Role of repeated exposure to morphine in determining its affective properties: place and taste conditioning studies in rats
- Cite this article as:
- Gaiardi, M., Bartoletti, M., Bacchi, A. et al. Psychopharmacology (1991) 103: 183. doi:10.1007/BF02244201
- 58 Downloads
Male Sprague Dawley rats were injected daily with saline (morphine naive rats) or 20 mg/kg morphine (morphine experienced rats), starting at least 12 days before training. Subsequent place and taste conditioning indicated that 2.5 mg/kg morphine caused a significant increase in the amount of time spent on the least preferred side by morphine experienced but not by morphine naive rats; furthermore, saccharin consumption was markedly decreased and slightly increased by 10–20 mg/kg morphine in naive and experienced rats, respectively. It was concluded that morphine experience enhances the reinforcing efficacy of morphine and broadens the conditions under which the drug is reinforcing; thus it possibly increases morphine abuse potential.