High concentrations of cholecystokinin receptor binding sites in the ventromedial hypothalamic nucleus.

The detailed distribution of cholecystokinin (CCK) receptors in rat hypothalamic nuclei has been mapped using the technique of in vitro receptor autoradiography. Using 125I-CCK-8 as the radiolabelled probe, high levels of CCK receptor binding sites were observed in the ventromedial hypothalamic nucleus (VMN), with lower levels in the compact zone of the dorsomedial nucleus (CDMN). Computer-generated colour-coded image analysis of the VMN indicated that the level of 125I-CCK-8 binding in this nucleus approximated to that in the CCK-receptor rich cerebral cortex. Detailed distribution studies throughout the VMN indicated a marked differential localization of CCK receptor binding sites, with 125I-CCK-8 localized in a "halo" formation within the nucleus. The presence of CCK receptors within the VMN is supportive of an important role for CCK and its receptors in homeostatic processes mediated by the hypothalamus.