A-delta fiber (Aδ fiber)

A-delta fibers are thin, myelinated axons that serve as the primary conduits for rapid nociceptive and thermal signaling from the periphery to the dorsal horn of the spinal cord (StatPearls, 2023). Characterized by conduction velocities of 5-30 m/s, they are responsible for the "first pain" sensation—the sharp, well-localized feeling immediately following an injury (NCBI, 2022). These fibers are physiologically distinct from the slower, unmyelinated C-fibers and the faster, non-nociceptive A-beta fibers (Wikipedia, 2024). In therapeutic applications, A-delta fibers are targeted by local anesthetics like lidocaine, which interrupt signal transmission by blocking voltage-gated sodium channels (PubMed, 2021). Chronic sensitization or damage to these fibers is a hallmark of neuropathic pain conditions, making them a focal point for analgesic research and neuromodulation (NIH, 2023). Their role in the "pain gate" theory also makes them relevant for transcutaneous electrical nerve stimulation (TENS) and other physical therapies.

Other names

A-delta nerve fiberAδ sensory neuronFast pain fiberType III afferent fiber

Inhibition of voltage-gated sodium channels to block action potential propagation along the myelinated axon.