| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Departments of Psychology (K.M.O., H.M.J., A.P.A.) and Zoology (C.J.A.), University of Wisconsin, Madison, Wisconsin 53706
Address all correspondence and requests for reprints to: Anthony P. Auger, Psychology Department, University of Wisconsin, Madison, 1202 West Johnson Street, Madison, Wisconsin 53706. E-mail: apauger{at}wisc.edu.
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Steroid hormones produce transient and lasting changes within the developing brain mainly through their actions on intracellular steroid receptors. Upon steroid hormone binding, steroid receptors undergo a conformational change and form dimer complexes with other ligand-bound receptors. Steroid receptors then bind to DNA and recruit additional proteins, including coactivators, to form a transcriptional complex. This complex then initiates gene transcription and thereby changes in protein expression (12). Not only are steroid receptors themselves important in regulating brain differentiation, but also the additional factors recruited to the transcriptional complex, such as coactivators, are equally important (13, 14).
Recent evidence has shown that steroid receptors can be activated in the absence of steroid hormone ligand by a variety of neurochemical compounds. For example, progestin receptors (PRs) can be activated in vitro in the absence of progesterone by the neurotransmitter dopamine (15), 8-bromoadenosine-cAMP (16), and neuropeptides (17, 18). More importantly, ligand-independent activation of progestin receptors is reported to occur in adult brain to influence behavior. Mani et al. (19) found that a centrally administered dopamine receptor agonist activates PR in a ligand-independent manner to induce lordosis in estradiol-primed rats. Further research has shown that LHRH and cAMP (20) as well as exposure to reproductive stimuli (21) can also activate PRs to induce sexual behavior in the absence of progesterone. These data indicate that PRs in the adult brain can be activated by factors other than steroid hormones to influence brain physiology and behavior.
Whereas progestin receptors influence some aspects of brain development, the majority of differences between males and females are due to estrogen receptor (ER) activation. Recent data indicate that ERs can also be activated in the absence of ligand. For example, ER
knockout mice fail to show normal uterine responses to epidermal growth factor (EGF) (22), suggesting that EGF may act through ER. In vitro evidence suggests that EGF (23), IGF-I (24), caveolin-1 (25), and activators of the protein kinase A and protein kinase C pathways (26) can also induce ER-dependent gene transcription by activating ER in the absence of estradiol. Uterine EGF (27) and IGF-I (28) also result in ER-dependent gene transcription that can be blocked by an ER antagonist in vivo. Ligand-independent activation of ER by both EGF and IGF-I can also induce female sexual behavior in the absence of estrogen (29), indicating that ligand-independent activation of ER occurs in the adult brain. Furthermore, ligand-independent activation of ER by IGF-I appears to induce adult neurogenesis (30).
Whereas evidence exists that ERs can be activated in vitro in the absence of estradiol by dopamine (15, 31, 32), it is unclear whether dopamine can activate ERs during brain development to influence sexual differentiation. Dopamine itself appears to play a role in sexual differentiation of the brain. During early postnatal development, males show increased hypothalamic dopamine content contrasted to females (33). Additionally, neonatally administered dopamine antagonists interfere with normal masculinization of sexual behavior in males (34, 35), and neonatal treatment with lisuride, a dopamine D1 receptor agonist, masculinizes rough-and-tumble social play and adult sex behavior in females (36, 37). Because masculinization of adult sex behavior is at least partially dependent on perinatal exposure to estradiol (1), this suggests that dopamine may activate ER to influence brain differentiation and subsequently social behavior.
Although there is evidence that ERs can be activated in a ligand-independent manner by dopamine in vitro, it is unclear whether dopamine can activate ERs in the developing brain. We now report that stimulation of dopamine D1-like receptors can lead to the activation of ERs within developing brain in a ligand-independent manner. Dopaminergic activation of ERs in developing brain increases the expression of an ER-responsive gene, PRs, and profoundly alters the later development of juvenile social play behavior.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Experiment 1: can treatment with a D1 receptor agonist induce PR in the developing brain?
