EFFECTS OF DRUG MANIPULATIONS ON ANTERIOR COMPONENTS OF SOMATOSENSORY-EVOKED POTENTIALS IN A PARKINSONIAN ANIMAL-MODEL

Somatosensory Evoked Potentials (SEPs) to median nerve stimuli were re corded in seven Cynomolgus monkeys before and after the induction of t he MPTP-parkinsonian syndrome. SEPs recorded after the onset of parkin sonism showed a significant amplitude reduction of an anterior negativ e component peaking at about 15 ms (N15), independent of the severity of symptoms. The amplitude decrease was not reversed by the administra tion of I-dopa, despite clinical improvement, or cholinergic, noradren ergic and gabaergic agents. Amplitudes of N15 and of parietal P15 comp onents were increased by the administration of the N-MDA antagonists k etamine and MK 801, and markedly increased when monkeys were given the anaesthetic agent etomidate. The present study shows that the reduced N15 SEP component of parkinsonian monkeys is similar to the reduced f rontal N30 SEP component evidenced by other authors in patients affect ed by Parkinson's disease. The attenuation of N15 is not related to de ficitary dopaminergic, noradrenergic, cholinergic and gabaergic system s. The implications of this finding and the role of glutamate toxicity are discussed.