Effect of heterotopic noxious conditioning stimulation on electrical and pressure pain thresholds in two different anatomical regions.
OBJECTIVE
The aims of the study were to investigate the influence of heterotopic noxious conditioning stimulation (HNCS) on pain thresholds in the orofacial and spinal regions and to find out whether there are gender differences in this respect.


METHODS
Thirty healthy subjects (15 of each sex) with a mean (SD) age of 25.1 (4.4) years participated. Pain thresholds to electrical (EPT) and pressure stimuli (PPT) were recorded in the masseter muscle and 1st upper incisor (tooth), as well as in the fingertip, before, during, and 5 and 15 min after a cold pressor task to the contralateral hand immersed in ice-cold water for a maximum of 5 min.


RESULTS
With the exception of the EPT in the orofacial region, all pain thresholds increased during the HNCS and then returned to baseline during the 15 min follow-up. The significant changes in EPT were greater in the finger than in the tooth, while the changes in PPT were greater in the masseter muscle than in the finger. Electrical stimuli in the finger induced greater significant changes of pain thresholds than pressure. In the orofacial region, pressure induced greater significant changes in pain thresholds during HNCS than electrical stimuli did. The HNCS induced pain of high intensity and unpleasantness, i.e. varying between 5 and 10 on the numeric rating scale (NRS). There were no gender differences in the response to the HNCS.


CONCLUSIONS
We conclude that, in general, HNCS induced by cold pressor stimulation increases pain thresholds, but the magnitude of the effect differs between the orofacial region and the finger and is influenced by the tissue and type of test stimuli.
Rosen
Annika
A
Institute of Odontology, Neuroscience Research Group, Huddinge, Sweden. annika.rosen@ki.se
Feldreich
Anna
A
Dabirian
Nakisa
N
Ernberg
Malin
M
D000222:Adaptation, Physiological; D000223:Adaptation, Psychological; D000328:Adult; D000704:Analysis of Variance; D003080:Cold Temperature; D003213:Conditioning, Psychological; D003791:Dental Pulp Test; D004558:Electric Stimulation; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology; D006801:Humans; D007180:Incisor / Q000294:innervation / Q000502:physiology; D007266:Inhibition, Psychological; D008297:Male; D016555:Matched-Pair Analysis; D008437:Maxilla; D009619:Nociceptors / Q000502:physiology*; D017288:Pain Threshold / Q000502:physiology / Q000523:psychology*; D010470:Perceptual Masking / Q000502:physiology*; D010812:Physical Stimulation; D011312:Pressure; D012016:Reference Values; D012737:Sex Factors; D018709:Statistics, Nonparametric