 13, 14). Pair-feeding studies suggest that the attenuation of weight gain in rats treated with PrRP cannot be accounted for solely by a reduction in food intake, suggesting that PrRP modulates not only feeding behavior but also energy expenditure (12, 15). Furthermore, mice or rats with a mutated PrRP receptor have an obese phenotype (16, 17).

In the rat, the majority of PrRP-expressing neurons reside within the nucleus of the tractus solitarius (NTS) and the ventrolateral medulla (VLM) (18, 19, 20), both regions that receive extensive gastrointestinal and autonomic vagal inputs (21). We have shown previously that PrRP neurons localized to the NTS and VLM are activated by cholecystokinin (CCK), and we have hypothesized that PrRP signaling may be important in relaying peripheral satiety signals, such as CCK, to higher brain feeding centers (13). PrRP-immunoreactive fibers and GPR10 mRNA expression have been demonstrated in a number of hypothalamic nuclei, including the paraventricular nucleus (PVN), supraoptic nucleus (SON), and dorsomedial hypothalamic nucleus (DMH) (18, 19, 20, 22, 23).

Based on its Arg-Phe-NH2 carboxyl-terminal sequence, PrRP is included in the growing list of RF-amide neuropeptides (for review see Ref. 24). Other members of this group, including neuropeptide FF (NPFF), have also been shown to modulate feeding behavior (24, 25, 26, 27). In vitro, PrRP and NPFF have equally high affinity for NPFF receptor 2 (NPFF-R2) (28), raising the possibility that PrRP could mediate its anorexic effects through this receptor rather than (or in addition to) GPR10.

Here we examine the effects of PrRP, NPFF, CCK, and bacterial lipopolysaccharide (LPS) on feeding in mice. LPS reduces feeding through activation of the hypothalamo-pituitary-adrenal axis (29, 30) and is used here to induce a stress-mediated anorexic response The anorexic effects of both PrRP and CCK, but not NPFF or LPS, were attenuated in mice lacking functional GPR10, suggesting a role for PrRP-GPR10 signaling in CCK-mediated satiety.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Animals and surgical procedures
Male C57B6J mice (25–30 g) were obtained from Charles River Laboratories (Sandwich, UK). Mice with a targeted deletion of the GPR10 gene (GPR10–/–) and wild-type mice (GPR10+/+) were provided by Millennium Pharmaceuticals (16) and subsequently bred in the animal unit of the University of Manchester. Male mice were used between 15 and 18 wk of age for all feeding experiments. All mice were provided with standard rodent chow (Beekay International, Hull, UK) and tap water ad libitum, unless stated otherwise, and housed at a constant ambient temperature of 21 C with a 12-h light, 12-h dark cycle.

For implantation of intracerebroventricular (icv) guide cannulae, mice were anesthetized with halothane (1–5% in O2) and placed in a stereotaxic frame. Guide cannulae were implanted above the lateral ventricle (0.4 mm posterior and 1.0 mm lateral to bregma) with the tip of the cannulae approximately 1.0 mm ventral to the surface of the scull according to the mouse atlas of Paxinos and Franklin (31). Cannula placement was confirmed on brain sections collected at the termination of the experiments. After surgery, animals were housed individually and allowed to recover for 7–10 d. All procedures were licensed under the United Kingdom Animals (Scientific Procedures) Act 1986 and approved by the local ethics committee.

Feeding experiments
Mice were acclimated to handling and wire mesh bottom cages leading up to all feeding experiments. Before fast-induced feeding, mice were fasted for 14 h (from the beginning of the dark phase) and injections carried out 2 h after the beginning of the light phase. During nocturnal feeding experiments, injections were carried out within 15 min of the commencement of the dark cycle. Intracerebroventricular injections were performed on conscious animals using minimal restraint. PrRP-31 (1–4 nmol; Bachem, St. Helens, UK), NPFF (2–8 nmol; Phoenix Pharmaceuticals, Karlsruhe, Germany), or vehicle (isotonic saline, 0.9% NaCl) was delivered icv in a volume of 1 µl over a period of 30 sec. Sulfated CCK26–33 (4–30 µg/kg; Bachem), LPS (125–500 µg/kg; Sigma, Poole, UK), or vehicle was injected ip in a volume of 2 µl/g.

For coadministration studies, mice were prefasted as above and injections carried out 2 h after the beginning of the light phase. The CRH receptor antagonist, astressin (7.5 mg/kg; Bachem) or the oxytocin receptor antagonist, [d(CH2)51,Tyr(Me)2,Orn8]-oxytocin (9 nmol; Bachem) was administered icv, alone or in conjunction with PrRP (4 nmol), in a volume of 1 µl. The dosages of antagonist were based on previous work by our group and others (15, 32).

