Galanin-binding sites in the female rat brain are regulated across puberty yet similar to the male pattern in adulthood.

Abstract

The neuropeptide galanin (GAL) has been implicated in a variety of neuroendocrine functions and has been shown to be regulated by gonadal hormones in several brain regions. We have used slice binding and quantitative autoradiography techniques to determine whether the activation of GAL pathways across puberty in female rats is associated with changes in the density of GAL binding in telencephalic and diencephalic regions as we previously observed in male rats. We have also asked whether sex differences in GAL immunoreactivity and GAL gene expression detected in some brain regions would be paralleled by sex differences in 125I-GAL-binding density in adult male and female rat brains. To control for intrinsic differences in the level of endogenous GAL synthesis and release, brain slices from prepubertal female and adult male and female rats were treated with guanosine 5'-triphosphate (GTP) to induce dissociation of endogenous GAL from its binding sites prior to incubation with radiolabeled ligand. 125I-GAL binding was significantly reduced in seven brain regions of adult compared with prepubertal female rats. These regions included the islands of Calleja (p < or = 0.03), the medial amygdaloid nucleus, posterodorsal division (p < or = 0.05), median eminence (p < or = 0.02), medial habenular nucleus (p < or = 0.05), rhomboid thalamic nucleus (p < or = 0.05), and paraventricular (p < or = 0.05) and intermediodorsal (p < or = 0.02) thalamic nuclei. Only one region, the lateral preoptic area, exhibited significantly enhanced 125I-GAL binding in adult female (p < or = 0.04) compared with prepubertal animals.(ABSTRACT TRUNCATED AT 250 WORDS)