The effects of adrenodemedullation, propranolol and ruthenium red on thermoregulation by capsaicin analogue resiniferatoxin were studied in male Wistar rats.
Thermoregulation was observed by the measurements of oxygen consumption and temperature of colon and skin, simultaneously every 5 minutes for 300 minutes after subcutaneous injection of resiniferatoxin(50gg/kg). The rats were studied at one to four weeks after adrenodemedullation. Fropranolol treatments were 2 times of intraperitoneal injections(5mg/kg) before 30 minutes and at the same tame of resiniferatoxin injection. Ruthenium red(10,zg/kg) was injected subcutaneously before 15 minutes and after 45 minutes of resiniferatoxin injection.
The results were as follows.
1. After resiniferatoxin(50ug/kg s.c.) administration, oxygen consumption showed double-peak response. It reached to the peak Ievel(12.8±0.5mL/min/kg075) at 50 minutes, then began to decrease. At 100 minutes it began to increase and maintained elevated level till 300 minutes. After resiniferatoxin injection, colon temperature showed biphasic pattern ; it decreased by 0.2t at 30 minutes, and then increased. Skin temperature began to increase immediately after resiniferatoxin injection, reached to 30.38±0.45 C at 50 minutes. Then it decreased slowly, but maintained elevated level till 300 minutes.
2. After resiriferatoxin(50ug/kg) administration in adrenodemedullated rats, oxygen consumption was reduced in early-increasing response of double-peak response but was not changed in late-increasing response. The temperature of colon and skin was not changed after adrenodemedullation, too.
3. Increments of oxygen consumption by resiniferatoxin administration was abolished by the treatment of propranola till 300 minutes. Changes of skin temperature by resiniferatoxin administration were not affected by propranolol (The peak level of skin temperature was 30.4±0.8t at 40 minutes. The temperature of colon was slightly decreased to 36.0±0.2t at 50 minutes).
4. Ruthenium red enhanced the increments of oxygen consumption to 14.7±0.8 and 14.9±0.5 m%Jmin/kg° ´ at 50 and 100 minutes after resiniferatoxin administration respectively while the decrement of oxygen consumption after the first peak was attenuated by ruthenium red treatment to 14.3± O.6mLJminikg5." at 70 minutes. There were no significant changes of skin temperature and colon temperature.
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