Protective Effect Of An AMPA Glutamate Receptor Antagonist On Neonatal Rat Models With Hypoxic-Ischemic Brain Damage

Objective: hypoxic-ischemic brain damage (HIBD) in the human perinatal period often leads to the death of neonates or long-term neurobehavioral dysfunction. But the mechanism of HIBD has not yet been recognized and there are not efficacious means of prevention and treatment. With the advance of study about HIBD, there is increasing evidence that AMPA glutamate receptor contributes to HIBD. Rat HIBD model was used in this research to study the expression of myelin basic protein (MBP), neurofilament (NF) proteins and number of hippocampal CA1 pyramidal cells in the hemisphere ipsilateral to the injury, also test spatial memory abilities and observe their changes after therapy with GYKI-52466, an selective AMPA glutamate receptor antagonist, to study the protective effect of GYKI-52466 on neonatal rat models with HIBD.Methods: 7-day-old Wistar rats were randomly divided into four groups:normal control group; sham-operated group; HIBD treated with saline group(HIBD group) and HIBD treated with GYKI-52466 group(treat group), respectively. Rats of normal control group were used to assess the critical ages of MBP, NF expression in the neonatal rat. Rats of the other three groups were killed at the directed time and brain tissues were prepared. Using hematoxylin-eosin (HE) staining and light-microscopy observed the histological feature and counts hyppocampal CA1 pyramidal cells of the ipsilateral hemisphere. White matter integrity was evaluated by densitometric analysis of MBP and NF immunostaining, and the amount of tissue injury was evaluated by morphometric measurements of cerebral hemisphere areas. Level of malondialdehyde (MDA), superoxide dismutase (SOD) and reduced glutathione (GSH) in brain were measured with biological-chemical methods. Cell apoptosis was examined with TUNEL method. Spatial learning and memory testing was conducted from postnatal day 30 (P30) using the Morris water maze. Results: (1) (L:R)AREA means ratio of left-to-right hemispheric cross-sectional area. Mean (L:R)AREA values were calculated. Comparison of mean (R:L)AREA values between the sham-operated and HIBD group illustrated the HIBD group sustained substantial loss of tussue(p<0.001). GYKI-52466 treatment resulted in a significant reduction in tissue loss (p<0.001) (2) MBP immunostaining is barely detectable on P8. On P11, MBP immunostaining is readily identified, concentrated in white matter tracts of the olfactory tract, corpus callosum, external and internal capsules, with MBP-positive processes extending into the overlying cortex. In the striatum periaxonal immunostaining can also be discerned. On P14, there is a further increase in MBP immunostaining both within white matter tracts and overlying cortex, and MBP expression generally present in the anterior commissure. (L:R)MBP means ratios of left-to-right hemispheric integrated optical density (IOD) values of MBP. The mean (L:R)MBP value of HIBD group was much lower than that of sham-operated group(p<0.02). Compared with HIBD group, the mean (L:R)MBP value of treat group was significantly higher(p<0.05). The patterns of immunoreactivity for MBP and NF-H proteins were similar in the four groups of rats.(3) The HIBD group displayed a pronounced reduction in CA1 neuron number in the hemisphere ipsilateral to the carotid ligation in comparison to sham-operated group (p<0.001). The treat group also displayed a significant CA1 neuron number reduction, but the extent of CA1 neuronal number reduction was significantly less than that of the HIBD group (p<0.001).(4) The percentages of TUNEL-positive cell in HIBD group was higher than that of sham-operated group (p<0.001). The percentage of TUNEL-positive cell in treat group significantly decreased when compared with HIBD group (p<0.01).(5) The SOD,GSH level of HIBD group were significantly lower than that of sham-operated group. The MDA content of HIBD group was significantly higher than that of sham-operated group (p<0.001). Compared with HIBD group, the SOD,GSH level increased (p<0.001, p<0.005) and the MDA content decrease...