Trigeminal neuropathic/inflammatory pain models and changes in TRG neuronal activities. A: Chronic constriction nerve injury (CCI) model. Three days after infraorbital nerve (ION) chronic constriction. Target trigeminal ganglion (TRG) neurons were labeled by fluorogold (FG). Whole-cell patch-clamp recordings under current-/voltage-clamp configurations were performed on medium/large-diameter CCI neurons. B: Axotomy-neighboring neuron model. In this model, we found mechanical allodynia in the territory of ION at 2 days after inferior alveolar nerve (IAN) transection. Uninjured TRG neurons innervating the territory of ION were labeled by FG and patch-clamp recordings under current-/voltage-clamp configuration was performed on medium-/large-diameter neurons. C: Axotomy-regenerated neuron model. In this model, we observed mechanical allodynia at 14 days after IAN transection. FG-injection at 14 days after IAN transection showed massive labeling of trigeminal ganglion containing FG-labeled small/large-diameter neurons and the patch-clamp recordings under current-/voltage-clamp configuration indicated axotomy-regenerated neurons. D: Inflammation model. Inflammation was induced by injection of CFA into the rat temporomandibular joint (TMJ). We found mechanical allodynia in the territory of ION at 2 days after CFA injection. In FG-labeled small-diameter TRG neurons innervating TMJ, the whole-cell patch-clamp recordings under current-/voltage-clamp configurations were performed on inflammatory neurons. Blackened circles indicate the trigeminal ganglion neurons. I-III: trigeminal nerves, IA: transient K current, IK: sustained K currents, ↑: increase, ↓: decrease, ▼: tendency for decrease in IK, but not significant, ▲: tendency for depolarization of membrane potential (Vm), but not significant, Depo: Depolarization, V-clamp : Voltage-clamp, I-clamp: Current-clamp.
Takeda et al. Molecular Pain 2011 7:5 doi:10.1186/1744-8069-7-5