On the day after birth [postnatal day (PN) 1], neonatal female rats (n = 6–7 per group) were given sc injections of 100 µg SKF 38393 (a dopamine D1-like receptor agonist), 100 µg cAMP, 100 µg estradiol benzoate, or vehicle. Drug dosages were based on published literature. One hundred micrograms estradiol benzoate (EB) is the dosage necessary to induce a male-typical level of estradiol in the brain of female rats during development (4). SKF 38393 and cAMP doses were adapted for neonates based on the dosages used to induce Fos expression during development and sexual behavior in adult rats (20, 38). Brains were collected 24 h after injection and immediately immersed in 5% acrolein overnight at 4 C and then placed in 0.1 M Tris-buffered saline (TBS) containing 30% sucrose at 4 C until sunk. Brains were sectioned at 40 µm using a cryostat at –20 C and stored in cryoprotectant at –20 C until processed for PR immunocytochemistry.
Experiment 2: can SKF 38393 induction of PR be blocked by an ER antagonist?
Female rat pups (n = 6 per group) were injected sc on PN1 with either 100 µg tamoxifen or vehicle and then 2 h later with either 100 µg SKF 38393 or vehicle. The dose of tamoxifen chosen has been previously reported to reduce masculinization of the sexually dimorphic nucleus of the preoptic area in neonatal male rats (39). Brains were collected 24 h after the second injection and immediately immersed in 5% acrolein overnight at 4 C and then placed in 0.1 M TBS containing 30% sucrose at 4 C until sunk. Brains were sectioned at 40 µm using a cryostat at –20 C and stored in cryoprotectant at –20 C until processed for PR immunocytochemistry.
Experiment 3: does neonatal treatment with estradiol alter social play behavior?
Newborn female rats (n = 4–7 per group) were injected sc once daily from PN0 to PN2 with either 100 µg tamoxifen or vehicle and then 3 h later with either 100 µg EB or vehicle. Newborn males (n = 5) were injected with vehicle according to the same paradigm. Animals were weaned on PN21 and housed in groups of six composed of mixed sexes and treatment groups. Each group contained at least one male and at least one female from each of the four treatment groups. Rough-and-tumble social play behavior was scored between PN25 and PN29 as described below. All animals were gonadally intact at the time of testing.
Experiment 4: does neonatal treatment with SKF 38393 alter social play behavior?
Newborn female rats (n = 6 per group) were injected sc with either 100 µg SKF 38393 or vehicle once daily from PN0 to PN2. Females were weaned on PN21 and housed in groups of six, with each cage containing mixed treatment groups. Each cage contained three animals from each of the two treatment groups. Rough-and-tumble social play behavior was scored between PN25 and PN29 as described below. All animals were gonadally intact at the time of testing. Previous studies have reported that treatment of neonatal rats for 10 d with a dopamine agonist, lisuride, can increase social play behavior (36). Our pilot studies suggested that 3 d of treatment with the more specific dopamine D1 receptor agonist, SKF 38393, could be sufficient to increase play behavior.
Experiment 5: can the SKF 38393-induced increase in social play be blocked by tamoxifen?
Newborn female rats (n = 7–8 per group) were injected sc once daily from PN0 to PN2 with either 100 µg tamoxifen or vehicle and then 2 h later with either 100 µg SKF 38393 or vehicle. Females were weaned on PN21 and housed in groups of six, with each group containing at least one animal from each of the four treatment groups. Rough-and-tumble social play behavior was scored between PN25 and PN29 as described below. All animals were gonadally intact at the time of testing.
Experiment 6: does SKF 38393 alter serum estradiol concentrations?
Newborn female rats (n = 4 per group) were sc injected with 100 µg SKF 38393, 100 µg estradiol benzoate, or vehicle on PN1. Animals were killed 6 h after injection and trunk blood collected. Blood samples were centrifuged for 10 min at 10,000 rpm at 4 C to separate plasma. Plasma was pipetted off and stored at –80 C until processed by enzyme immunoassay for estradiol.
