Journal of Obesity & Metabolic Syndrome

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J Korean Soc Study Obes 1998; 7(4): 309-315

Published online December 30, 1998

Copyright © Korean Society for the Study of Obesity.

Effects of Capsaicin Analogue Reciniferatoxin on Thermoregulation in Rat

Tai Hee Lee1, Naoko Okane, Akiko Kobayashi, Toshimasa Osaka, Shuji Inoue

Department of Internal medicine1, Chonnam National University, Medical School, Kwangju, Korea, National Institute of Health and Nutrition, Tokyo, Japan

Abstract

We studied the effects of capsaicin analogue resiniferatoxin on thermoregulation in male Wistar rats. Between 90 minutes before subcutaneous injection of capsaicin(5mg/kg), and resiniferatoxin(50㎍/㎏, 3㎍/㎏) respectively in rats and 10 hours after it, we measured the temperatures of colon and skin every 5 minute and oxygen consumption every 10 minute. And we also measured the temperatures of colon and skin oxygen consumption in capsaicin-desensitized rats and in adrenal medulla-removed rats with the same method respectively. The results were as follows.
After capsaicin(5mg/kg s.c.) injection, oxygen consumption began to increase at 6 min, and reached to 17.2±0.4mL/min/㎏????, then slowly decreased. But oxygen consumptions were increased significantly till 400 minute. Temperatures of colon showed biphasic pattern(i.e., decreased to 35.5±0.3℃ at 40 min, thereafter increased slowly). Temperature of skin increased to 30.9±0.2℃ at 50 minute, and returned to basal level at 120 minute. In capsaicin-desensitized rats, oxygen consumption was not changed, and colonic temperature showed biphasic pattern; it decreased by 0.2℃ at 30 minute, then increased. Temperature of skin began to increase immediately after resiniferatoxin injection, reached to 30.38±0.45℃ at 50 minute. Then it decreased slowly, but maintained elevated level till 300 minute. Also oxygen consumption showed biphasic pattern. It reached to the peak level(12.8±0.5mL/min/㎏????) at 50 minute, then began to decrease. At 100 minute, it began to increase, and maintained elevated level till 300 minute. In resiniferatoxin(3㎍/㎏ s.c.)-injection group, the temperatures of colon and skin, and oxygen consumption began to change at 100 minute. These changes showed similar pattern with capsaicin(5mg/kg s.c.) injection group. In capsaicin-desensitized rats, significant change did not occur.
In adrenodemedullated rats, oxygen consumption decreased significantly and colonic temperature decreased by 0.7±0.2℃ compared to normal rats after capsaicin injection. After resiniferatoxin(50㎍/㎏) injection in adrenodemedullated rats, oxygen consumption reduced early-increasing response of biphasic response but did not change late-increasing response, the temperatures of colon and skin. After resiniferatoxin(3㎍/㎏) injection, it did not influence heat production.
These results suggest that the effect of resiniferatoxin on heat production does not depend merely on catecholamine, and the mechanism of resiniferatoxin-induced heat production are different from that of capsaicin-induced heat production.

Keywords: Resiniferatoxin, Capsaicin, Thermoregulation, Catecholamine, Adrenodemedullation