Electrochemical detection of K(+)-evoked quantal secretory events from isolated rat type I carotid body cells

Using amperometric techniques, electrochemical events associated with vesicular transmitter release were recorded from isolated rat type I carotid body cells when exposed to a solution containing 50 mM K+. Events were enhanced in amplitude by preloading cells with the catecholamine precursor, L-beta-3,4-dihydroxyphenylalanine (L-DOPA). K(+)-evoked secretion was abolished by the non-selective Ca2+ channel blocker Cd2+ (100 microM) and markedly reduced by the L-type Ca2+ channel blocker nifedipine (5 microM). Our results indicate that secretion from isolated rat type I cells can be monitored electrochemically and we demonstrate a major role for L-type Ca2+ channels in mediating K(+)-evoked secretion.