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

Abstract

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 temperature and sex steroids act upon a common neural substrate to influence behavior, it is unclear where temperature and hormone effects are integrated. To begin to address this question, we identified areas of the leopard gecko brain that express androgen receptor (AR) and estrogen receptor (ER) mRNA. We gonadectomized adult female and male geckos from an incubation temperature that produces a female-biased sex ratio and another temperature that produces a male-biased sex ratio. Females and males from both temperatures were then treated with equivalent levels of various sex steroids. Region-specific patterns of AR mRNA expression and ER mRNA expression were observed upon hybridization of radiolabeled (35S) cRNA probes to thin sections of reproductive 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 most of the oviduct but not in the luminal epithelium. Within the brain, labeling for AR mRNA was conspicuous in the anterior olfactory nucleus, the lateral septum, the medial preoptic area, the periventricular preoptic area, the external nucleus of the amygdala, the anterior hypothalamus, the ventromedial hypothalamus, the premammillary nucleus, and the caudal portion of the periventricular nucleus of the hypothalamus. Expression of ER mRNA was sparse in the septum and was prominent in the ventromedial hypothalamus, the caudal portion of the periventricular nucleus of the hypothalamus, and a group of cells near the torus semicircularis. Many of these brain regions have been implicated in the regulation of hormone-dependent, sex-typical reproductive and agonistic behaviors in other vertebrates. Consequently, these nuclei are likely to control such behaviors in the leopard gecko and also are candidate neural substrates for mediating temperature effects on behavior.

Steroid hormones alter neuroanatomy and aggression independently in the tree lizard

“…These findings are corroborated by other researchers who have demonstrated the presence of androgen and estrogen receptors within the reptilian limbic system [46,48,53,61], as well as presence of the enzyme aromatase [62] in these regions.…”

Distribution of estrogen receptor alpha mRNA in the brain and inner ear of a vocal fish with comparisons to sites of aromatase expression

“…Our results show striking conservation in ER␣ distribution between fishes and mammals (Table 1; also see Davis and Moore, 1996;Jacobs et al, 1996;Rhen and Crews, 2001, for other vertebrate groups). As expected, ER␣ mRNA was found in preoptic areas (PPa, PM) and ventral hypothalamic areas, as in every other study to date.…”

Molecular cloning of P450 aromatase from the leopard gecko and its expression in the ovary

“…The leopard gecko is easily tamed, and is easy to breed in the laboratory, unlike other squamata. Some genes related to reproduction, such as sex steroid-hormone receptors [31], gonadotropin-releasing hormone [32] and its receptor [33], proopiomelanocortin [25], have already been cloned in this animal. Physiological experiments using this molecular information have also been conducted [24,25].…”