Construction of a pilocarpine-induced temporal lobe epilepsy model in mice based on severe seizure behavior

Objective To explore the approach to establish a temporal lobe epilepsy model via intraperitoneal pilocarpine injection in C57BL/6J mice, and to summarize behavioral indicators predicting successful modeling during the acute phase of epileptic seizures after pilocarpine administration, aiming to offer a practical mice model for future epilepsy research.MethodsThirty C57BL/6J substrain mice (primary subjects) and forty C57BL/6N substrain mice (control subjects) were selected to establish a temporal lobe epilepsy model by inducing seizures through a single intraperitoneal injection of pilocarpine. The mice from the two substrains were each divided into 3 groups, and were injected intraperitoneally with 300 mg/kg, 330 mg/kg, or 360 mg/kg of pilocarpine, respectively. Motor seizure behaviors were observed and compared between the two substrains of C57BL/6 mice post pilocarpine injection, and the spontaneous recurrent seizures (SRS) were continuously monitored from the 7th day after injection. On the 28th day post-injection, the mice were euthanized and the histopathological changes in their hippocampi were examined. ResultsAfter pilocarpine administration, C57BL/6N mice displayed characteristic motor seizures followed by the onset of status epilepticus (SE). Conversely, C57BL/6J mice showed fewer instances of typical motor seizure behavior and the subsequent SE. Instead, they more often exhibited systemic tremors lasting several seconds to tens of seconds following limb twitching. This behavior is classified as “severe seizure (SS)” in current study. Following intraperitoneal injection of 330 mg/kg and 360 mg/kg pilocarpine, C57BL/6J mice displaying SS during the acute phase of seizure might exhibit SRS after a latency period. The percentage of spontaneous seizures observed in C57BL/6J mice post-modeling (70%) was comparable to that seen in C57BL/6N mice (75%) which developed SRS subsequent to SE. C57BL/6J mice displayed characteristic pathological alterations associated with temporal lobe epilepsy in the hippocampi after 28 d following pilocarpine injection, including increased mossy fiber sprouting and neuronal death. ConclusionsWhen inducing an epilepsy model via intraperitoneal pilocarpine injection in C57BL/6J mice, the behavioral criteria to predict the successful establishment of the model could be either the occurrence of SE or the manifestation of SS.