Figure 8
Vi/Vc-RVM circuitry is necessary for the development of contralateral hyperalgesia. The proposed pathway involved in the development of contralateral orofacial hyperalgesia following unilateral deep tissue inflammatory hyperalgesia. Unilateral CFA masseter inflammation leads to increased IL-1β activation of IL-1R in the ipsilateral Vi/Vc. Direct or indirect activation of the RVM through NK1-R activation leads to descending serotonergic facilitation of pain to the contralateral Vi/Vc. Activation of 5-HT3 receptors in the contralateral Vi/Vc leads to contralateral orofacial hyperalgesia.