Effects of psychotropics on the periodic fluctuation in EEG synchronized with respiratory rhythms during cough reflex

It is known that the psychotropics reduce the cough reflex. To clarify the relation between the higher centers and cough reflex, we investigated the psychotropics property of the respiratory periodic fluctuation in EEG during cough reflex and after administration of psychotropics. Male mongrel dogs immobilized were maintained with artificial respiration. The efferent activities of phrenic nerve and scalp EEG were recorded, and on the basis of the resulting observations, crosscorrelation coefficients were computed using a digital computer. The cough reflex was accompanied by an increase in crosscorrelation coefficient (C. C.) between EEG and phrenic nerve activities. the C. C. between EEG and phrenic nerve activities decreased after iv administration of chlorpromazine ( mg/kg), while administration of imipramine (1-3 mg/kg) and diazepam (1-3 mg/kg) increased the C. C., respectively. The increase in the C. C. observed during cough reflex was inhibited by iv administration of these three drugs. The fact that the C. C. increased during cough reflex suggested that the ascending output from respiratory center to the higher center reinforced during this period. Furthermore, it is suggested that the psychotropics inhibited the neuronal mechanisms of the brain stem that plays an important role in cough reflex by acting upon the feedback loop located between the respiratory center and the higher centers.