Expressions of NMDA receptor subunits NR1 and NR2B in the hypothalamus of severe burn rats / 中华创伤杂志

ABSTRACT

ObjectiveTo observe the early changes of N-methyl-D-aspartic acid (NMDA) receptor subunit NR1 and NR2B expressions in the hypothalamus so as to discuss the underlying mechanism of the excitability alternation of hypothalamus-pituitary-adrenal (HPA) axis following severe burn in rats.MethodsA total of 40 Sprague-Dawley rats were randomized into the control group and the experimental groups ( including 6,24 and 48 hours after burn) and a 30％ total body surface area full-thickness burn was induced by immersing the shaved dorsum into boiling water for 40 s.Then,the expression changes of the NMDA receptor subunits NR1 and NR2B in the hypothalamus tissue were examined by using immunohistochemistry and Western blot.Results There was an obvious enhancement of the excitability of HPA axis and obvious changes of serum concentration of cortisol and hemodynamics.The serum concentrations of cortisol of the experimental groups reached the peak at 6 hour after burn and were significantly higher than the control group even 48 hours later (P ＜ 0.05 ).Systolic pressure (SP),diastolic pressure (DP) and left ventricular systolic pressure (LVSP) of the experimental groups were all decreased at 6 hours after burn,of which SP and DP were still lower than the control group at 48 hours after burn (P ＜0.05).Based on the Western blot assay,the NR1 level was increased and reached the peak (1.12 ±0.27) in the experimental groups and 0.45 -±0.15 in the control group at 24 hours after burn (P ＜ 0.05).In the meantime,the NR2B level was decreased significantly and reached the lowest for 0.65 ±0.21 at 6 hours after burn,with statistical difference in comparison with 1.38 ±0.51 in the control group (P ＜0.05.The NR2B level recovered to pre-burn level for 1.25 ±0.30 at 48 hours in the experimental groups,with no statistical difference compared with 1.38 ± 0.51 in the control group (P ＞ 0.05 ).The immunohistochemistry results on hypothalamus paraventricular nucleus (PVN) was consistent with the Western blot results.ConclusionThe persistent plasticity changes of hypothalamus subunits NR1 and NR2B may be on of important mechanisms for early excitability alteration of HPA axis after severe burn.