Reversible blockade, induced by the neurotoxin MPTP, of corticofugal impulse activity to neurons of the caudate nucleus in cats.

It has been demonstrated in acute experiments in cats anesthetized with nembutal and immobilized with ditilin [succinylcholine iodide--Translator] that the number of neurons of the caudate nucleus responding to a single stimulation of the motor cortex with action potentials with a latent period less than 8.0 msec in the first 10-12 days after a course of injections of MPTP (5 mg/kg daily for 5 days, intramuscularly) decreased significantly as compared with the control. Their number is gradually restored by the 45th-54th day after the administration of the neurotoxin. A one-time injection of the dopaminomimetic, apomorphine (5 mg/kg, intramuscularly), also significantly decreases the number of neurons with a latent period of the responses less than 8.0 msec for 5 h in the intact animals, and is incapable of removing the blockade of the corticoneostriatal impulse activity in animals with an MPTP-induced dopamine deficit. The hypothesis is advanced that dopamine exerts a protective inhibitory influence on the conduction of corticofugal glutamatergic impulse activity to neurons of the neostriatum.