PHARMACOLOGICAL CHARACTERIZATION OF CCKB RECEPTORS IN HUMAN BRAIN - NO EVIDENCE FOR RECEPTOR HETEROGENEITY

In this paper, cholecystokinin (CCK) B-type binding sites were charact erized with receptor binding studies in different human brain regions (various parts of cerebral cortex, basal ganglia, hippocampus, thalamu s, cerebellar cortex) collected from 22 human post mortem brains. With the exception of the thalamus, where no specific CCK binding sites we re found, a pharmacological characterization demonstrated a single cla ss of high affinity CCK sites in all brain areas investigated. Recepto r densities ranged from 0.5 fmol/mg protein (hippocampus) to 8.4 fmol/ mg protein (nucleus caudatus). These CCK binding sites displayed a typ ical CCKB binding profile as shown in competition studies by using dif ferent CCK-related compounds and non-peptide CCK antagonists discrimin ating between CCKA and CCKB sites. The rank order of agonist or antago nist potency in inhibiting specific sulphated [propionyl-H-3]cholecyst okinin octapeptide binding was similar and highly correlated for the b rain regions investigated as demonstrated by a computer-assisted analy sis. Therefore it is concluded that CCKB binding sites in human cerebr al cortex, basal ganglia, cerebellar cortex share identical ligand bin ding characteristics.