Immunohistochemistry
In separate experiments, mice received an icv injection of either PrRP (4 nmol) or vehicle. All animals were provided with food and water ad libitum leading up to and during these experiments. Ninety minutes after injection, mice were anesthetized with sodium pentobarbitone (0.5 g/kg; Rhone Merieux, Harlow, UK), and perfused transcardially with heparinized isotonic saline followed by 4% paraformaldehyde in 0.1 M phosphate buffer. Brains were removed and postfixed for a further 24 h, equilibrated to 30% sucrose, and frozen at –80 C. Frozen 30-µm sections were cut using a sledge microtome and collected into 0.1 M phosphate buffer. Free-floating sections were incubated overnight in rabbit polyclonal anti-c-Fos antibody (1:5000; Calbiochem, Nottingham, UK) followed by biotin-conjugated goat antirabbit IgG antibody (1:500; Vector Laboratories, Burlingame, CA) and streptavidin-biotinylated horseradish peroxidase complex (Amersham Biosciences, Little Chalfont, UK). Immunoreaction was visualized using nickel-intensified diaminobenzidine (Vector Laboratories). Sections were mounted and coverslipped and high-magnification digital pictures collected. For dual immunolabeling, sections were processed as above followed by either guinea pig antioxytocin antibody (1:10,000; Abcam, Cambridge, UK) or guinea pig anti-CRH (1:5000; Peninsula Laboratories Inc., San Carlos, CA). Processing was repeated as above, except that nickel was not added to the diaminobenzidine.

The number of neurons expressing c-Fos immunoreactivity was counted bilaterally in brain nuclei according to the atlas of Paxinos and Franklin (31) using SigmaScan digital analysis software. The mean number of neurons per section was determined for each animal using a minimum of three, and typically five, sections per animal for each area of interest. The counting of c-Fos immunoreactive nuclei was carried out by an observer blinded to the treatment groups.

Corticosterone enzyme immunoassay
To compare the effects of LPS and CCK on corticosterone release, blood was collected from mice into heparinized tubes via cardiac puncture at the time of culling (n = 38). Plasma was isolated and frozen at –20 C until use. Plasma corticosterone concentration was measured with a commercially available enzyme immunoassay kit (IDS Ltd., Boldon, UK), following the manufacturer’s instructions.

Statistical analyses
Data are presented as mean ± SE. For studies involving C57B6J mice, data were analyzed using a one-way ANOVA with a Dunnet’s post hoc test. A two-way ANOVA with Bonferroni’s post hoc test was used in all studies involving the transgenic mice.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
PrRP-induced satiety
Intracerebroventricular administration of PrRP (1–4 nmol) at the onset of the dark period caused a significant reduction in ad libitum food consumption in C57B6J mice (Fig. 1AGo, n = 6–7 mice/group). Over the first hour, PrRP reduced food intake by approximately 50% (vehicle: 0.26 g ± 0.03; 1 nmol PrRP: 0.14 ± 0.02; 2 nmol PrRP: 0.12 ± 0.01; 4 nmol PrRP: 0.14 ± 0.04; all doses: P < 0.05). Similarly, administration of PrRP (1–4 nmol, icv) to mice that had been prefasted for 14 h reduced food intake upon refeeding (Fig. 1BGo). In contrast to the effect of PrRP on nocturnal feeding, higher concentrations of PrRP (2 or 4 nmol) were required to significantly reduce food intake in prefasted animals (food intake at 1 h: vehicle: 0.53 g ± 0.05; 1 nmol PrRP: 0.42 ± 0.08; 2 nmol PrRP: 0.32 ± 0.06, P < 0.05; 4 nmol PrRP: 0.17 ± 0.04, P < 0.01), possibly due to the strong endogenous orexigenic signals activated by the fasting. Under both feeding conditions, the anorexigenic effects of PrRP were most potent over the first hour of feeding.


Figure 1
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  		FIG. 1. Food intake in mice is reduced by PrRP. A, PrRP (1–4 nmol, icv) caused a significant reduction in ad libitum nocturnal feeding in C57B6J mice (n = 6–7 mice/group). B, PrRP (1–4 nmol) also reduced refeeding in mice that had been prefasted for 14 h (n = 6 mice/group). *, P < 0.05, **, P < 0.01, one-way ANOVA with Dunnet’s post hoc test.

 
In line with the attenuated food intake, PrRP administration (4 nmol, icv, n = 5) produced a pattern of neuronal activation, as assessed by c-Fos immunohistochemistry, commonly associated with altered feeding behavior (Fig. 2Go). Specifically, significant increases in the number of c-Fos-positive neuronal profiles, relative to controls (n = 4), were noted in the hypothalamic PVN, central amygdala, SON, lateral parabrachial nucleus, and locus ceruleus as well as the NTS and dorsal motor nucleus of the vagus nerve (DMV). Nonsignificant increases in c-Fos immunoreactive profiles were also detected in the area postrema.


