Browsing by Author "Swain, Yayi"
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Item BEHAVIORAL PREDICTORS OF INDIVIDUAL DIFFERENCES IN OPIOID ADDICTION VULNERABILITY(2021-04) Swain, YayiUnderstanding behavioral predictors of individual differences in opioid addiction vulnerability could provide critical insights into the mechanisms underlying opioid addiction and could lead to more effective treatments. However, very few behavioral predictors of individual differences in opioid self-administration (SA), a key preclinical model of opioid addiction, have been established. The goal of this dissertation was to evaluate several potential behavioral predictors of individual differences in morphine SA in rats, and to establish novel methodologies for studying opioid addiction vulnerability using the SA paradigm. Study 1 showed that spontaneous locomotor activity in a novel environment, an animal model of sensation-seeking that predicts SA of several drugs of abuse (e.g., stimulants), did not predict individual differences in morphine SA. Study 2 found that greater severity of anhedonia-like behavior during withdrawal from acute morphine exposure (withdrawal-induced anhedonia, WIA) predicted subsequent lower acquisition, demand, and reinstatement of morphine SA. Study 3 showed the feasibility of using regularized factor analysis on morphine SA measures, and revealed that a common latent factor underlies four separate measures of morphine SA. Additionally, while acquisition, demand and morphine-induced reinstatement associated closely with the common latent Addiction factor, stress-induced reinstatement did not. Overall, these studies extended the opioid individual differences literature by establishing WIA as one of the first behavioral predictors of opioid SA, and also expanded the range of analytical tools to be utilized in preclinical behavioral studies.Item Locomotor activity does not predict individual differences in morphine self-administration in rats(2018-08) Swain, YayiUnderstanding factors contributing to individual differences in opioid addiction vulnerability is essential for developing more effective preventions and treatments. Sensation seeking has been implicated in addiction to several drugs of abuse, yet its relationship with individual differences in opioid addiction vulnerability has not been well established. The primary goal of this study was to evaluate the relationship between locomotor activity in a novel environment, a preclinical model of sensation-seeking, and individual differences in acquisition of i.v. morphine self-administration (SA) in rats. A secondary goal was to evaluate the relationship between activity and elasticity of demand (reinforcing efficacy) for morphine measured using a behavioral economic approach. Following an initial locomotor activity screen, animals were allowed to acquire morphine SA at a unit dose of 0.5 mg/kg/infusion in 4 hour/day sessions (Experiment 1) or 0.2 mg/kg/infusion in 2 hour/day sessions (Experiment 2) until infusion rates were stable. Unit price was subsequently manipulated via progressive reductions in unit dose (Experiment 1) or increases in response requirement per infusion (Experiment 2). Activity levels were not correlated with acquisition of morphine SA in either experiment. Morphine consumption was generally well described by an exponential demand function in both experiments (R2 values > 0.95 for rats as a group), but activity did not correlate with behavioral economic measures. Locomotor activity in a novel environment did not predict individual differences in acquisition of morphine SA. These data complement findings from some human studies and suggest that the role of sensation seeking in individual differences in opioid addiction vulnerability may be limited.