FOS IMMUNOPOSITIVE NEURONS IN THE SUBTHALAMIC NUCLEUS FOLLOWING REVERSAL OF PARKINSONIAN SYMPTOMS BY ANTAGONISM OF EXCITATORY AMINO-ACID TRANSMISSION IN THE ENTOPEDUNCULAR NUCLEUS OF THE MONOAMINE DEPLETED RAT

Drug-induced dyskinesias are a major drawback of the dopaminergic ther apies currently employed to treat Parkinson's disease. It is commonly speculated that these dyskinesias may be mediated by functional change s within the striatum. Recent research has, therefore, focused on find ing new modes of therapy which will alleviate parkinsonian symptoms wi thout directly altering neurotransmission in the striatum. It has rece ntly been demonstrated that the behavioural symptoms observed in dopam ine-depleted rodents can be alleviated by blockade of excitatory neuro transmission in the entopeduncular nucleus. A series of experiments wa s conducted in order to determine whether this manipulation affected t he pattern of Fos immunoreactivity in the basal ganglia elicited by do pamine depletion. The results demonstrated that the most striking chan ge in Fos levels was found in the subthalamic nucleus, indicating that reversal of parkinsonian symptoms in this manner cannot be considered as a simple redress in the balance of activity in the output structur es of the basal ganglia.