Thermoreception and nociception of the skin: a classic paper of Bessou and Perl and analyses of thermal sensitivity during a student laboratory exercise

Abstract

About four decades ago, Perl and collaborators were the first ones who unambiguously identified specifically nociceptive neurons in the periphery. In their classic work, they recorded action potentials from single C-fibers of a cutaneous nerve in cats while applying carefully graded stimuli to the skin (Bessou P, Perl ER. Response of cutaneous sensory units with unmyelinated fibers to noxious stimuli. J Neurophysiol 32: 1025-1043, 1969). They discovered polymodal nociceptors, which responded to mechanical, thermal, and chemical stimuli in the noxious range, and differentiated them from low-threshold thermoreceptors. Their classic findings form the basis of the present method that undergraduate medical students experience during laboratory exercises of sensory physiology, namely, quantitative testing of the thermal detection and pain thresholds. This diagnostic method examines the function of thin afferent nerve fibers. We collected data from nearly 300 students that showed that 1) women are more sensitive to thermal detection and thermal pain at the thenar than men, 2) habituation shifts thermal pain thresholds during repetititve testing, 3) the cold pain threshold is rather variable and lower when tested after heat pain than in the reverse case (order effect), and 4) ratings of pain intensity on a visual analog scale are correlated with the threshold temperature for heat pain but not for cold pain. Median group results could be reproduced in a retest. Quantitative sensory testing of thermal thresholds is feasible and instructive in the setting of a laboratory exercise and is appreciated by the students as a relevant and interesting technique.

An Improved Model of Heat-Induced Hyperalgesia—Repetitive Phasic Heat Pain Causing Primary Hyperalgesia to Heat and Secondary Hyperalgesia to Pinprick and Light Touch

“…A significant gradual increase of heat pain to repeated conditioning heat stimuli was found, which was already present in the second block of heat stimuli. However, there may be confounding factors, namely a slow increase of stimulus efficacy upon fast stimulus repetition [29], [30], but also pronounced primary afferent fatigue to repeated heat stimuli [29], [31]–[33] and some degree of centrally mediated habituation [29], [34]. In line with the assumption of primary afferent fatigue, a prominent loss of warm sensitivity was observed in the conditioned skin area.…”

Thermal grill‐evoked sensations of heat correlate with cold pain threshold and are enhanced by menthol and cinnamaldehyde

“…This might suggest that a central difference signal proportional to the difference between COLD and HPC inputs may contribute to the processing of cold stimuli under normal conditions. Indeed, this may contribute to the considerable variability in temperature values reported for CPT (Namer et al, 2005(Namer et al, , 2008Hatem et al, 2006;Kuhtz-Buschbeck et al, 2010;Fig . 3).…”

Internal Wave Turbulence Near a Texel Beach

“…Now, this is an area where surface water temperatures reach T w  = 29°C, near the range of neutral human ambient skin-temperature at which both warm and cold fibers are active. Human thermoception starts at 0.5–1°C T-difference, from physiology experiments of small body-surfaces around 32°C [1]–[3], but body cooling reduces local thermal sensitivity [4]. However, regular beach visitors in countries like the Netherlands (T w ≤20°C) confirm: slow minute-like T-variations can be sensed, when seas are calm.…”