Altered expression of orexin 1 and endocannabinoid 1 receptors of the hippocampus in three pentylenetetrazol, pilocarpine and kainate seizure models

Seizure is synchronous and abnormal brain neuronal activity that leads to activation of different receptors capable of enhancing or suppressing seizure activity such as orexin receptor 1 (OXR1) and/or endocannabinoid receptor 1(CBR1). The time of activation for the receptors may influence seizure control. Therefore, this study aimed to investigate the latency for and the change of the expression of OXR1 or CBR1 following seizures in three pentylenetetrazol (PTZ), kainic acid (KA), and Pilocarpine seizure models.

Fifty-six male Wistar rats were allocated in the three PTZ, KA, and Pilocarpine groups. Seizure intensity was calculated upon latencies to seizures (from injection to seizure; latency 1 and from seizure to tonic-clonic; latency 2) and seizure duration. OXR1 and CBR1 gene expressions were evaluated using RT-PCR and the results were compared with the control group (without seizure induction).

Our study showed that latency 1 and 2 significantly increased in the KA and Pilocarpine models compared with PTZ, while the seizure duration reduced. Relatively, the expression of OXR1, four hours, and CBR1, instantly and four hours following the PTZ application was augmented. The expression of OXR1 and CBR1, one week following KA perfusion was enhanced, while the increase in the receptor expressions was demonstrated 28 days after Pilocarpine injection.

Results of the study demonstrated that the shorter the latency of seizures in a model and longer the seizure durations, the increase in the OXR1 and CBR1 may be hastened.