Research reportEvaluation of spontaneous recovery of behavioral and brain injury profiles in zebrafish after hypoxia

•Short-term hypoxia produced four distinct behavioral stages in adult zebrafish.•Brain damage and behavioral impairments were observed in zebrafish after hypoxia.•Effects induced by hypoxia were reversed after recovery under normoxic conditions.•Behavioral impairments recovered more quickly than brain damage following a return to normoxic conditions.

Cerebral hypoxia-ischemia can lead to motor and sensory impairments which can be dependent on the extent of infarcted regions. Since a better understanding of the neurochemical mechanisms involved in this injury is needed, the use of zebrafish as a cerebral hypoxia model has become quite promising because it could improve the knowledge about hypoxia-ischemia. In the current study, we aimed to investigate the spontaneous recovery of brain and behavioral impairments induced by hypoxia in adult zebrafish. Brain injury levels were analyzed by spectrophotometric measurement of mitochondrial dehydrogenase activity by staining with 2,3,5-triphenyltetrazolium chloride, and behavioral profiles were assessed by the open tank test. The induction of hypoxia substantially decreased mitochondrial activity in the brain and impaired behavior. The spontaneous recovery of fish subjected to hypoxia was assessed after 1, 3, 6, 24, and 48 h under normoxia. The quantification of brain injury levels showed a significant increase until 24 h after hypoxia, but after 48 h this effect was completely reversed. Regarding behavioral parameters, we verified that locomotor activity and vertical exploration were impaired by hypoxia and these effects were reversed after 3 h under normoxia. Taken together, these results show that zebrafish exhibited transient cerebral and behavioral impairments when submitted to hypoxia, and 1 h under normoxic conditions was insufficient to reverse both effects. Therefore, our data help to elucidate the time window of spontaneous recovery in zebrafish after hypoxia and also the behavioral phenotypes involved in this phenomenon.