[Heterogeneity of the rat respiratory way responses to serotonin]

In stimulation of preganglionic and postganglionic nervous fibres of the trachea and stimulation of preganglionic nervous fibres of the bronchi, serotonin strengthened reduction of a smooth muscle to 114 %. Methysergide (1.0 mkg) reduced responses to serotonin to 74-77 % on the trachea and practically didn't influence the bronchi. Against ketanserinum (1.0 mkg) serotonin is dose-dependent and reduced trachea's amplitude of the constriction to 60-63% and bronchi's amplitude of the constriction to 75-79%. Hexamethonium (100.0 mkg) reduced the serotonin amplitude of the constriction of the trachea at stimulation of postganglionic nerve to 64% and the bronchi at all kinds of irritation to 82-84%. Atropine (1.0 mkg) reduced effect of serotonin in stimulation of postganglionic nerve and tracheal smooth muscles to 75-77%. On preparations of bronchi, atropine reduced the serotonin effects in stimulation of preganglionic nervous fibres to 83% and strengthened to 117% in smooth muscles in stimulation of preganglionic nerve. Thus, there is heterogeneity of responses of smooth muscles of different sites of the tracheal-bronchial pathways of the rat to serotonin.