PR immunocytochemistry
Sections representing half of the brain from each animal were washed three times for 5 min each in 0.1 M TBS (pH 7.4) and then placed in TBS containing 1% H2O2 and 20% normal goat serum for 1 h to reduce endogenous peroxidase activity and nonspecific staining. Sections were then incubated in PR antibody (catalog no. A0098, DAKO USA, Carpinteria, CA; 1:1000 dilution) overnight at room temperature in TBS containing 0.3% Triton X-100 (TTBS), 2% normal goat serum, and 0.5% gelatin. After primary incubation, sections were washed three times for 5 min each in TTBS and then incubated in biotinylated goat antirabbit IgG (catalog no. BA-1000, 1:500 dilution; Vector Laboratories, Burlingame, CA) for 90 min at room temperature. Sections were then washed three times for 5 min each in TTBS and two times for 5 min each in TBS. After washes, sections were incubated in Vectastain ABC (catalog no. PK-6100, 1:400 dilution; Vector Laboratories) for 1 h. Sections were rinsed three times for 5 min each in TBS then treated with Vector SG (catalog no. SK-4700, diluted as directed; Vector Laboratories) for 30 min. Developed sections were mounted on gelatin-coated slides and coverslipped using Permount mounting medium. Omission of PR primary eliminated all immunoreactivity.
Computer-aided image analysis
Brain areas examined include the medial preoptic area (mPOA), dorsolateral bed nucleus of the stria terminalis (BST), ventromedial hypothalamus (VMH), central amygdala (CeA), and arcuate nucleus. One section per area was matched according to the rat brain atlas of Paxinos and Watson (40).
Bilateral counts of PR-immunoreactive cells were obtained using an BX61 microscope (Olympus, Melville, NY) fitted with an Olympus FV II digital camera, connected to a PC compatible computer. The software used for analysis was Olympus MicroSuite (Soft Imaging System Corp., Lakewood, CO). Data were analyzed with a one-way ANOVA and Tukey post hoc comparison tests using the SigmaStat Statistical Analysis System 2.03 software (Jandel Scientific, Corta Madera, CA).
Rough-and-tumble play behavioral testing
The social play behavior paradigm was similar to those published by Casto et al. (41) and Meaney and McEwen (42). Animals were weaned on PN21 and housed in groups of six containing animals from all treatment groups and maintained in these groups throughout the experiment. Animals were coded on the tails with a Sharpie marker to identify individuals. Rough-and-tumble social play behavior was scored on PN25–29, using a paradigm adapted from Casto et al. (41) and Meaney and McEwen (42). Animals were videorecorded for four 2-min trials per day over 5 d, with two trials occurring 3 h after lights-off and two trials occurring 6 h after lights-off, for a total observation time of 40 min per animal. The intertrial interval was 2 min. All animals were videotaped in their home cages. The tapes were scored by an observer blind to the treatment groups. All animals in a cage were observed and scored simultaneously. The play behavior scores were calculated by totaling the number of times each animal engaged in wrestling/boxing, biting, pinning, and pouncing over the entire observation time. Play behaviors were scored using the following criteria adapted from Casto et al. (41) and Meaney and McEwen (42): 1)wrestling/boxing: two animals engaged in rolling and tumbling over each other or making jabbing movements at each other with the forepaws; 2) biting: one rat biting another; 3) pouncing: one rat pounces or lunges at another; and 4) pinning: one rat standing over another, with its forepaws on the ventral surface of the opposing rat. Behavioral data were analyzed using a two-tailed Student t test (experiment 4) and a one-way ANOVA with Tukey post hoc comparison tests (experiments 3 and 5).
Estradiol enzyme immunoassay
An estradiol enzyme immunoassay kit (catalog no. 58251, Cayman Chemical, Ann Arbor, MI) was used. Estradiol standards were prepared according to the manufacturer’s instructions. The standard containing the highest concentration of estradiol was removed and another lower standard was created by diluting the lowest standard to allow the detection of lower levels of estradiol. After the preparation of estradiol standards, the standards, controls, and serum samples were loaded into a 96-well plate precoated with mouse antirabbit IgG. Next, estradiol acetylcholinesterase tracer was added, followed by estradiol antiserum. Tracer and antiserum were not added to specific control wells. The plate was then incubated for 1 h at room temperature on an orbital shaker. The plate was then rinsed five times with wash buffer, and then Ellman’s reagent was added to the empty wells. The plate was then developed in the dark on an orbital shaker until the absorbance of the maximum binding wells equaled 0.3 AU. After development, the plate was read at a wavelength of 415 nm with a plate reader. The results were calculated using a computer spreadsheet program provided by Cayman Chemicals (www.caymanchem.com/eiatools/promo/kit).
