Diurnal time course of heat pain perception in healthy humans

• Published in: Neuroscience letters Vol. 489; no. 2; pp. 122 - 125
• Main Authors: Bachmann, C.G., Nitsche, M.A., Pfingsten, M., Gersdorff, N., Harder, C., Baier, P.C., Antal, A., Treede, R.D., Paulus, W., Happe, S.
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 04.02.2011; Elsevier
• Subjects: Adult; Biological and medical sciences; Chronobiology; Circadian Rhythm; Circadian variation; Female; Fundamental and applied biological sciences. Psychology; Heat pain; Humans; Laser-evoked potentials; Male; Middle Aged; Pain - parasitology; Pain - physiopathology; Pain Perception; Thermal sensitivity; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vertebrates: nervous system and sense organs; Circadian variation; ESS; BDI; LEP; Laser-evoked potentials; EOG; Thermal sensitivity; Heat pain; NRS; PSQI; Human; Temperature; Electrophysiology; Environmental factor; Biological rhythm; Circadian rhythm; Heat; Sensitivity; Pain; Evoked potential; Perception
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/j.neulet.2010.11.080

▶ Circadian latencies of laser evoked potentials did not significantly vary during the day, as demonstrated with laser stimulation of the foot every 2h from 8a.m. to 10p.m. in 15 healthy subjects. ▶ Healthy humans do not exhibit any clinically relevant diurnal variations in their heat pain sensitivity. Rapid skin heating by infrared lasers can be used to investigate the integrity of the nociceptive system by activating A-delta and C fibers. The aim of our study was to analyze if healthy humans exhibit any clinically relevant diurnal variations in their heat pain sensitivity. Circadian A-delta fiber function was analyzed by studying N2 and P2 components of laser-evoked potentials (LEP) and pain thresholds evoked by laser stimulation of the foot every 2h from 8a.m. to 10p.m. in 15 healthy subjects. Heat stimuli were generated by an infrared Tm-YAG laser and were delivered to an area of 4cm×4.5cm on the dorsum of the right or left foot in 3 runs of incremental and decremental intensities. After each stimulus subjects were asked to classify the intensity of pain with a numeric rating scale (NRS). LEPs were recorded with fixed stimulus intensities that were 1.5× of the pain threshold. Data were collected with the SynAmps System (Neuroscan, El Paso, USA) and averaged across 35–40 trials. Laser-induced heat pain thresholds and circadian latencies of LEP did not significantly vary during the day. Our results correspond with previous studies that did not detect any consistent significant diurnal variations in perception of heat pain perception using contact thermodes. The intensity of pain perception did not demonstrate any correlation with mood or sleep parameters as measured with the Beck Depression Inventory (BDI), the subjective sleep scales Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS).