Ionic mechanisms of the action of taurine on cerebellar Purkinje cell dendrites in vitro: intradendritic study.

The ionic mechanisms underlying the inhibitory action of taurine on Purkinje cell dendrites in guinea pig cerebellar slices were investigated with the Ca spikes intracellularly recorded from the dendrites of Purkinje cells. Taurine-induced hyperpolarization was found to be inverted at a membrane potential of about--125 mV and was largely reduced by the decrease of external Cl- concentration. As the hyperpolarization was associated with an increase in a membrane conductance, it was suggested that taurine hyperpolarizes the Purkinje cell dendrite primarily by increasing a Cl conductance. It was also found that taurine greatly flattened the rising phase of the Ca spike, suggesting that taurine may abolish Ca spikes by blocking the entry of Ca ions into Purkinje cell dendrites. The after-hyperpolarization following each Ca spike was also found to be decreased by taurine, probably as a consequence of the blockade of the entry of Ca ions into the dendrite. This taurine-induced decrease of the after-hyperpolarization appears to be responsible for the transient small depolarization which usually occurs before Ca spikes are abolished by taurine.