A Single Hypoxic Event Ameliorates Pilocarpine Induced Hyperkinetic Movements in Planaria

Abstract

Intermittent hypoxia or hypoxia therapy is exposing an individual to oxygenation conditions that are below atmospheric levels in a planned or acute timeframe. Hypoxia therapy is a potentially novel therapeutic strategy for a variety of pathologies including: mitochondrial disorders, exercise training, and mild cognitive impairments. Mitochondrial dysfunction, hyperkinetic movements, and cognitive impairments are hallmarks of seizures and status epilepticus (SE). A seizure can be considered uncontrolled electrical activity in the brain and SE is a seizure lasting more than 30 minutes, or multiple seizures without regaining con-sciousness in between. We examined the possibility of using the Pilocarpine model for seizure like activity on brown planaria (Dugesia tigrine). Pilocarpine is a muscarinic acetylcholine receptor agonist capable of creating seizure related brain damage. We utilized 5 mM dosages of pilocarpine and then measured open field behaviour for 3 minutes. Mobility and aversive hyperkinetic movements were observed throughout the measurement phase. After exposure to 5 mM pilocarpine, the planaria displayed behaviours consistent with seizures (e.g. aversive hyperkinetic movements and decreased mobility). Additionally, we measured the effects of an acute hypoxic event on Planaria behaviour. We used 25% carbonated water to create a hypoxic environment for the planaria and then measured mobility and hyperkinetic movements for 3 minutes. We noted that exposure to the hypoxic environment produced no changes in behaviour. However, the aversive hyperkinetic movements produced with pilocarpine administration were completely absent when a brief (3 minutes) hypoxic episode followed the pilocarpine exposure (p < 0.05). Aversive behaviours remained present when the ordering of pilocarpine and hypoxia were counterbalanced. This ordering effect was consistent across 40 trials. Further evaluation of the pilocarpine seizure model and intermittent hypoxia on planarian behaviour is warranted.