Synergistic interactions between COMT-/MAO-inhibitors and L-Dopa in MPTP-treated mice.
Four experiments were performed to investigate the anti-akinesia effects of combining a sub-threshold dose (5 mg/kg, s.c.) of L-Dopa with different doses and combinations of COMT and MAO inhibitors upon the hypokinesia observed in MPTP-treated mice. Ro 40-7592 (1 and 3 mg/kg, s.c.), a novel COMT inhibitor, 60 min before L-Dopa reinstated both locomotion and rearing during a 2-hr interval after L-Dopa in MPTP mice; control mice were unaffected. The combination of Ro 40-7592 (3 mg/kg, s.c.) and pargyline (5 mg/kg, s.c.), a MAO inhibitor, with L-Dopa produced increases in both the peak effect and duration of action indicating a distinct potentiation of the effects of Ro 40-7592 by pargyline. L-Deprenyl, a MAOB inhibitor, together with L-Dopa, restored locomotion and rearing behaviour at all three doses applied (1, 3 and 10 mg/kg, s.c.); in control mice, motor activity was stimulated at the higher doses (3 and 10 mg/kg, s.c.), independent of L-Dopa administration. Combining L-Deprenyl (3 mg/kg, s.c.) with Ro 40-7592 (3 mg/kg, s.c.) one hr before L-Dopa to MPTP mice potentiated the restorative effects of each compound by itself, although no increase in peak effect was obtained. In the control mice, L-Deprenyl plus Ro 40-7592 or L-Deprenyl, by itself, stimulated motor activity following injection of L-Dopa. Marked dopamine (DA) depletions in the striatum of MPTP-treated mice were evident. The present results demonstrate that the effects of the COMT/MAO inhibitors in combination, and in conjunction with L-Dopa (at a dose that was without effect by itself), were well in excess of a summation of their individual effects. It was concluded therefore that a synergism of the restorative, anti-akinesic action of these compounds in MPTP-treated mice could offer a broader therapeutic spectrum in the treatment of Parkinson's disorder.
Fredriksson
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A
Department of Psychiatry, Uppsala University, Ulleråker, Sweden.
Archer
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T
D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007980:Levodopa / Q000494:pharmacology*; D008124:Locomotion / Q000187:drug effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D008996:Monoamine Oxidase Inhibitors; D007980:Levodopa; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine