Slow depolarizing response from supporting cells in the goldfish saccule.

Potentials were recorded intra- and extracellularly from the saccular macula of anaesthetized goldfish. Sound-evoked responses recorded intracellularly consisted of positive microphonic potentials, nerve responses and a slow depolarizing potential. Of these three potentials, only the slow depolarization was peculiar to intracellular records. It rose and fell exponentially with time constants of about 30 and 200 ms, respectively. The amplitude of slow depolarization never exceeded 5-6 mV, even when a loud sound was applied. It is argued that the impaled cell was a supporting cell and the slow depolarization presumably reflected a rise of extracellular K+ concentration, during sound stimulation. It was also shown that this nerve response, which was resistant to the action of tetrodotoxin, probably represented the excitatory post-synaptic current that flows into the dendrites of afferent fibres. Efferent stimulation suppressed the nerve response.