Diffuse noxious inhibitory controls (DNICs): psychophysical evidence in man for intersegmental suppression of noxious heat perception by cold pressor pain

Abstract

Counterirritation, the phenomenon of one painful stimulus reducing pain caused by a second noxious stimulus, has been recognized clinically for decades. Recently a physiological mechanism to explain counterirritation was described and termed diffuse noxious inhibitory controls (DNICs). Nevertheless, few psychophysical studies have examined systematically the effects of a noxious conditioning stimulus on pain perception. The present study examined the perception of painful heat stimuli on the face before, during and after the subject submerged a hand in painfully cold water (5 degrees C) for 5 min (cold pressor pain). We found that the subjects' ratings of the heat stimuli were significantly, although not completely, reduced during the cold pressor pain; this attenuation of pain perception continued after the noxious conditioning stimulus was withdrawn. Similarly, the pain threshold was significantly increased from 45.7 degrees C to 47.3 degrees C while the hand was in cold water and this threshold remained elevated after the cold water was terminated. Since DNICs have been found to completely and selectively inhibit the activity of only one type of pain transmission neuron (wide dynamic range), our data suggest that these neurons are involved in the perception of pain intensity. However, the persistence of residual pain perception in the presence of noxious conditioning stimuli indicates the importance of other nociceptive pathways.

Effects of Acupuncture on Sensory Perception: A Systematic Review and Meta-Analysis

“…It also remains unclear to what extent the test stimuli might interfere with the treatment effect. For example, strong noxious stimulation is known to activate aspects of the endogenous pain-modulating network [129][130][131]; a phenomenon known as counter irritation. It is postulated that the main underlying mechanisms namely DNIC is also involved in the analgesic effect of acupuncture [98,[132][133][134].…”

Neurophysiological observation of the nociceptive system using electrocutaneous stimulation

“…The inter stimulus interval between two successive stimuli was randomly varied between 4 and 6 seconds. The inhibitory effect of the CPT can persist for 5-10 minutes after withdrawal of the hand [134]. Therefore, to be sure that there was no effect of CPT in a subsequent protocol we waited 15 minutes between the CPT and the control protocol and between the two blocks.…”

“…Time to hand withdrawal and re-immersion was recorded. Pain intensity and unpleasantness increases rapidly [169] and peaks in the first 20-45 seconds [134]. Therefore, electrical stimuli at the left fingertip were applied 30 seconds after hand immersion.…”

Psychophysical methods for improved observation of nociceptive processing

“…A 3-min cold pressor task was used as the nociceptive conditioning stimulus Talbot, Duncan, Bushnell, & Boyer, 1987). Subjects were asked to immerse their right hand up to the wrist in a polystyrene container filled with water and crushed ice (water temperature was between 0° and 3° Celsius).…”

“…Temporary changes in the nociceptive threshold can also be caused by an experimental perturbation (Chapter 2; . For example, the cold pressor test is widely used for inducing central changes in the nociceptive system to study endogenous inhibition Talbot, Duncan, Bushnell, & Boyer, 1987). During the cold pressor test, subjects immerse an extremity into cold water for a short period of time, which induces pain.…”