EFFECTS OF ACUTE AND CHRONIC ELECTROCONVULSIVE TREATMENT ON INTERSTITIAL CONCENTRATIONS OF SOMATOSTATIN IN THE RAT HIPPOCAMPUS AND STRIATUM

1. Effects of acute and chronic electroconvulsive treatment (ECT) and sham-ECT on extracellular concentrations of somatostatin-like immunore activity (SS-LI) from the hippocampus and striatum of awake rats were studied with in vivo microdialysis in combination with a high-sensitiv ity radioimmunoassay. 2. Acute ECT and sham-ECT did not affect hippoca mpal or striatal SS-LI concentrations during the first 4 hr after the treatment. However, 24 hr later acute ECT significantly decreased SS-L I concentrations from both areas by approximately 40%. 3. Chronic ECT and sham-ECT did not influence basal hippocampal or striatal SS-LI con centrations. 4. Administration of a challenge ECT in animals treated c hronically with ECT or sham-ECT did not affect hippocampal or striatal SS-LI concentrations during the first 4 hr after the treatment. Howev er, 24 hr later hippocampal and striatal SS-LI levels were decreased b y 30-40% in all groups. 5. The delayed ECT-induced changes in regional , extracellular concentrations of SS-LI may be secondary to increased somatostatin metabolism and are perhaps related to the therapeutic or adverse effects of this antidepressant treatment.