While animals and humans reliably self-administer drugs of abuse, the motivations underlying drug use are not understood. Human cocaine users retrospectively self-report both positive and negative affective states as potent precipitating factors for returned drug use. In laboratory animals it has been difficult to ascertain affective state during cocaine self-administration. For example, a rat that has experienced abstinence after cocaine self-administration might be responding to relieve withdrawal surrounding a negative affective state, or to obtain the positively reinforcing effects of the drug. Over the last fifteen years, the hypothesis that the affective states of rodents can be reliably indexed through ultrasonic vocalizations (USVs) has received much support;50-kHz USVs and 22-kHz USVs are consistently correlated with indices of positive and negative affective states, respectively, in adult rats in a variety of experimental paradigms. However, rodent USVs have not been reported during drug-seeking behavior. In order to assess affective state using an animal model of drug-seeking and relapse, we will record USVs of adult rats during cocaine self-administration and reinstatement behavior. Detailed video analyses will be utilized to determine the behaviors occurring during USV production. Furthermore, infusion of dopamine or acetylcholine into nucleus accumbens (NAcc) shell or core, respectively, unconditionally elicits USVs in rats, implicating a key structure in drug abuse in the production of USVs. Therefore, we will record NAcc core and medial shell neurons during self- administration, withdrawal, and reinstatement behavior, concurrently with USV recordings. Preliminary results of USV recordings during cocaine self-administration revealed a high prevalence of 22-kHz calls typically associated with negative affect, perhaps providing novel support for the hypothesis that one mechanism by which cocaine-seeking behavior occurs is through relief of negative affect by negative reinforcement. However, because our preliminary results were derived from a cocaine self-administration schedule of reinforcement that prevented drug 'satiety', we will also examine differences in USV production using a higher dose of cocaine that allows rats to attain drug satiety, to test whether this reduces the proportion of 22-kHz calls or increases the proportion of 50- kHz calls. These data may provide novel insight into the role of affect in various drug-seeking behaviors as well as the potential involvement of NAcc subregions during these processes.
Complex affective and motivational factors are involved in substance abuse. Animal models provide substantial insight into drug abuse, in terms of behavioral, pharmacological, neurochemical, neuroanatomical and neurophysiological measures obtained. Animal drug abuse literature lacks a description of animal ultrasonic vocalizations (USVs), which have been demonstrated to signal different affective states. Virtually all the above measures obtained in animal models of drug abuse could be enhanced if they were coupled to corresponding USVs signaling affective state. Indeed, USV production is linked primarily to a neural structure heavily implicated in drug abuse: the nucleus accumbens. Proposed experiments will explore the relationships of USVs and accumbens firing patterns during cocaine self-administration, withdrawal, tests of cocaine cue reactivity, and relapse. Results could enlighten interpretations 1) of what animals may be processing during what are considered """"""""drug seeking"""""""" behaviors, and 2) of potential affective correlates of neurophysiological activity.
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