Posttraumatic epilepsy (PTE) is defined as recurrent and unprovoked seizures occurring >1 week after traumatic brain injury (TBI). Animal studies of PTE are lengthy and expensive. In this study, we developed a cost-effective PTE animal model using zebrafish to bridge the gap between in vitro studies and low-throughput animal studies.
We used two different sets of parameters (G1 and G2) to induce closed-head TBI in adult zebrafish using pulsed high-intensity focused ultrasound. Injured fish and naive controls were evaluated for behavioral deficits and spontaneous behavioral seizure activity up to 21 days postinjury (DPI). We also assessed behavioral seizure susceptibility to a subconvulsive dose of pentylenetetrazole (PTZ; 2.5 mmol·L ) and recorded electrophysiological signals to confirm seizure activity up to 40 DPI. In addition, we investigated injury-related changes in the blood-brain barrier and expression levels of various proteins altered in rodent and human TBI.
The G2 parameters resulted in a more severe TBI, with a mortality rate of 25%, as well as motor dysfunction and heightened anxiety persisting at 21 DPI. One hundred percent of the G2 group showed spontaneous myocloniclike behavior, and 80% demonstrated tonic-clonic-like behavioral seizures by 21 DPI. Such activities were not detected in the naive group. After the application of 2.5 mmol·L PTZ, 100% of injured zebrafish had cloniclike seizures at 21 DPI, versus 30% of the naive group. We also demonstrated electrographic seizure activity at 40 DPI, which was not detected in the naive controls. Lastly, we observed acute blood-brain barrier dysfunction and increased levels of HMGB1 and ratios of phosphorylated/total Akt and tau through 21 DPI.
Together, the results indicate that severe TBI in the adult zebrafish leads to similar behavioral and physiological changes to those of more traditional models, including the development of PTE, and suggest this may be a useful model that can accelerate research in TBI/PTE.
© 2020 International League Against Epilepsy.