抄録
We have studied the effect of chewing in the stress-induced suppression of hippocampal memory process, by measuring the long-term potentiation (LTP) on the hippocampal CA1 region of rats that underwent a restraint stress with or without chewing a wooden stick. Adult male rats were divided into three conditions: the restraint stress condition (stressed; ST), the voluntary chewing condition during the restraint state (chewing; SC), and the control condition without any treatments (control; CT). The rats in the SC group required 24 h to regain the stress-attenuated magnitude of LTP to the control level, while that in the ST group required 48 h. This sooner recovery of LTP in the SC group was associated with the larger number of functioning NMDA receptors, since bath-applied glycine augmented the LTP of both of the SC and ST groups at 24 h post-stress survival period to the level of the CT group with the same treatment. We also observed suppressed plasma level of adrenocorticotropic hormone in the SC group, showing 59% of that in the ST groups, at the end of the stress exposure. These findings suggest that chewing may suppress stress responses in the hypothalamic-pituitary-adrenal axis and the following corticosterone secretion, leading to the sooner recovery of hippocampal memory process. [J Physiol Sci. 2008;58 Suppl:S50]
