ATP-INHIBITED K-POTENTIAL OF IDENTIFIED LEECH NEURONS( CHANNELS AND MEMBRANE)

The effect of the ATP-inhibited K+ channel on the membrane potential o f leech Retzius neurons was analyzed using electrolyte-filled single-b arrelled microelectrodes. The membrane potential was independent of th e external nutrient supply during a period of 11 h, probably because t he internal energy reserves were sufficient. The K+ channel activator HOE 234 -4-(2-oxo-1-pyrrolidinyl)-6-phenylsulfonylchromane hemihydrate , 500 mu M) induced a membrane hyperpolarization. In the presence of H OE 234, action potentials occurred with a reduced after-hyperpolarizat ion and were discharged in bursts, possibly because of an inhibition o f Ca2+ channels. The blocker of ATP-inhibited K+ channels tolbutamide did not significantly alter the membrane potential. In the absence of tolbutamide, the metabolic inhibitors iodoacetate, azide and cyanide ( 10 mM) evoked membrane hyperpolarizations, but in the presence of 1 mM tolbutamide their hyperpolarizing actions were reduced or abolished w hile membrane depolarizations were intensified. We conclude that ATP-i nhibited K+ channels in the soma membrane of leech Retzius neurons pro vide coupling of cellular metabolism to electrical activity and ionic fluxes. (C) 1998 Elsevier Science B.V. All rights reserved.