Investigation of penicillin-induced epilepsy model in female rats with different estrous cycles by ECoG method

Abstract

Aim: Epilepsy is a chronic neurological disease characterized by recurrent seizures resulting from an imbalance in neuronal excitation. It is known that there is a tendency for seizures to cluster in both men and women at certain periods. This study aims to compare electrocorticogram (ECoG) recordings in an experimentally induced epilepsy model using penicillin, conducted at different estrous cycles of female rats. Subjects and Methods: Prior to commencing the epilepsy experiments, vaginal smears were collected from the animals every morning for 1 week, at the same time each day, for cytological examination. After confirming that the estrous cycles (proestrus, estrous stage, metestrus, and diestrus) of the animals were normal and healthy, the experiment was initiated. Additionally, H and E staining was performed on the ovaries of the rats sacrificed at the end of the experiment to validate the estrous cycle phases. A total of 32 adult female Wistar rats were divided into four groups (proestrus, estrus, metestrus, and diestrus), each consisting of eight rats. The penicillin-induced epilepsy model involved anesthetizing the rats with 1.25 mg/kg urethane intraperitoneally, followed by the injection of penicillin G (500 IU, 2.5 μL, i.c.) into the cortex region through a skull opening. ECoG recordings were conducted using PowerLab analysis for 180 min. Statistical analysis of the results was performed using the SPSS program version 22 (IBM Corp., Armonk, NY, USA). One-way analysis of variance (ANOVA) and independent samples t-test were employed for groups with normally distributed data, while the Kruskal–Wallis test and Mann–Whitney U-test were used for groups with nonnormally distributed data. Statistical significance was set at P < 0.05. Results: Histological evaluation confirmed that vaginal smears and ovarian histopathology were consistent with each other, validating the data pertaining to the groups. In the ECoG recording results, the spike-wave frequency between 6 and 10 min was higher in the metestrus group compared to the proestrus (P = 0.004), estrus (P = 0.046), and diestrus (P = 0.025) groups. No significant differences were observed among the groups in terms of spike-wave amplitude and latency. Conclusion: Our study using a penicillin-induced epilepsy model in female Wistar rats demonstrated that the spike-wave frequency was highest during the metestrus phase. This finding provides valuable insights for future studies aiming to understand and mitigate the sensitivity observed during the metestrus phase, which is characterized by rapid progesterone withdrawal.

Keywords

• electrocorticography
• epilepsy
• estrous cycle
• female rat
• penicillin