Figure 2
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  		FIG. 2. PrRP-induced c-Fos expression. Representative photomicrographs of c-Fos immunohistochemistry 90 min subsequent to icv administration of vehicle (left panels) or PrRP (4 nmol; right panels). PrRP caused an increase in c-Fos immunoreactivity, relative to vehicle in the PVN (A); SON (B); central amygdala (CeA) (C); lateral parabrachial nucleus (lPBN) (D); and NTS, area postrema (AP), and DMV (E). Bar, 100 µm (A–C), 150 µm (D), 90 µm (E).

 
PrRP-mediated satiety requires GRP10
Mice with a targeted disruption of GPR10 exhibit adult-onset obesity including a significant increase in body fat (16). GPR10–/– mice that are maintained on normal rat chow become significantly heavier than age-matched congenetic wild-type mice and exhibit an increased accumulation of fat pad mass (data not shown; also Ref. 16). The obese phenotype in these mice suggests that effective GPR10 signaling is essential to the regulation of body weight and energy storage.

To determine whether GRP10 is required for PrRP-mediated satiety, PrRP was administered to GPR10+/+ and GPR10–/– mice (Fig. 3AGo). PrRP (2 nmol, icv, n = 5–6 mice/group) significantly reduced fast-induced food intake in GPR10+/+ mice (vehicle: 0.65 g ± 0.09; PrRP: 0.32 g ± 0.10; P < 0.05) but had no measurable effect on mice lacking GPR10 (vehicle: 0.55 g ± 0.09; PrRP: 0.73 g ± 0.05). Analysis of 1 h food intake by two-way ANOVA identified a significant interaction between mouse genotype and the effect of PrRP (P = 0.006), strongly suggesting that PrRP requires GPR10 to reduce food intake in mice. A significant interaction was also observed when the concentration of PrRP was raised to 4 nmol (P = 0.03). In contrast, icv administration of NPFF (4 nmol, n = 5–6 mice/group) caused a significant reduction in feeding in both GPR10+/+ and GPR10–/– mice (Fig. 3BGo). In addition to the attenuation of PrRP-mediated anorexia, the induction of c-Fos in neurons of the PVN (Fig. 3CGo) and SON (Fig. 3DGo) in response to PrRP administration (4 nmol, n = 9 mice/group) was significantly reduced in mice lacking functional GPR10.


Figure 3
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  		FIG. 3. PrRP anorexia requires GPR10. A, PrRP (2 nmol, n = 5–6 mice/group) significantly reduced fast-induced food intake in GPR10+/+ mice, compared with mice treated with vehicle, but had no measurable effect on mice lacking GPR10. B, NPFF (4 nmol, n = 5–6 mice/group) caused a significant reduction in fast-induced feeding in both GPR10+/+ and GPR10–/– mice by 2 h after injection. C and D, The induction of c-Fos in response to PrRP (4 nmol, n = 9 mice/group) was significantly reduced in the PVN (C) and SON (D) of GPR10–/– mice. *, P < 0.05, **, P < 0.01, two-way ANOVA with Bonferroni’s post hoc test.

 
PrRP-induced anorexia involves CRH and oxytocin signaling
In rats, PrRP has been shown to activate oxytocin and CRH neurons in the PVN (6, 7, 33). In the present study, administration of PrRP to wild-type mice caused an induction of c-Fos within oxytocin expressing neurons of the PVN (Fig. 4Go, A–C), which was significantly reduced in mice lacking GPR10 (Fig. 4DGo). Based on the pattern of c-Fos expression, PrRP is also likely to induce c-Fos expression in CRH neurons. Unfortunately, as has been noted by other groups, we were unable to adequately label the soma of CRH-expressing neurons in the mouse PVN to achieve reliable dual-immunopositive cell counts (Fig. 4Go, E–F).


Figure 4
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  		FIG. 4. Activation of oxytocin and CRH neurons by PrRP. PrRP administration-induced c-Fos (black staining) expression in oxytocin neurons (brown staining) within the PVN (A, vehicle; B, GPR10+/+ + PrRP; C, GPR10–/– + PrRP). Quantification demonstrated that significantly fewer oxytocin neurons expressed c-Fos in response to PrRP in GPR10–/– mice (white bars), when compared with wild types (black bars) (D). c-Fos immunoreactivity was also observed in CRH-expressing neurons of the PVN in GPR10+/+ mice after PrRP administration (E–F, F is higher magnification of E). Unfortunately, labeling of neuronal soma with anti-CRH antibodies was not clear enough to allow quantification. *, P < 0.05, **, P < 0.01, two-way ANOVA with Bonferroni’s post hoc test.

