Objective: To determine whether AQP4 expression is associated with lactate (Lac) and Nacetyl aspartate (NAA) and with apparent diffusion coefficient (ADC) abnormality after rat cerebral ischemia. Methods: The time courses of ADC and lactate and NAA assessed by proton magnetic resonance spectroscopy (1HMRS) were investigated at the time point of 6 h, and 1, 3, 7 d after rat cerebral ischemia induced by middle cerebral artery occlusion. Expression of AQP4 mRNA and protein were measured using RT-PCR and West blot analysis respectively. Results: Significant reductions of NAA concentration and increases of lactate concentration were found after rat cerebral ischemia. The expressions of AQP4 mRNA and protein were increased at 6 h, and reached the peak at 1-3 d, then began to decrease at 7 d after rat cerebral ischemia. The expression of AQP4 was significantly correlated with NAA (rRT =-0.856, rw =-0. 927, P＜0. 01), and with lactate (rW=0. 473, rRT=0. 413, P＜0. 05), and with ADC values during the period of 1-7 d after rat cerebral ischemia (rW=0. 984, rRT= -0. 925, P＜0.05). In addition, correlations between Lac and the ADC values(r=-0. 677, P＜0. 05)and between NAA and ADC values during the period of 1-7 d after rat cerebral ischemia (r= 0. 909, P＜0.05) were also observed. Conclusion: The data suggest that AQP4 is involved in the transport of water when brain edema is formed and cell membrane integrity is lost.