The Na/K-ATPase Regulation By Neurotransmitters In Ontogeny

Abstract

Activity of the Na/K–ATPase from rat brain synaptic membranes is inhibited by NA (noradrenaline). However, during fractionation of cytozole from nerve endings, two non-homogeneous peaks are found (SF a, 60–100 kD and SF i, ~10 kD), which influence the Na/K–ATPase activity, both directly and SF a NA-dependently. Joint action of NA and synaptic factors (SF a and SF i) on the Na/K-ATPase, represents a sum of four different processes: 1) NA, without synaptic factors, inhibits the Na/K-ATPase; 2) At low SF a concentrations NA-dependent Na/K-ATPase activatory mechanism is evident; 3) At high SF a concentrations NA-independent Na/K-ATPase is activated; 4) The low-molecular SF i protein inhibits the Na/K-ATPase. Regulation of the Na/K-ATPase activity by NA, SF a and SF i, obtained in similar conditions from two weeks old and one year old rats, is different. In older rats SF i is characterized with strong Na/K-ATPase inhibition; in younger rats SF i does not change the Na/K-ATPase activity. The NA- and SF i -dependent inhibition and activation ratio is different in young and elder rats. In two week olds NA/SF i activatory mechanism is stronger, while in one year olds NA-dependent inhibition of the Na/K-ATPase is prevailing. These experimental data indicate that regulation of the Na/K-ATPase activity has an important role in synaptic transmission and that this process has noteworthy, albeit presently unknown, functional importance in integrative activity of the brain.