Involvement Of μ‐Opioid Receptors Of Ventral pallidum In Morphine Conditioned Place Preference

TL;DRAbstract

The effects of repeated bilateral intra‐vp injections of different doses of morphine on the acquisition of morphine‐induced cpp in rats were investigated using an unbiased 3‐days schedule of place conditioning. Animals receiving once‐daily subcutaneous (s.c.) injections of morphine (0.5,2.5,5,or 7.5mg/kg) or saline (1.0ml/kg,s.c.) showed a significant place preference in a dose‐dependent manner. The maximum response was observed with 5 mg/kg morphine. Three days intra‐vp injections of morphine (1,3 or 5 microg/rat) followed by 5 days free of the drug, significantly elicited morphine‐induced place preference in combination with an ineffective dose of morphine (0.5mg/kg,s.c.). Moreover, pre‐treatment with the different doses of naloxone (0.5,1, or 2mg/kg,i.p.) reversed the morphine (5microg/rat) response on the acquisition of morphine (0.5mg/kg) cpp. On the other hand, our results showed that three days intraperitoneal injections of different doses of naloxone (0.5,1 or 2mg/kg) followed

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