Profile of anticonvulsant action of levetiracetam, tiagabine and phenobarbital against seizures evoked by DMCM (methyl-6,7-dimethoxy-4-ethyl-β-carboline-3-carboxylate) in neonatal rats

Levetiracetam (LEV) and tiagabine (TGB) are utilized for the treatment of seizures, including neonatal seizures. However, relatively little is known about the preclinical therapeutic profile of these drugs during brain development. The relative paucity of information regarding these drugs in neonatal animals may be due to their unusual profile of anticonvulsant action in experimental models. LEV and TGB are without effect against seizures in several common screening models (e.g., the maximal electroshock test, maximal pentylenetetrazole seizures), instead showing preferential efficacy against models of partial seizures. We have recently described a method for reliably evoking partial seizures in neonatal animals by systemic administration of the chemoconvulsant, DMCM (Kulick et al., 2014, Eur. J. Pharmacol., doi:10.1016/j.ejphar.2014.06.012). DMCM is a negative allosteric modulator of GABAA receptors, and offers a wide separation between doses required to evoke complex partial as compared to tonic-clonic seizures. Here we used DMCM to evaluate the effect of LEV and TGB against seizures in postnatal day (P) 10 rat pups. We compared the profile of LEV and TGB to that of phenobarbital (PB), the most widely utilized anticonvulsant in neonates. We found that LEV significantly protected against DMCM seizures when administered in doses of 10 mg/kg and greater. TGB protected against DMCM-evoked seizures when administered in doses of 1 mg/kg or greater. PB protected against DMCM-evoked seizures when administered in doses of 5 mg/kg or greater. These data provide preclinical evidence for the efficacy of LEV and TGB in neonates and underscore the utility of DMCM for screening anticonvulsant action in neonatal animals.