Planarian as an Animal Model for Experimental Acute Seizure

Abstract

Epilepsy is among the most prevalent neurological disorders characterized by recurring spontaneous seizures. Seizures represent a clinical manifestation of uncontrolled, excessively synchronized neural cell activity. The extent of brain damage from seizures depends on their duration and intensity. Regrettably, there is no effective remedy for epilepsy. The aim of this investigation is to assess whether the planaria worm Dugesia dorotocephala could serve as a model to aid in identifying and developing treatments for epilepsy that can target acute seizures. Currently, various models, such as marine models, are used to evaluate antiseizure medications (ASM). However, they are very expensive, and there are ethical concerns. Alternatively, invertebrate models offer a cost-effective research opportunity in the drug discovery process for ASM. Planaria belong to the flatworm family and inhabit marine freshwater and terrestrial environments. Dugesia dorotocephala is the dominant species of aquatic planaria across North America. D. dorotocephala presents as a viable invertebrate model for epilepsy studies due to its cost-effectiveness, vertebrate-like neurons, and quantifiable behaviors, unlike other invertebrates or larger animals. They have been used in various pharmacology and environmental toxicology studies related to age, memory, and regeneration. In this study, planaria were exposed to different concentrations of pilocarpine, a common chemoconvulsant to study their behavior upon exposure. Following the observation, planaria were euthanized and preserved in either formaldehyde or Golgi solution for neurohistological assessment. Six distinct behavioral phenotypes were observed in planaria: dorsal oscillations, head oscillations, tail dorsal expansion, C-shape, head flick, and tail flick. Dorsal oscillation frequencies were significantly increased among experimental groups compared to the control and exhibited dose dependence. Additionally, pilocarpine disrupted the motility of the planaria. Pilocarpine-induced seizures in planaria can serve as a model to evaluate acute seizures and antiseizure medication, which is essential in developing therapeutic interventions for human patients suffering from epilepsy.