Platelet serotonin-2 receptor binding sites in depression and suicide

In order to examine the role of serotonin-2 (5HT2) receptors in depression and suicide, we determined 5HT2 receptors using 125I-lysergic acid diethylamide (LSD) as the binding ligand in platelets obtained from 20 normal control and 23 drug-free depressed patients. Our results indicate significantly increased 125I-LSD binding sites (Bmax) in the platelets of depressed patients compared with normal control subjects. We also observed that a subgroup of depressed patients with a recent history of suicide attempts or suicidal ideation had significantly higher 5HT2 binding sites as compared with nonsuicidal depressed patients and normal controls. There were no significant differences in the apparent dissociation constant (Kd) values in the platelets of depressed patients compared with normal control subjects. To examine if the baseline 5HT2 receptors are related to either the severity of illness or treatment response, we determined the relationships of the baseline Bmax and Kd with baseline Hamilton Depression Rating Scale (HDRS) and Brief Psychiatric Rating Scale (BPRS) scores and change in scores after treatment. We found no significant correlation between baseline Bmax and Kd with the baseline HDRS or BPRS scores or change in these scores after psychoactive drug treatment. These results thus indicate increased platelet 5HT2 receptors in depression, but much more so in depressed patients with suicidal ideation or attempts.