Perinatal testosterone exposure is critical for the development of the male-specific sexually dimorphic gastrin-releasing peptide system in the lumbosacral spinal cord that mediates erection and ejaculation
© Oti et al. 2016
Received: 27 November 2015
Accepted: 4 January 2016
Published: 12 January 2016
In rats, a sexually dimorphic spinal gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord projects to spinal centers that control erection and ejaculation. This system controls the sexual function of adult males in an androgen-dependent manner. In the present study, we assessed the influence of androgen exposure on the spinal GRP system during a critical period of the development of sexual dimorphism.
Immunohistochemistry was used to determine if the development of the spinal GRP system is regulated by the perinatal androgen surge. We first analyzed the responses of neonates administered with anti-androgen flutamide. To remove endogenous androgens, rats were castrated at birth. Further, neonatal females were administered androgens during a critical period to evaluate the development of the male-specific spinal GRP system.
Treatment of neonates with flutamide on postnatal days 0 and 1 attenuated the spinal GRP system during adulthood. Castrating male rats at birth resulted in a decrease in the number of GRP neurons and the intensity of neuronal GRP in the spinal cord during adulthood despite testosterone supplementation during puberty. This effect was prevented if the rats were treated with testosterone propionate immediately after castration. Moreover, treating female rats with androgens on the day of birth and the next day, masculinized the spinal GRP system during adulthood, which resembled the masculinized phenotype of adult males and induced a hypermasculine appearance.
The perinatal androgen surge plays a key role in masculinization of the spinal GRP system that controls male sexual behavior. Further, the present study provides potentially new approaches to treat sexual disorders of males.
KeywordsAndrogens Sexual differentiation Gastrin-releasing peptide Male sexual function Spinal cord
Early in life, androgens such as testosterone (T) and 5α-dihydrotestosterone (DHT) play a key role in the sexual differentiation of the central nervous system through a mechanism that is mediated by signaling through the nuclear androgen receptor (AR) [1–4]. In males, a considerable amount of T secreted transiently from the testes represents the “androgen surge” that masculinizes the developing brain as well as the external and internal genitalia [3–5]. Sex differences caused by the androgen surge are restricted to a limited period called the “sensitive” or “critical” period [4, 5]. For example, a critical period in rats occurs 18–27 days after fertilization when masculinization of the brain and spinal cord typically depends on transiently higher levels of circulating androgens [3, 4].
The spinal nucleus of the bulbocavernosus (SNB), which is located in the lumbosacral spinal cord (L5–S1 level), is homologous to Onuf’s nucleus in humans  and innervates the perineal-striated muscles attached to the base of the penis; the bulbocavernosus (BC) muscles in mammals such as rats [7, 8], mice , and monkeys . The SNB-BC neuromuscular system is male-dominant in adults, and this sexual dimorphism is caused by sex differences in perinatal androgen exposure [7, 8]. Although androgens appear to play an important role in the establishment of SNB motoneuron number [11–14], somal size [15, 16], and neuromuscular synapse elimination , estrogens might also be critically involved in SNB dendritic development . Taken together, these results suggest that, in the developing SNB-BC neuromuscular system, somal and dendritic growth may occur through separate developmental mechanisms, and that androgens and estrogens act synergistically to support normal masculine SNB dendritic development [8, 18].
Gastrin-releasing peptide (GRP), a brain-gut peptide, is expressed and distributed widely in the central nervous system as well as in the gastrointestinal tract of mammals . GRP regulates many physiological processes, including food intake , circadian rhythms , anxiety , and the sensation of itch [23, 24]. Further, we demonstrated that neurons that express GRP (GRP neurons) in the lumbosacral spinal cord mediate the function of spinal centers that promotes penile reflexes during the sexual behavior of rats [25, 26]. Further, the number of GRP neurons in the lumbar spinal region (L3–L4 level) is greater in males than that in females [25, 26]. These GRP neurons project axons into the more caudal lumbosacral spinal cord (L5–S1 level), forming synaptic contacts with neurons in the sacral parasympathetic nucleus (SPN) and motor neurons in the SNB [25–30]. These nuclei control erection and ejaculation in an androgen-dependent manner during adulthood [26, 31, 32]. However, little is known about the effects of the androgen surge during perinatal development of this sexually dimorphic spinal GRP system.
