EFFECT OF REPEATED ELECTROCONVULSIVE SHOCK ON STRIATAL L-DOPA AND DOPAMINE METABOLISM - AN IN-VIVO STUDY

A course of treatments with electroconvulsive shock (ECS) has been rep orted to reestablish L-dopa efficacy in patients with advanced Parkins on's disease. We wished to determine if ECS could modify L-dopa and do pamine metabolism in an animal model of Parkinson's disease. Therefore , we administered repeated ECS (8 ECS at 48 hr intervals) to rats with partial destruction of the nigrostriatal dopamine pathway and used th e cerebral microdialysis technique to monitor extracellular concentrat ions of dopamine and dopamine metabolites (DOPAC and HVA) in the corpu s striatum. The control group of animals received sham-ECS treatments. Basal dopamine levels were decreased by 20% in animals receiving repe ated-ECS versus sham-ECS. DOPAC levels, on the other hand, were increa sed by 84% in animals receiving repeated-ECS. HVA levels were equal in the two groups. Following L-dopa administration, dopamine and HVA lev els increased equally in control animals and animals which had previou sly received repeated-ECS. DOPAC concentrations were uniformly greater in rats receiving repeated-ECS. When ECS was administered acutely, do pamine levels increased 390% and returned to baseline values in 75 min utes, DOPAC and HVA were unchanged, and 5HIAA levels decreased 30%. We conclude that 1) acute ECS administration produces a transient, marke d release of striatal dopamine and 2) repeated ECS can reset the level of basal dopamine release, a finding compatible with ECS-induced dopa mine receptor supersensitivity, and 3) neither single nor repeated adm inistration of ECS has a major effect on the formation of dopamine or HVA from exogenously administered L-dopa although there was a strong t endency for increased DOPAC formation. ECS may exert its putative anti parkinsonian effect by enhancing - dopamine receptor sensitivity.