Maintenance of arterial pressure in infant rats during moderate and extreme thermal challenge

Abstract

It has recently been demonstrated in week‐old rats that extreme cold challenges that lead to significant bodily cooling result in decreased cardiac rate. To determine whether pups are able to maintain arterial pressure in the face of decreasing cardiac rate in extreme cold, we measured blood pressure in unanesthetized week‐old rats. Instrumented pups were thermally challenged and thermoregulatory and cardiovascular responses were monitored. Despite pronounced decreases in cardiac rate in the cold, pups were able to maintain mean arterial pressure (MAP), presumably by increasing peripheral resistance. At the lowest air temperature (17°C) pups emitted ultrasonic vocalizations, and these emissions were accompanied by pulsatile increases in intraabdominal pressure (IAP) and MAP. We hypothesize that these pulsatile increases in IAP during extreme cooling reflect the use of the abdominal compression reaction to increase venous return during periods of diminished cardiac output. © 1998 John Wiley & Sons, Inc. Dev Psychobiol 32: 169–176, 1998

Thermoregulatory competence and behavioral expression in the young of altricial species?Revisited

“…More detailed experimental manipulations of air temperature supported this finding . Therefore, whether this vocalization is interpreted as a communicatory act designed to elicit maternal retrieval to the nest (e.g., Hofer & Shair, 1978) or as an acoustic byproduct of respiratory (Blumberg & Alberts, 1990) and/or cardiovascular (Kirby & Blumberg, 1998) maneuvers, the incidence of ultrasound production during extreme cooling, but not during moderate cooling, points out yet another qualitative difference between these two ranges of air temperature.…”

“…(adapted from Blumberg, Sokoloff, & Kirby, 1997). would in turn suggest that such pups are facing related hemodynamic difficulties such as decreased arterial blood pressure. But, when blood pressure was monitored from the descending abdominal aorta in weekold pups during moderate and extreme cooling, no such decreases in blood pressure were detected (Kirby & Blumberg, 1998). As Table 1 shows, blood pressure is the one variable measured thus far that does not exhibit a change across the transition from moderate to extreme cold exposure.…”

Prairie vole pups show potentiated isolation‐induced vocalizations following isolation from their mother, but not their father

“…Communicatory functions of USV, which are almost by definition social, have been repeatedly demonstrated: calls by pups guide and elicit retrieval by their mothers (Bowers, Perez‐Pouchoulen, Edwards, & McCarthy, ; Brunelli, Shair, & Hofer, ; Ehret, ; Sewell, ). Although there have been attempts to attribute USV production to thermoregulatory (Blumberg & Alberts, ; Blumberg, Efimova, & Alberts, ; Blumberg & Sokoloff, ) and/or cardiovascular processes (Blumberg, Sokoloff, & Kent, ; Kirby & Blumberg, ; Kirby, Sokoloff, Perdomo, & Blumberg, ), these hypotheses have not been supported by direct tests (Hofer & Shair, ; Shair, Brunelli, Masmela, Boone, & Hofer, ; Shair & Jasper, ), and summarized in (Shair, ), except in the case of recovery from deep hypothermia (Hofer & Shair, ).…”

Group and individual regulation of physiology and behavior: A behavioral, thermographic, and acoustic study of mouse development

“…For instance, when a lactating mother rat or mouse detects a pup’s ultrasonic vocalizations (USVs), she exhibits behavioral arousal, orientation, approach [17–19] and typically retrieves it back to the nest [20]—an adaptive outcome for the pup. Within this context, infant USVs have been variously characterized as byproducts of thermogenic efforts [21] or other, temperature-dependent regulatory maneuvers [22–23], and as communicatory signals of isolation-induced emotional distress [24–26]. The observation that contact with other pups reduces USV production [27–28] can be claimed as evidence on either side of this debate.…”