INHIBITION OF GASTROINTESTINAL MOTILITY BY MPTP VIA ADRENERGIC AND DOPAMINERGIC MECHANISMS

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrine (MPTP) was i njected intraperitoneally in mice and caused an acute inhibition (of o ver 60%) of gastrointestinal motility, which was measured by the trans it of charcoal. This inhibition was not related to conversion of MPTP to MPP(+). Administration of the beta-adrenergic blocker propranolol s ignificantly reduced, but did not completely block, the effect of MPTP . The dopaminergic blocker haloperidol also partly reversed the effect s of MPTP. When these blockers were administered together, the action of MPTP was fully blocked. The results indicate that the toxin acted b y releasing catecholamines (presumably norepinephrine and dopamine), t hereby inhibiting motility.