Expression of the galanin receptor subtype Gal-R2 mRNA in the rat hypothalamus

The distribution of galanin receptor subtype 2 (Gal-R2) mRNA-expressing cells was examined by in situ hybridization in the rat hypothalamus using a full-length rat 35S-riboprobe. Gal-R2 receptor mRNA-expressing cells were found at moderate to high levels of expression in most nuclei and regions of hypothalamus. The labeling was observed within well-defined anatomical nuclei: preoptic, suprachiasmatic, periventricular, paraventricular, arcuate, dorsomedial, mammillary nuclei. The supraoptic and ventromedial nuclei were almost devoid of labeling. Some scattered labeled cells were also observed in the pituitary. This distribution of Gal-R2 mRNA-expressing cells corresponds well with that of galanin binding sites studies. As compared to the distribution of the galanin receptor subtype 1 (Gal-R1), our results indicate that the Gal-R2 type is differentially distributed, although a significant overlap exists in some regions such the preoptic area, arcuate and dorsomedial nuclei. The functional implications of these results are discussed in light of the role of galanin receptors plays in neuroendocrine regulation and feeding behavior.