Gene expression profile of sodium channel subunits in the anterior cingulate cortex during experimental paclitaxel-induced neuropathic pain in mice
Paclitaxel, a chemotherapeutic agent, causes neuropathic pain whose supraspinal pathophysiology is not fully understood. Dysregulation of sodium channel expression, studied mainly in the periphery and spinal cord level, contributes to the pathogenesis of neuropathic pain. We examined gene expression of sodium channel subunits by real time PCR in the anterior cingulate cortex (ACC) at day 7 post first administration of paclitaxel, when mice had developed paclitaxel-induced thermal hyperalgesia. The ACC was chosen because increased activity in the ACC has been observed during neuropathic pain. In the ACC of control animals the Ct values for Nav1.4, Nav1.5, Nav1.7, Nav1.8 and Nav1.9 were above 30 and/or not detectable in some samples. Thus, comparison in mRNA expression between control and paclitaxel treated animals was done for Nav1.1, Nav1.2, Nav1.3, Nav1.6, Nax as well as Navβ1-Navβ4. Paclitaxel treatment significantly increased the mRNA expression of Nav1.1, Nav1.2, Nav1.6 and Nax, but not Nav1.3, sodium channel alpha subunits compared to vehicle-treated controls. Amongst the sodium channel beta subunits treatment with paclitaxel significantly increased the expression of Navβ1 and Navβ3, but not Navβ2 and Navβ4, compared to vehicle-treated controls. These findings suggest that during PINP there is differential upregulation of sodium channels in the ACC, which might contribute to the increased neuronal activity observed in the area during neuropathic pain.