Objective To explore the effect of monosodium glutamate (MSG) on the expression of 5\|HT in gastroenteric mucosa of rat. Methods Immunohistochemical technique was used to detect the expression of 5\|HT. The immuno\|activity and the density of positive cells were measured by image analysis. Results The immuno\|activity and the density of 5\|HT positive cells(EC cell) in the experimental group are higher than that in control group. The effect by 120d is the most significant, followed by that of 52d. Statistical analysis showed a significant difference ( P