Objective: To explore the effect and mechanism of dexamethasone (DEX) in the prevention of central pontine myelinolysis (CPM) in rats.
Methods: Hyponatremia was induced in rat by subcutaneous injection of Vasopressin Tannate and intraperitoneal injection of 2.5% dextrose in water for 3 d, the rats of Group A received a bolus of 1 mol/L NaCl (2 ml/kg) and DEX (5 mg/kg) simultaneously at the 4th day; the rats of Group B were treated with DEX after 24 h of the injection of 1 mol/L NaCl; the rats in Group C received a bolus of 1 mol/L NaCl and saline simultaneously; Group D was the control group. The demyelinative lesions were evaluated by myelin staining. The Evans blue (EB) contents of brain were detected to evaluate the blood-brain-barrier permeability after rapid correction of hyponatremia. The expression of inducible nitric oxide synthase (iNOS) in brains was evaluated by Western blotting.
Result: CPM was induced successfully in rats. The EB contents of Group A, B and C had no significant difference at 0 h after injection of hypertonic saline compared with Group D. The EB contents of Group C began to increase significantly at 6 h after injection of hypertonic saline, peaked at 24 h; the expression of iNOS in brains began to increase after 3 h after the rapid correction of hyponatremia. The rate of morbidity in Group C was 66.7%. The demyelinative lesions were rarely seen in Group A, the EB contents of brain decreased significantly compared with Group C at the same time point (P<0.05), the iNOS expression was also inhibited. DEX could not prevent the attack of CPM at Group B, the rate of morbidity (75%) had no significant difference compared with Group C (P>0.05).
Conclusion: Early treatment with DEX can protect blood-brain-barrier and inhibit the expression of iNOS to prevent the attack of CPM.