The effect of adrenaline on the K+ -activated hyperpolarization of the sympathetic ganglion cell membrane in bullfrogs

Abstract

Effects of adrenaline on K+ -activated hyperpolarization of bullfrog sympathetic ganglion cells, preganglionic nerve axons and splanchnic nerve axons were studied. The K+ -activated hyperpolarization recorded from ganglion-postgangaline (0.3 mM). On the other hand, the K+ -activated hyperpolarization of postganglionic, preganglionic nerve axons and splanchnic nerve axons was not affected under the same experimental conditions. The facil-tatory effect of adrenaline on the K+ -activated hyperpolization was gradually intensified when the application of adrenaline was sustained for up to 60 min. The effect was reversible. The K+ -activated hyperpolarization recorded from ganglion cell-bodies by intracellular microelectrodes was similarly augmented by adrenaline (0.1 mM). Adrenaline in this concentration, however, caused no significant changes of the membrane potential and conductance in the presence of ouabain (0.002 mM) which completely and reversibly inhibited K+-activated hyperpolarization. Noradrenaline showed similar but less effected and isoproterenol showed no significant effect on the K+ -activated hyperpolarization. The facilitatory effect of adrenaline was inhibited in the presence of phentolamine but not of DCI. These results suggested that the intraganglionic membrane of ganglion cells possessed some kind of adrenergic alpha-receptors and the electrogenic Na+ pump of ganglion cells was accelerated by some unknown mechanism when adrenaline reacted to these receptors.