Serotonin-induced pulmonary responses are mediated by the 5-HT2 receptor in the mouse

C57BL/6 mice exhibit acute transient decreases in lung conductance (GL) and dynamic compliance (Cdyn) after intravenous administration of serotonin (5-HT). To identify the specific agonist receptor subtypes responsible for this bronchoconstriction, we measured changes in pulmonary function in C57BL/6 mice in response to intravenous infusion of 5-HT receptor subtype-selective agonists and to 5-HT in the presence of antagonists selective for the 5-HT2 or 5-HT3 receptor subtypes. Agonists selective for the 5-HT1A/1B/1D or 5-HT3 receptor subtypes induced minimal or undetectable pulmonary responses, whereas infusion of alpha-methyl-5-hydroxytryptamine, a 5-HT2 receptor-selective agonist, led to dose-related decreases in Cdyn and GL. The selective 5-HT3 receptor antagonist, LY278584 maleate, (1.0 mg/kg i.v.) caused no detectable reduction in the response to 100 micrograms/kg of 5-HT. In contrast, treatment with the 5-HT2 receptor antagonist LY53857 (10 micrograms/kg i.v.) resulted in a significant diminution of the pulmonary response observed after infusion of 100 micrograms/kg of 5-HT. Dose-response relationships were established for 5-HT in experiments in which each mouse was treated with a single dose of 5-HT without antagonist or after LY53857. Compared with responses to doses of 5-HT of more than 100 micrograms/kg in the absence of antagonist, pulmonary responses to 5-HT after infusion of 10 micrograms/kg of LY53857 were significantly reduced; 100 micrograms/kg of LY53857 nearly abolished the responses to all doses of 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS)