Impaired Learning and Abnormal Open‐field Behaviours of Rats After Early Postnatal Anoxia and the Beneficial Effect of the Calcium Antagonist Nimodipine

Abstract

Abstract Perinatal anoxia/hypoxia is considered a serious risk factor for normal brain development. Anoxia induced by repeated asphyxia at 2 and 4 days after birth resulted in a transient hyperactivity in the small open‐field, and a behavioural depression in adult open‐field activity of male Wistar rats. The same treatment impaired adult learning behaviour in pole‐jumping conditioned avoidance and appetitively motivated hole‐board test situations. The calcium entry blocker nimodipine (in doses of 3 and 10 mg/kg) prevented the anoxia‐induced changes in orientation motility in the open‐field tests and almost fully antagonized the learning deficit in the hole‐board test. The behavioural deficit seen during acquisition of the pole‐jumping conditioned avoidance response was ameliorated to a lesser degree. The results indicate that the maintenance of calcium homeostasis during the early postnatal phase of brain development is crucial to prevent anoxia‐induced behavioural abnormalities.