 
Complementary to the c-Fos immunolabeling studies, PrRP-induced anorexia was significantly reduced by the CRH receptor antagonist, astressin (Fig. 5AGo; 1 h food intake: vehicle: 0.85 g ± 0.06, PrRP: 0.38 ± 0.06; astressin: 0.76 ± 0.07; astressin + PrRP: 0.66 ± 0.07). Furthermore, coadministration of an oxytocin receptor antagonist attenuated the effect of PrRP on feeding (Fig. 5BGo; 1 h food intake: vehicle: 0.70 g ± 0.06, PrRP: 0.41 ± 0.10; oxytocin receptor antagonist: 0.75 ± 0.04; oxytocin receptor antagonist + PrRP: 0.57 ± 0.09).


Figure 5
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  		FIG. 5. Attenuation of PrRP-induced anorexia by CRH and oxytocin receptor antagonists. Coadministration of the CRH receptor antagonist, astressin, significantly reduced the effect of PrRP on refeeding (A; n = 12–16 mice/group). PrRP-induced anorexia was also attenuated by an oxytocin receptor antagonist (B; n = 6–8 mice/group). OT ra, Oxytocin receptor antagonist. *, P < 0.05, one-way ANOVA with Bonferroni’s post hoc test.

 
Involvement of GPR10 in CCK-mediated satiety
Based on the hypothesis that PrRP signaling might play a role in mediating the central effects of peripheral satiety factors, the ability of CCK to reduce feeding in the transgenic mice was examined. As expected, administration of CCK (4–30 µg/kg, ip, n = 6 mice/group) caused a significant reduction in food intake over the first hour of nocturnal feeding in GPR10+/+ mice (Fig. 6AGo). In contrast, GPR10–/– mice exhibited no significant decrease in feeding after CCK administration, suggesting a central role for GPR10 in mediating CCK-induced satiety.


Figure 6
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  		FIG. 6. CCK- and LPS-induced anorexia in GPR10 mice. Administration of CCK (4–30 µg/kg, ip, n = 6–10 mice/group) caused a dose-dependent reduction in food intake over the first hour of nocturnal feeding in GPR10+/+ mice (A). In contrast, GPR10–/– mice exhibited no significant decrease in feeding after CCK administration. Unlike CCK, LPS (125–500 µg/kg, n = 6 mice/group) caused a significant reduction in feeding in both wild-type and GPR10–/– mice (B). **, P < 0.01, ***, P < 0.001, two way ANOVA with Bonferroni’s post hoc test.

 
In contrast to the effects observed with CCK, the strong immunogenic agent, LPS (125–500 µg/kg, ip), reduced fast-induced feeding in both the wild-type and knockout mice when compared with vehicle-treated animals (n = 5 mice/group; Fig. 6BGo). Treatment with LPS (500 µg/kg; n = 6) also led to a dramatic rise of plasma corticosterone 90 min after injection in both the wild-type and knockout mice (GPR10+/+ vehicle: 46.4 ng/ml ± 8.9, LPS: 290.0 ±70.2, P < 0.05; GPR10–/– vehicle: 40.8 ± 5.2, LPS: 283.3 ± 67.7, P < 0.05). The GPR10+/+ mice exhibited a small increase in corticosterone after administration of 15 µg/kg CCK (vehicle: 46.4 ng/ml ± 8.9, CCK: 70.4 ng/ml ± 5.2; P = 0.16; n = 16); no such increase was observed in the GPR10–/– mice (vehicle: 40.8 ± 5.2, CCK: 37.9 ng/ml ± 6.9).


   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
These findings support a role for PrRP, and its receptor GPR10, in the regulation of feeding behavior and body weight in mice. Central administration of PrRP leads to a GPR10-dependent reduction in food intake under both fast-induced and nocturnal feeding conditions. Furthermore, the significance of endogenous PrRP-GPR10 signaling is demonstrated by the fact that GPR10 knockout mice become heavier than congenetic wild types due primarily to an increased accumulation of fat stores. The abnormal feeding behavior (16) and weight gain in these animals may be due in part to a disruption of CCK satiety signaling. As we have shown, GPR10 knockout mice do not reduce feeding in response to peripherally administered CCK, suggesting that PrRP and GPR10 are involved in mediating the central satiating actions of CCK. The recent demonstration that a GPR10 gene mutation is the primary cause of the obese phenotype in the Otsuka Long-Evans Tokushima Fatty rat further iterates the significance of this signaling pathway in energy homeostasis (17).

Our present results in the mouse are in line with published findings implicating PrRP-GPR10 signaling as a regulator of feeding behavior in rats. Central administration of PrRP has been shown to reduce feeding in rats (12, 13, 14, 34, 35), and the expression of PrRP mRNA is reduced in obese Zucker as well as fasted and lactating rats (12). It is possible that the anorexigenic effects of PrRP are indirect because PrRP is known to be involved in other processes, such as blood pressure regulation and stress response (8, 11, 14, 35, 36). However, a number of observations indicate that PrRP may act as a natural satiety factor. For example, PrRP reduces food intake in rats by shifting the behavioral satiety sequence to the left without disrupting the behavioral sequence (13) and does not induce a conditioned taste aversion (12). Furthermore, we have shown here that LPS, which activates the hypothalamus-pituitary-adrenal axis and acts as a nonphysiological anorexigen, is equally effective in both wild-type and GPR10-deficient animals.

