Audiogenic Kindling Stimulation Fails to Induce Cerebral Overexpression of P-Glycoprotein and Limbic Crises in the GASH/Sal Model of Epilepsy.

Experimental evidence indicates that a high seizure burden can induce cerebral overexpression of P-glycoprotein (P-gp) at the blood-brain barrier, a phenomenon associated with drug-resistant epilepsy under the "transporter hypothesis", but also at the neuronal level, linked to a reduced seizure threshold, increased seizure severity (SS), status epilepticus (SE), and a high spontaneous death (SD) rate. In contrast, we recently described a progressive reduction in SS and the absence of SE and SD in GASH/Sal hamsters subjected to 45 audiogenic seizures. Here, we examined SS, SE, and the SD, and the expression of P-gp, erythropoietin receptor (EPO-R), hypoxia-inducible factor 1 alpha subunit (HIF-1α) and cyclooxygenase 2 (COX-2), in the brains of GASH/Sal hamsters following 20 audiogenic kindling stimulations (AUK-20). SS was evaluated using the midbrain and limbic severity scales; gene expression was assessed by RT-qPCR and P-gp protein levels were measured by immunohistochemistry and Western blot (IHC/WB) analysis. A modest decrease in midbrain SS was observed, without an increase in the already low limbic SS scores, and no SE or SD events occurred. P-gp levels remained low in both IHC and WB analyses. At the mRNA level, we detected increased EPO-R expression, decreased HIF-1α, and increased COX-2 without an accompanying increased in Abcb1b. Unlike findings from other experimental epilepsy models, AUK-20 in GASH/Sal hamsters does not enhance limbic SS, trigger SE or SD, or induce P-gp overexpression in the brain. Independently of the implications for drug resistance, the lack of cerebral P-gp overexpression without increased SS in the AUK-20-GASH/Sal model supports a potential role of P-gp in modulating seizure severity and epilepsy-associated mortality risk.