Authors :
Presenting Author: Walter Besio, Phd – University of Rhode Island
Wencesalo Sanchez, BS – Interdisciplinary Center for Health Sciences Milpa Alta Unit – National Polytechnic Institute; Luisa Rocha, PhD – Professor, Department of Pharmacobiology, Center for Research and Advanced Studies, Mexico City, Mexico; Daniel Fonseca-Barriendos, MS – Department of Pharmacobiology – Center for Research and Advanced Studies, Mexico City, Mexico
Rationale:
Transcranial focal electrical stimulation (TFS) is a non-invasive neuromodulation strategy.
1 (1) In animal models, TFS induces anticonvulsant
2 and antiepileptogenic effects.
3 At present the duration of the effect of TFS are unknown. The present study focused to assess the duration of the effect of TFS on hippocampal excitability in normal rats.
Methods:
Male Wistar rats (300-350 g, n=5) were implanted with a tripolar electrode in the ventral hippocampus and a concentric tripolar electrode (diameter 6 mm) on the skull. Seven days after the surgery, the after-discharge threshold (ADT) was estimated. For this purpose, we applied a train of 1 s square pulses of 1 ms, 60 Hz, starting with 10
μA and increasing the current intensity by 20% every two minutes until evoking a behavioral change. Immediately afterwards, the animals received TFS (biphasic square pulses 200 ms, 300 Hz, at 100 μA for 2 min). Subsequently, stimulation in the hippocampus was applied according to the threshold previously determined at 30 min, 60 min, 6 h, 12 h, 24 h and behavioral changes were recorded after each stimulation. The implant site of the electrodes and their functionality were evaluated at the end of the experiment by histological analysis. Two rats did not receive TFS and were used as controls.
Results:
ADT in control rats was 378 ± 68 μA and its repetitive application induced stage I throughout the experiment. ADT of the experimental group was 228 ± 57 μA. However, once the animals received TFS, the hippocampal electrical stimulation using ADT parameters did not induce behavioral changes throughout the experiment. This effect was evident in 4 (80%) of the animals that received TFS, while one rat (20%) presented this effect only at 30 min after TFS.
Conclusions:
Our results indicate that TFS decreases hippocampal excitability. However, further experiments are necessary to evaluate other parameters of TFS to induce a long-term effect.
1 Besio W, Sharma V & Spaulding J. [The effects of concentric ring electrode electrical stimulation on rat skin]. Annals of Biomedical Engineering. 2010; PMID: 20087776
2 Santana-Gómez C, Alcántara-González D, et al. [Transcranial focal electrical stimulation reduces the convulsive expression and amino acid release in the hippocampus during pilocarpine-induced status epilepticus in rats]. Epilepsy & Behavior. 2015; PMID: 26006058 3 Valdés-Cruz A, Villasana-Salazar B, et al. [Transcranial focal electrical stimulation via concentric ring electrodes in freely moving cats: Antiepileptogenic and postictal effects]. Experimental Neurology. 2019; PMID: 31301285
Funding: None