The analgesia effect and plasma corticosterone reaction during stress in adult rats treated neonatally with monosodium glutamate

In the present investigation,it was found that the number ofβ-endorphin(βEND)-immunoreactive neurons of hypothalamic arcuate nucleus(ARC)in MSGtreated rats decreased by 60.7 %.No significant differences in the baseline pain thresholdand the baseline corticosterone(CS)level were observed between the MSG-treatedgroup and the control group.After electrical foot shock for 30 min,the analgesia effect was decreased significantly(P0.001)in MSG-treated rats,while the CS levelsof both MSG-treated rats and control rats were increased remarked(P0.01).The results suggest that the β-END neurons of ARC were involved in analgesia,but not in CSreaction during stress.