To study the mechanisms underlying the development of the sexually dimorphic spinal GRP system in rats, we first determined the effects of administering the anti-androgen flutamide to neonatal male rats. Further, we castrated newborn male rats to prevent the production of endogenous androgens. In addition, we administered androgens to neonatal female rats to evaluate their effect on the development of the male-specific spinal GRP system during a critical period.
Male and female Wistar rats (Charles River Japan, Yokohama, Japan) were housed under a 12-h light/dark cycle and were provided unlimited access to water and rodent chow. The Committee for Animal Research, Okayama University, Japan authorized the experimental procedures.
Flutamide treatment of male neonates
To determine if the development of the sexually dimorphic spinal GRP system is regulated by the androgen surge, flutamide [33, 34] (Sigma-Aldrich, St. Louis, MO, USA) or sesame oil (Nacalai, Kyoto, Japan) (control) was administered to male neonates under deep, cool anesthesia. Male pups from multiple dams were randomly divided into the groups as follows: male pups were injected subcutaneously (s.c.) with 0.25 mg flutamide in 100 μl of sesame oil on the day of birth (PND 0) and 24 h later (PND 1) (designated the demasculinization group, n = 5). This treatment resulted in a demasculinization of behavior in adult rats [33, 34]. Male pups (n = 5) from the same cohort were injected s.c. with 100 μl of sesame oil (designated the control group).
Orchiectomy (ORX) and testosterone propionate (TP) treatment of male neonates
To examine the effects of the androgen surge on GRP expression in the lumbosacral spinal cord, neonates under deep, cool anesthesia were castrated and administered TP or sesame oil. Male pups from multiple dams were randomly divided into three groups. On PND 0, males (n = 3) underwent bilateral ORX to ablate androgen production and were then injected s.c. with 1.0 mg of TP (Nacalai) in 100 μl sesame oil and again on PND 1 for the purpose of androgen replacement (masculinization group) [35, 36]. Other males (n = 4) underwent bilateral ORX on PND 0 and were injected s.c. with 100 μl of sesame oil. Control males (n = 6) were sham-operated and injected s.c. with 100 μl of sesame oil on PNDs 0 and 1. On PND 30, which is approximately the onset of puberty, ORX or ORX + TP males were deeply anesthetized with 2 % isoflurane and implanted s.c. with 50-mm Silastic capsules (inner diameter = 1.59 mm, outer diameter = 3.18 mm; Compagnie de Saint-Gobain, Courbevoie, France) containing crystalline T (Tokyo Chemical, Tokyo, Japan) to maintain T levels similar to those of males at puberty for 50 days [26, 37]. Intact control males were implanted s.c. with empty 50-mm Silastic capsules.
Ovariectomy (OVX) and TP or DHT treatments of female neonates
To assess the effect of androgen administration on the development of the male-specific spinal GRP system during a critical period in females, neonatal females under deep, cool anesthesia were administered androgens or sesame oil. Female pups from multiple dams were randomly assigned to five treatment groups. On PNDs 0 and 1, females (n = 5) were injected s.c. with 0.1 or 1.0 mg of TP in 100 μl of sesame oil, and other females (n ≥ 3) were injected s.c. with 0.1 or 1.0 mg with the non-aromatizable androgen DHT (Sigma-Aldrich) in 100 μl of sesame oil on PNDs 0 and 1 (all groups were designated masculinization groups). These doses of TP and DHT approximate the physiological levels present in female neonates [35, 38, 39]. Females (n = 6) from the same cohort were injected with 100 μl of sesame oil on PNDs 0 and 1 and served as controls. On PND 30, all females under deep isoflurane anesthesia underwent bilateral OVX to remove circulating estrogens, and 50-mm Silastic capsules containing T were immediately implanted s.c. into their backs where they remained for 54 days to maintain the levels of T similar to those of the males described above.
