EFFECTS OF ADRENALINE ON THE ACTION POTENTIAL OF SYMPATHETIC GANGLION CELLS IN BULLFROGS

Abstract

The effects of catecholamines (adrenaline [epinephrine], noradrenaline [norepinephrine, NA] and isoproterenol) on ionic conductance changes during the generation of action potentials of bullfrog sympathetic and spinal ganglion cells were studied with intracellular microelectrodes. In sympathetic ganglion cells, adrenaline (3 .times. 10-5-1 .times. 10-3 M) reversibly decreased the peak amplitude and positive after-potential of action potentials and prolonged the spike potential duration without changes in the resting membrane potential and conductance in the Ringer solution. The maximum rates of rise and fall of spike potentials were decreased. NA action was similar to that of adrenaline but isoproterenol showed no effects. Adrenaline (3 .times. 10-5-3 .times. 10-4 M) markedly depressed the peak amplitude and maximum rate of rise of both TEA[tetraethylammonium chloride]-potential and Ca-potential produced either in TEA solution containing TTX tetrodotoxin or in the isotonic CaCl2 solution. Similar actions were observed with NA but not isoproterenol. In spinal ganglion cells, catecholamines showed no effects on the action potentials in Ringer and TEA solutions. Adrenaline apparently inhibited the increases in Ca2+, K+ and Na+ conductances during the action potential generation of sympathetic ganglion cells.