Pain in a balance: noxious events engage opposing processes that concurrently modulate nociceptive reactivity.
Studies have shown that noxious cutaneous stimulation engages physiologically different antinociceptive systems to inhibit a spinal reflex, tail withdrawal from radiant heat. Two experiments are reported that examine the relationship between the inhibition of the tail-flick response and brain-mediated responses to nociception. The induction of a spinally mediated antinociception was accompanied by an increase in latency to vocalize to a noxious thermal stimulus, suggesting pain inhibition. Physiological manipulations that eliminated the inhibition of the tail-flick reflex restored vocalization to thermal stimulation and revealed a concurrent sensitization that generally heightened behavioral reactivity. The results suggest that net pain is regulated by 2 opposing processes, a selective inhibition of nociceptive signals within the spinal cord and a general sensitization that heightens stimulus processing.
Crown
Eric D
ED
Department of Psychology, Texas A&M University, USA. ercrown@utmb.edu
Grau
James W
JW
Meagher
Mary W
MW
D000344:Afferent Pathways / Q000187:drug effects; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D004597:Electroshock / Q000009:adverse effects; D008297:Male; D009271:Naltrexone / Q000008:administration & dosage; D009292:Narcotic Antagonists; D009433:Neural Inhibition / Q000502:physiology*; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000503:physiopathology* / Q000517:prevention & control; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000502:physiology*; D010812:Physical Stimulation / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013116:Spinal Cord / Q000503:physiopathology*; D014828:Vocalization, Animal / Q000187:drug effects / Q000502:physiology
D009292:Narcotic Antagonists; D009271:Naltrexone