Autoradiographic localization of kappa opiate receptors in CNS taste and feeding areas

Recent evidence suggests that kappa opiate receptors may play a key role in the regulation of appetite [21]. Such evidence implies that kappa receptors might be localized within specific brain areas known to regulate ingestive behaviors. On the basis of this implication we employed an in vitro film autoradiographic technique using 3H-ethylketocyclazozine as ligand to identify putative kappa receptors [7] within CNS “taste” nuclei [23] and surrounding areas. Coronal cryostat sections of rat brain were incubated with ligand in the presence of D-Ala 2, D-Leu 5-enkephalin (DADLE) and morphine, apposed to LKB Ultrofilm for 60 days, processed and kappa receptor densities evaluated with the aid of a hand held photometer and video image analyzer. Highest kappa receptor densities were found within various gustatory and feeding sites including the rostral pole of the nucleus of the solitary tract, parabrachial nuclei, ventral posterior and medial portions of the thalamus, medial hypothalamus, medial nuclei of the amygdala and bed nucleus of the stria terminalis. Various other midline and medial limbic areas also showed significant kappa densities.