Cholecystokinin receptors in brain: effects of obesity, drug treatment, and lesions.

High affinity binding sites specific for cholecystokinin (CCK) and related peptides have been identified in brain. These receptors are regionally distributed, with the greatest density in the caudate nucleus and olfactory bulbs. The number of forebrain CCK receptors increases postnatally to a peak density at 12 days of age and then falls to adult concentrations by 26 days of age. Cerebral cortical (but not hypothalamic) CCK receptors were 15-18% higher (p less than 0.05) in obese rats and mice when compared with their lean littermates; however, CCK receptors were unchanged after 96 hours of fasting in normal rats. Chronic reserpine treatment (0.75 mg/kg/day X 7 days) caused a 48% increase (p less than 0.001) in the number of cerebral cortical CCK receptors, but had no effect on receptors in the caudate nucleus. Chronic d-amphetamine sulfate (5 mg/kg twice daily X 7 days) had no effect on CCK binding in cortex or caudate nucleus. Approximately 75% of the CCK receptors in the caudate nucleus are susceptible to destruction by kainic acid, indicating that they are predominantly localized to neuronal cell bodies; the remaining 25% were destroyed by severing caudal afferents to the caudate nucleus, indicating a possible presynaptic localization.