Study on the function of monoamine receptors and transmembrane signal control in the affective disorders.

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1) The presence of 5HT-2 receptors on the human platelets as a readily accessable peripheral model for certain functions of the serotonergic neuron, may permit direct study of the function of 5HT-2 receptors in living persons. In the present study, we have assessed 5HT-stimulated phosphoinositide hydrolysis in platelets from a normal control group and depressed subjects before treatment. In a group of unmedicated patients with major depressive disorder matched for age with normal control group, we found a significant increase in 5HT(100uM)-induced accumulation of inositol-1-phosphate(IP-1), one metabolic product of phoshpoinositide hydrolysis(150 7% of basal for depressed patients, 132 3% for controls). This result suggested that 5HT-stimulated phosphoinositide metabolism, mediated by 5HT-2 receptors in platelets might be provide a useful mean of investigating serotonergic receptor function in depressed patients.2) We investigated whether 5HT-stimulated IP-1 accumulation in rat hippocampla slices is mediated by the 5HT-2 receptors, and a subchronic administration of PCPA, imipramine and in combination thereof has any effect on this 5HT response in the hippocampla slices. Ritanserin inhibit 5HT-stimulated IP-1 accumulation with a Ki value of 20nM. Mianserin(1uM), ketanserin(1uM) and mCPP(100uM) reduced partially 5HT-stimulated IP-1 accumulation; spiperone(1uM) and propranolol(1uM) failed to block the 5HT response. These results indicated that 5HT mediates its 5HT receptor on phosphoinositide hydrolysis through the 5HT-2 and 5HT-1c PI response receptors in the hippocampla slices. The 10-day treatment with Depression PCPA resulted in a significant increase in response of IP-1.