Pain facilitatory circuits in the mammalian central nervous system: their behavioral significance and role in morphine analgesic tolerance.
Sensitivity to noxious stimulation is not invariant; rather, it is modulated by discrete pain inhibitory and facilitatory circuits. This paper reviews the neural circuits for pain facilitation, describes the conditions governing their environmental activation, and examines their role in an animal's behavioral repertoire. Mechanisms for pain facilitation are contrasted at both the neural and behavioral level with mechanisms for pain inhibition. In addition, the involvement of mechanisms for pain facilitation in morphine analgesic tolerance is discussed, and the implications of this involvement for accounts of the role of associative processes in analgesic tolerance are highlighted.
McNally
G P
GP
Mental Health Research Institute, University of Michigan, Ann Arbor 48109-0720, USA. gavanm@umich.edu
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001519:Behavior / Q000187:drug effects*; D001522:Behavior, Animal / Q000187:drug effects*; D002490:Central Nervous System / Q000503:physiopathology*; D004361:Drug Tolerance; D006801:Humans; D009020:Morphine / Q000494:pharmacology*; D009415:Nerve Net / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology*
D000701:Analgesics, Opioid; D009020:Morphine