SEMIQUANTITATIVE DISTRIBUTION OF GALANIN-RECEPTOR (GAL-R1) MESSENGER-RNA-CONTAINING CELLS IN THE MALE-RAT HYPOTHALAMUS

The semiquantitative distribution of mRNA encoding for rat galanin rec eptor !GAL-RI was examined by in situ hybridization in the rat hypotha lamus using a S-35-riboprobe. Most hypothalamic nuclei expressed GAL-R 1 mRNA. In the anterior hypothalamus, high levels of expression were f ound in the medial preoptic area, paraventricular and supraoptic nucle i. Numerous cells also expressed the GAL-R1 mRNA with a moderate level of expression in the periventricular region. Very few GAL-R1-expressi ng cells were present in the suprachiasmatic nucleus. In the medial hy pothalamus, numerous expressing cells were detected in the dorsomedial and ventromedial nuclei. The arcuate nucleus was moderately labeled t hroughout its rostrocaudal extent; labeled cell bodies were visible in the ventromedial and ventrolateral subdivisions as well. These result s indicate that the GAL-R1 mRNA is not only expressed in anterior hypo thalamic nuclei but also in the mediobasal hypothalamus and periventri cular region. This hypothalamic distribution correlates well with that of I-125-GAL-binding sites and GAL-immunoreactive fibers. This distri bution represents the morphological substrate for GAL roles in the hyp othalamic regulation of neuroendocrine, behavioral and autonomic funct ions.