What is the rationale behind electroconvulsive therapy for depression? which neurotransmitters are affected? how long does the effect last? thanks!

The mechanism of: action for ECT is not completely understood. Many years ago people who when into diabetic coma sometimes had a lifting of depression so insulin was first used. Electricity was next used to produce a seizure which is what seems to help. Today the pt is sedated and the treatment is much easier. The post seizure state seems to be what helps. Peace and good health.