Effects of 5-HT receptor stimulation on economic demand for fentanyl after intermittent and continuous access self-administration in male rats.

The relative value of and motivation for abused drugs often increases with drug experience and differs based on drug availability. Here, we determined how different intake patterns of fentanyl, a μ-opioid agonist, alter economic demand for fentanyl and how 5-HT receptor stimulation affects economic demand for fentanyl. We used a within-session demand threshold procedure to characterize changes in economic demand for fentanyl before and after intermittent or continuous access schedules.