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
). Interestingly, SKF 38393 and cAMP was without effect on PR cell number within the mPOA and the VMH. In contrast, estradiol induced PR immunoreactivity in the mPOA, and VMH as well as the CeA (P < 0.05). Estradiol treatment did not statistically alter PR cell number within the BST; however; this is consistent with findings by Greco et al. (44).
|
antagonist?). Interestingly, whereas SKF 38393 was without effect on PR immunoreactivity within the mPOA, neonatal treatment with tamoxifen lead to a small but statistically significant increase in PR immunoreactivity contrasted to vehicle-only-treated animals within the mPOA (P < 0.05). This indicates that tamoxifen acts as a weak agonist within this particular brain region. No significant effects were present in the VMH.
|
and Table 1). Treatment of females with estradiol increased the frequency of social play behavior contrasted to control females (P < 0.0001). Estradiol-treated females engaged in social play at levels statistically similar to those of control males. The estradiol-induced increase in social play was completely blocked by prior treatment with the ER antagonist, tamoxifen, indicating that ERs are required for estrogen regulation of social play behavior.
|
|
).
Experiment 5: can the SKF 38393-induced increase in social play be blocked by tamoxifen?
As expected, neonatal treatment with SKF 38393 increased the instances of juvenile social play behavior on PN25-PN29 contrasted to controls (P < 0.001, Fig. 3). More importantly, prior treatment with the ER antagonist, tamoxifen, completely blocked SKF 38393-induced social play behavior, indicating ERs are required for SKF 38393 regulation of social play behavior. Tamoxifen treatment alone was without effect on social play behavior.
Experiment 6: does SKF 38393 alter serum estradiol concentrations?
Although estradiol treatment dramatically increased serum estradiol concentrations above control levels (P = 0.002, Fig. 4), SKF 38393 treatment did not alter serum estradiol concentrations.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
and ERß during development (45). Estradiol treatment did not alter PR cell number within the BST, even though this region contains high levels of both ER and ERß during development (45); however, this finding is consistent with those published previously by Greco et al. (44). Interestingly, treatment with SKF 38393 and cAMP increased PR only within the BST and CeA contrasted to control females. SKF 38393 had no effect on PR expression within the mPOA or VMH (Fig. 1). These data suggest the possibility that ligand-independent and ligand activation of ER are functionally distinct at least with respect to PR expression in some areas. This idea is supported by recent in vitro studies indicating that ligand-independent activation of ER by protein kinase A occurs through a different pathway and has a different functional consequence on ER expression than does ligand activation (46).
Because estradiol is known to regulate PR expression during development (47) and the expression of PR in developing brain is dependent on ER (48), the up-regulation of PR by cAMP and SKF 38393 suggests that dopamine can induce ER-regulated gene expression during brain development. To confirm that SKF 38393-induced PR expression was a result of ER activation, we treated female rats with the ER antagonist, tamoxifen, 2 h before injection of SKF 38393 or estradiol. We found that the SKF 38393 induction of PR in the BST and CeA was completely blocked by prior treatment with tamoxifen, indicating that ER is a critical component for this induction (Fig. 2). This suggests that stimulation of dopamine D1 receptors leads to the activation of ER in a ligand-independent manner in restricted regions of developing brain. These results are consistent with previous studies showing ligand-independent activation of ER by dopamine in vitro (15, 31, 32) and by IGF-I in the adult brain (30).
