Synapse
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Pain is evoked by noxious body stimulation or through negative emotional events and memories. There are several caveats to the simple proposition that pain and emotion are linked in the cingulate cortex (CG). In this study, we investigated whether mild noxious heat stimuli could affect the neuronal activity in the CG of rats with sciatic nerve ligation. ⋯ Under this condition, there were no significant changes in the levels of immediate-early genes such as c-fos, c-jun, JunB, and Fra1 in the CG between nerve-ligated and sham-operated rats. However, mild noxious heat stimuli under a neuropathic pain-like state produced a marked increase in the phosphorylated-c-jun (p-c-jun) immunoreactivity, which is commonly used to map neurons in the brain that can be activated after N-methyl-D-aspartate receptor activation. These findings raise the possibility that mild noxious heat stimuli under a peripheral nerve injury may increase the release of glutamate and promote its related postneuronal activity in the CG.