Pharmacological dissection of the paradoxical pain induced by a thermal grill

Abstract

. Pharmacological dissection of the paradoxical pain induced by a thermal grill.. PAIN, Elsevier, 2008, 135 (3), pp.291-9.

Effects of morphine on the experimental illusion of pain produced by a thermal grill

“…Our findings complement our previous pharmacological study showing that TGIP can be selectively modified by a low dose of the NMDA receptor antagonist, ketamine 22 . In contrast, the morphine-induced reduction in paradoxical pain was associated with a reduction of normal pain.…”

“…This phenomenon, also called the "thermal grill illusion of pain" (TGIP), was described more than a century ago by Thunberg 29 and characterised during the first part of the XXth century 3 . It has been reinvestigated recently using modern techniques because of its potential value for studying pain mechanisms and the interactions between nociceptive and thermal sensory systems 4,8,11,17,19,22,25 . Painful sensation evoked by normally non-painful stimuli is reminiscent of thermal allodynia often observed in pathological conditions; thus, the investigation of TGIP may also have clinical implications.…”

“…Recent studies demonstrated that stimulation with a thermal grill, with temperatures well below the heat and cold pain thresholds, is capable of producing a painful burning sensation in a large proportion of healthy volunteers 4,8,22,25 , although a subpopulation (25-30%) of subjects are less responsive 4,22 . Additionally, the occurrence and intensity of paradoxical pain was directly related to the magnitude of the difference in temperature between the warm and cold bars of the grill 4 .…”

“…We recently demonstrated for the first time that the thermal grill paradoxical pain could be modified pharmacologically 22 . We showed that intravenous injection of a low (sub-anaesthetic) dose of ketamine selectively reduced the intensity of the paradoxical pain, without affecting normal thermal (heat and cold) painful or nonpainful sensations.…”

Human Experimental Pain Models for Assessing the Therapeutic Efficacy of Analgesic Drugs

“…Ketamine was not significantly different from placebo in affecting this response (Niesters et al, 2011). A trial applying the "thermal grill" found that ketamine reduced the "paradoxical pain" but not the normal heat pain sensations and nonpainful heat sensations (Kern et al, 2008).…”