IONIC CONTRIBUTIONS TO THE OSCILLATORY FIRING ACTIVITY OF RAT PURKINJE-CELLS INVITRO

Oscillatory firing activity in cerebellar Purkinje cells (PCs) can be maintained by intrinsic ionic conductances in the apparent absence of excitatory and inhibitory synaptic input as demonstrated by application of TTX or antagonists of amino acid-mediated transmission or both. Bursting activity in these cells is associated with a region of ZSR (zero slope resistance, the beginning part of a negative slope resistance region) of the whole cell quasi-steady-state I-V relationship. Blockade of Na+ current by TTX unmasked the ZSR region in all PCs tested. Based on current and voltage clamp experiments, hyperpolarization-activated cation current (I(h)) participates in the rhythmic firing activity by influencing the amplitude and duration of the interburst interval and the resultant pattern of the burst generation. Blockade of I(h) with cesium (Cs+) retards the membrane rebound from the after-hyperpolarization and results in longer and more negative hyperpolarizations between bursts. However, Cs+ did not affect the presence and characteristic of the ZSR region of the whole cell quasi-steady-state I-V curve.