G. Sokoloff et Ms. Blumberg, THERMOGENIC, RESPIRATORY, AND ULTRASONIC RESPONSES OF WEEK-OLD RATS ACROSS THE TRANSITION FROM MODERATE TO EXTREME COLD-EXPOSURE, Developmental psychobiology, 30(3), 1997, pp. 181-194
Previously, it was reported that week-old rats exposed to air temperat
ures that elicited submaximal levels of heat production (designated mo
derate cold exposure) remained asleep and did not vocalize (Blumberg &
Stolba, 1996). In contrast, pups exposed to air temperatures that eli
cited maximal levels of heat production (designated extreme cold expos
ure) woke rip and emitted ultrasonic vocalizations. We now report on t
he physiological and behavioral responses of pups in the transitional
region between moderate and extreme air temperatures. Small decreases
in air temperature across the transition resulted in pronounced decrea
ses in physiological temperature and concomitant increases in ultrasou
nd production. In a second experiment, it was shown that during modera
te cold exposure respiratory frequency increased as air temperature de
creased but, as extreme air temperatures were reached respiratory freq
uency was maximized as ultrasound production began. The results from t
hese two experiments illustrate how air temperatures that differ by as
little as 2 degrees C can differentially modify the physiological and
behavioral responses of neonates. (C) 1997 John Wiley & Sons, Inc.