Thermogenesis, myoclonic twitching, and ultrasonic vocalization in neonatal rats during moderate and extreme cold exposure.
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 < or = air temperature < or = 32.5 degrees C), pups at both ages increased heat production, maintained an elevated interscapular temperature, and maintained baseline levels of myoclonic twitching, a behavior commonly associated with active sleep. During extreme cold exposure (21 degrees C < or = air temperature < or = 25 degrees C), pups at both ages continued producing metabolic heat, but now exhibited pronounced decreases in interscapular temperature and decreased rates of myoclonic twitching. Furthermore, the 7-8-day-old pups exhibited significant increases in ultrasound production, and males vocalized more than females. These results suggest the presence of a narrow subthermoneutral zone in neonates in which nonshivering thermogenesis is regulated and sleep-related behaviors are protected.
Blumberg
M S
MS
Department of Psychology, University of Iowa, Iowa City 52242, USA. mark-blumberg@uiowa.edu
Stolba
M A
MA
D000064:Acclimatization / Q000502:physiology*; D002001:Adipose Tissue, Brown / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001833:Body Temperature Regulation / Q000502:physiology*; D005260:Female; D008297:Male; D009043:Motor Activity / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012768:Shivering / Q000502:physiology; D012894:Sleep Stages / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology*