Thermoregulation and pain perception: Evidence for a homoeostatic (interoceptive) dimension of pain.
BACKGROUND
Experimental and clinical observations of interactions between the nociceptive and thermoceptive systems have suggested that they could be part of the homoeostatic system relating to the condition of the body, described as 'interoception'. Homoeostatic physiological systems are extensively interconnected. Thus, consistent with this hypothesis, we would expect thermoregulatory challenges to be associated with changes in pain perception.


METHODS
The effects of whole-body warming or cooling inducing significant changes in mean body temperature were tested in 15 healthy volunteers (29 ± 6 years old) on: (i) the paradoxical burning pain induced by the application of simultaneous non-noxious thermal stimuli with a 'thermal grill' and (ii) the 'normal' pain evoked by noxious thermal stimuli.


RESULTS
Whole-body warming and cooling induced changes in opposite direction of the threshold of the paradoxical pain induced by the thermal grill, consisting of an increase by 1.2 ± 1.7 °C (p = 0.02) during the warming session and a nonsignificant decrease by 0.7 ± 2.7 °C (p = 0.15) during the cooling session. In addition, there was a correlation (r = 0.54; p = 0.002) between the magnitude of the change in mean body temperature and the magnitude of the change in the threshold of the paradoxical pain induced by the thermal grill. By contrast, the thermal challenges induced no significant change in pain evoked by noxious hot or cold stimuli.


CONCLUSIONS
Our results are consistent with the notion that pain has a homoeostatic (interoceptive) dimension and showed that the thermal grill-induced pain is a unique experimental model to investigate this differentiable pain dimension.
INSERM U987, Centre d'Evaluation et de Traitement de la Douleur, Hôpital Ambroise Paré, Boulogne-Billancourt, France.|Department of Anesthesiology and Intensive Care, Hôpital Cochin, AP-HP, Paris, France.
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Alfonsi
INSERM U987, Centre d'Evaluation et de Traitement de la Douleur, Hôpital Ambroise Paré, Boulogne-Billancourt, France.
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Adam
INSERM U987, Centre d'Evaluation et de Traitement de la Douleur, Hôpital Ambroise Paré, Boulogne-Billancourt, France.|Université Versailles-Saint-Quentin, Versailles, France.
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Bouhassira
D000328:Adult; D001833:Body Temperature Regulation / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D065812:Interoception / Q000502:physiology*; D008297:Male; D058748:Pain Perception / Q000502:physiology*; D013697:Thermosensing / Q000502:physiology*; D055815:Young Adult