Effect of tibolone and raloxifene on the tail temperature of oestrogen-deficient rats

Oestradiol, clonidine, tibolone and raloxifene were tested for their effects on the tail temperature of oestrogen deficient rats, a potential new model that can be used to test compounds that may be of use in the treatment of hot flushes in humans. Rats underwent ovariectomies or sham operations and their tail temperature and physical activity were measured telemetrically. Oestrogen depletion affected tail temperature in the rats' active, but not their resting phase. During the transition from the resting to the active phase, tail temperature in normal rats dropped by about 6 degreesC, but only by approximately 1 degreesC after ovariectomy. Treatment of the ovariectomised rats with oestrogen, clonidine or tibolone dose-dependently restored the drop in tail temperature. However, raloxifene did not change the tail temperature of ovariectomised rats. Thus, tibolone and raloxifene have different effects on the temperature regulation in the tail. This method of measuring tail temperature free of stress in ovariectomised rats may serve as a useful procedure for selecting compounds that are of potential use in the treatment of hot flushes. (C) 2001 Elsevier Science B.V. All rights reserved.