Summary of fiber properties in the absence of TRPA1
| Fiber type | Adaptation property | Conduction velocity | Mechanical threshold | Known regions of innervation in hairy skin | Proposed TRPA1 expression related to fiber properties | Effects of TRPA1 absence on mechanical firing frequency | Physiological role in hairy skin |
|---|---|---|---|---|---|---|---|
| Aβ | SA | >10 m/s | Low (most) | Merkel cells | Medium- to large-diameter neurons and keratinocytes around the Merkel cells | ↓ | Fine touch two-point discrimination |
| Aδ-AM | SA | 1.2–10 m/s | High | Free nerve endings in epidermis and dermis | Small- to medium-diameter nociceptors and keratinocytes | ↓ | Fast pain nociceptor |
| C | SA | <1.2 m/s | High (Trpa1−/− have an increased threshold) | Free nerve endings in epidermis and dermis | Small- to medium-diameter nociceptors and keratinocytes | ↓ | Slow pain nociceptor |
| Aβ | RA | >10 m/s | Low | Tylotrich and guard hairs | Medium- to large-diameter neurons and keratinocytes in the hair follicle | ↑ | Hair movement |
| Aδ-D-hair | RA | 1.2–10 m/s | Very low (<1 mN) | Down hairs | Medium-diameter neurons and keratinocytes in the hair follicle | ↑ | Hair movement |