The Effect of Neurostimulation in Depression

Abstract

There have been reports of the medical use of electricity since the classical antiquity, but only in the second half of the eighteenth century the effects of electricity in animals and humans were systematically studied, establishing the foundations for the electroconvulsive therapy (ECT), magnetic seizure therapy (MST), transcranial direct-current stimulation (tDCS), vagus nerve stimulation (VNS), deep brain stimulation (DBS), and repetitive transcranial magnetic stimulation (TMS). The most important difference between these methods is that ECT and MST induce seizures, while the other methods produce more subtle acute effects. Magnetic stimulation methods seem to produce an effect that is similar to the one induced by direct electrical stimulation. Nevertheless, all techniques induce electrical currents in the brain, producing functional and structural modifications. Neurostimulation induces neuronal depolarization and increase or decrease of neuron excitability, producing immediate changes in membrane receptors and channels. These effects are followed by a cascade of changes within the neuron, including changes in gene expression and second messengers. Neurostimulation modulates glutamatergic, serotonergic, dopaminergic, GABAergic, and cholinergic neurotransmission. The HPA and sympathoadrenal systems are also modulated by neurostimulation, which reduces the release of corticotrophins and cortisol. These techniques also play a role in the regulation of glial cell activity, neuroinflammation, and oxidative stress.