EN
Neuromodulation is a therapeutic technique that involves modification of neural function via external stimulation, usually in the form of electrical impulses. Prominent examples of neuromodulative therapies include vagus nerve stimulation for epilepsy, Alzheimer’s disease, and even deep brain stimulation for Parkinson’s disease. Trigeminal nerve stimulation (TNS) has also been applied as a therapeutic tool in a variety of disease processes and has shown efficacy in the treatment of epilepsy and depression. AIM(S): The aim of the present study was to evaluate if transcutaneous TNS (t-TNS) could affect the hippocampal EEG activity. METHOD(S): Male Wistar rats were implanted with a tungsten microelectrode for recording hippocampal formation (HPC) field activity. Furthermore, two uninsulated tungsten electrodes were used for t-TNS in eye‑ear line in anesthetized rats. The stimulation was conducted at three point: closer to the eye (point 1), in the middle of line eye-ear (point 2), and closer to the ear (point 3). The following t‑TNS intensities ware tested: 4, 6, 8, and 10 mA. The remaining parameters of stimulation were constant: pulse duration (1 ms), train duration (10 s), frequency (10 Hz). RESULTS: Stimulation only in the point closer to the ear and in the eye-ear line was found to be productive in inducing nicely developed and well-synchronized hippocampal theta rhythm. However, t‑TNS in the range below 6 mA was found to be subthreshold (theta rhythm was not observed in HPC). Theta activity was observed at point 3 during stimulation only when the intensity of stimulation was equal or higher than 6 mA. CONCLUSIONS: Only the point located closer to the ear in the eye-ear line was found to be effective in inducing t‑TNS theta rhythm. The effectiveness of t‑TNS on hippocampal theta rhythm was determined by its intensity and density of trigeminal nerve endings. FINANCIAL SUPPORT: These studies were supported by The National Centre of Research and Development (grant no. 01.02.00‑00‑0023/17‑001).