Phasic dopamine release in the nucleus accumbens in response to ultrasonic vocalizations serving a pro-social communicative function in rats

Abstract

Rats emit distinct types of ultrasonic vocalizations (USV), which serve as situation-dependent affective signals. Juvenile and adult rats produce 50-kHz USV in appetitive situations such as social play, whereas 22-kHz USVs occur in aversive situations like social defeat. While 50-kHz USV induce social approach in the recipient, supporting the notion that they serve as social contact calls, 22-kHz USV lead to freezing, indicating an alarming function. Opposite behavioral responses are paralleled by distinct brain activation patterns; with 22-kHz USV inducing activation in amygdala and periaqueductal gray, both involved in the regulation of anxiety and fear, whereas 50-kHz USV evoke neuronal activation in the nucleus accumbens (NAcc). The NAcc is strongly implicated in appetitive behavior, which is critically modulated by dopaminergic input that encodes reward and reward-predicting stimuli. Therefore, we hypothesized that NAcc dopamine signaling is involved in social approach towards pro-social 50-kHz USV and tested whether 50-kHz USV elicit phasic dopamine release in NAcc using fast-scan cyclic voltammetry. Our results show that phasic dopamine release occurs during playback of pro-social 50-kHz but not alarming 22-kHz USV. As 50-kHz USV emission depends on NAcc dopamine signaling, the NAcc may serve as the functional link between detection and production of 50-kHz USV, which is particularly relevant in social reciprocal communicatory signals. This study was supported by NIH grant R01-DA027858; DFG grant Schw 559/8 – 3.