Platelet alpha 2-adrenergic receptors in depressed patients and healthy volunteers: the effects of desipramine.

Binding parameters (Bmax and Kd) of alpha 2-adrenergic receptors were studied in platelets from 14 depressed patients and 18 control subjects. Using 3H-clonidine (a partial alpha 2-adrenergic agonist) as the ligand and membranes, prepared from platelets isolated under physiological conditions, we found no significant differences in Bmax and Kd between medication free patients and control subjects. Platelet binding parameters in the depressed patients did not correlate with plasma levels of norepinephrine, epinephrine or MHPG. Age had a significant positive effect on platelet alpha 2-adrenergic receptor Bmax in both groups, and may have masked the patient-control differences. Treatment with desipramine for 28 days had no effect on the binding parameters in depressed patients when compared to pretreatment values. Adding desipramine to platelets of control subjects 'in vitro' did also not affect binding parameters. Our findings suggest that receptor binding studies with a partial alpha 2-adrenergic agonist in platelet membranes are not a useful model to test the hypothesis of a central supersensitive adrenergic system in depression.