Methamphetamine-induced modification of dopamine metabolism in cultured striatal astrocytes

The role of striatal astrocytes in the metabolic processing (by deamination) of methamphetamine-released dopamine is not known. To investigate the relationship between methamphetamine and dopamine metabolism, we measured 6-hydroxydopamine, dopamine and, 3,4-dihydroxyphenylacetic acid (DOPAC) concentrations following methamphetamine treatment of cultured striatal astrocytes prepared from 1-2 day-old rats. Addition of low concentrations of dopamine (5 x 10(-5) to 5 x 10(-4) M) to cultured astrocytes increased DOPAC levels in a dose-dependent fashion while higher concentrations (5 x 10(-3) to 10(-2) M) inhibited its metabolism and induced formation of 6-hydroxydopamine. Under the same experimental conditions, 10(-4) M dopamine in combination with methamphetamine (10(-5) to 10(-3) M) inhibited DOPAC formation and increased dopamine levels in a dose-dependent fashion, but the formation of intracellular 6-hydroxydopamine was not evident. Deprenyl (10(-5) or 10(-4) M), an inhibitor of monoamine oxidase B, and pargyline (10(-5) or 10(-4) M), a non-selective monoamine oxidase inhibitor, completely inhibited DOPAC formation and increased dopamine levels, while clorgyline (10(-5) or 10(-4) M), an inhibitor of monoamine oxidase-A, only partially inhibited DOPAC formation (42 or 45% of control, respectively). These results support the hypothesis that methamphetamine inhibits monoamine oxidase and causes increases in dopamine levels in cultured striatal astrocytes.