Chewing augments stress-induced increase of pERK-immunoreactive cells in the rat cingulate cortex

The eff ;ects of chewing during restraint stress on the anterior, mid- and posterior cingulate cortices were investigated in rats using immunohistochemistry to detect the expression of phosphorylated extracellular signal-regulated kinase 1 and 2 (pERK1/2), a marker of responding cells. The rats were divided into three groups: control (no immobilization), stress-only (immobilized), and stress-with-chewing (immobilized and allowed to chew a wooden stick). Significant increases in the number of pERK1/2-immunoreactive cells in the anterior, mid- and posterior cingulate cortices were noted in the stress-only group when compared with the control group (p < 0.05). Furthermore, the number of pERK1/2-immunoreactive cells in the anterior, mid- and posterior cingulate cortices in the stress-with-chewing group was also significantly higher than that in the stress-only group (p < 0.05). These findings indicate that the cingulate cortex plays a role in the negative-feedback effect and might be an essential part of the brain where the ameliorating effects of chewing against stress are produced.