Drugs of Abuse Craving in Free-Choice Experimental Conditions
Given that the techniques used to test drug abuse liability are not free from criticism, a series of oral free-choice experimental procedures was adopted. Firstly, to rats water-deprived for 23h, a choice between pure and fentanyl citrate (5µg/ml) or buprenorphine (25 µg/m1) or etonitazene HC1 (5µg/ml), a very potent µ-opiate, containing aspartame solution, adopted as very potent sweetener, was daily offered. Even if behavioural effects were evident and exhibited tolerance and dependence, no preference was shown. In a second procedure, when the same free-choice was allowed for 24h, no evident behavioural effects and no preference for etonitazene or a stimulant drug, cocaine HCL (300 µg/ml), were detected. However, it was possible to select a group of etonitazene preferring rats. When etonitazene was offered in a free-choice only 1 day over 3, rats exhibited preference versus etonitazene even if evident behavioural effects were absent. Finally, when a gustatory marker (100 µg/ml) was introduced into one of the two solutions, using 1 or 24h schedule, and adopting etonitazene or morphine (500 µg/ml), preference was always shown for the less bitter solution.
KeywordsWithdrawal Syndrome Fentanyl Citrate Drinking Session Morphine Dependence Precipitate Withdrawal
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