• Wei Xiong and Long-Chuan Yu.
• Laboratory of Neurobiology and The National Laboratory of Biomembrane and Membrane Biotechnology, College of Life Science, Peking University, Beijing 100871, China.
• Neurosci. Lett. 2006 May 15; 399 (1-2): 167-70.

AbstractIt is well known that there are three types of opioid receptors, mu- (MOR), delta- (DOR), and kappa-opioid receptor (KOR) in the central nervous system. The present study investigated the involvement of opioid receptors in morphine-induced antinociception in the nucleus accumbens (NAc) of rats. The hindpaw withdrawal latencies to thermal and mechanical stimulation increased markedly after intra-NAc administration of morphine. The antinociceptive effects induced by morphine were dose-dependently inhibited by intra-NAc administration of the non-selective opioid receptor antagonist naloxone. Furthermore, the morphine-induced antinociception was significantly attenuated by subsequent intra-NAc injection of the MOR antagonist beta-funaltrexamine or the KOR antagonist nor-binaltorphimine, but not the DOR antagonist naltrindole. The results indicate that MOR and KOR, but not DOR are involved in the morphine-induced antinociception in the NAc of rats.

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