Postsynaptic serotonergic activity in depressive patients: evaluation of the neuroendocrine strategy

The possible occurrence of hypersensitive postsynaptic serotonin (5-hydroxytryptamine; 5-HT) receptors in depressive patients was investigated using a neuroendocrine strategy: determination of neuroendocrine parameters after activation of the serotonergic system. Activation was achieved by oral administration of l-tryptophan and l-5-hydroxytryptophan (5-HTP). The neuroendocrine parameters measured were the plasma concentrations of prolactin, growth hormone, thyroid stimulating hormone, and cortisol. Since administration of 5-HT precursors caused no significant change in the hormone concentrations, evaluation of neuroendocrine function after stimulation with 5-HT precursors does not appear to provide a reliable index of human postsynaptic serotonergic activity.