PARADOXICAL SLEEP DEPRIVATORY EFFECT OF A SINGLE LOW-DOSE OF MPTP WHICH DID NOT PRODUCE DOPAMINERGIC CELL LOSS

In a previous study, we reported on a selective and long-lasting parad oxical sleep (PS) deprivation in cats following repeated administratio n of the Parkinson syndrome-inducing neurotoxin N-methyl-4-phenyl-1,2, 3,6-tetrahydropyridine (MPTP). While the characteristic motor deficits occurred only from the 2nd to 3rd day of a 5-day long administration of 5 mg/kg per day MPTP i.p., the PS deprivation started immediately a fter the first injection and lasted altogether for 11 -1 3 days. The m otor deficiencies induced by repeated administration of MPTP are mainl y due to the selective depletion of dopaminergic neurons in the nigros triatal system as the histological and biochemical data show. The imme diate onset of PS deprivation and the PS recovery, despite the definit e cell loss, suggests a mechanism independent of cell destruction. In our present study we investigated the occasional histological and the PS-deprivatory effect of a single low dose of MPTP in cats. A single i njection of 2 mg/kg MPTP i.p. resulted in PS deprivation lasting for 2 .5-3.5 h. The duration of other sleep stages showed no significant cha nge and PS recovery was without rebound phenomenon, as in the case of repeated administration. Even a higher single dose of MPTP (5 mg/kg) r esulted in no visibly detectable nigrostriatal cell loss. We suggest t hat the changes in monoamine release and/or turnover are involved in t he PS deprivatory effect of MPTP.