[Reactions of the neurons of the bulbar respiratory center area to microiontophoretic application of opiate substances and serotonin].

Morphine, codeine and serotonin (5-HT) were microelectrophoretically applied to inspiratory, expiratory and unspecific reticular neurons located in the region of the bulbar respiratory center in anesthetized cats. Opiate agonists exerted distinct inhibitory effects on inspiratory, expiratory and inspecific neurons. With 5-HT inhibition prevailed in all three types of neurons. The inhibitory effects of GABA were more profound and prolonged in comparison with the depressing effects of opiate agonists and 5-HT. The latters depressed peak frequency of each rhythmic burst of respiratory neurons, while GABA abolished the rhythmic activity. The existence of specific opiate and 5-HT receptors in neurons of the bulbar respiratory center region is discussed.