Serotonin uptake and imipramine binding in rat platelets after chronic dexamethasone and amitriptyline treatment.

Chronic adrenocorticotrophin treatment was shown to decrease platelet 5HT uptake, increase Km and decrease Vmax. Similarly, chronic dexamethasone treatment decreased 5HT uptake, but had no effect on the Kd and Bmax of high affinity imipramine binding sites in the platelets. Chronic amitriptyline treatment induced similar changes, with the exception that the drug induced a decrease in the number of high affinity imipramine binding sites. Chronic dexamethasone treatment potentiated the effects of amitriptyline and decreased the IC50 of imipramine and desipramine as 5HT uptake inhibitors in vitro. The results suggest that whereas 5HT uptake is related to high affinity imipramine binding sites, it can be modified independently of the high affinity imipramine binding.