Abstract
SummaryOur rudimentary knowledge about rat intraspecific vocal system of information exchange is limited by experimental models of communication. Rats emit 50-kHz ultrasonic vocalizations in appetitive states and 22-kHz ones in aversive states. Both affective states influence heart rate. We propose a behavioral model employing exposure to pre-recorded playbacks in home-cage-like conditions. Fifty-kHz playbacks elicited the most vocalizations (>60 calls per minute, mostly of 50-kHz type), increased heart rate, and locomotor activity. In contrast, 22-kHz playback led to abrupt decrease in heart rate and locomotor activity. Observed effects were more pronounced in singly housed rats compared with the paired housed group; they were stronger when evoked by natural playback than by corresponding artificial tones. Finally, we also observed correlations between the number of vocalizations, heart rate levels, and locomotor activity. The correlations were especially strong in response to 50-kHz playback.
Highlights
Ultrasonic vocalizations (USV) of adult rats are divided into two main categories: 22-kHz and 50-kHz USV
Except for the Periods of Ultrasonic Playback, Rats’ Behavior Remained Relatively Constant Locomotor activity, measured as distance traveled, was the same during the 10-min silence period (Figure 1A) at an average speed of 2 cm/s (Figures 2A and 2B; Tables S1A and S3), which declined during the playback session to 1 cm/s (Figures 3A, 3C, 3E, and 3G)
There Were Correlations between the Distance Traveled, Number of Vocalizations, and Heart Rate Changes we investigated the correlations between selected categories of Heart rate (HR) levels, USV emissions, distance traveled, and time spent near the speaker (Data S1)
Summary
Ultrasonic vocalizations (USV) of adult rats are divided into two main categories: 22-kHz and 50-kHz USV The former usually accompany aversive situations (fear, anxiety, social aggression, predator scent/presence, unfamiliar humans, air-puff). Playback studies, i.e. with the presentation of recorded or prepared calls, can offer some simplification by replacing one of the animals with a speaker They proved not to be effective to evoke USV emissions (White and Barfield, 1989; White et al, 1993; Wohr and Schwarting, 2007, 2009; Sadananda et al, 2008; Berg et al, 2018). We wanted to first verify whether rats, under low stress experimental conditions, would vocalize to pre-recorded USV played from a speaker
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