Selective regulation of pain affect following activation of the opioid anterior cingulate cortex system.
Morphine and surgical cingulotomy, or transection of the anterior cingulate cortex (ACC), provides relief of chronic pain by selectively decreasing the affective dimension of the condition without altering sensory processing. Clinical reports suggest that morphine might be acting at the level of the ACC to alter the complex experience of pain. Therefore, the purpose of this experiment was to directly examine the functional role of the ACC in processing the aversive nature of pain induced by ligation of the L5 spinal nerve. Systemic administration of low dose morphine produced a selective attenuation of pain affect, as indicated by a decrease in the aversiveness of noxious cutaneous stimulation in nerve-damaged animals, with no alteration of mechanical paw withdrawal threshold. Supraspinally, microinjection of morphine into the ACC produced a selective naloxone reversible reduction in pain affect, as indicated by a decrease in the aversiveness of noxious cutaneous stimulation in nerve-damaged animals, with no alteration of response to mechanical stimulation. These data demonstrate the central role of the ACC opioid system in selectively processing the aversive quality of noxious mechanical stimulation in animals with a persistent pain condition.
The University of Texas at Arlington, Department of Psychology, Box 19528, Arlington, TX 76019, USA. sc1001@dental.umaryland.edu
Stacey C
SC
LaGraize
Jasenka
J
Borzan
Yuan Bo
YB
Peng
Perry N
PN
Fuchs
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D002540:Cerebral Cortex / Q000502:physiology; D004723:Endorphins / Q000502:physiology*; D004924:Escape Reaction / Q000187:drug effects; D006179:Gyrus Cinguli / Q000502:physiology*; D008297:Male; D008845:Microinjections; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement / Q000187:drug effects; D010523:Peripheral Nervous System Diseases / Q000503:physiopathology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000502:physiology*
D004723:Endorphins; D009292:Narcotic Antagonists; D011957:Receptors, Opioid; D009270:Naloxone; D009020:Morphine