Rat pups reduce ultrasonic vocalization after exposure to an adult male rat

Abstract

We examined how the experience of a threatening stimulus alters subsequent behavior in a situation where the immediate threat is absent. A small huddle of 12-day-old rats was exposed to a potentially infanticidal adult male rat for 5 min. During male exposure, pups were significantly more immobile than control pups. Thirty, 60, and 180 min after male exposure, the pups were isolated for 5 min from litter and dam in an unfamiliar environment. When isolated, pups that had been previously exposed to the male emitted significantly fewer ultrasonic vocalizations than controls, but did not differ in immobility. Low levels of vocalization were apparent 30 and 60 min after male exposure and were not evident at 180 min. The pups seemed to have adjusted their behavior to a potential male threat in a different context for a limited period of time. ß

Acquisition and expression of a socially mediated separation response

“…It is well known that when 2-weekold, dam-reared pups are exposed to the presence or even the odor of an adult male rat, they exhibit a fear-related suppression of behavior that continues even after the male is removed including USV inhibition [95,105,111] (see Figure 2 Adult Male). This quieting response is presumed to have evolved due to selection pressure: young rats show similar responses to odors of predators [109]; adult male rats are known to practice infanticide [15,67].…”

“…Vocal rates in the third period validate differentiation of contact quieting and behavioral inhibition. Pups exposed to the adult male continue to suppress USV after the male is removed [95,111].The re-isolation period also demonstrates that the response of the pup to its dam differs from its reaction to a littermate. A brief interaction of an isolated pup with its anesthetized dam or another adult female causes maternal potentiation, the increase in USV rate in the subsequent isolation (Figure 2 Dam).…”

“…Vocal rates in the third period validate differentiation of contact quieting and behavioral inhibition. Pups exposed to the adult male continue to suppress USV after the male is removed [95,111].…”

Adaptations or pathologies? Long-term changes in brain and behavior after a single exposure to severe threat

“…If they had been exposed to a potentially infanticidal male before isolation, they suppressed vocalization for an hour but not 3 h after the male exposure. Suppression of vocalization might reduce the likelihood of attracting the male, but also the likelihood that the mother would find and retrieve them [69].…”

Acoustic alterations of ultrasonic vocalization in rat pups induced by perinatal hypothyroidism

“…The dam approaches the pups in response to their USVs, retrieves them, and returns them to the nest (Schwarting and Wöhr, 2012). In contrast to this, the pups suppress USVs upon contact with an unknown male adult rat (Takahashi, 1992;Shair et al, 1997;Wiedenmayer et al, 2003), possibly because adult male rats often attack and kill pups in order to mate with their dam (Hofer, 2010).…”