Satiety induced by peripheral administration of CCK involves the activation of vagal afferent neurons that terminate primarily in the NTS (37, 38, 39, 40). Due to the fact that PrRP neurons in the NTS are activated by CCK, but not by lithium chloride (13), it is reasonable to propose that PrRP mediates some of the anorexigenic effects of CCK. This is supported by our current findings and is consistent with the loss of responsiveness of rats to CCK when brain stem noradrenergic neurones are lesioned (41) because PrRP neurons are a subset of the A2 cell group (34, 42). However, the mechanism by which PrRP-GPR10 signaling might mediate CCK-induced satiety remains unclear. GPR10 mRNA and PrRP binding activity have been demonstrated within the dorsal vagal complex of the medulla (18, 19, 20, 43), and so PrRP may act to regulate vagovagal reflexes. Direct injection of PrRP into the DMV can alter gastric motor function by the presynaptic modulation of glutamatergic neurones (44). PrRP-induced anorexia may also involve direct projections from brain stem nuclei (VLM and NTS) to motor nuclei within the spinal cord because PrRP-immunoreactive processes have been observed in the spinal cord (42, 45). However, the feeding response induced by PrRP is likely to involve the activation of CRH- and oxytocin-expressing neurons within the hypothalamus, as has been shown for other homeostatic modulators of feeding, including CCK and leptin (46, 47, 48, 49) Administration of leptin, CCK, or PrRP to mice leads to a robust induction of c-Fos in the PVN, and as we demonstrate here, coadministration of PrRP with antagonists for either the CRH receptor or the oxytocin receptor attenuates the effect of PrRP on feeding in mice. Pretreatment with an oxytocin receptor antagonist has also been shown to reduce the ability of peripheral CCK to inhibit feeding in rats (32, 47). CRH- and oxytocin-expressing neurons are known to project from the PVN to the dorsal vagal complex, suggesting that CRH or oxytocin axons are anatomically positioned to interact with NTS neurons that receive CCK-induced vagal signals as well as modify outgoing motor signals from the DMV.

Consistent with the ability of CRH-receptor antagonism to reduce the actions of PrRP observed in the current study, PrRP has been shown previously to trigger stress hormone release, including ACTH and corticosterone (7, 50). PrRP immunoreactivity terminals are known to make synaptic contact with CRH neurones within the PVN, and icv administration of the peptide to rats induces c-Fos expression in CRH neurons (7). Similar to PrRP, CCK has been shown to increase plasma levels of ACTH and corticosterone in rats (51, 52). Interestingly, CCK failed to increase plasma corticosterone levels in GPR10–/– animals, further indicating that PrRP neurons may serve to relay CCK-initiated signals to higher brain centers including the PVN and amygdala. By contrast, both the corticosterone release and anorexia produced by the chemical stressor, LPS, were maintained in the GPR10-deficient mouse.

The unresponsiveness of GPR10–/– mice to CCK may contribute to the development of obesity these animals. Gu et al. (16) reported that GPR10–/– mice are hyperphagic when maintained on normal rodent chow. However, we have not observed these animals to be consistently hyperphagic and may instead involve a change in meal patterning. We have previously shown that central administration of PrRP can increase body temperature and oxygen consumption in rats (12, 15). It is therefore likely that the loss of PrRP-induced energy expenditure probably exacerbates weight gain in animals lacking functional GPR10-PrRP signaling.

Finally, PrRP is a RF-amide neuropeptide, members of which have an evolutionarily conserved role in the regulation of feeding (24). Members of this group have been shown to modulate feeding behavior in rodents and other vertebrates and invertebrates (24, 25, 26, 27). In vitro, PrRP and NPFF have equally high affinity for NPFF-R2, the putative receptor for NPFF (28), raising the possibility of cross-talk between family members. However, our observations indicate that the anorexic properties of PrRP are not mediated through NPFF-R2 (at least at the doses tested here) but require GPR10 function. The ability of NPFF to reduce food intake in the GPR10–/– mice suggests that NPFF-R2 expression is maintained in these animals.

In summary, we provide important evidence that PrRP reduces food intake in mice, and that GPR10 is required for such PrRP-induced anorexia. In addition, the obese phenotype and altered CCK responsiveness of the GPR10–/– mice imply that PrRP-GPR10 pathway may have a role in normal satiety signaling and energy homeostasis.


   Acknowledgments
 
We thank Cath Lawrence, Nao Kimura, and Lorraine Schmidt for their expert assistance and Millennium Pharmaceuticals for providing the GPR10 knockout mice.


