Effects of 5-hydroxytryptamine on rapidly adapting pulmonary stretch receptor activity in the rabbit

In anesthetized rabbits, intravenous administration of 5-hydroxytryptamine (5-HT, 10, 20, 40 and 80 micrograms/kg) led to an increase of rapidly adapting pulmonary stretch receptor activity. The magnitude of the increase was dose-dependent. The excitatory responses to any doses of 5-HT were not inhibited by prior treatment with isoprenaline (100-150 micrograms). The results indicate that the stimulation of rapidly adapting pulmonary stretch receptors by 5-HT is not caused by contraction of the airway smooth muscle.