Expression pattern of sex steroid hormone receptors in the adult male rabbit brain

Progesterone (P4), estradiol (E2), and testosterone (T) are crucial for reproduction and are pivotal in several vertebrate central nervous system (CNS) functions. These hormones act by binding to their corresponding receptors, including those intracellularly located, such as progesterone receptor (PR), estrogen receptor (ER), and androgen receptor, which in this manuscript we named testosterone receptor (TR). The expression pattern of these receptors in the rabbit male brain is unknown. We studied PR, ER, and TR expression at mRNA and protein levels in several intact adult male brain regions by RT-qPCR and Western blot. We found the highest PR mRNA levels in the prefrontal cortex (PC) and the preoptic area (POA). PR protein content (110 kDa) was similar in all the analyzed brain regions. Maximum ERα mRNA levels were found in the mesencephalon (MSC) compared with the scarce levels presented in POA and cerebellum (CER). The two leading ERα bands (54 and 66 kDa) showed comparable content among analyzed brain regions, except in the olfactory bulb (OB). Considerable TR mRNA levels were found in the analyzed brain areas except in CER. TR protein (110 kDa) content was also high in MSC. The CER showed the lowest PR, ERα, and TR mRNA levels, but the corresponding protein contents were similar to those of different areas. These data reflect regional variability in the expression of sex steroid hormone receptors in the adult male rabbit brain. They constitute the basis for defining the distribution pattern of these receptors in the rabbit brain; in addition, they would allow comparisons to be made with reports of the expression of these receptors in female rabbit brains and the search for understanding their role in rabbits.