   Footnotes
 
This work was supported by the Biotechnology and Biosciences Research Council and The Wellcome Trust.

Disclosure summary: all authors have nothing to declare.

First Published Online June 22, 2006

Abbreviations: CCK, Cholecystokinin; icv, intracerebroventricular; LPS, lipopolysaccharide; NPFF, neuropeptide FF; NPFF-R2, NPFF receptor 2; NTS, nucleus of the tractus solitarius; PrRP, prolactin-releasing peptide; PVN, paraventricular nucleus; SON, supraoptic nucleus; VLM, ventrolateral medulla.

Received June 6, 2006.

Accepted for publication June 12, 2006.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Hinuma S, Habata Y, Fujii R, Kawamata Y, Hosoya M, Fukusumi S, Kitada C, Masuo Y, Asano T, Matsumoto H, Sekiguchi M, Kurokawa T, Nishimura O, Onda H, Fujino M 1998 A prolactin-releasing peptide in the brain. Nature 393:272–276[CrossRef][Medline]
  2. Samson WK, Resch ZT, Murphy TC, Chang JK 1998 Gender-biased activity of the novel prolactin releasing peptides: comparison with thyrotropin releasing hormone reveals only pharmacologic effects. Endocrine 9:289–291[CrossRef][Medline]
  3. Jarry H, Heuer H, Schomburg L, Bauer K 2000 Prolactin-releasing peptides do not stimulate prolactin release in vivo. Neuroendocrinology 71:262–267[CrossRef][Medline]
  4. Watanobe H, Schioth HB, Wikberg JE, Suda T 2000 Evaluation of the role for prolactin-releasing peptide in prolactin secretion induced by ether stress and suckling in the rat: comparison with vasoactive intestinal peptide. Brain Res 865:91–96[CrossRef][Medline]
  5. Takahashi K, Yoshinoya A, Arihara Z, Murakami O, Totsune K, Sone M, Sasano H, Shibahara S 2000 Regional distribution of immunoreactive prolactin-releasing peptide in the human brain. Peptides 21:1551–1555[CrossRef][Medline]
  6. Maruyama M, Matsumoto H, Fujiwara K, Noguchi J, Kitada C, Hinuma S, Onda H, Nishimura O, Fujino M, Higuchi T, Inoue K 1999 Central administration of prolactin-releasing peptide stimulates oxytocin release in rats. Neurosci Lett 276:193–196[CrossRef][Medline]
  7. Matsumoto H, Maruyama M, Noguchi J, Horikoshi Y, Fujiwara K, Kitada C, Hinuma S, Onda H, Nishimura O, Inoue K, Fujino M 2000 Stimulation of corticotropin-releasing hormone-mediated adrenocorticotropin secretion by central administration of prolactin-releasing peptide in rats. Neurosci Lett 285:234–238[CrossRef][Medline]
  8. Seal LJ, Small CJ, Kim MS, Stanley SA, Taheri S, Ghatei MA, Bloom SR 2000 Prolactin releasing peptide (PrRP) stimulates luteinizing hormone (LH) and follicle stimulating hormone (FSH) via a hypothalamic mechanism in male rats. Endocrinology 141:1909–1912[Abstract/Free Full Text]
  9. Sun B, Fujiwara K, Adachi S, Inoue K 2005 Physiological roles of prolactin-releasing peptide. Regul Pept 126:27–33[CrossRef][Medline]
  10. Laurent P, Becker JA, Valverde O, Ledent C, de Kerchove d’Exarde A, Schiffmann SN, Maldonado R, Vassart G, Parmentier M 2005 The prolactin-releasing peptide antagonizes the opioid system through its receptor GPR10. Nat Neurosci 8:1735–1741[CrossRef][Medline]
  11. Maruyama M, Matsumoto H, Fujiwara K, Noguchi J, Kitada C, Fujino M, Inoue K 2001 Prolactin-releasing peptide as a novel stress mediator in the central nervous system. Endocrinology 142:2032–2038[Abstract/Free Full Text]
  12. Lawrence CB, Celsi F, Brennand J, Luckman SM 2000 Alternative role for prolactin-releasing peptide in the regulation of food intake. Nat Neurosci 3:645–646[CrossRef][Medline]
  13. Lawrence CB, Ellacott KL, Luckman SM 2002 PRL-releasing peptide reduces food intake and may mediate satiety signaling. Endocrinology 143:360–367[Abstract/Free Full Text]
  14. Seal LJ, Small CJ, Dhillo WS, Kennedy AR, Ghatei MA, Bloom SR 2002 Prolactin-releasing peptide releases corticotropin-releasing hormone and increases plasma adrenocorticotropin via the paraventricular nucleus of the hypothalamus. Neuroendocrinology 76:70–78[CrossRef][Medline]