After receiving the treatments described above, 11–12-week-old male and female rats were administered an overdose of sodium pentobarbital (100 mg/kg body weight) and perfused through the left ventricle with 100 ml of physiological saline followed by 200 ml of 4 % paraformaldehyde in 0.1 M phosphate buffer (PB; pH 7.4). Their spinal cords were immediately removed and fixed in the fixative described above for 3 h at room temperature.
Immunohistochemistry (IHC) and immunofluorescence
The fixed lumbrosacral spinal cords were cryoprotected by immersing them in 25 % sucrose in 0.1 M PB for 48 h at 4 °C, quickly frozen using powdered dry ice, and cut into 30-μm-thick cross or horizontal sections using a cryostat (CM3050 S, Leica, Nussloch, Germany). Endogenous peroxidase activity was eliminated by incubating the sections in absolute methanol containing 1 % H2O2 for 30 min and then rinsed three times with phosphate buffered saline (PBS; pH 7.4) for 5 min. This procedure was omitted for samples subjected to immunofluorescence analysis. After blocking nonspecific binding sites with 1 % normal goat serum and 1 % bovine serum albumin in PBS containing 0.3 % Triton X-100 for 1 h at room temperature, the sections were incubated with a primary rabbit antiserum against GRP (1:2000 dilution) (11081; AssayPro, St. Charles, MO, USA) . The specificity of the anti-GRP serum for the detected GRP in the spinal cord was demonstrated previously . Immunoreactive (ir) products were detected using a streptavidin-biotin kit (Nichirei, Tokyo, Japan) and diaminobenzidine (Dojindo, Kumamoto, Japan) [24, 26, 40].
To determine the sites of projection of GRP-ir axons, we performed immunofluorescence analysis of the expression of GRP and neuronal nitric oxide synthase (nNOS). The latter serves as a marker for neurons in the SPN. To detect nNOS, we used a mouse monoclonal antibody (A-11, 1:5000 dilution; Santa Cruz Biotechnology, Santa Cruz, CA, USA). Both primary antibodies were combined to probe the sections. Alexa Fluor 546-conjugated anti-mouse IgG (Molecular Probes, Eugene, OR, USA) and Alexa Fluor 488-conjugated anti-rabbit IgG (Molecular Probes) were used for detection (each diluted 1:1000). Immunostained sections were imaged using a confocal laser scanning microscope (FluoView 1000, Olympus, Tokyo, Japan).
We first counted GRP neurons in the lumbosacral spinal cord. The immunofluorescence analysis of GRP expression (GRP-ir) in neurons of the anterior lumbar spinal cord (L3–L4 level) was performed as described above using horizontal sections (approximately 18–22 30-μm-thick sections per animal) [26, 30, 37]. Briefly, we counted the number of GRP-ir cell bodies at ×200 magnification in all sections and analyzed a 600-μm2 area localized to the midline at the center. We acquired 5–15 micrographs per section, the number of which depended on the distribution of the GRP-ir neurons. These digital micrographs were selected and processed using Adobe PhotoShop (Adobe Systems, San Jose, CA, USA) and printed at 300 dots per inch on a photographic paper. GRP neurons were identified by their following characteristics: densely immunostained, anatomical localization (mainly dorsal, dorsolateral, or both to the central canal in lamina X of the lumbar segments III–IV), relatively large cell bodies (diameters approximately 20–30 μm), and clear round nuclei (diameters approximately 10–15 μm). To avoid overestimating cell number, only GRP-ir neurons that contained a round, transected nucleus were counted. Because the mean diameter of the nuclei in the GRP neurons is much smaller than the 30-μm-thick sections, this analysis reduced the overestimation of the number of neurons. All micrographs were coded and evaluated without the knowledge of the experimental group designation, and the code was not broken until the analysis was complete.
