Galanin in the bed nucleus of the stria terminalis and medial amygdala of the rat: lack of sexual dimorphism despite regulation of gene expression across puberty.

Abstract

Neurons in the bed nucleus of the stria terminalis (BNST) and the medial amygdala (AMe) coexpress vasopressin and galanin (GAL) in the adult male rat. Here, we have asked whether GAL gene expression, like vasopressin gene expression in these same neurons, exhibits sexual dimorphism and whether GAL pathways in the BNST and AMe are activated with puberty in female rats as we have previously observed in male rats. In Exp 1, in situ hybridization histochemistry and quantitative autoradiography were used to compare GAL gene expression in the BNST and AMe of prepubertal (24-day-old) and adult (90-day-old) male and female rats. In the BNST, both the number of GAL mRNA-expressing neurons (F = 41.98; P < or = 0.0001; males, P < or = 0.007; females, P < or = 0.001) and the intensity of labeling (F = 40.35; P < or = 0.0001; males, P < or = 0.004; females, P < or = 0.002) were significantly increased in adult compared to prepubertal animals of both sexes. In the AMe of both males (P < or = 0.001) and females (P < or = 0.001), the intensity of labeling was significantly enhanced across puberty (F = 66.29; P < or = 0.0001); however, the number of GAL mRNA-expressing neurons in this region did not change. We found no evidence for sexual dimorphism of GAL gene expression in either brain region. In Exp 2, we replicated our observations of a lack of sexual dimorphism of GAL gene expression in the BNST of adult male and female rats. These findings are consistent with the hypothesis that GAL neurons in the BNST and AMe are steroid sensitive in both sexes. However, our failure to detect any differences in either the number of GAL mRNA-expressing neurons or the level of expression between male and female rats at either age indicates that these pathways do not exhibit sexual dimorphism.