Abstracts

Rationale:
Pentylenetetrazole (PTZ) is a GABA-A receptor antagonist commonly used to induce acute seizures in mouse models of epilepsy. The benefits of acute PTZ are its ease of administration and reliability to evoke seizures. Prior studies suggest age, background, and sex are variables that influence seizure susceptibility in animal models of epilepsy. Most recently, a study demonstrated social isolation is an additional factor influencing pilocarpine-induced seizures. However, no study has evaluated whether social isolation influences PTZ-induced seizures in wild-type mice.
Method:
We included data from both published and unpublished cohorts over a seven year period (2013-2020) that injected single doses of PTZ intraperitoneally (IP). The primary endpoint was generalized tonic-clonic seizures, as behaviorally indicated by loss of balance and continuous, uncontrollable jerking (Racine score of 5), occurring within 10 minutes of injection. Variables evaluated included sex, age, background strain, dose, and housing (social v. isolated). Non-parametric Spearman correlation was conducted for each variable compared to seizure response followed by a multivariate logistic regression analysis.
Results:
Two-hundred eighty-five mice from serial cohorts were included, with a median age of 9 weeks (range 26 weeks), dose range of 40-65 mg/kg, background strain (77.2% C57BL/6J or 22.8% mixed background), and housing (83.5% social or 16.5% isolated). One-hundred eighty-eight were male (66.0%) and ninety-seven were female (34.0%). In response to IP PTZ injection, 28.7% of males (54/188) and 30.0% of females (29/97) had a generalized tonic-clonic seizure. Additionally, 29.5% of C57BL/6J mice seized (65/220) and 27.7% of mixed background mice seized (18/65). When stratifying by housing conditions, 53.2% of isolated mice seized (25/47), while only 24.4% of socially-housed mice seized (58/238). In univariate analysis significant correlations were identifiedbetween seizures and PTZ dose (r=0.28, p< 0.0001), age (r=-0.18, p=0.002), and housing (r=0.24, p< 0.0001), but not background strain (r=-0.02, p=0.774) or sex (r=0.01, p=0.837). However, in  multivariate analysis, the main drivers of seizure susceptibility were dose (odds ratio (OR) 1.16, 95% confidence interval (CI) 1.11 - 1.22), age (OR 1.11, CI 1.02 - 1.20), mixed background strain (OR 2.58, CI 1.18 - 5.91), and social isolation (OR 16.68, CI 6.73 - 45.353). Our study used a restricted age range (6-32 weeks) with 75.1% of mice in the “young adult” range (214/285) and only two background strains, which potentially limits the scope and generalizability of our results.