Psychophysical Evidence for Long-Term Potentiation of C-Fiber and A -Fiber Pathways in Humans by Analysis of Pain Descriptors

Hansen N, Klein T, Magerl W, and Treed R-D. Psychophysical evidence for long-term potentiation of C-fiber and A -fiber pathways in humans by analysis of pain descriptors. J Neurophysiol 97: 2559 –2563, 2007. First published January 10, 2007; doi:10.1152/jn.01125.2006. Long-term potentiation of human pain perception (nociceptive LTP) to single electrical test stimuli was induced by high-frequency stimulation (HFS) of cutaneous nociceptive afferents. Numerical pain ratings and a list of sensory pain descriptors disclosed the same magnitude of nociceptive LTP (23% increase for 60 min, P 0.001), whereas affective pain descriptors were not significantly enhanced. Factor analysis of the sensory pain descriptors showed that facilitation was restricted to two factors characterized by hot and burning ( 41%) and piercing and stinging ( 21%, both P 0.01), whereas a factor represented by throbbing and beating was not significantly increased ( 9%, P 0.47). The increased perception of the burning pain quality for 1 h after HFS is interpreted as a LTP-like facilitation of the conditioned cutaneous C-fiber pathway. Additionally, the increase of the stinging pain quality supplied evidence for facilitation of a sharpness-sensitive A -fiber pathway.