Regular articleBoth estrogen receptors and androgen receptors contribute to testosterone-induced changes in the morphology of the medial amygdala and sexual arousal in male rats
Section snippets
Animals and surgery
Forty-nine adult male Long-Evans rats (Harlan) were selected from a pool of 60 for their display of at least two ejaculations during a preoperative copulation test. Animals were housed in standard rat cages (27 × 49 × 20 cm) with food and water freely available. Animals in different treatment conditions were distributed evenly among the cages, such that each treatment group received equivalent housing and social stimulation. Lights in the colony were set to a 12:12 schedule, with lights off at
Body, brain, and seminal vesicle weights
Animal body weights were the same at the onset of the experiment and, as expected, untreated castrates gained less weight than did sham-operated controls (P = 0.002). Among the castrates, E2 treatment, also as expected (Wade, 1972), caused the animals to gain less weight during the experiment (P = 0.01), but DHT had no effect on body weight (P = 0.6; Table 1), and there was no statistical interaction of the two steroids on this measure. Although the mean brain weight of sham castrates was less
Discussion
The overall objective of this work was to determine which gonadal steroid receptor is responsible for the steroid-dependent plasticity in the MePD of adult rats. In a former study, we found that after 30 days, blank-treated castrates had significantly smaller MePD regional volumes and somata than did sham castrates. Testosterone treatment was able to prevent the reductions in volume and soma size in castrate males, and significantly increased somal and volume measures in adult females (Cooke et
Conclusion
Interconnections between the MeA and other sexually dimorphic circuits appear to underlie the expression of male sexual behavior in rodents (Newman, 1999). Having previously found that the morphology of one subnucleus of the circuit, the MePD, was dependent upon circulating testosterone in adulthood, we now report that stimulation of both ARs and ERs appears to be required for testosterone to maintain MePD morphology fully. Furthermore, both androgenic and estrogenic stimulation appears to be
Acknowledgements
NIH NS045195 and NIH MH58703 grants supported this research. The authors thank the reviewers for their thoughtful comments on the manuscript. We also thank B.D. Sachs for advice on the construction of the NCE chamber, which was made by Ted Claire. R. Sethi provided assistance with histology.
References (54)
- et al.
Organizational and activational effects of sex steroids on brain and behaviora reanalysis
Horm. Behav.
(1985) - et al.
Implantation of dihydrotestosterone proprionate into the lateral septum or medial amygdala facilitates copulation in castrated male rats given estradiol systemically
Horm. Behav.
(1982) - et al.
Activation of sexual behavior in male rats by combined subcutaneous and intracranial treatments of 5 alpha-dihydrotestosterone
Horm. Behav.
(1989) - et al.
Sexual differentiation of the vertebrate brainprinciples and mechanisms
Front. Neuroendocrinol.
(1998) - et al.
Photoperiod and social cues influence the medial amygdala but not the bed nucleus of the stria terminalis in the Siberian hamster
Neurosci. Lett.
(2001) Characteristics of sex behaviour in male rats following castration
Anim. Behav.
(1966)- et al.
Differential effects of testosterone metabolites upon the size of sexually dimorphic motoneurons in adulthood
Horm. Behav.
(1992) Dihydrotestosterone stimulates mounting behavior but not lordosis in female rats
Physiol. Behav.
(1984)- et al.
Fos induced by mating or noncontact sociosexual interaction is colocalized with androgen receptors in neurons within the forebrain, midbrain, and lumbosacral spinal cord of male rats
Horm. Behav.
(1998) - et al.
Differences in responsiveness to testosterone of penile reflexes and copulatory behavior of male rats
Horm. Behav.
(1983)
Aromatase immunoreactivity in the rat braingonadectomy sensitive hypothalamic neurons and an unresponsive “limbic ring” of the lateral septum-bed nucleus-amygdala complex
J. Steroid Biochem. Mol. Biol.
Importance of the medial amygdala in rat penile erection evoked by remote stimuli from estrous females
Behav. Brain. Res.
Testosterone-induced plasticity of synaptic inputs to adult mammalian motoneurons
Brain Res.
Estrogenic regulation and sex dimorphism of growth-associated protein 43 kDa (GAP-43) messenger RNA in the rat
Mol. Brain Res.
Sexual dimorphisms in the mammalian limbic system
Prog. Neurobiol.
Regulation of noncontact erection in rats by gonadal steroids
Horm. Behav.
Hormonally induced neuronal plasticity in the adult motoneurons
Brain Res. Bull.
Effect of androgen on the expression of gap junction and b actin mRNAs in adult rat motoneurons
Neurosci. Res.
Estradiol increases neural specific class II-b-tubulin mRNA levels in the developing female hypothalamus by regulating mRNA stability
Mol. Cell. Neurosci.
Pubertal and seasonal plasticity in the amygdala
Brain Res.
Regulation of aromatase gene expression in the adult rat brain
Brain Res. Bull.
Rat cerebral cortical estrogen receptorsmale-female, right-left
Exp. Neurol.
Mounting behavior and lordosis behavior in castrated male rats treated with testosterone proprionate, or with estradiol benzoate or dihydrotestosterone in combination with testosterone proprionate
Horm. Behav.
Testosterone regulates substance P within neurons of the medial nucleus of the amygdala, the bed nucleus of the stria terminalis and the medial preoptic area of the male golden hamster
Brain Res.
The role of gonadal steroid receptor activation in the restoration of sociosexual behavior in adult male rats
Horm. Behav.
Gonadal hormones and behavioral regulation of body weight
Physiol. Behav.
Testosterone, androstenedione, and dihydrotestosteroneeffects on mating behavior of male rats
Horm. Behav.
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2019, Behavioural Brain ResearchCitation Excerpt :Permount was added, coverslipped and air-dried. Digital photographs were taken at 4X with a light microscope (Optisum) and images were analysed with the software TOUP VIEW to obtain the number of squared micrometers (μm2) of four sexually dimorphic regions: the sexually dimorphic nucleus of the medial preoptic area (SDN-POA) and suprachiasmatic nucleus (SCN) [12,19], identified according to plate 23 of the rat brain atlas [20]; the posterodorsal region of the medial amygdala (MeApd) [21,22] and ventromedial hypothalamus (VMH) [23] according to plate 30 of the same rat brain atlas. A number of photos (5–10) were taken and the Nissl stained regions were assessed by two different observers following a blind analysis.