Figure 6. Schematic of cutaneous mechanosensory afferents underlying sanshool-induced tingling paresthesia.

The putative cutaneous innervation pattern of sanshool-sensitive (left) and sanshool-insensitive (right) mechanosensory afferents examined in this study are shown (Brown and Iggo 1967; Burgess et al., 1968). The dermal and epidermal layers of the skin are represented in yellow and brown, respectively. Thickness of sensory fibers represents degree of myelination. Application of sanshool to the skin induces tonic or bursting activation of subsets of fibers, leading to sensation of tingling paresthesia (bottom).