Before perfusing the rats with formaldehyde, circulating blood was collected from the cardiac left ventricle, and the plasma was stored at −80 °C. To measure the T concentration, each plasma sample was assayed using a T enzyme immunoassay kit (Cayman Chemical, Ann Arbor, MI, USA) .
The number of GRP-ir neurons in the lumbar spinal cord of each group of animals was presented as the mean ± standard error of the mean (s.e.m.). The sex differences between males treated with flutamide and controls were assessed using the Student’s t test (mean ± s.e.m.). Statistical analyses of the number of GRP-ir neurons, the optical density of GRP-ir fibers, and plasma T concentrations (mean ± s.e.m.) were performed using one-way analysis of variance (ANOVA). When the significant main effects were found using ANOVA, the post hoc Tukey’s test or the Steel-Dwass test was performed.
Administration of flutamide demasculinizes the spinal GRP system of neonatal male rats
Effects of the androgen surge on neonatal development of the spinal GRP system in males
Neonatal administration of androgens masculinizes the spinal GRP system of females
In the present study, we used rats to identify the mechanisms of sex-specific hormonal regulation, particularly androgen signaling, that mediate the development of the sexually dimorphic spinal GRP system. Here, we demonstrate that androgen treatment of neonates altered the spinal GRP system in adulthood. We were interested to find that neonatal androgen treatment induced complete masculinization of the spinal GRP system in XX females. To our knowledge, this is the first demonstration that the spinal cords of XX females were completely masculinized with respect to the spinal GRP system and that this male-specific sexual dimorphism persisted into adulthood.
Androgens masculinize the spinal GRP system in XX females
In the present study, DHT treatment of female neonates increased the number and fiber density of GRP neurons in the lumbosacral spinal cord. This upregulation of the spinal GRP system in females approximated that of the adult males and led to a hypermasculine appearance. The intensities of GRP-fibers at the SPN and DGC were increased by treating neonates with TP, and the effect was dependent on the concentration of TP, although there were no significant changes in the number of GRP neurons in TP-treated groups. Thus, treating females with TP had no significant effect on the number of GRP-positive neurons, although TP increased the optical density of GRP-positive fibers. These findings indicate the possibility that administration of TP to neonates did not affect the number of GRP neurons but increased the level of ARs in the GRP neurons or altered androgen sensitivity. The higher levels of exogenous androgens, which are present in pubescent males, might increase the density of GRP-positive fibers during adulthood.
Together, these results indicate that DHT treatment of neonates induced masculinization of the spinal GRP system in contrast to the partial affect of TP. Because DHT binds with a higher affinity to the AR than the T, these differences in androgen actions suggest that the doses of TP used here were lower than the threshold level required to induce an effect in the developing spinal cord. Comparing these results with the SNB neuromuscular system in rats, the combination of prenatal and postnatal TP treatments can induce a complete masculinization of the SNB system in females [14, 39]. Goldstein and Sengelaub  found that the treatment of female perinatal rats with DHT propionate treatment increases the motoneuron number, somal size, and dendritic arborization in the SNB to the levels of an adult male. Our present results are consistent with these studies, suggesting that the androgen surge during perinatal life plays a significant role in masculinization of the spinal GRP system as well as that of the SNB-BC neuromuscular system. The synergistic effects of androgens on these spinal systems may play an important role in normal sexual differentiation in the rat spinal cord.
Effects of androgens on sexual differentiation of the spinal GRP system during a critical period
Neonatal blockade of the androgen surge using the anti-androgen flutamide decreases the number and density of GRP neurons in the adult male spinal cord, although the endogenous T level is maintained or increased in adulthood [41, 42]. Moreover, we demonstrated that neonatal ORX decreased the number and density of GRP neurons in adulthood despite T supplementation administered around puberty (PND 30). Further, neonatal administration of TP to ORX pups, which might mimic the androgen surge, prevented the loss of the number or density of GRP neurons in the spinal cord during adulthood. We suggest therefore that the mechanisms involved in the neonatal effects of androgens on the spinal GRP system are related to the anti-apoptotic or neurotrophic effects of androgens in males during a critical period or are associated with the effects of epigenetic modifications.
