Developmental differences in temporal patterns and potentiation of isolation‐induced ultrasonic vocalizations: Influence of temperature variables

Abstract

The present study examined the relationship between the thermal environment and core body temperature in producing age-related patterns of ultrasonic vocalizations (USVs). Implanted telemetry devices allowed on-line measurement of core body temperature during an extended period of isolation and after maternal contact, both as a function of age and thermal environment. At 12 or 17 days of age, rat pups were isolated for 30 min in either a cool or a warm environment, returned home for 5 min, and then re-isolated for 10 min. Number of USVs, body temperature, and behavioral activity were measured. During initial isolation in a cool environment, 12-day-olds displayed relatively stable patterns of ultrasounding and body temperature across time whereas older animals showed a time-dependent increase in USV calling and in core temperature. During re-isolation, 12-day-olds potentiated their USV calling at both ambient temperatures while 17-day-olds did not. The overall results suggest a strong dependence between USV calling, core body temperature, and ambient temperature during initial isolation at both ages-a finding in agreement with interpretations of USVs as an acoustic by-product of thermal challenge. In contrast, during re-isolation, USV calls, core body temperature, and ambient temperature functioned independently-a finding in agreement with interpretations of USVs as a representation of an emotional state.

Acquisition and expression of a socially mediated separation response

“…Thermal cues are not an essential factor in the elicitation of USV potentiation: potentiation will occur to an anesthetized dam with a very reduced body temperature or in a thermoneutral environment [43,61,93] …”

“…Thermal cues are not an essential factor in the elicitation of USV potentiation: potentiation will occur to an anesthetized dam with a very reduced body temperature or in a thermoneutral environment [43,61,93]. As potentiation can occur after contact with either an active or anesthetized (passive) dam, movement of the dam cannot be a necessary factor either [41,96].…”

“…Pups taken from the litter pile and placed in contact with their anesthetized dam in a novel cage will vocalize at a potentiated rate upon her removal [43], in comparison with littermates isolated directly in the novel cage (see Figure 6). Thermal cues are not an essential factor in the elicitation of USV potentiation: potentiation will occur to an anesthetized dam with a very reduced body temperature or in a thermoneutral environment [43,61,93] …”

“…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). A pup exposed to a littermate or several littermates (or home cage shavings which also elicit 'contact quieting') shows no such elevated response (Figure 2 Littermate) [17,42,61].…”

Differential effects of ethanol and midazolam upon the devaluation of an aversive memory in infant rats

“…Given these limitations, the measurement of ultrasonic vocalizations (USVs) in socially isolated infant rats has provided a useful and sensitive test for anxiolytic effects in early infancy. Rat pups emit USVs when placed in isolation from their dam and littermates (Kraebel et al, 2002) or when exposed to stressors such as low temperature (Blumberg and Alberts, 1990). These responses have been described as distress calls related to crying observed in other mammal species (Wilson and Insel, 1991) and are sensitive to several pharmacological manipulations.…”