Photoperiod and pinealectomy do not affect cold-induced deposition of brown adipose tissue in the Long-Evans rat.
Brown adipose tissue is a major thermogenic effector of cold-induced nonshivering thermogenesis. Previous studies indicate that melatonin and/or short photoperiod are involved in the increase in brown fat deposition seen in certain cold-acclimated rodents. The present study was undertaken, in part, to determine whether the pineal is a necessary component in the cold-induced increase in thermogenic capacity characteristic of the cold-acclimated laboratory rat. Under a 12L:12D light cycle, pinealectomized rats did not differ from sham-operated rats in their ability to increase brown fat deposition in the cold (5 degrees C). Moreover, in a subsequent set of experiments performed at 9 degrees C, intact rats maintained at a short photoperiod (9L:15D) exhibited the same degree of brown fat hypertrophy/hyperplasia as did those kept at a long photoperiod (15L:9D). These data thus indicate that: (a) the intact pineal is not necessary for the cold-induced increase in brown adipose tissue occurring in the cold-acclimated rat; and (b) photoperiod does not significantly modulate the magnitude of this increase.
D002001:Adipose Tissue, Brown / Q000033:anatomy & histology* / Q000502:physiology; D000818:Animals; D001833:Body Temperature Regulation; D003080:Cold Temperature; D008027:Light; D008297:Male; D010507:Periodicity; D010870:Pineal Gland / Q000502:physiology*; D051381:Rats