DISTRIBUTION OF MESSENGER-RNA FOR CCK-B RECEPTOR IN THE BRAIN OF MASTOMYS-NATALENSIS - ABUNDANT EXPRESSION IN TELENCEPHALIC NEURONS

The distribution of chelecystokinin B (CCK-B) receptors in the Mastomy s brain was studied using Northern blot analysis and in situ hybridiza tion technique. By Northern blot analysis using P-32-labeled cDNA prob e, the cortex had the highest hybridization signal of CCK-B receptor m RNA in the brain. The olfactory bulb and hippocampus showed a moderate level of signals. In situ hybridization using S-35-labeled cRNA probe s revealed a wide and region-specific distribution of CCK-B receptor m RNA in the telencephalon. Throughout the cerebral cortex, labeled cell s were found in all layers, with higher intensities in layers II, V an d VI. Pyramidal cells of the layer II of the piriform cortex showed th e highest level of signals in the brain. In the hippocampus, most of t he pyramidal cells of the Ammon's horn were labeled, although labeled cells were not detected in other layers. Distinct signals were also de tected in the various amygdaloid nuclei, caudate-putamen, reticular th alamic nucleus, hypothalamic ventromedial nucleus and inferior collicu lus. This distribution pattern may further support the prominent exist ence of CCK-B receptors in the brain particularly in the telencephalon .