A single brain stem substrate mediates the motivational effects of both opiates and food in nondeprived rats but not in deprived rats.
Drug-naive and morphine-dependent rats both preferred places paired with morphine over unfamiliar neutral places. Morphine-dependent, but not naive, rats avoided places paired with the lack of morphine (i.e., withdrawal). Food-sated and food-deprived rats both preferred places paired with food over unfamiliar neutral places. Food-deprived, but not sated, rats avoided places paired with the lack of food (i.e., hunger). Lesions of the tegmental pedunculopontine nucleus (TPP) blocked the morphine- and food-conditioned place preferences in drug-naive and food-sated rats, respectively. TPP lesions failed to block morphine- and food-conditioned place preferences as well as morphine withdrawal-conditioned and hunger-conditioned place aversions in morphine-dependent and food-deprived rats, respectively. These results suggest that separate neural mechanisms subserve deprivation- and non-deprivation-induced motivation.
Bechara
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A
Department of Anatomy, University of Toronto, Ontario, Canada.
van der Kooy
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D
D000818:Animals; D001070:Appetitive Behavior / Q000187:drug effects / Q000502:physiology; D001143:Arousal / Q000187:drug effects / Q000502:physiology*; D001245:Association Learning / Q000187:drug effects / Q000502:physiology; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology; D001931:Brain Mapping; D001933:Brain Stem / Q000187:drug effects / Q000502:physiology*; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D006815:Hunger / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009020:Morphine / Q000008:administration & dosage; D009042:Motivation; D011149:Pons / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*; D012931:Social Environment
D011957:Receptors, Opioid; D009020:Morphine