Platelet 5-HT receptor binding during depressive illness and tricyclic antidepressant treatment

5-Hydroxytryptamine (5-HT) receptor binding was determined in intact human platelets using 125I-iodolysergic acid diethylamide (125I-iodoLSD). The assay revealed that platelets possess a single population of specific binding sites for 125I-iodoLSD which have a high affinity for the 5-HT2 receptor antagonists, ketanserin and spiperone. There was no difference in platelet 125I-iodoLSD receptor binding between depressed patients and controls. However, treatment with tricyclic antidepressants increased the number of 125I-iodoLSD receptor binding sites without significantly altering their affinity.