1987 Volume 30 Issue 4 Pages 272-276
It is not yet well understood where are the acting sites of the lidocaine in the auditory system. Our previous study has shown that injection of lidocaine reduced the spontaneous discharge rate transiently in guinea pigs.
This study was further aimed to elucidate the effects of lidocaine on the cochlear nerve by recording the single nerve action potentials which were evoked by electrical pulse applied to the cochlea through the round window membrane before and after intravenous injection of lidocaine.
One minute after intravenous injection of lidocaine, the threshold of spikes responding to the electrical stimuli was twice as much as that of preinjection. It decreased linearly and took 36 min. for full recovery.
Decrease of spontaneous discharge rate started about 10 seconds earlier than prolongation of latency of the spikes by the electrical stimuli after initiation of lidocaine injection. These results indicate that intravenous injection of lidocaine acts directly on the cochlear nerve and causes transient decrease of its excitability.
