Abstract
There have been many reports on multiplicity of monoamine oxidase (MAO) in many organs. It was reported that ethanol activated MAO activity in liver, but no concreted reports have been appeared on the effect of alcohol on MAO in brain. Male Wistar strain rats were used in this experiment. An intraperitoneal injection of ethanol (0.8 g/kg) resulted a transient increase in MAO activity 1 hour after administration with a peak of ethanol concentration in blood and at 48 hours after the injection the second increase was observed with no detection of ethanol in blood. Ethanol, at a concentration of 1 M, caused marked increase in MAO activity in vitro with serotonin and tyramine as substrates. The mechanism of the action of ethanol on MAO in brain mitochondria was studied by Lineweaver-Burk's double reciprocal plots. When serotonin used as substrate, both straight lines which obtained with and without 1 M ethanol, crossed on the abscissa, but when tyramine used as substrate, these two lines crossed on the ordinate.
Addition of 1 M ethanol in the reaction mixture did not show any changes in pS-activity curves and in pH-optima of MAO in brain mitochondria with serotonin and tyramine as substrates. The reversibility of activation of MAO activity with 1 M ethanol was studied by means of dialysis. It was found to be reversible. These results revealed three findings, such as, the first, there are two different types of MAO in rat brain, the second, initial activation of MAO might be caused by direct effect of ethanol and the third, the second activation of it might be caused by indirect effect of ethanol.
