Further evidence that various 5-HT receptor subtypes modulate central respiratory activity: in vitro studies with SR 46349B.

The ability of SR 46349B [trans,4-([3Z)3-(2-dimethylaminoethyl)oxyimino- 3(2-flurophenyl)propen-1-yl]phenol hemifumarate], a 5-HT2 receptor antagonist, to block the changes in respiratory activity induced by serotonin was analysed by using brain stem-spinal cord preparations from newborn rats. The increases in respiratory frequency elicited by serotonin (and 5-HT1A receptor agonist) were not suppressed by SR 46349B. The tonic discharge of cervical motoneurons and the depression of inspiratory hypoglossal activity elicited by serotonin (and 5-HT2 receptor agonist) were reduced in a dose-dependent manner by SR 46349B. These results confirm that activation of 5-HT1A and 5-HT2 receptors influences respiratory frequency and motoneuronal output, respectively.