Vagus nerve stimulation (vns) in chronic depression: mechanisms of synaptic plasticity

Chronic depression refractory to conventional treatments represents one of the major challenges in contemporary psychiatry, requiring innovative neuromodulatory interventions to restore the mental health of patients. Vagus Nerve Stimulation, originally developed for the control of epileptic seizures, has demonstrated remarkable efficacy in the management of severe depressive episodes that do not respond to standard pharmacotherapy. The present article consists of a systematic review of the scientific literature with the main objective of elucidating the synaptic plasticity mechanisms promoted by this physical therapy. Through a careful and exhaustive search in the SciELO, LILACS, and BVS databases, prioritizing studies conducted by Brazilian researchers in the last decade, the most relevant articles on the subject were selected and critically analyzed. The findings indicate that Vagus Nerve Stimulation modulates cerebral monoaminergic pathways, activating projections from the locus coeruleus and raphe nuclei, which results in a sustained increase in the release of norepinephrine and serotonin. Furthermore, a significant elevation in the expression of Brain Derived Neurotrophic Factor is observed, promoting hippocampal neurogenesis and the restructuring of prefrontal neural networks. It is concluded that the therapy induces long lasting neurobiological modifications that reverse the plasticity deficits associated with chronic depression, consolidating the intervention as a robust and promising therapeutic alternative for refractory patients, although expanding access to this high cost technology in the healthcare system remains a considerable barrier that demands efficient public policies.(AU)