The Effect of Intravenous Lidocaine on the Lesponse of Medullary Inspiratory Neurons to CO_2 in Cats

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The effect of intravenous lidocaine on the response of medullary inspiratory neurons to CO_2 was studied in 11 urethane-anesthetized ventilated cats. Lidocaine was administrated at a subconvulsive dose through a venous cannula by means of a constant-rate infusion pump (0.3-0.5mg・kg^<-1>・min^<-1>). We compared the number of spikes before and after CO_2 administration in a lidocaine-free state. Then, we likewise compared the number of spikes before and after CO_2 administration in a lidocaine administered-state. The rate of increase of spikes per mmHg of PaCO_2 was 1.49±0.72 spike・mmHg^<-1> in the control lidocaine-free group, and 0.96±0.51 spike・mmHg^<-1> in the lidocaine-administered group. The response to CO_2 was significantly suppressed in the lidocaine group (p<0.05). These results suggest that systemic lidocaine suppresses respiratory center in the urethane-anesthetized cats.