Single transient exposure to low-frequency low-intensity electrical stimulation produces ketamine-like effects in human iPSC-derived dopaminergic neurons via Ca2+-dependent BDNF and mTOR signaling

Electrical stimulation (ES) is emerging as a non-pharmacological neuromodulation strategy, but its direct impact on human dopaminergic neurons and its relationship to rapid-acting antidepressant mechanisms remain unclear. This study aimed to investigate whether brief biphasic low-frequency low-intensity (LF-LI) ES can induce structural and molecular plasticity in human induced pluripotent stem cell (iPSC)-derived mesencephalic dopaminergic neurons, identify the underlying signaling mechanisms, and evaluate its potential to rescue cortisol-induced impairments as in-vitro endocrine model of depression. iPSC-derived dopaminergic neurons were exposed to LF-LI ES using a custom culture-compatible stimulator, and structural plasticity was quantified three days later by computer-assisted morphometry. Pharmacological blockers, quantitative PCR and Western blot analyses were employed to assess calcium influx, brain-derived neurotrophic factor (BDNF)-TrkB-extracellular signal-regulated kinase (ERK)-mTOR signaling, and dopamine D3 auto-receptor roles in mediating LF-LI ES effects. A single 1h LF-LI ES session at 4 mA induced robust increases in maximal dendrite length, primary dendrite number, and soma area, comparable to 1 μM ketamine. LF-LI ES rapidly enhanced ERK and p70-S6K phosphorylation and required L-type voltage-gated calcium channels, TrkB and mTOR, as their inhibition prevented structural remodeling. LF-LI ES increased dopamine D3 auto-receptors mRNA, and its antagonism attenuated LF-LI ES-induced plasticity. In cortisol-treated neurons, LF-LI ES fully reversed dendritic hypotrophy and soma shrinkage. In conclusion, brief LF-LI ES elicits long-lasting, ketamine-like structural and molecular plasticity in human dopaminergic neurons and rescues stress hormone-induced impairments, supporting LF-LI ES-based neuromodulation approaches targeting dopaminergic circuits in major depressive disorder and treatment-resistant depression.