The aim of the present series of experiments was to outline the influence ofdifferent doses of cocaine during training, training schedule, training length andabstinence duration to modulate subsequent extinction and reinstatement patterns.Abram Amsel??s general theory of persistence were used to both design and explainvarious aspects of these models.For Experiment 1, rats self-administered cocaine (0.25, 0.50 or 1.00 mg/kg)intravenously and were then tested in an extinction preparation using saline infusions (5days) and then only the stimulus light as the reinforcer (3 days). Experiment 2 examinedschedules by magnitude interactions by training rats on two fixed-ratio (FR) schedules(FR-1 or FR-10 using either 0.25 or 1.00 mg/kg cocaine). Animals were tested in anextinction protocol (10 days; no stimulus light) and subsequently tested for reinstatement(1 day) that utilized presentations of the stimulus light. Experiment 3 addressed theeffects of training length (15 or 30 days of training using either 0.25 or 1.00 mg/kgcocaine) using the same protocol as in Experiment 2. Experiment 4 examined the modulation potential of two abstinence lengths (15 or 30 days using either 0.25 or 0.50mg/kg cocaine) using the same conditions as Experiment 2.Experiment 1 indicated the greatest resistance to extinction using the lowesttraining dose (0.25 mg/kg). The removal of saline caused an apparent extinction burstindicative of reward seeking. Experiment 2 showed that animals trained under partialreinforcement schedules persisted more during extinction. Furthermore, rats trainedusing 1.00 were more resistant than those trained with 0.25 mg/kg. Reinstatement ofdrug seeking was more pronounced in rats trained using an FR-10 schedule. Experiment3 indicated greater resistance to extinction in rats trained for 15 versus 30 days. Ratstrained on 0.50 mg/kg for 30 days showed less cue-induced reinstatement than thosetrained for 15 days. Experiment 4 showed increased resistance to extinction when ratswere trained on 0.25 mg/kg and forced to abstain for 30 versus 15 days. Directionallyopposite effects were apparent in groups trained with 0.50 mg/kg. Reinstatement dataindicated greater responsivity to cues by animals abstaining for 30 versus 15 days.
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