Preclinical Validation of Electrodes for Single Anodal Transcranial Direct Current Stimulation on Rat Model With Chronic Stress-Induced Depression

Transcranial direct current stimulation (tDCS) is an effective and safe noninvasive brain stimulation (NIBS) procedure to modulate neuronal excitability. The present preclinical study was carried out to validate the impact of the innovative high definition (HD) fabricated spiking Au/AgCl electrodes via a noninvasive tDCS procedure on a rat model with depression-like behavior. In this study, a chronic stress-induced depression-like behavior rat model was developed over a period of 14 days. Furthermore, the aftereffects of NIBS procedures were investigated by providing a tDCS dose (<inline-formula> <tex-math notation="LaTeX">${2.00} \text {mA} \times {5.00} \text {min}$ </tex-math></inline-formula>) by placing the electrodes on the interested region of the rat brain. This study was performed in healthy rats, control rats with depression-like behavior, and tDCS treated rats, which were used to examine the differential aftereffects of tDCS dose. After single tDCS dose, a significant increase in average band power of electroencephalogram (EEG) has been observed (<inline-formula> <tex-math notation="LaTeX">$\text {F}{(}{2},{15}{)} = {8.376}; {P} = {0.0036}$ </tex-math></inline-formula>) alongside a significant increase in the glutamate level of hippocampus (HPC; <inline-formula> <tex-math notation="LaTeX">$\text {F}{(}{2},\!{15}{)} = {8.919}; {P} = {0.0028}$ </tex-math></inline-formula>), a significant reduction in immobility time (<inline-formula> <tex-math notation="LaTeX">$\text {F}{(}{2},{15}{)} = {7.552}; {P} = {0.0054}$ </tex-math></inline-formula>), and a significant increase in the percentage sucrose intake has been observed (<inline-formula> <tex-math notation="LaTeX">$\text {F}{(}{2}, {15}{)} = {5.941}; {P} = {0.0126}$ </tex-math></inline-formula>). In addition, immunohistochemistry (IHC) showed a significant increase in the Iba1 protein expression in microglia cell in the both cortex and HPC region (<inline-formula> <tex-math notation="LaTeX">${P} &lt; {0.05}$ </tex-math></inline-formula>). Hence, the fabricated electrodes can deliver a tDCS dose that can penetrate up to the cortex and HPC regions from the surface of brain noninvasively within tolerable and safety limits.