Response Calls Evoked by Playback of Natural 50-kHz Ultrasonic Vocalizations in Rats

Abstract

Rats are highly social animals known to communicate with ultrasonic vocalizations (USV) of different frequencies. Calls around 50 kHz are thought to represent a positive affective state, whereas calls around 22 kHz are believed to serve as alarm or distress calls. During playback of natural 50-kHz USV, rats show a reliable and strong social approach response toward the sound source. While this response has been studied in great detail in numerous publications, little is known about the emission of USV in response to natural 50-kHz USV playback. To close this gap, we capitalized on three data sets previously obtained and analyzed USV evoked by natural 50-kHz USV playback in male juvenile rats. We compared different rat stocks, namely Wistar (WI) and Sprague-Dawley (SD) and investigated the pharmacological treatment with the dopaminergic D2 receptor antagonist haloperidol. These response calls were found to vary broadly inter-individually in numbers, mean peak frequencies, durations and frequency modulations. Despite the large variability, the results showed no major differences between experimental conditions regarding call likelihood or call parameters, representing a robust phenomenon. However, most response calls had clearly lower frequencies and were longer than typical 50-kHz calls, i.e., around 30 kHz and lasting generally around 0.3 s. These calls resemble aversive 22-kHz USV of adult rats but were of higher frequencies and shorter durations. Moreover, blockade of dopamine D2 receptors did not substantially affect the emission of response calls suggesting that they are not dependent on the D2 receptor function. Taken together, this study provides a detailed analysis of response calls toward playback of 50-kHz USV in juvenile WI and SD rats. This includes calls representing 50-kHz USV, but mostly calls with lower frequencies that are not clearly categorizable within the so far known two main groups of USV in adult rats. We discuss the possible functions of these response calls addressing their communicative functions like contact or appeasing calls, and whether they may reflect a state of frustration. In future studies, response calls might also serve as a new read-out in rat models for neuropsychiatric disorders, where acoustic communication is impaired, such as autism spectrum disorder.

Hearing, touching, and multisensory integration during mate choice

“…USVs in rats have been classified into pleasure or reward calls that occur in the 50 kHz range (Wöhr, 2018 ; Berz et al, 2022 ) and alarm or fear calls that are emitted in the 20 kHz range (Lenell et al, 2021 ). Similar to mice, rat calls contain information about dominance status (Xiao et al, 2004 ; Portfors, 2007 ) and genetic background (Sales, 1979 ), results that have been recently confirmed (Bogacki-Rychlik et al, 2021 ; Berz et al, 2022 ). Interestingly vocalizations may signal sickness in rats as well (Kirsten et al, 2015 ).…”

Gestational hypoxia in late pregnancy differentially programs subcortical brain maturation in male and female rat offspring

“…Ultrasonic vocalizations (USVs) are dependent on multiple brain maturation domains, especially a functional nigrostriatal pathway in the brain [34][35][36]. USVs are calls emitted by rodents to other rodents to relay information [37][38][39]. They are innate behaviors and not learned [40,41].…”

Tickle contagion in the rat somatosensory cortex

“…out of tickling. Playback of 50-kHz USVs is reported to induce response calls, 52 social approach, 53 and increased c-fos expression in the frontal cortex and the nucleus accumbens. 54 Whereas our audio playback experiment did not induce observer’s response, USVs emitted by the live demonstrator out of tickling led to USV emission ( Figure 1 K) and activation of trunk somatosensory cortex ( Figure 5 ) in the observer animals.…”