The negative immunoregulatory effects of serotonin (5-HT) moduline, an endogenous 5-HT1B receptor antagonist with anti-anxiety properties

Background: Serotonin (5-HT) has negative immunoregulatory effects by reducing the interferon-gamma (IFNgamma)/interleukin-10 (IL-10) production ratio by stimulated immune cells. Leukocytes have functional 5-HT1B receptors. 5-HT moduline, an endogenous 5-HT1B receptor antagonist, may antagonize the 5-HT1B agonist-induced proliferation of immune cells. Aims: To examine the effects of 5-HT moduline on the stimulated production of IFNgamma, tumor necrosis factor alpha (TNFalpha) and IL-10. Results: 5-HT moduline, 10(-6) M and 10(-5) M, significantly reduced the production of IFNgamma and the IFNgamma/IL-10 ratio. 5-HT moduline 10(-5)M significantly reduced the production of TNFa. The combination of 5-HT, 15 mug/mL, with 5-HT moduline, 10(-6) M and 10(-5) M, further decreases the IFNgamma/IL-10 production ratio. Interpretation: 5-HT moduline has negative immunoregulatory effects.