Effects of a @entity460 channel blocker on spontaneous neural noise and gross action potential waveforms in the XXXX cochlea.

@entity840 @entity3931 @entity4176 @entity460 @entity141
The effects of the L-type @entity141 channel blocker @entity3931 on the spectrum of the spontaneous neural noise (SNN) and the waveform of the gross sound-evoked compound action potential (CAP) were investigated by perilymphatic perfusion in the @entity840 cochlea. Both the SNN and the CAP were reversibly suppressed by @entity3931 . The percentage reduction in SNN was dose-dependent in a manner very similar to the results obtained with the measures of CAP threshold changes. The reduction in the peak SNN caused by 10 microM @entity3931 was the same as that caused by 500 microM @entity4176 , which totally eliminated any neural responses. For 1 microM @entity3931 there was an apparent dissociation between the SNN and CAP changes such that the SNN could be markedly suppressed with only very small changes in CAP thresholds. These results imply that spontaneous release of neurotransmitter from the inner hair cell is more sensitive to block of @entity460 channels than evoked release. There was no evidence for any marked shift caused by @entity3931 , in the position of the main (900 Hz) spectral peak in the SNN. Comparison of the CAP waveform before and after @entity3931 perfusion showed that the CAP waveforms were unchanged despite the change in sensitivity. These data do not support the notion of any significant postsynaptic site of action of @entity3931 . The data hence provide further support for an exclusively presynaptic role for L-type @entity141 channels in the regulation of both evoked and spontaneous neurotransmitter release from inner hair cells.
