[Effect of gamma-aminobutyric acid and noradrenaline on the ATPase activity of rat brain tissue].

Inasmuch as the highest concentrations of transmitter substances occur in the mesodiencephalic region of the brain, which according to our results possesses quite high Na+,K+-ATP-ase activity, in the present study we tried the effect of norepinephrine (NE) and gamma-aminobutyric acid (GABA) on Na+, K+-ATP-ase activity of rat mesodiencephalic region. The results obtained indicate that in homogenates NE (5-10(-4) M) stimulates Na+, K+-ATP-ase activity about 3.6 times, while equimolar amounts of GABA have no effect. Higher concentrations of GABA (1.10(-3) M and 3.10(-3) M), as well as changes in the length of the preincubation period with GABA, failed to affect enzyme activity. Effect of transmitters was next studied on ATP-ase activity of synaptosomal fractions of the mesodiencephalic region. Here also a statistically significant increase of enzyme activity was observed from NE but not from GABA. Changes in ATP-ase activity of rat brain synaptosomal fractions were also not observed in in vivo studies 20 min after i.p. administrations of 5 mg/kg GABA. The results of the present study indicate that NE stimulates Na+, K+-ATP-ase activity of rat brain mesodiencephalic region while under the given experimental conditions GABA does not seem to have any effect.