[Central action of beta-phenylethylamine derivatives (10). Effect of L-Dopa on metaraminol induced motor activity (author's transl)].

The present experiments were undertaken in investigate the effects of Ro4-4602 plus L-Dopa on biphasic action induced by metaraminol (MA) in mice. The following results were obtained: Spontaneous motor activity (SMA) suppressed by MA was recovered by pretreatment of Ro4-4602 plus L-Dopa and increased by more than 100 mg/kg of L-Dopa. However, SMA was increased by more than 400 mg/kg of L-Dopa in saline pretreated mice. In MA pretreated mice, SMA by L-Dopa markedly increased in proportion to the doses of MA. The peak time of SMA by L-Dopa in MA pretreated mice was observed to be faster than that in saline pretreated mice. When L-Dopa was injected into MA and saline pretreated mice, there was no significant difference of brain dopamine content between the two groups. From the above results, it is considered that the enhanced effect of L-Dopa in MA pretreated mice may be due to production of a supersensitivity to catecholamines in the central nervous system. MA induced hyper-motor activity was enhanced by pretreatment of Ro4-4602 plus L-Dopa which have no influence on SMA.