Modulation of behavioral responses and CA1 neuronal death by nitric oxide in the neonatal rat's hypoxia model

INTRODUCTION: Neonatal hypoxia leads to cognitive and movement impairments that might persist throughout life. Hypoxia impairs hippocampal blood circulation and metabolism. The exact mechanisms underlying hypoxia‐induced memory impairment are not fully understood. Nitric oxide (NO) is a key neuromodulator that regulates cerebral blood flow. In this study, we aimed to evaluate the possible role of NO on behavioral and histomorphometric changes in the hippocampus following hypoxia in neonate rats. MATERIAL AND METHODS: Neonate male rats (n = 28) were randomly divided into 4 groups: control, hypoxia, hypoxia plus L‐NAME (20 mg/kg), and hypoxia plus L‐arginine (200 mg/kg). Drugs were injected intraperitoneally for seven consecutive days. Hypoxia was induced by keeping rats in a hypoxic chamber (7% oxygen and 93% nitrogen intensity). Ten to 14 days after hypoxia, behavioral changes were measured using a shuttle box, a rotarod, and an open field test. The histological changes in the hippocampus were measured using H&E and Nissl staining methods. RESULTS: Findings showed that hypoxia caused significant atrophy in the hippocampus. Furthermore, the administration of L‐NAME decreased the atrophy of the hippocampus in comparison with the hypoxic group. Behavioral results showed that hypoxia impaired memory performance and motor activity responses. Additionally, the administration of L‐NAME improved behavioral performance in a significant manner compared with the hypoxic group. CONCLUSIONS: Hypoxia damaged the neurons of hippocampal CA1 region and induced memory impairment. The NOS inhibitor, L‐NAME, significantly attenuated the negative effects of hypoxia on behavior and observed changes in the hippocampus.