ANALYSIS OF SPONTANEOUS ELECTRICAL-ACTIVITY IN CEREBELLAR PURKINJE-CELLS ACUTELY ISOLATED FROM POSTNATAL RATS

Whole-cell patch recording techniques were used to analyze spontaneous electrical activity in cerebellar Purkinje: cells acutely isolated fr om postnatal rats, Spontaneous activity was present in 65% of the cell s examined, and it included simple and complex firing patterns which p ersisted under conditions that eliminated residual or reformed synapti c contacts, Under voltage clamp, both spontaneous and quiescent cells displayed similar voltage-dependent conductances, Inward current was c arried by Na+ through tetrodotoxin (TTX)-sensitive channels and by Ca2 + through P-type and T-type Ca channels, P-type current was present in all cells examined. T-type current was found in <50%, and it did not correlate with spontaneous activity, We found no evidence of a transie nt (A-type) potassium current or hyperpolarization-activated cationic current in either spontaneous or quiescent cells. Spontaneous activity did correlate with a lower activation threshold of the Na current, re sulting in substantial overlap of the activation and inactivation curv es. TTX reduced the holding current of spontaneous cells clamped betwe en -50 and -30 mV, consistent with the presence of a Na ''window'' cur rent, We were unable, however, to measure a persistent component of th e Na current using voltage steps, a result which may reflect the compl ex,eating properties of Na channels. An Na window current could provid e the driving force underlying spontaneous activity, as well as platea u potentials, in Purkinje cells, (C) 1997 John Wiley & Sons, Inc.