[Comparative-biochemical study of phosphoinositides as functionally active components of excitable nerve fiber membranes]

Abstract

The effect of acetylcholine (ACh) and cyclic 3',5'-adenosine monophosphate (cAMP) on phosphoinositide (PI) metabolism and associated changes of the permeability of the nervous fibers in the crustaceans Carcinum maenas and Eriphia spinifrons, as well as in the frog Rana temporaria, has been investigated. It was shown that ACh induces a significant decrease in the content of triphosphoinositides (TPI) in the nervous fibers of the crabs and increases their potassium permeability, which in its turn results in depolarization of the fibers. ACh did not affect frog nervous fibers. cAMP significantly increases the incorporation of 32P into TPI fraction of crab nervous fibers during conduction of excitation and also facilitates repolarization of the fibers after application of ACh. Proserine effectively protects nervous fibers from the influence of ACh, indicating possible participation of acetylcholinesterase in TPI hydrolysis. The data obtained suggest that PI are involved into the regulation of membrane permeability of crab nervous fibers to potassium ions.