Effect of electroconvulsive shock (ECS) treatment on the histaminergic system in rat brain: biochemical and behavioural studies.

The effects of electroconvulsive shock (ECS) on brain histamine (HI) levels, 1-histidine decarboxylase (HD) and HI-methyltransferase (HMT) activities, and H2-receptor--mediated hypothermia were studied in rats. Single (x1) and repeated (x10, once daily) ECS had practically no effect on both HI levels and HMT activities in the rat hypothalamus, cerebral cortex and rest of the brain. ECS x10 significantly increased HI accumulation. ECS x1 (only after 24 h) and ECS x10 resulted in marked elevation of the brain HD activity; the most pronounced effect was observed in the cerebral cortex. Repeated, but not single, ECS reduced the hypothermic action of various centrally given histamine H2-receptor agonists (HI, 4-methylHI, dimaprit and impromidine). It is suggested that prolonged treatment with ECS activates the central histaminergic system in the rat. The histaminergic neurons in the cerebral cortex seem to be especially affected by repeated ECS.