抄録
The escape behavior, phosphorylation of ERK in the trigeminal spinal nucleus caudalis (Vc) and Vc neuronal activity to noxious and non-noxious stimulation of the face were precisely analyzed in the rats with the chronic constriction nerve injury (CCI) of the infraorbital nerve (ION). The thresholds for escape from mechanical stimulation applied to the whisker pad area ipsilateral to the ION-CCI were significantly lower than that for the contralateral whisker pad more than 14 days after the ION-CCI. A large number of pERK-LI cells were expressed in the Vc 7 days after ION-CCI. The pERK-LI cells were restricted in the superficial laminae of the caudal Vc following mechanical stimulation of the whisker pad region. The number of pERK-LI cells was increased following increase in the mechanical stimulus intensity. Twenty one WDR neurons were recorded from Vc and response properties of these neurons were precisely analyzed. The afterdischarges of WDR neurons on the ipsilateral side relative to the CCI were significantly larger at 7 days after the operation than that of naive rats. Noxious evoked responses of WDR neurons were significantly enhanced at 7 days after ION-CCI. The evoked responses to 50 degree C heat stimulation of the face were significantly higher than naive rats. The present findings suggest that an activation of the intracellular MAP kinase cascade reflects the enhancement of the Vc neuronal excitability following ION-CCI and play an important role in the development of the mechano-allodynia induced by the trigeminal nerve injury. [J Physiol Sci. 2007;57 Suppl:S155]
