[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 of beta-endorphin (beta-END)-immunoreactive neurons of hypothalamic arcuate nucleus (ARC) in MSG-treated rats decreased by 60.7%. No significant differences in the baseline pain threshold and the baseline corticosterone (CS) level were observed between the MSG-treated group and the control group. After electrical foot shock for 30 min, the analgesia effect was decreased significantly (P < 0.001) in MSG-treated rats, while the CS levels of both MSG-treated rats and control rats were increased remarked (P < 0.01). The results suggest that the beta-END neurons of ARC were involved in analgesia, but not in CS reaction during stress.