Distribution of androgen and estrogen receptor mRNA in the brain and reproductive tissues of the leopard gecko, Eublepharis macularius

Incubation temperature during embryonic development determines gonadal sex in the leopard gecko, Eublepharis macularius. In addition, both incubation temperature and gonadal sex influence behavioral responses to androgen and estrogen treatments in adulthood. Although these findings suggest that temp erature and sex steroids act upon a common neural substrate to influence be havior, it is unclear where temperature and hormone effects are integrated. To bogie to address this question, we identified areas of the leopard geck o brain that express androgen receptor {AR) and estrogen receptor {ER) mRNA . We gonadectomized adult female and male geckos from an incubation tempera ture that produces a female-biased sex ratio and another temperature that p roduces a male-biased sex ratio. Females and males from both temperatures w ere then treated with equivalent levels of various sex steroids. Region-spe cific patterns of AR mRNA expression and ER mRNA expression were observed u pon hybridization of radiolabeled (S-35) cRNA probes to thin sections of re productive tissues (male hemipenes and female oviduct) and brain. Labeling for AR mRNA was very intense in the epithelium, but not within the body, of the male hemipenes. In contrast, expression of ER mRNA was prominent in mo st of the oviduct but not in the luminal epithelium. Within the brain, labe ling for AR mRNA was conspicuous in the anterior olfactory nucleus, the lat eral septum, the medial preoptic area, the periventricular preoptic area, t he external nucleus of the amygdala, the anterior hypothalamus, the ventrom edial hypothalamus, the premammillary nucleus, and the caudal portion of th e periventricular nucleus of the hypothalamus. Expression of ER mRNA was sp arse in the septum and was prominent in the ventromedial hypothalamus, the caudal portion of the periventricular nucleus of the hypothalamus, and a gr oup of cells near the torus semicircularis. Many of these brain regions hav e been implicated in the regulation of hormone-dependent, sex-typical repro ductive and agonistic behaviors in other vertebrates. Consequently, these n uclei are likely to control such behaviors in the leopard gecko and also ar e candidate neural substrates for mediating temperature effects on behavior . J. Comp. Neurol. 437:385-397, 2001 (C). 2001 Wiley-Liss, Inc.