We previously reported an entirely feminine pattern or a hyperfeminine appearance of the spinal GRP system in genetic males using two AR-deficient models as follows: (i) genetically male (XY) rats carrying a testicular feminization mutation of AR genes express a defective AR protein [26, 37] and (ii) a mouse line specifically lacking AR genes in the nervous system . Nonetheless, analysis of these mutants did not address the involvement of AR in the development of the sexually dimorphic spinal GRP system during neonatal life because these two models lack AR function.
In contrast, a large body of literature shows that the androgen surge during a critical period also plays a pivotal role in the sexual differentiation of the rat brain [3, 4]. However, the masculinization of the brain appears to depend on estrogens converted from T by the enzymatic activities of the cytochrome P450 aromatase expressed in the brain [3, 4, 43]. The sexually dimorphic nucleus of the preoptic area (SDN-POA) is one of the most important in the brain that is involved in the regulation of male sexual behavior in rats [3, 4, 44]. Many studies have shown that the volume of the SDN-POA is several times larger in adult male rats than that in adult female rats [43–45]. Treating female rats with testosterone as well as a synthetic estrogen, diethylstilbestrol immediately before and after birth enlarges the size of the SDN-POA of adults to that of normal males , whereas the SDN-POA is smaller and feminized in adult male rats castrated at birth [3, 4]. Thus, it is suggested that estrogens are exclusively responsible for the establishment of this sexual dimorphism in the brain [3, 4, 43]. Similarly to the brain, it is likely that estrogens might play a role in a normal masculinization of the spinal GRP system. On the other hand, we show here that disrupting androgen signaling on PNDs 0 and 1 significantly attenuated the spinal GRP system, suggesting that these 2 days (PNDs 0 and 1) might be sufficient for masculinization of the spinal GRP system in rats. These findings also suggested that the incomplete demasculinization of the spinal GRP system in male rats may be attributed to the unpreventable effects of neonatal surgery or treatment on the androgen surge during embryonic life, the level of secreted T before castration on the day of birth, or both.
Somatosensory GRP system in the spinal cord
Evidence indicates that the expression of GRP in the spinal DH is involved in the transmission of the itch sensation [23, 24]. We did not detect significant effects on the expression of GRP following neonatal administration of androgens or their antagonists on the expression of GRP in the adult spinal DH. Long-term ORX (28 days) or ORX combined with TP treatment of adult rats did not change the density of GRP-fibers in the DH of either sex [26, 37]. These results are consistent with present data, suggesting that androgens do not affect the expression of GRP in the spinal somatosensory system. These and the present findings show that the differences between the sexual and somatosensory systems in the spinal cord are not mediated by different modes of androgen signaling and that only one system is androgen sensitive.
We demonstrated that the androgen surge during a critical period in rats plays a key role in the development of the sexually dimorphic GRP system in the lumbosacral spinal cord. Further understanding of the mechanisms of sexual differentiation in the spinal cord may provide new avenues for treating male sexual disorders.
dorsal gray commissure
neuronal nitric oxide synthase
sexually dimorphic nucleus of the preoptic area
spinal nucleus of the bulbocavernosus
sacral parasympathetic nucleus
We are grateful to Dr. S. Marc Breedlove (Neuroscience Program, Michigan State University, MI) for his valuable discussion and for reading this manuscript. This work was supported in part by a KAKENHI grant from the Ministry of Education, Science, Sports, Culture and Technology (MEXT), Japan (to KT, 26870496 and 15J40220; and HS, 24680039, 15K15202, and 15H05724) by the Naito Memorial Grant for Natural Science Researches, Japan (to KT and HS), by the Kato Memorial Bioscience Foundation, Japan (to HS), by the Life Science Foundation of Japan (to HS), by the Ryobi Teien Memory Foundation, Japan (to HS), and by the Co-operative Study HVEM (H-1250M) of the National Institute for Physiological Sciences, Okazaki, Japan (to HS). The authors would like to thank Enago (www.enago.jp) for the English language review. TO and KT are supported by the Research Fellowships of JSPS for Young Scientists.
