Effect of low frequency stimulation of olfactory bulb and olfactory epithelium on epileptiform activity and synaptic plasticity following pentylenetetrazol administration in rats

Background: The anticonvulsant effect of olfactory bulb (OB) and olfactory epithelium (OE) electrical stimulation was investigated in anesthetized and freely moving animals. Methods: Male Wistar rats were anesthetized with urethane (1.5 g/kg). Stimulating electrodes were bilaterally placed either in OB or OE. Another electrode was placed in the CA1 area for recording epileptiform discharges (EDs) following pentylenetetrazol (PTZ, i.v.) injection and evoked field potentials following Schaffer collateral stimulation. Rats were divided into PTZ and control groups. Each group received stimulation (1 Hz) either in OB (OBS) or OE (OES). ED threshold and duration, and the ability to generate long-term potentiation (LTP) were assessed. Finally, the effect of OBS on acute PTZ-induced seizure and working memory was investigated in freely moving animals. OBS significantly increased the ED threshold when applied at 250 µA and decreased ED duration when applied at 125 and 250 µA. Results: Applying OES had a small effect on the ED threshold but significantly decreased ED duration when applied at 125 and 250 µA. Both OBS and OES mitigated the PTZ-induced increase in basal synaptic transmission. Meanwhile, OBS and OES significantly restored the LTP generation following PTZ injection in anesthetized rats. In addition, applying OBS in freely moving animals reduced the seizure severity and restore working memory impairment. Conclusions Obtained data showed that the OB and OE may be considered as effective targets for electrical brain stimulation to attenuate epileptiform activity and seizure severity. In addition, both OBS and OES decreased the seizure-induced impairment in LTP generation.