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Investigating the Behavioural and Neurobiological Bases of a Morphine Occasion Setter

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Title: Investigating the Behavioural and Neurobiological Bases of a Morphine Occasion Setter
Author: Nolan, Caitlin J
Department: Department of Psychology
Program: Neuroscience
Advisor: Choleris, Elena
Abstract: Interoceptive stimuli elicited by drugs of abuse form associations with exteroceptive cues. Feature positive (FP) and feature negative (FN) occasion setters can disambiguate associations of exteroceptive conditioned stimuli and appetitive unconditioned stimuli. Here we investigate effect of this learning history on morphine reward. Male and female rats were assigned to FP or FN training, and received daily alternating morphine or saline injections before each training session. On morphine sessions, FP rats received white noise presentations that were followed by sucrose; sucrose was withheld on saline sessions. FN rats learned the opposite contingency. After discrimination, rats underwent place conditioning where morphine was paired with a distinctive context of a 2-sided chamber. In pairing sessions, rats received alternating morphine or saline injections. During test, rats had access to both sides with no injections. Regardless of training history, male rats spent more time on the morphine-paired side. In female rats, however, FN learning inhibited morphine reward. These data indicate that a history of occasion setting learning affects the rewarding value of morphine differently in male and female rats.
Date: 2022-04
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