Orthovanadate inhibits adrenaline-induced hyperpolarization in amphibian sympathetic ganglia.
The adrenaline-induced hyperpolarization of neurones in sympathetic ganglia of Rana pipiens was recorded by means of the sucrose gap technique. This hyperpolarization was inhibited in a concentration-dependent manner by sodium orthovanadate (0.1-1.0 mM). Although orthovanadate inhibited the hydrolysis of ATP by preparations of microsomal Na+/K+ ATPase from frog nerve (IC50 = 3.0 microM), extracellularly-applied orthovanadate did not inhibit electrogenic sodium pumping in intact sympathetic ganglia of Rana pipiens. This and other observations that extracellularly-applied orthovanadate did not enter sympathetic neurones and did not have access to intracellular enzyme systems. It is suggested that orthovanadate acts at an extracellular site to inhibit the adrenaline-induced hyperpolarization.
Rafuse
P E
PE
Department of Pharmacology, University of Alberta, Edmonton, Canada.
Smith
P A
PA
Walker
R J
RJ
D000818:Animals; D002490:Central Nervous System / Q000201:enzymology; D004837:Epinephrine / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005728:Ganglia, Sympathetic / Q000187:drug effects*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010084:Oxidation-Reduction; D011892:Rana catesbeiana; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014638:Vanadates / Q000494:pharmacology*
D014638:Vanadates; D000254:Sodium-Potassium-Exchanging ATPase; D004837:Epinephrine