Isolation‐induced ultrasonic vocalizations in pups: A comparison between Long‐Evans, Sprague–Dawley, and Wistar rats

Abstract

Rat pup ultrasonic vocalizations (USV) are usually studied in outbred rats belonging to either Long-Evans, Sprague-Dawley, or Wistar stocks, but these were not compared so far. We therefore performed a stock comparison and analyzed USV of male pups (postnatal day 11) belonging to these three stocks. Pups of all three stocks showed substantial isolation-induced USV, but differed in various call features, like call numbers, peak frequency, and frequency modulation. Also, three different call types were identified by means of a quantitative approach based on peak frequency and frequency modulation, and it was found that their proportions differed between stocks. These results are discussed with respect to functional aspects of pup USV.

Early Life Maternal Separation and Maternal Behaviour Modulate Acoustic Characteristics of Rat Pup Ultrasonic Vocalizations

“…To our knowledge only two studies characterized acoustic characteristics of isolation USVs in normally reared Sprague Dawley pups into types distinguished by frequency 16,26 . In a comparative study of the three most widely used outbred strains (Wistar, Long Evans, and Sprague Dawley), Wöhr and Schwarting tested PND11 pups during a single ten minute isolation, then classified the calls into three clusters by frequency and frequency modulation 16 . Calls classified as Type 1 and 2 in their study resemble the low and high frequency calls described here, but they further classified low frequency calls (~39.6 kHz) into a third class that had large frequency modulation (called Type 3).…”

“…Given that our maternal behaviour observations did not distinguish among pups within the litter, we are limited to speculating that males are more likely to reflect effects of maternal care on USVs. A recent series of studies examining strain differences between the three most common inbred rat strains found that peak frequencies and the proportion of low/high frequency isolation-induced USVs were conserved between the sexes in unrelated male and female Sprague Dawley rat pups 16,45 .…”

“…Second, while it was initially believed that pup vocalizations were limited to 40-kHz calls 8 , later studies showed that isolation calls range from 5–120 kHz, but seem to concentrate around two frequency ranges, 35–40 kHz and 50–70 kHz 8,9,15 . USV calls can be additionally discriminated by duration: on average, low frequency calls are longer and higher frequency calls are shorter 9,10,16 . In a small study in Long Evans rat pups, the number of low frequency (40-kHz) calls increased upon a single exposure to rough maternal behaviour, while high frequency (66-kHz) calls were unaffected 9 .…”

Biological Functions of Rat Ultrasonic Vocalizations, Arousal Mechanisms, and Call Initiation

“…This pattern of emitting vocalizations could appear by the natural vocal selection that was demonstrated in infant rats [ 35 ]. Although there are some differences in the number of emitted calls, peak frequency, and frequency modulation among male and female pups of the main laboratory strains of Wistars, Long–Evans, and Sprague Dawley rats [ 36 , 37 ], the principle of locating the calling pup remains the same.…”

An Immune Rat Model of Autism: Does Environmental Enrichment Alter Higher Social Functioning?

“…A very recent study that used the same poly I:C treatment (5 mg/kg on GD 15) as was used in the present study also found that poly I:C animals called less but that the call duration did not differ between treatment groups (Potasiewicz et al, 2020). Further, SD rat pups produce fewer calls and spend less time calling than Long Evans and Wistar rats (Schwarting & Wöhr, 2018). Also, in rat pups, the number of calls is more affected by the stress caused by maternal separation than other call features like call duration (Stark et al, 2020).…”