High-affinity 3H-serotonin binding to caudate: inhibition by hallucinogens and serotoninergic drugs.

Serotonin binds specifically to calf caudate tissue with high affinity, having a dissociation constant of 2 nM and a binding site density of 14 fmoles per milligram of protein. Among many drugs tested, only serotonin agonists and antagonists inhibited this binding. Agonist potencies ranged from bufotenin (6 nM) to tryptamine (270 nM), and antagonist potencies from LSD (9.5 nM) to metergoline (25 nM).

Study at a glance

Abstract

The specific binding of 3H-serotonin to calf caudate homogenate was studied. The dissociation constant was 2nM and the number of specific sites was 14fmoles/mg protein. Of many drugs tested, inhibition of specific 3H-serotonin binding occurred almost exclusively with serotonin agonists and antagonists. The concentrations for 50% inhibition of 3H-serotonin binding by serotonergic agonists follow: bufotenin, 6nM; 5-methoxytryptamine, 12 nM; psilocin, 35nM; dimethyltryptamine, 220 nM; and tryptamine, 270 nM. The concentrations for the antagonists were: LSD 9.5 nM; methysergide 16nM and metergoline 25nM.