ACTION OF MOGUISTEINE ON THE ACTIVITY OF TRACHEOBRONCHIAL RAPIDLY ADAPTING RECEPTORS IN THE DOG

We have studied the effects of moguisteine, a new non-narcotic, periph erally acting antitussive compound, on tracheobronchial rapidly adapti ng irritant receptors (RARs). Experiments were carried out on dogs ana esthetized with a mixture of urethane and alpha-chloralose, paralysed with gallamine, vagotomized and artificially ventilated, Single unit a ction potentials identified as originating from tracheobronchial RARs were recorded from the peripheral cut end of the right vagus nerve, Th e activity of these receptors was recorded together with oesophageal p ressure and arterial blood I pressure, Fourteen RARs were challenged w ith moguisteine (200 mu g.kg(-1) i.v.) in 0.4% dimethylsulphoxide (DMS O) or 0.4% DMSO alone (vehicle), Receptor activity was recorded before (control) and at 2, 5, 10, 15, 20, 30 and 45 min after administration of the challenging compounds. When the results at intervals of 2, 5, 10, 15 and 20 min were averaged for each dog, it mas found that moguis teine decreased the mean activity of the 14 receptors to 75% of the co ntrol value (p<0.05); the greatest inhibition occurred 10-20 min after moguisteine administration. DMSO did not significantly affect the act ivity of these endings, Oesophageal pressure, arterial blood pressure and cardiac frequency were not altered during the experimental procedu res. The overall results indicate the presence of an inhibitory effect of moguisteine on rapidly adapting irritant receptors that could acco unt for the antitussigenic effect of this compound.