Regulation of Auditory Responses in the Central Nucleus of the Inferior Colliculus by Tetraethylammonium-Sensitive Potassium Channels

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Abstract
The role of potassium channels in regulating spontaneous firing and sound-evoked responses in the central nucleus of the inferior colliculus was studied by recording single-unit activity before and during iontophoretic application of a nonspecific potassium channel blocker, tetraethylammonium (TEA). Tone bursts and sinusoidal amplitude-modulated tones were used to evoke auditory responses. Our results show that release of TEA increased the width of spikes for all neurons tested. There was an increase in spontaneous firing for most of the neurons. There was also an increase in responses to tone bursts for most of the neurons, although in some cases there was a reduction in the evoked responses. TEA also increased the firing rate in responses to sinusoidal amplitude-modulated sounds in the majority of the neurons tested. For some neurons, the change in firing reduced the selectivity of responses for particular rates of modulation. There was also a reduction in the synchrony of action potentials to the modulation envelope in many cells. Our results show that potassium channels are important for regulating the strength of sound-evoked responses and the level of spontaneous activity, and determining the temporal properties of responses to amplitude-modulated sounds.