The region-specific induction of PR by SKF 38393 in developing brain appears to correlate with the distribution of dopaminergic innervation. SKF 38393 increases PR within the BST and CeA but not the mPOA or VMH. This pattern correlates with the expression of the dopamine D1 receptor marker, DARPP-32. DARPP-32, a dopamine- and cAMP-regulated phosphoprotein, is found primarily within cells containing dopamine D1 receptors (49) and is expressed at high levels within the BST and CeA. In contrast, low levels of DARPP-32 immunoreactivity are found within the mPOA and VMH (50). This suggests that the lack of SKF 38393-induced PR in the mPOA and VMH may be due to lower levels of dopamine D1 receptors within these regions. The BST and CeA also express more dopamine D1 receptors and tyrosine hydroxylase immunoreactivity than the mPOA or VMH (51, 52). Because tyrosine hydroxylase is involved in the synthesis of dopamine, these data indicate that the BST and CeA are more heavily innervated by dopamine than the mPOA and VMH.
Hormonal activation of steroid receptors during development is known to organize sex differences in the BST (2) and CeA (53). Both of these regions are involved in development of social behavior (54, 55, 56), with the CeA being critical for sexual differentiation of juvenile social play (54). The region-specific induction of PR by SKF 38393 in the CeA and BST suggests that ligand-independent activation of ER by dopamine during development may alter behaviors associated with these brain regions later in life. For example, the BST and CeA modulate numerous nonsexual social behaviors (e.g. social play behavior), whereas the mPOA and VMH modulate sexual behavior. Because the BST and CeA are targets of dopaminergic-induced ligand-independent activation of ER, we examined the ability of the dopamine D1-like receptor agonist, SKF 38393, to alter the development of prepubertal social play behavior by treating neonatal female rats with SKF 38393 or vehicle. As expected, animals treated with SKF 38393 showed higher levels of social play behavior, contrasted to vehicle-treated animals. These results are consistent with previous studies showing masculinization of rough-and-tumble play in response to neonatal treatment with the dopamine agonist lisuride (36, 37), indicating dopamine modifies the development of social play behavior. To determine whether the increase in social play by SKF 38393 was due to ER activation, we attempted to block the effect with tamoxifen. We found that prior treatment with the ER antagonist, tamoxifen, completely blocked the SKF 38393-induced increase in social play, indicating that ER is a critical component in mediating dopaminergic regulation of social play behavior (Fig. 3). These data suggest that stimulation of dopamine D1 receptors can activate ER in a ligand-independent manner within developing brain and have lasting consequences on social behavior.
The development of social play behavior is known to be sexually dimorphic, with males engaging in more social play behavior contrasted to females (9). The sexually dimorphic patterns of social play are organized by exposure to testosterone during the perinatal period. Castration of neonatal males before PN6 reduces the frequency of social play to female-typical levels (9, 57). Additionally, peripheral testosterone (58) treatment and implants of testosterone into the amygdala (43, 59) during the early neonatal period both masculinize the social play behavior of females. The effects of testosterone on the sexual differentiation of social play have been attributed to activation of androgen receptors. Meaney and Stewart (9) found that although peripheral treatment with testosterone and its androgenic metabolite, dihydrotestosterone, masculinized social play behavior, 5 µg EB had no effect. It is possible that the lack of effect of EB was due to the dosage. Recent data indicate that it takes 100 µg peripheral EB to reach male-typical levels of estradiol in the brain (4), leaving open the possibility that estradiol may influence social play behavior. Furthermore, males rendered insensitive to androgens by the testicular feminization mutation showed decreased levels of play behavior (60). Although testicular feminization mutation males showed lower frequencies of play behavior contrasted to normal males, they did tend to engage in play more frequently than females, providing support for the idea that ERs may play a role in differentiating social play behavior. We examined the ability of a male-like dose of estradiol to influence the development of social play behavior by treating neonatal female rats with 100 µg estradiol or vehicle. Control males engaged in significantly more social play contrasted to control females. This is consistent with previously reported sex differences in social play behavior (9). Estradiol-treated females engaged in significantly more social play behavior contrasted to vehicle-treated females. The levels of social play exhibited by estradiol-treated females were statistically similar to those exhibited by control males. More importantly, the estradiol-induced increase in social play behavior was completely blocked by prior treatment with tamoxifen, indicating that ER is required for estradiol regulation of social play.