  15. Lawrence CB, Liu YL, Stock MJ, Luckman SM 2004 Anorectic actions of prolactin-releasing peptide are mediated by corticotropin-releasing hormone receptors. Am J Physiol Regul Integr Comp Physiol 286:R101–R107
  16. Gu W, Geddes BJ, Zhang C, Foley KP, Stricker-Krongrad A 2004 The prolactin-releasing peptide receptor (GPR10) regulates body weight homeostasis in mice. J Mol Neurosci 22:93–103[CrossRef][Medline]
  17. Watanabe TK, Suzuki M, Yamasaki Y, Okuno S, Hishigaki H, Ono T, Oga K, Mizoguchi-Miyakita A, Tsuji A, Kanemoto N, Wakitani S, Takagi T, Nakamura Y, Tanigami A 2005 Mutated G-protein-coupled receptor GPR10 is responsible for the hyperphagia/dyslipidaemia/obesity locus of Dmo1 in the OLETF rat. Clin Exp Pharmacol Physiol 32:355–366[CrossRef][Medline]
  18. Roland BL, Sutton SW, Wilson SJ, Luo L, Pyati J, Huvar R, Erlander MG, Lovenberg TW 1999 Anatomical distribution of prolactin-releasing peptide and its receptor suggests additional functions in the central nervous system and periphery. Endocrinology 140:5736–5745[Abstract/Free Full Text]
  19. Ibata Y, Iijima N, Kataoka Y, Kakihara K, Tanaka M, Hosoya M, Hinuma S 2000 Morphological survey of prolactin-releasing peptide and its receptor with special reference to their functional roles in the brain. Neurosci Res 38:223–230[CrossRef][Medline]
  20. Lee Y, Yang SP, Soares MJ, Voogt JL 2000 Distribution of prolactin-releasing peptide mRNA in the rat brain. Brain Res Bull 51:171–176[CrossRef][Medline]
  21. Saper CB 2004 Central autonomic system. In: Paxinos G, ed. The rat nervous system. 3rd ed. San Diego: Elsevier Academic Press; 761–794
  22. Fujii R, Fukusumi S, Hosoya M, Kawamata Y, Habata Y, Hinuma S, Sekiguchi M, Kitada C, Kurokawa T, Nishimura O, Onda H, Sumino Y, Fujino M 1999 Tissue distribution of prolactin-releasing peptide (PrRP) and its receptor. Regul Pept 83:1–10[CrossRef][Medline]
  23. Maruyama M, Matsumoto H, Fujiwara K, Kitada C, Hinuma S, Onda H, Fujino M, Inoue K 1999 Immunocytochemical localization of prolactin-releasing peptide in the rat brain. Endocrinology 140:2326–2333[Abstract/Free Full Text]
  24. Dockray GJ 2004 The expanding family of RF-amide peptides and their effects on feeding behaviour. Exp Physiol 89:229–235[Abstract/Free Full Text]
  25. Murase T, Arima H, Kondo K, Oiso Y 1996 Neuropeptide FF reduces food intake in rats. Peptides 17:353–354[CrossRef][Medline]
  26. Sunter D, Hewson AK, Lynam S, Dickson SL 2001 Intracerebroventricular injection of neuropeptide FF, an opioid modulating neuropeptide, acutely reduces food intake and stimulates water intake in the rat. Neurosci Lett 313:145–148[CrossRef][Medline]
  27. Nicklous DM, Simansky KJ 2003 Neuropeptide FF exerts pro- and anti-opioid actions in the parabrachial nucleus to modulate food intake. Am J Physiol Regul Integr Comp Physiol 285:R1046–R1054
  28. Engstrom M, Brandt A, Wurster S, Savola JM, Panula P 2003 Prolactin releasing peptide has high affinity and efficacy at neuropeptide FF2 receptors. J Pharmacol Exp Ther 305:825–832[Abstract/Free Full Text]
  29. Langhans W 1996 Bacterial products and the control of ingestive behavior: clinical implications. Nutrition 12:303–315[CrossRef][Medline]
  30. Gayle D, Ilyin SE, Flynn MC, Plata-Salaman CR 1998 Lipopolysaccharide (LPS)- and muramyl dipeptide (MDP)-induced anorexia during refeeding following acute fasting: characterization of brain cytokine and neuropeptide systems mRNAs. Brain Res 795:77–86[CrossRef][Medline]
  31. Paxinos G, Franklin KBJ 2001 The mouse brain. San Diego: Academic Press
  32. Olson BR, Drutarosky MD, Stricker EM, Verbalis JG 1991 Brain oxytocin receptor antagonism blunts the effects of anorexigenic treatments in rats: evidence for central oxytocin inhibition of food intake. Endocrinology 129:785–791[Abstract/Free Full Text]
  33. Onaka T 2004 Neural pathways controlling central and peripheral oxytocin release during stress. J Neuroendocrinol 16:308–312[CrossRef][Medline]
