INVIVO NEUROCHEMICAL EFFECTS OF ELECTROCONVULSIVE SHOCK STUDIED BY MICRODIALYSIS IN THE RAT STRIATUM

The present study examined the effects of electroconvulsive shock (ECS) on interstitial concentrations of dopamine (DA), its metabolites DOPAC and HVA and the serotonin metabolite 5-HIAA in the striatum of freely moving rats using on-line microdialysis. DA increased sharply following a single ECS. Interstitial concentrations of DOPAC, HVA and 5-HIAA also increased significantly. The ECS-induced increase in DA varied as a function of days following implantation of the microdialysis probe, being 1300%, 305% and 300% of baseline 24, 48 and 72 h after surgery, respectively. In contrast, the response of the metabolites to ECS did not differ across days following surgery, being approximately 130%, 140% and 110% of baseline for DOPAC, HVA and 5-HIAA, respectively. Seizure activity induced by the convulsant agent flurothyl did not influence dialysate DA concentrations, suggesting that the ECS-induced DA release was related to the passage of current and not to the seizure activity. Interstitial concentrations of acetylcholine and choline in the striatum increased by approximately 20% and 140%, respectively, in response to a single ECS. The DA (but not the DOPAC or HVA) response to ECS was refractory to a second ECS delivered 2 h after the first. A second ECS delivered 24 h after the first produced the normal increase in DA. The ECS-induced increase in DA was attenuated following repeated ECS (eight treatments, one every second day). Baseline DOPAC and HVA concentrations were significantly elevated by repeated ECS. These results demonstrate that acute ECS produces a transient and somewhat selective increase in extracellular concentrations of DA, that this effect is reduced after repeated ECS, and that the increase is not due to the seizure activity itself. They also indicate that repeated ECS produces presynaptic change compatible with increase DA synthesis and/or turnover. These finding may be relevant to recent reports of ECS efficacy in the treatment of Parkinson's disease.