Animal models of drug abuse show emotional regulation of motivated behaviors
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Intense craving for a drug is a critical feature of addiction and a strong trigger for drug use and relapse. Though positive and negative affective states in rodents can be monitored in real-time through ultrasonic vocalization (USV) emissions, few animal studies have determined the role of emotional status as a motivational factor for abuse of drugs other than psychostimulants. Our laboratory has recently developed reliable, high-speed analysis techniques (WAAVES) to compile USV counts and acoustic characteristics during morphine self-administration sessions. We found that while chronic and intermittent morphine access showed comparable levels of locomotor activity throughout all morphine self-administration, intermittent access induced a significantly higher proportion of frequency-modulated (FM) USVs during and before these sessions. We then used WAAVES to analyze USVs in male selectively-bred high-alcohol-drinking (HAD-1) rats during an alcohol drinking paradigm called drinking-in-the-dark (DID). USVs were analyzed for daily 7-hours sessions across 8 weeks. The findings revealed that male HAD-1 rats have a baseline negative affect that is enhanced by alcohol intake. Additionally, we found that the mean frequency of both positive and negative affect USVs was decreased by ethanol consumption. The final study in this dissertation examined USVs before, during, and after drinking in both male and female HAD-1 rats. We found that male HAD-1 rats had a higher proportion of negative-affect USVs relative to positive-affect USVs than female HAD-1 rats, regardless of EtOH experience. However, within-groups analyses revealed that EtOH did increase negative affect relative to the animals’ baseline affect. Furthermore, female HAD-1 rats had an elevated negative affect that persisted after alcohol drinking. This effect was not observed in Control animals.