  34. Ellacott KL, Lawrence CB, Rothwell NJ, Luckman SM 2002 PRL-releasing peptide interacts with leptin to reduce food intake and body weight. Endocrinology 143:368–374[Abstract/Free Full Text]
  35. Vergoni AV, Watanobe H, Guidetti G, Savino G, Bertolini A, Schioth HB 2002 Effect of repeated administration of prolactin releasing peptide on feeding behavior in rats. Brain Res 955:207–213[CrossRef][Medline]
  36. Samson WK, Resch ZT, Murphy TC 2000 A novel action of the newly described prolactin-releasing peptides: cardiovascular regulation. Brain Res 858:19–25[CrossRef][Medline]
  37. Moran TH, McHugh PR 1982 Cholecystokinin suppresses food intake by inhibiting gastric emptying. Am J Physiol 242:R491–R497
  38. Smith GP, Gibbs J, Jerome C, Pi-Sunyer FX, Kissileff HR, Thornton J 1981 The satiety effect of cholecystokinin: a progress report. Peptides 2(Suppl 2):57–59
  39. Woods SC 2004 Gastrointestinal satiety signals I. An overview of gastrointestinal signals that influence food intake. Am J Physiol Gastrointest Liver Physiol 286:G7–G13
  40. Moran TH, Kinzig KP 2004 Gastrointestinal satiety signals II. Cholecystokinin. Am J Physiol Gastrointest Liver Physiol 286:G183–G188
  41. Mantella RC, Rinaman L, Vollmer RR, Amico JA 2003 Cholecystokinin and D-fenfluramine inhibit food intake in oxytocin-deficient mice. Am J Physiol Regul Integr Comp Physiol 285:R1037–R1045
  42. Chen C, Dun SL, Dun NJ, Chang JK 1999 Prolactin-releasing peptide-immunoreactivity in A1 and A2 noradrenergic neurons of the rat medulla. Brain Res 822:276–279[CrossRef][Medline]
  43. Ellacott KL, Donald EL, Clarkson P, Morten J, Masters D, Brennand J, Luckman SM 2005 Characterization of a naturally occurring polymorphism in the UHR-1 gene encoding the putative rat prolactin-releasing peptide receptor. Peptides 26:675–681[CrossRef][Medline]
  44. Grabauskas G, Zhou SY, Das S, Lu Y, Owyang C, Moises HC 2004 Prolactin-releasing peptide affects gastric motor function in rat by modulating synaptic transmission in the dorsal vagal complex. J Physiol 561:821–839[Abstract/Free Full Text]
  45. Yano T, Iijima N, Kataoka Y, Hinuma S, Tanaka M, Ibata Y 2001 Developmental expression of prolactin releasing peptide in the rat brain: localization of messenger ribonucleic acid and immunoreactive neurons. Brain Res Dev Brain Res 128:101–111[Medline]
  46. Masaki T, Yoshimichi G, Chiba S, Yasuda T, Noguchi H, Kakuma T, Sakata T, Yoshimatsu H 2003 Corticotropin-releasing hormone-mediated pathway of leptin to regulate feeding, adiposity, and uncoupling protein expression in mice. Endocrinology 144:3547–3554[Abstract/Free Full Text]
  47. Blevins JE, Eakin TJ, Murphy JA, Schwartz MW, Baskin DG 2003 Oxytocin innervation of caudal brainstem nuclei activated by cholecystokinin. Brain Res 993:30–41[CrossRef][Medline]
  48. Blevins JE, Schwartz MW, Baskin DG 2004 Evidence that paraventricular nucleus oxytocin neurons link hypothalamic leptin action to caudal brain stem nuclei controlling meal size. Am J Physiol Regul Integr Comp Physiol 287:R87–R96
  49. Schwartz MW, Seeley RJ, Campfield LA, Burn P, Baskin DG 1996 Identification of targets of leptin action in rat hypothalamus. J Clin Invest 98:1101–1106[Medline]
  50. Samson WK, Keown C, Samson CK, Samson HW, Lane B, Baker JR, Taylor MM 2003 Prolactin-releasing peptide and its homolog RFRP-1 act in hypothalamus but not in anterior pituitary gland to stimulate stress hormone secretion. Endocrine 20:59–66[CrossRef][Medline]
  51. Kamilaris TC, Johnson EO, Calogero AE, Kalogeras KT, Bernardini R, Chrousos GP, Gold PW 1992 Cholecystokinin-octapeptide stimulates hypothalamic-pituitary-adrenal function in rats: role of corticotropin-releasing hormone. Endocrinology 130:1764–1774[Abstract/Free Full Text]
  52. Katsuura G, Ibii N, Matsushita A 1992 Activation of CCK-A receptors induces elevation of plasma corticosterone in rats. Peptides 13:203–205[CrossRef][Medline]



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