Involvement of endogenous cholecystokinin in tolerance to morphine antinociception in the nucleus accumbens of rats.
Cholecystokinin (CCK) is an endogenous anti-opioid peptide in the central nervous system. The present study investigated the effects of endogenous CCK on tolerance to morphine antinociception in the nucleus accumbens (NAc) of rats. Chronic administration of morphine to NAc induced marked tolerance to antinociception. Intra-NAc administration of the CCK2 receptor antagonist LY225910 inhibited not only the development but also the expression of chronic morphine-induced antinociceptive tolerance. However, intra-NAc injection of LY225910 did not influence the antinociception induced by intra-NAc administration of morphine in the intact rats. The results indicate that endogenous CCK plays an important role in morphine-induced antinociceptive tolerance in the NAc of rats.
Xiong
Wei
W
Laboratory of Neurobiology and The National Laboratory of Biomembrane and Membrane Biotechnology, College of Life Science, Peking University, Beijing 100871, China.
Yu
Long-Chuan
LC
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D002766:Cholecystokinin / Q000187:drug effects / Q000502:physiology*; D004361:Drug Tolerance / Q000502:physiology*; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D017288:Pain Threshold / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D000701:Analgesics, Opioid; D009020:Morphine; D002766:Cholecystokinin