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- Breedlove SM, Arnold AP. Hormonal control of a developing neuromuscular system. I. Complete demasculinization of the male rat spinal nucleus of the bulbocavernosus using the anti-androgen flutamide. J Neurosci. 1983;3:417–23.PubMedGoogle Scholar
- Breedlove SM, Arnold AP. Hormonal control of a developing neuromuscular system. II. Sensitive periods for the androgen-induced masculinization of the rat spinal nucleus of the bulbocavernosus. J Neurosci. 1983;3:424–32.PubMedGoogle Scholar
- Matsuda K, Sakamoto H, Kawata M. Androgen action in the brain and spinal cord for the regulation of male sexual behaviors. Curr Opin Pharmacol. 2008;8:747–51.PubMedView ArticleGoogle Scholar
- Morris JA, Jordan CL, Breedlove SM. Sexual differentiation of the vertebrate nervous system. Nat Neurosci. 2004;7:1034–9.PubMedView ArticleGoogle Scholar
- Phoenix CH, Goy RW, Gerall AA, Young WC. Organizing action of prenatally administered testosterone propionate on the tissues mediating mating behavior in the female guinea pig. Endocrinology. 1959;65:369–82.PubMedView ArticleGoogle Scholar
- Onufrowicz B. Notes on the arrangement and function of the cell groups in the sacral region of the spinal cord. J Nerv Ment Dis. 1899;26:498–504.View ArticleGoogle Scholar
- Breedlove SM, Arnold AP. Hormone accumulation in a sexually dimorphic motor nucleus of the rat spinal cord. Science. 1980;210:564–6.PubMedView ArticleGoogle Scholar
- Sengelaub DR, Forger NG. The spinal nucleus of the bulbocavernosus: firsts in androgen-dependent neural sex differences. Horm Behav. 2008;53:596–612.PubMedPubMed CentralView ArticleGoogle Scholar
- Wee BE, Clemens LG. Characteristics of the spinal nucleus of the bulbocavernosus are influenced by genotype in the house mouse. Brain Res. 1987;424:305–10.PubMedView ArticleGoogle Scholar
- Ueyama T, Mizuno N, Takahashi O, Nomura S, Arakawa H, Matsushima R. Central distribution of efferent and afferent components of the pudendal nerve in macaque monkeys. J Comp Neurol. 1985;232:548–56.PubMedView ArticleGoogle Scholar
- Breedlove SM. Hormonal control of the anatomical specificity of motoneuron-to-muscle innervation in rats. Science. 1985;227:1357–9.PubMedView ArticleGoogle Scholar
- Freeman LM, Watson NV, Breedlove SM. Androgen spares androgen-insensitive motoneurons from apoptosis in the spinal nucleus of the bulbocavernosus in rats. Horm Behav. 1996;30:424–33.PubMedView ArticleGoogle Scholar
- Nordeen EJ, Nordeen KW, Sengelaub DR, Arnold AP. Androgens prevent normally occurring cell death in a sexually dimorphic spinal nucleus. Science. 1985;229:671–3.PubMedView ArticleGoogle Scholar
- Sengelaub DR, Arnold AP. Development and loss of early projections in a sexually dimorphic rat spinal nucleus. J Neurosci. 1986;6:1613–20.PubMedGoogle Scholar
- Goldstein LA, Kurz EM, Sengelaub DR. Androgen regulation of dendritic growth and retraction in the development of a sexually dimorphic spinal nucleus. J Neurosci. 1990;10:935–46.PubMedGoogle Scholar
- Verhovshek T, Buckley KE, Sergent MA, Sengelaub DR. Testosterone metabolites differentially maintain adult morphology in a sexually dimorphic neuromuscular system. Dev Neurobiol. 2010;70:206–21.PubMedPubMed CentralView ArticleGoogle Scholar