Although the neonatal ovary does not begin producing steroid hormones until PN8 (61), we needed to confirm that treatment with SKF 38393 did not result in early maturation of the ovary. We tested this by measuring serum estradiol concentrations 6 h after treatment with SKF 38393, estradiol, or saline vehicle. We found that SKF 38393 did not alter serum levels of estradiol, indicating that the changes in gene expression and behavior by SKF 38393 occurred independently of changes in serum estradiol concentrations. This is consistent with previous work demonstrating that cAMP did not alter neonatal ovarian synthesis of estrogens before PN14 (43). Furthermore, if SKF 38393 was causing peripheral release of estradiol, then this released estradiol would have increased PR expression within the mPOA and VMH; however, SKF 38393 treatment altered only PR expression within the BST and the CeA. Alternatively, a localized increase in estradiol levels may have occurred within the BST and CeA but not the mPOA and VMH. Recent data suggest that synthesis of estradiol can occur in newborn rat brain (4). Therefore, we cannot rule out the possibility that SKF 38393 stimulated local synthesis of estradiol.
In summary, our data indicate that the dopamine receptor agonist, SKF 38393, activates ER in a ligand-independent manner within developing brain to induce gene expression and subsequently alters social play behavior. Because there are no clear data on the role of PRs in the development of social play behavior, it is likely that the induction of PR expression and the regulation of social play behavior by ER are separate phenomena. However, these data do suggest that the activity of ER in developing brain can be regulated by both steroid hormones and dopamine. Our data illustrate a potential pathway by which endogenous or exogenous signals from the environment, leading to changes in dopamine transmission, can activate ERs and have lasting consequences on the development of social behavior.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
First Published Online May 26, 2005
Abbreviations: BST, Bed nucleus of the stria terminalis; CeA, central amygdala; EB, estradiol benzoate; EGF, epidermal growth factor; ER, estrogen receptor; mPOA, medial preoptic area; PN, postnatal day; PR, progestin receptor; TBS, Tris-buffered saline; TTBS, TBS containing Triton X-100; VMH, ventromedial hypothalamus.
Received April 26, 2005.
Accepted for publication May 16, 2005.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
(ER) signaling. caveolin-1 drives ligand-independent nuclear translocation and activation of ER. J Biol Chem 274:33551–33556 in insulin-like growth factor-1 (IGF-1)-induced uterine responses and in vivo evidence for IGF-1/estrogen receptor cross-talk. J Biol Chem 277:8531–8537 and progestin receptor proteins in the female rat forebrain: effects of estradiol treatment. Endocrinology 142:5172–5181 and ß immunoreactive profiles in the postnatal rat brain. Brain Res Dev Brain Res 145:117–139[CrossRef][Medline]
transcription does not require proteasome activity and protects the receptor from ligand-mediated degradation. Endocrinology 145:2730–2738 expression. J Neurobiol 47:176–182[CrossRef][Medline]
This article has been cited by other articles:
 |
|
 |
|
  J. R. Kurian, M. E. Bychowski, R. M. Forbes-Lorman, C. J. Auger, and A. P. Auger Mecp2 Organizes Juvenile Social Behavior in a Sex-Specific Manner J. Neurosci., July 9, 2008; 28(28): 7137 - 7142. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. S. Quadros and C. K. Wagner Regulation of Progesterone Receptor Expression by Estradiol Is Dependent on Age, Sex and Region in the Rat Brain Endocrinology, June 1, 2008; 149(6): 3054 - 3061. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. Bao, C. Cao, X. Zhang, F. Jiang, S. V. Nicosia, and W. Bai Suppression of {beta}-Amyloid Precursor Protein Signaling into the Nucleus by Estrogens Mediated through Complex Formation between the Estrogen Receptor and Fe65 Mol. Cell. Biol., February 15, 2007; 27(4): 1321 - 1333. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C A Wilson and D C Davies The control of sexual differentiation of the reproductive system and brain Reproduction, February 1, 2007; 133(2): 331 - 359. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Baum Possible Contribution of Neonatal Ligand-Independent Activation of Estradiol Receptors to Male-Typical Sexual Differentiation of Brain and Behavior Endocrinology, September 1, 2005; 146(9): 3702 - 3704. [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
