Antagonism of orexin type 1 receptors in the locus coeruleus attenuates signs of naloxone-precipitated morphine withdrawal in rats

作者：Azizi Hossein; Mirnajafi Zadeh Javad; Rohampour Kambiz; Semnanian Saeed^*

来源：Neuroscience Letters, 2010, 482(3): 255-259.

DOI：10.1016/j.neulet.2010.07.050

• Orexin
• Orexin type 1 receptor
• Locus coeruleus
• Naloxone
• Morphine withdrawal

It has been shown that orexin neuropeptides contribute to morphine-induced physical dependence. The locus coeruleus (LC), which receives a dense extra-hypothalamic orexinergic projection, is a key brain region implicated in the expression of somatic signs of morphine withdrawal syndrome. The aim of the present study is to investigate the role of LC orexin type 1 receptors (OXR1) on naloxone-precipitated morphine withdrawal signs in rats. Adult male Wistar rats were rendered dependent on morphine by subcutaneous (s.c.) injection of morphine sulfate (10 mg/kg) at an interval of 12 h for 9 days. On day 10, naloxone (1 mg/kg i.p.) was injected 2 h after morphine administration. Somatic signs of withdrawal were then evaluated in a clear Plexiglas test chamber (30 cm diameter, 50 cm height) for 25 min. One group of animals received intra-LC SB-334867-A, a selective OXR1 antagonist, (100 mu M, 0.2 mu l) immediately before naloxone. In the control group, SB-334867-A vehicle was microinjected into the LC in the same manner. The results showed that intra-LC OXR1 receptor blockade significantly decreased the somatic signs of withdrawal including chewing, diarrhea, scratching, teeth chattering, wet-dog shake and ptosis. These results suggest that activation of OXR1 in the LC might be involved in the expression of withdrawal signs in morphine dependent rats.

• 出版日期2010-10-4