European journal of pharmacology
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Clinical Trial Controlled Clinical Trial
Diffuse noxious inhibitory controls in man: involvement of an opioidergic link.
In man, heterotopic painful thermal conditioning stimuli induce parallel decreases in the spinal nociceptive flexion (RIII) reflex and the concurrent sensation of pain elicited by electrical stimulation of the sural nerve at the ankle. Such phenomena may be related to the diffuse noxious inhibitory controls (DNIC) which were initially described in the rat and subsequently documented in humans. In nine subjects in the present study, a 2-min application of a moderately noxious temperature (46 degrees C) to the contralateral hand strongly depressed the RIII reflex elicited in the biceps femoris muscle by electrical stimulation of the sural nerve at 1.2 times the reflex threshold. ⋯ During all the experimental sessions, heart and respiratory rates remained stable at their control levels. It is concluded that the loop subserving DNIC which ascends from--and redescends to--the spinal cord involves an opioidergic link in man as in experimental animals. Possible implications for hypoalgesia based on the principles of counter-irritation or elicited by naloxone are discussed.