Abstracts

Rationale: The Wistar Audiogenic Rat (WAR) is a rodent strain capable of developing epileptic seizures in response to intense sound stimulation (audiogenic seizures, AS). Along the chronic protocol of AS (audiogenic kindling, AuK), the initially brainstem-dependent seizures give rise to forebrain-dependent seizures through a process called limbic recruitment. Cannabidiol (CBD) is a compound present in Cannabis and has been implicated in seizure treatment. However, little is known about CBD effects in chronic protocols of epilepsies, especially regarding the behavioral seizures expression. Therefore, the aim of this study was to verify the potential CBD anticonvulsant and antiepileptogenic effects by neuroethological methods (flowcharts) in a chronic protocol of epileptic seizures. Methods: WARs and Wistars (n=9-11/group; CEUA: 057/2017) were submitted to the AuK (20 acoustic stimuli, twice a day). Animals were placed in an acrylic box and sound (120 dB) was applied for 1 minute, or until the development of tonic seizures. Animal behavior was analysed second-to-second during 3 minutes: 1 before, 1 during, and 1 after the stimulus. Behaviors were grouped in different clusters: wild running (WR), tonic-clonic seizures (TC), limbic seizures (LI), grooming, and others. CBD (25 mg/kg; i.p.) or vehicle treatment were initiated 24 h before the first stimulus and were maintained along the whole protocol (1 h before each stimulus). The statistical analysis provides frequency, duration, and the strength of interactions between behaviors pairs (significant interactions, X2 ≥ 3.84). Results: Chronic CBD treatment attenuated brainstem seizures (p<0,05) and prevented the development of limbic seizures (p<0,05) in WARs. At the 1st stimulus, neuroethological analysis showed a reduction in time of the WR behaviors in the CBD-treated group. Moreover, a cluster with 3 grooming behaviors appeared in the CBD group, but no grooming was observed in the vehicle group. Regarding the post-sound period of the 1st stimulus, CBD attenuated the TC seizures, with fragmented expression (no interactions) and disappearance of hindlimb extension, when compared to the vehicle group. After 20 stimuli, during the sound exposure, the vehicle group presents a cluster with 5 different types of LI behaviors with 3 interactions between them. However, the CBD-treated group presents only 1 LI component and a complex cluster of grooming behaviors (7 different types), which were not observed in the vehicle group. In the post-sound period of the 20th stimulus, vehicle-treated WARs present 6 TC behaviors with 4 interactions, while in the CBD group all TC behaviors disappeared. Moreover, 3 different grooming behaviors appeared in the CBD group. Post-ictal behaviors (immobility and apnea) displayed by vehicle animals, totally disappeared in the CBD group. Wistars did not present any seizure, confirming the specific effect of the acoustic stimulation in WARs. Conclusions: Our results showed that CBD attenuated brainstem seizures and prevented limbic recruitment along the AuK, indicating its anticonvulsant activity and suggesting antiepileptogenic effects. Neuroethological analysis indicates a reduction in the number of seizure behaviors and interactions between behavior pairs in both, brainstem and limbic seizures. Additionally, there is an increase in grooming behaviors in the CBD-treated group, coincident with the suppression of seizure behaviors. Funding: No funding