Abstract
We previously demonstrated that changes in brain monoamine levels 4 weeks after withdrawal from repeated administration of beta-phenylethylamine (PEA) are different from changes 4 weeks after methamphetamine (MAP) withdrawal. Monoamine oxidase (MAO) is physiologically important in the metabolism of monoamines. In the present study, we measured MAO activity radiometrically 4 weeks after the withdrawal from repeated PEA or MAP administration in rats. Reverse tolerance to stereotyped behavior was induced after repeated administration of PEA or MAP in rats and was maintained for at least 4 weeks after withdrawal of either drug. To measure MAO activity, either 5-hydroxytryptamine (5-HT) (a specific substrate for type A MAO), or benzylamine (a specific substrate for type B MAO) was used as a substrate. There was no significant change in MAO activity after withdrawal of either drug. We concluded that MAO is not responsible for the changes in brain monoamine levels observed after withdrawal from repeated PEA or MAP administration in rats.
