Ms. Blumberg et Ma. Stolba, THERMOGENESIS, MYOCLONIC TWITCHING, AND ULTRASONIC VOCALIZATION IN NEONATAL RATS DURING MODERATE AND EXTREME COLD-EXPOSURE, Behavioral neuroscience, 110(2), 1996, pp. 305-314
Physiological and behavioral responses of 2- and 7-8-day-old rats were
monitored during moderate and extreme cold exposure. During moderate
cold exposure (30 degrees C less than or equal to air temperature less
than or equal to 32.5 degrees C), pups at both ages increased heat pr
oduction, maintained an elevated interscapular temperature, and mainta
ined baseline levels of myoclonic twitching, a behavior commonly assoc
iated with active sleep. During extreme cold exposure (21 degrees C le
ss than or equal to air temperature less than or equal to 25 degrees C
), pups at both ages continued producing metabolic heat, but now exhib
ited pronounced decreases in interscapular temperature and decreased r
ates of myoclonic twitching. Furthermore, the 7-8-day-old pups exhibit
ed significant increases in ultrasound production, and males vocalized
more than females. These results suggest the presence of a narrow sub
thermoneutral zone in neonates in which nonshivering thermogenesis is
regulated and sleep-related behaviors are protected.