Concurrence of cortex and platelet serotonin2 receptor binding characteristics in the individual and the putative regulation by serotonin.

Changes in the central and peripheral serotonergic receptor activity have been reported to be involved in depression and suicidality. To elucidate the interdependence between central and peripheral receptor sites and their regulation by serotonin, we estimated intra-individual serotonin2 receptor binding characteristics in porcine cortex synaptosomes and in platelet membranes using 3H-LSD as ligand and ketanserin as competitor and quantified the relevant serotonin concentrations. A positive correlation between the apparent half maximal saturation concentration, KD, of the receptor in cortex synaptosomes and platelet membranes (r = 0.65, p = 0.0046, n = 18), and between the apparent maximal binding capacity, Bmax, of the receptor in cortex synaptosomes and platelets (r = 0.52, p = 0.027, n = 18) was observed. The blood serotonin concentrations correlated negatively with the maximal binding capacity, Bmax, in platelets (r = -0.77, p = 0.0002, n = 18). These results suggest that the binding characteristics of the central and peripheral serotonin2 receptor are similar, and that the platelet receptor activity may be regulated by blood levels of serotonin.