Effects of Taurine and GABA on Ca spikes and Na spikes in cerebellar Purkinje cells in vitro: Intrasomatic study

Abstract

For the purpose of throwing some light on the inhibitory neuronal mechanisms in the cerebellum, particularly that by interneurons, the effects of taurine, a strong candidate for the transmitter of stellate interneurons, on spontaneous and evoked Ca spikes and Na spikes in Purkinje cells in guinea pig cerebellar slices were intrasomatically investigated in comparison with GABA, the transmitter of basket interneurons. In common, both amino acids hyperpolarized Purkinje cell membrane, inhibited somatic Na spikes and dendritic Ca spikes, and decreased somatic membrane resistance. Taurine applied focally onto Purkinje cell dendrites, however, was found to block Ca spikes and decrease the membrane resistance more potently than when it was applied onto the soma. GABA applied onto Purkinje cell somata was more potent in blocking somatic Na spikes and in decreasing the membrane resistance than taurine applied onto the somata. The dendritic sites of Purkinje cells, which were sensitive to iontophoretically applied taurine, responded also to focal electrical stimulation in an inhibitory manner. These results not only suggest that Purkinje cell dendrites are the primary site of action for taurine, but also support the previous concept that taurine acts as a transmitter in the dendritic interneuron, stellate cells.