Regulation of the galanin system in the brainstem and hypothalamus by electroconvulsive stimulation in mice

Induction of seizures by electroconvulsive stimulation (ECS) is amongst the most efficacious treatments for major depression. However, the working mechanism by which ECS exerts its antidepressant effects remains elusive. The galanin system is regulated by ECS in seizure-prone brain regions and has been shown to modulate depression-like behaviour. To further explore its potential role in the antidepressant effects of ECS the galanin system was investigated by in situ hybridisation and [(125)I]-galanin receptor binding during repeated ECS in the locus coeruleus, dorsal raphe and discrete nuclei of the hypothalamus. Adult mice were treated with ECS once daily for 14 consecutive days, a paradigm previously shown to exert antidepressant-like effects. Significant increases in galanin transcription were found in the locus coeruleus and dorsomedial nuclei of the hypothalamus. In addition, GalR2 mRNA levels in the ventro- and dorsomedial nuclei of the hypothalamus were upregulated whereas no GalR1 mRNA upregulation was observed. [(125)I]-galanin receptor binding was downregulated in the ventromedial nuclei of the hypothalamus and dorsal raphe. These data show that the galanin system is regulated by repeated ECS in brain regions involved in monoaminergic neurotransmission and stress modulation thus indicating a possible role of the galanin system in the therapeutic effects of ECS.