Study on the effect of nitric oxide synthase on the learning and memorizing ability of rats after traumatic brain injury

Objective: To explore the influence of neuronal nitric oxide synthase(nNOS) and inducible nitric oxide synthase(iNOS) on the spatial learning ability and memory of rats following traumatic brain injury(TBI),and to observe the curative effect of 7-nitroindazole(7-NI) and aminoguanidine(AG).Methods: Two hundred and fifty male Wistar rats were randomly divided into 5 groups.Severe closed brain injury models were made according to Marmarou;immunohistochemical staining was used to detect the expression of nNOS and iNOS in the hippocampus CA1 region of the rats;TUNEL in situ was applied in determination of the apoptosis cells in the hippocampus CA1 region;the spatical learning ability and memory of the rats after injury was measured by means of Morris Water maze.Results: nNOS and iNOS expressed significantly in the hippocampus CA1 region of the rats.nNOS immuno-reactivity peaked at 6hr after injury(P<0.05),iNOS peaked at 3 days after injury(P<0.05),and TUNEL positive cells peaked at 3 days after injury(P<0.05).The number of positive cells decreased significantly 6 hours after injury in the treatment groups compared with that in the trauma group(P<0.05).And 3 days after injury,positive cells decreased in all the three groups,with the combination therapy group the most obvious.Conclusions: The decrease of learning and memorizing ability of the rats after TBI is associated with the nerve toxicity of NOS.7-NI and AG protect the nerve by inhibiting the activity and expression of nNOS and iNOS,which may improve the spatial learning ability and memory of rats.