ADRENERGIC AND SEROTONINERGIC RECEPTORS MEDIATE THE IMMUNOLOGICAL ACTIVATION OF CORTICOSTERONE SECRETION IN MALE-RATS

In order to elucidate the mechanism of action of immune agents on cort icosterone secretion, the present study evaluated the possible involve ment of some neuronal pathways (serotoninergic, noradrenergic/adrenerg ic) in the lipopolysaccharide (LPS)-induced corticosterone release in male rats. Serotoninergic antagonists, mianserin (5-HT2C receptor bloc ker) or pindolol (5HT(1A) receptor blocker) or noradrenergic/adrenergi c antagonists, prazosin (alpha(1)-adrenoceptor blocker) or propranolol (beta-adrenoceptor blocker), were intraperitoneally (i.p.) injected b efore (5 min ) the administration of LPS. In each experiment a group o f rats i.p. injected with vehicle served as controls. Animals were sac rificed by decapitation 90 min after administration of LPS and trunk b lood was collected for corticosterone radioimmunoassay. Results showed that pretreatment with mianserin, but not with pindolol, significantl y reduced plasma corticosterone levels following administration of LPS (p < 0.05); prazosin attenuated the plasma corticosterone response to LPS (p < 0.05), while propranolol did not induce significant change. The present study indicated that serotoninergic and noradrenergic/adre nergic pathways are involved in the immunoeuroendocrine modulation of hypothalamus-pituitary-adrenal function in rats. In particular, it is probably mediated by the activation of 5-HT2C receptors and of alpha(1 )-adrenoceptors, while type 1A serotonin receptors or beta-adrenocepto rs do not seem to be involved in such a phenomenon.