Regulation of the galanin system by repeated electroconvulsive seizures in mice

Even though induction of seizures by electroconvulsive stimulation (ECS) is a treatment widely used for major depression in humans, the working mechanism of ECS remains uncertain. The antiepileptic effect of ECS has been suggested to be involved in mediating the therapeutic effect of ECS. The neuropeptide galanin exerts antiepileptic and antidepressant-like effects and has also been implicated in the pathophysiology of depression. To explore a potential role of galanin in working mechanisms of ECS, the present study examined effects of repeated ECS on the galanin system using QRT-PCR, in situ hybridization, and [(125) I]galanin receptor binding. ECS was administered to adult mice daily for 14 days, and this paradigm was confirmed to exert antidepressant-like effect in the tail suspension test. Prominent increases in galanin gene expression were found in several brain regions involved in regulation of epileptic activity and depression, including the piriform cortex, hippocampal dentate gyrus, and amygdala. Likewise, GalR2 gene expression was up-regulated in both the central and the medial amygdala, whereas GalR1 gene expression showed a modest down-regulation in the medial amygdala. [(125) I]galanin receptor binding in the piriform cortex, hippocampus, and amygdala was found to be significantly down-regulated. These data show that the galanin system is regulated by repeated ECS in a number of brain regions implicated in seizure regulation and depression. These changes may play a role in the therapeutic effect of ECS.