Fig. 4.

The role of inhibitory parvalbumin-expressing interneurons in gating low-threshold tactile input. Under normal conditions, inhibitory parvalbumin-expressing interneurons (iPV, green) mediate presynaptic inhibition of A-LTMR input (red) and postsynaptic inhibition of both vertical cells (blue, V) and PKCγ-expressing interneurons (blue, PKCγ). Peripheral nerve injury results in a reduction of iPV excitability (iPV, grey), leading to spinal disinhibition. The loss of iPV-mediated inhibition allows A-LTMR input to activate vertical cells directly, and through a polysynaptic route incorporating PKCγ-expressing interneurons and transient central cells (TC, blue). Under these conditions, vertical cells can relay A-LTMR input activate projection neurons (PN, black) in lamina I and recruit pain circuits. Based on references 48, 60, 123, 125