Repeated electroconvulsive shock produces long-lasting increases in messenger RNA expression of corticotropin-releasing hormone and tyrosine hydroxylase in rat brain. Therapeutic implications.

Electroconvulsive shock (ECS) is a highly effective therapy for the treatment of major depression, but its mechanisms of action are not known. We report that repeated ECS in rats produces enduring changes in two clinically relevant stress-responsive brain systems: (a) the hypothalamic-pituitary-adrenal axis regulated by corticotropin-releasing hormone (CRH) in the paraventricular nucleus; and (b) the NE system in the locus coeruleus regulated by tyrosine hydroxylase (TH). CRH and TH mRNA levels in these brain regions were assessed by in situ hybridization histochemistry. A single interaural ECS elevated TH but not CRH mRNA measured 24 h later. Repeated daily treatments (3, 7, or 14) elevated both mRNAs, maximally with 7, correlating with the time course of clinical efficacy. The elevations persisted for 3 (CRH) or 8 wk (TH) after the ECS. No other therapeutic treatment is known to produce such long-lasting changes in central nervous system gene expression. The time course of events (delayed onset, long duration) implicate CRH as a principal mediator of the antidepressant effects of ECS. The locus coeruleus-NE system may be important in initiating the central nervous system response.