Mesolimbic dopamine drives the diurnal variation in opiate-induced feeding.
Pharmacology Biochemistry and Behavior. 2005-07-01; 81(3): 569-574
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Barbano MF(1), Stinus L, Cador M, Ahmed SH.
(1)Laboratoire de Neuropsychobiologie des Désadaptations, Centre National de la Recherche Scientifique, UMR 5541, Université Victor Segalen Bordeaux 2 – 146, rue Léo Saignat, BP 31, 33076 Bordeaux Cedex, France.
Brain opioid peptides modulate feeding behavior and opiate drugs have powerful
orexigenic effects in mammals. Recent studies have shown that opiate-induced
eating depends, though not exclusively, on mu-opioid receptors located in the
ventral striatum. Here we report that morphine orexigenic effects vary with the
time of day according to a biphasic pattern. The effects first increase and then
decrease during the light phase, with the peak effect occurring in the middle of
this phase. This diurnal profile is shifted toward the dark phase after dopamine
deafferentation of the ventral striatum. Consequently, the peak effect of
morphine is delayed and occurs just before the dark phase. This finding suggests
that mesolimbic dopamine transmission contributes to the neural mechanisms that
normally drive the circadian timing of opioid-dependent feeding.