The Na/K-atpase regulation by neurotransmitters in ontogeny

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 (SFa, 60-100 kD and SFi, similar to 10 kD), which influence the Na/K-ATPase activity, both directly and SF a NA-dependently. Joint action of NA and synaptic factors (SFa and SFi) 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 SFa concentrations NA-dependent Na/K-ATPase activatory mechanism is evident; 3) At high SFa concentrations NA-independent Na/K-ATPase is activated; 4) The low-molecular SFi protein inhibits the Na/K-ATPase. Regulation of the Na/K-ATPase activity by NA, SFa and SFi, obtained in similar conditions from two weeks old and one year old rats, is different. In older rats SFi is characterized with strong Na/K-ATPase inhibition; in younger rats SFi does not change the Na/K-ATPase activity. The NA- and SFa-dependent inhibition and activation ratio is different in young and elder rats. In two week olds NA/SFa 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.