IDENTIFICATION AND CHARACTERIZATION OF SEROTONIN 5-HT4, RECEPTOR-BINDING SITES IN HUMAN BRAIN - COMPARISON WITH OTHER MAMMALIAN-SPECIES

Specific binding for the 5-HT4-selective radioligand [H-3]GR 113808 ha s been identified in human and calf brain membranes. Using human tissu e the distribution of the binding was heterogeneous throughout differe nt brain regions, being highest in the caudate nucleus. For this regio n a K-d value of 0.59 +/- 0.08 nM and a B-max of 225 +/- 2.6 fmol/mg w ere obtained. Other regions with substantial densities were the lentic ular nucleus, the substantia nigra, the hippocampus and the frontal co rtex, whereas no binding could be detected in the cerebellum. The abil ity of several standard compounds in displacing the radioligand was co mpatible with the labelling of 5-HT4 receptors. Correlation analysis s howed no significant differences amongst data obtained for these compo unds using human, calf and guinea-pig membranes.