Abstract
Genesis of coughing were studied electrophysiologically in cats, using a new antitussive drugs (Oxymetebanol, 14-Hydroxy-dihydro-6β-thebainol-1-4-methyl ether). Results are as follows:
1. Codeine and oxymetebanol depress the cough reflex evoked by repetitive stimulation (20Hz) of the superior laryngeal nerve (SLN). The depressive effects represented by ED50 (i. v.) were 0.08 (0.02_??_0.27)mg/kg for oxymetebanol and 1.4 (0.88_??_2.24)mg/kg for codeine.
2. Codeine and oxymetebanol depress the centrally-induced cough reflex evoked by the stimulation of the nucleus tractus solitarius.
3. Synaptically evoked potentials recorded within the nucleus tractus solitarius follow-ing stimulation of the SLN were not influenced by either drug at the dose mentioned above. Spike discharges also, evoked by a single stimulation of SLN were not influenced by either codeine or oxymetebanol.
4. The negative synaptic potentials induced in the ipsilateral hypoglossal nucleus (20 msec latency) by the stimulation of the SLN were not influenced by codeine up to 8.0mg/kg or by oxymetebanol up to 2.0mg/kg.
5. Oxymetebanol and codeine with stimulation of the SLN had no influence on synaptic potentials recorded at the caudal portion of the ambiguus nucleus, the high density region of expiratory neurons.
6. Burst discharges of the ambiguus motoneurons induced by 20Hz repetitive stimulation of the SLN were depressed by 1.0mg/kg of oxymetebanol and 2.0mg/kg of codeine, however the short latency response of these neurons evoked by a single shock stimulation was not influenced when the dosages mentioned above were utilized.
Central inter-relationships between cough reflex and the evoked potential in the medulla oblongata have been discussed.
