Abstracts

Rationale: Neonatal seizures and seizures of infancy represent a significant cause of morbidity. 30-40% of infants and children with seizures will fail to achieve seizure remission with current anti-epileptic drug (AED) treatment. Moreover, pharmacotherapy during critical periods of brain development can adversely affect nervous system function. We, and others, have shown that early life exposure to AEDs including phenobarbital, phenytoin, and valproate are associated with induction of enhanced neuronal apoptosis during a confined period of postnatal development in rats. Thus, identification of new therapies for neonatal/infantile epilepsy syndromes that provide seizure control without neuronal toxicity is a high priority. We previously evaluated drugs targeting the cannabinoid system and reported anti-seizure effects with both a mixed cannabinoid receptor 1 and 2 agonist (WIN 55,212-2) and a specific cannabinoid receptor 1 agonist (ACEA). However, the apoptotic profile of these drugs was unknown. Methods: We examined the effect of WIN 55,212-2 (WIN) and ACEA administration on neuronal apoptosis in developing rats.  Postnatal day 7 (P7) rat pups (n=6-8/treatment) were treated with a single dose of WIN 55,212-2 (1, 3, and 10 mg/kg), ACEA (8 mg/kg) or DMSO (vehicle). P7 animals were examined as this time point because the developing brain displays peak vulnerability to drug-induced neuronal apoptosis. 24 hours post-treatment, tissue was collected for analysis of neuronal cell death. Coronal sections were collected and stained using Fluoro-Jade B to label degenerating neurons. Profiles of apoptosis were measured from several brain regions including: cingulate cortex, striatum, and lateral septum. Fluorescent images were taken from three sequential sections at approximately 200um intervals for each brain region and quantification of degenerating neurons were quantified by counting the Fluoro-Jade B positive cells. Results: We found that all doses of WIN 55,212-2 tested induced neuronal apoptosis above DMSO control levels. At 1mg/kg, WIN induced significant apoptosis in the cingulate cortex (p   Conclusions: These results indicate that during a developmentally sensitive neonatal period, drugs targeting the cannabinoid system induce neuronal apoptosis in a CB-receptor dependent manner. While the anti-seizure effects we reported in P10 neonates were promising, our present results suggest that induction of neuronal apoptosis may limit the potential of these drugs. These data provide further need for the evaluation of new therapies for neonatal epilepsies that exert seizure control without increasing apoptosis of the developing brain. Funding: Center for Excellence in Regulatory Science and Innovation (CERSI) Fellowship to MNHNIH – KL2TR00143202 to PAF