- Jordan CL, Letinsky MS, Arnold AP. The role of gonadal hormones in neuromuscular synapse elimination in rats. I. Androgen delays the loss of multiple innervation in the levator ani muscle. J Neurosci. 1989;9:229–38.PubMedGoogle Scholar
- Burke KA, Widows MR, Sengelaub DR. Synergistic effects of testosterone metabolites on the development of motoneuron morphology in a sexually dimorphic rat spinal nucleus. J Neurobiol. 1997;33:1–10.PubMedView ArticleGoogle Scholar
- Panula P, Nieminen O, Falkenberg M, Auvinen S. Localization and development of bombesin/GRP-like immunoreactivity in the rat central nervous system. Ann N Y Acad Sci. 1988;547:54–69.PubMedView ArticleGoogle Scholar
- Ladenheim EE, Taylor JE, Coy DH, Moore KA, Moran TH. Hindbrain GRP receptor blockade antagonizes feeding suppression by peripherally administered GRP. Am J Physiol. 1996;271:R180–4.PubMedGoogle Scholar
- Shinohara K, Tominaga K, Isobe Y, Inouye ST. Photic regulation of peptides located in the ventrolateral subdivision of the suprachiasmatic nucleus of the rat: daily variations of vasoactive intestinal polypeptide, gastrin-releasing peptide, and neuropeptide Y. J Neurosci. 1993;13:793–800.PubMedGoogle Scholar
- Merali Z, Bedard T, Andrews N, Davis B, McKnight AT, Gonzalez MI, et al. Bombesin receptors as a novel anti-anxiety therapeutic target: BB1 receptor actions on anxiety through alterations of serotonin activity. J Neurosci. 2006;26:10387–96.PubMedView ArticleGoogle Scholar
- Sun YG, Chen ZF. A gastrin-releasing peptide receptor mediates the itch sensation in the spinal cord. Nature. 2007;448:700–3.PubMedView ArticleGoogle Scholar
- Takanami K, Sakamoto H, Matsuda KI, Satoh K, Tanida T, Yamada S, et al. Distribution of gastrin-releasing peptide in the rat trigeminal and spinal somatosensory systems. J Comp Neurol. 2014;522:1858–73.PubMedView ArticleGoogle Scholar
- Sakamoto H, Kawata M. Gastrin-releasing peptide system in the spinal cord controls male sexual behaviour. J Neuroendocrinol. 2009;21:432–5.PubMedView ArticleGoogle Scholar
- Sakamoto H, Matsuda K, Zuloaga DG, Hongu H, Wada E, Wada K, et al. Sexually dimorphic gastrin releasing peptide system in the spinal cord controls male reproductive functions. Nat Neurosci. 2008;11:634–6.PubMedPubMed CentralView ArticleGoogle Scholar
- Dobberfuhl AD, Oti T, Sakamoto H, Marson L. Identification of CNS neurons innervating the levator ani and ventral bulbospongiosus muscles in male rats. J Sex Med. 2014;11:664–77.PubMedView ArticleGoogle Scholar
- Oti T, Satoh K, Saito K, Murata K, Kawata M, Sakamoto T, et al. Three-dimensional evaluation of the spinal local neural network revealed by the high-voltage electron microscopy: a double immunohistochemical study. Histochem Cell Biol. 2012;138:693–7.PubMedView ArticleGoogle Scholar
- Sakamoto H, Arii T, Kawata M. High-voltage electron microscopy reveals direct synaptic inputs from a spinal gastrin-releasing peptide system to neurons of the spinal nucleus of bulbocavernosus. Endocrinology. 2010;151:417–21.PubMedView ArticleGoogle Scholar
- Sakamoto H, Matsuda K, Zuloaga DG, Nishiura N, Takanami K, Jordan CL, et al. Stress affects a gastrin-releasing peptide system in the spinal cord that mediates sexual function: implications for psychogenic erectile dysfunction. PLoS ONE. 2009;4:e4276.PubMedPubMed CentralView ArticleGoogle Scholar
