Effects of adrenaline on the action potential of sympathetic ganglion cells in bullfrogs

Abstract

The effects of catecholamines (adrenaline, noradrenaline 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 (3X10(-5)-1X10(-3)M) reversibly decreased the peak amplitude and positive after-potential of action potentials, and prolonged the duration of spike potentials without changes in the resting membrane potential and conductance in the Ringer solution. The maximum rates of rise and fall of spike potentials were also decreased. The action of noradrenaline was similar to that of adrenaline, but isoproterenol did not show any effects. Adrenaline (3X10(-5)-3X10(-4)M) markedly depressed the peak amplitude and maximum rate of rise of both TEA-potential and Ca-potential produced either in TEA solution containing TTX or in the isotonic CaCl2 solution. Similar actions were observed with noradrenaline but not isoproterenol. In spinal ganglion cells, catecholamines did not show any effects of the action potentials in Ringer and TEA solutions. It was concluded that adrenaline inhibited the increases in Ca2+, K+ and Na+ conductances during the generation of action potentials of sympathetic ganglion cells.