Individual behavioural predictors of amphetamine-induced emission of 50 kHz vocalization in rats

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HIGHLIGHTSMotivation (latency to approach reward) and tendency to emit USVs were studied.Approach latency and 50kHz USVs after saline predict AMPH-induced USV emission.Approach latency and saline 50kHz USVs represent distinct predictors for AMPH USVs.Without sensitization, AMPH selectively increased Trill subtype of USVs.Acute AMPH-induced 50kHz USVs show elevated average sound frequency.Measurement of ultrasonic vocalizations (USVs) produced by adult rats represents a highly useful index of emotional arousal. The associations found between 50kHz USV production and a variety of behavioural and pharmacological protocols increasingly suggests they serve as a marker of positive motivational states. This study used a powerful within-subjects design to investigate the relationships among individual differences in approach to a sweet-food reward, predisposition to emit 50kHz USVs spontaneously, and 50kHz USVs emission following acute systemic administration of amphetamine. Both approach motivation and predisposition to call were found to not correlate with each other but did predict 50kHz USV response to acute amphetamine. These two behavioural phenotypes appear to represent dissociable predictors of acute amphetamine-induced emission of 50kHz USVs in a non-sensitization paradigm. In contrast to that, a measure of sucrose preference was not found to predict 50kHz USV emission following amphetamine. Acute amphetamine was also found to increase average sound frequency of emitted USVs and selectively increase the proportion of Trill subtype 50kHz USVs. Together, these data demonstrate that acute amphetamine-induced 50kHz USVs in the adult rat represent more than just a univariate motivational state and may represent the product of dissociable subsystems of emotional behavior.

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