Objectives: Electroconvulsive therapy (ECT) is a well-established effective treatment strategy in treatment-refractory depression. However, despite ECT's widespread use, the exact neurobiological mechanisms underlying its efficacy are not fully understood. Over the past 3 decades, extensive work in rodents, primates, and humans has begun to delineate the impact of electroconvulsive seizures (ECS) and ECT on neurotransmission systems commonly implicated in depression. In the current review, we will focus on two major biogenic amine systems, namely serotonin and dopamine.
Methods: The database of PubMed was searched for preclinical studies describing the effects of ECS on the serotonergic and dopaminergic system using behavioral sensitization paradigms, in vivo brain microdialysis, messenger RNA and protein expression, electrophysiology, and positron emission tomography. Additionally, human data describing ECT's effects on neurotransmitter turnover, receptor binding, and functional imaging were reviewed together with relevant genetic association studies.
Results: Literature research resulted in 40 published original studies related to ECS/ECT and the serotonergic system, whereby only three were studies in humans. Regarding dopamine, 15 preclinical and 12 human studies were found in PubMed database.
Conclusions: Converging data obtained from genetic and imaging studies in humans have corroborated many of the earlier preclinical and clinical findings relating to enhancement of serotonergic neurotransmission and activation of the mesocorticolimbic dopamine system after ECS/ECT. Moreover, it seems that these effects are evident at various levels, including neurotransmitter release, receptor binding, and overall neurotransmission. Future studies combining convergent modalities could enhance our understanding of the mechanisms underlying ECT's profound antidepressant effect and would support the development of better pharmacological and somatic treatment approaches for refractory depression.