On the sites of antitussive action of d-3-methyl-N-methylmorphinan (AT-17).

The sites of antitussive action of d-3-methyl-N-methylmorphinan (AT-17) were studied. It was assumed from the following results that AT-17 acts on the cough centre per se. a) When AT-17 was given by the routes leading to the brain stem such as the cerebello-medullar cistern, far smaller doses were sufficient to obtain the same effect as that by i.v. administration. b) It showed neither effect on the afferent pathway for cough reflex nor influence on pulmonary stretch receptors. c) Decerebration exerted no influence on the antitussive efficacy. d) It definitely depressed the potentials of both the recurrent and internal intercostal nerves evoked by the superior laryngeal nerve stimulation. e) Micro-injection of AT-17 into the bilateral solitary nuclei or their adjacent regions inhibited coughs induced by peripheral stimulation. f) In deafferentated and decerebrate cats, AT-17 increased the spontaneous discharges of the phrenic nerve, whereas codeine decreased them.