Various pain stimulations cause an increase of the blood glucose level

The relationship between pain stimulation and the blood glucose level was studied in ICR mice. We examined the possible change of the blood glucose level after the pain stimulation induced by acetic acid injected intraperitoneally (i.p.),, formalin injected subcutaneously (s.c.) into the hind paw, or substance P (SP), glutamate, and proinflammatory cytokines (TNF-alpha and IFN-gamma) injected intrathecally (i.t.). We found in the present study that acetic acid, formalin, SP, TNF-alpha, and IFN-gamma increased the blood glucose level. The blood glucose level reached at maximal state 30 min and returned to normal level 2 h after the pain stimulation in a fasting group. Furthermore, acetic acid, formalin, SP, TNF-alpha, and IFN-gamma caused the elevation of the blood glucose level in D-glucose-fed group only in an additive manner. However, i.t. injection of glutamate did not alter the blood glucose level in a fasting group. In contrast, i.t. injection of glutamate enhanced the blood glucose level in the D-glucose-fed group. Our results suggest that the blood glucose level appears to be differentially regulated by various pain stimulation induced by acetic acid, formalin, SP, glutamate, and pro-inflammatory cytokines.