- Kozyrev N, Lehman MN, Coolen LM. Activation of gastrin-releasing peptide receptors in the lumbosacral spinal cord is required for ejaculation in male rats. J Sex Med. 2012;9:1303–18.PubMedView ArticleGoogle Scholar
- Truitt WA, Coolen LM. Identification of a potential ejaculation generator in the spinal cord. Science. 2002;297:1566–9.PubMedView ArticleGoogle Scholar
- Zhang JM, Konkle AT, Zup SL, McCarthy MM. Impact of sex and hormones on new cells in the developing rat hippocampus: a novel source of sex dimorphism? Eur J Neurosci. 2008;27:791–800.PubMedPubMed CentralView ArticleGoogle Scholar
- Zhang JM, Tonelli L, Regenold WT, McCarthy MM. Effects of neonatal flutamide treatment on hippocampal neurogenesis and synaptogenesis correlate with depression-like behaviors in preadolescent male rats. Neuroscience. 2010;169:544–54.PubMedPubMed CentralView ArticleGoogle Scholar
- Hagiwara H, Funabashi T, Mitsushima D, Kimura F. Effects of neonatal testosterone treatment on sex differences in formalin-induced nociceptive behavior in rats. Neurosci Lett. 2007;412:264–7.PubMedView ArticleGoogle Scholar
- Holman SD, Hutchison JB. Lateralized action of androgen on development of behavior and brain sex differences. Brain Res Bull. 1991;27:261–5.PubMedView ArticleGoogle Scholar
- Sakamoto H, Takanami K, Zuloaga DG, Matsuda K, Jordan CL, Breedlove SM, et al. Androgen regulates the sexually dimorphic gastrin-releasing peptide system in the lumbar spinal cord that mediates male sexual function. Endocrinology. 2009;150:3672–9.PubMedPubMed CentralView ArticleGoogle Scholar
- Goldstein LA, Sengelaub DR. Timing and duration of dihydrotestosterone treatment affect the development of motoneuron number and morphology in a sexually dimorphic rat spinal nucleus. J Comp Neurol. 1992;326:147–57.PubMedView ArticleGoogle Scholar
- Sengelaub DR, Nordeen EJ, Nordeen KW, Arnold AP. Hormonal control of neuron number in sexually dimorphic spinal nuclei of the rat: III. Differential effects of the androgen dihydrotestosterone. J Comp Neurol. 1989;280:637–44.PubMedView ArticleGoogle Scholar
- Sakamoto H, Saito K, Marie-Luce C, Raskin K, Oti T, Satoh K, et al. Androgen regulates development of the sexually dimorphic gastrin-releasing peptide neuron system in the lumbar spinal cord: evidence from a mouse line lacking androgen receptor in the nervous system. Neurosci Lett. 2014;558:109–14.PubMedView ArticleGoogle Scholar
- Mikkila TF, Toppari J, Paranko J. Effects of neonatal exposure to 4-tert-octylphenol, diethylstilbestrol, and flutamide on steroidogenesis in infantile rat testis. Toxicol Sci. 2006;91:456–66.PubMedView ArticleGoogle Scholar
- McCormick CM, Mahoney E. Persistent effects of prenatal, neonatal, or adult treatment with flutamide on the hypothalamic-pituitary-adrenal stress response of adult male rats. Horm Behav. 1999;35:90–101.PubMedView ArticleGoogle Scholar
- McCarthy MM. Estradiol and the developing brain. Physiol Rev. 2008;88:91–124.PubMedPubMed CentralView ArticleGoogle Scholar
- Sakamoto H. Brain-spinal cord neural circuits controlling male sexual function and behavior. Neurosci Res. 2012;72:103–16.PubMedView ArticleGoogle Scholar
- Dohler KD, Coquelin A, Davis F, Hines M, Shryne JE, Gorski RA. Pre- and postnatal influence of testosterone propionate and diethylstilbestrol on differentiation of the sexually dimorphic nucleus of the preoptic area in male and female rats. Brain Res. 1984;302:291–5.PubMedView ArticleGoogle Scholar