J Korean Soc Study Obes 1998; 7(4): 296-308
Published online December 30, 1998
Copyright © Korean Society for the Study of Obesity.
Tai Hee Lee, Min Young Chung, Dong Jin Chung, Byung-ju Park1, Toshimasa Osaka2, Akiko Kobayashi2, Shuji Inoue2, Shuichi Kimura2
Department of Internal medicine and Biochemistry, Chonnam National University, Medical School and college of Dentistry Kwangju, Korea1, National Institute of Health and Nutrition, Japan2
We examined the function of putative sensory fibers that are contained in intercostal nerves and innervate interscapular brown adipose tissue(IBAT) in urethane-anesthetized rats. Warming of the IBAT to 40~44℃ by use of two small heaters placed bilaterally on the skin above the IBAT attenuated the subsequent noradrenaline-induced thermogenesis(NIT) of the IBAT. In this range of warming, higher IBAT temperatures resulted in more attenuation. Denervation of IBAT blocked the effect of thermal stimulation on the NIT. Thus, activation of warm-sensitive or heat-nociceptive nerve fiber in the IBAT contain calcitonin gene-related peptide(CGRP) and substance P, which are considered to exert actions in the peripheral tissue, we tested the effect of injection of these neuropeptides into the IBAT. Administration of 5.2nmol CGRP but not substance P or vehicle saline mimicked the effect of thermal stimulation of IBAT. Because the neuropeptide-containing primary sensory neurons are characterized by their sensitivity to capsaicin, we also tested the effects of capsaicin(1mg/kg, s.c.) administration and found that it also attenuated the NIT. Denervation of the IBAT or pretreatment with capsazepine, a capsaicin receptor antagonist, blocked the effect of capsaicin. We propose that temperature-and capsaicin-sensitive nerve fibers release CGRP to attenuate the NIT of brown adipocytes.
Keywords: Heat nociceptor, Thermosensitive fiber, Brown adipose tissue, Noradrenaline, Calcitonin gene-related peptide, Temperature regulation