Effect of delay on self-administration of remifentanil under a drug versus drug choice procedure in rhesus monkeys.
Abstract Rationale. The stimuli associated with drug reinforcement may be particularly relevant to drug abuse and relapse. Objectives. The study measured behavior maintained by conditioned reinforcing stimuli in an observing response procedure. Methods. The experiment was conducted with rhesus monkeys in three stages: 1) discriminative control was established by reinforcing responding on one lever with either intravenous cocaine or remifentanil in the presence of one stimulus and extinguishing the response in the presence of another stimulus, 2) discriminative control was suspended by not presenting the stimuli, and 3) a final stage was implemented wherein the stimuli from the first stage were presented only when one or more responses were made on a second (observing) lever. Results. Under FR1 conditions, observing responses were maintained at low rates, but increased markedly when the response requirement was increased. Conclusions. The procedure maintained observing responses quite well and may be useful to an analysis of conditioned reinforcement based on drug reinforcement.