Central and peripheral temperature changes in sheep following ovariectomy

Area of Science:

• Veterinary Medicine
• Reproductive Endocrinology
• Animal Physiology

Background:

• Menopause in women is associated with vasomotor symptoms like hot flashes.
• The domestic ewe (Ovis aries) is increasingly utilized as a model for human reproductive physiology.

Purpose of the Study:

• To investigate if ovariectomized ewes experience periodic body temperature increases (hot flashes) analogous to those in menopausal women.
• To assess the effect of 17 beta-estradiol on these temperature fluctuations.

Main Methods:

• Eighteen ewes underwent ovariectomy (OVX), ovariectomy with estradiol implant (OVXE), or sham surgery.
• Subcutaneous temperature loggers were implanted in the carotid artery, abdomen, thigh, and axilla.
• Body temperatures were recorded every 2.5 minutes for 59 days, with readings analyzed in 1-hour intervals to mitigate circadian rhythm effects.

Main Results:

• Carotid and abdominal logger sites provided the most reliable temperature data.
• Ovariectomized ewes showed a significantly higher percentage of hot flash events compared to sham-operated ewes at both carotid (63% vs. 37%) and abdominal (32% vs. 17%) sites.
• Estradiol treatment in OVXE ewes resulted in a reduction in hot flash frequency compared to OVX ewes.
• Early post-ovariectomy data (first 7 days) indicated a higher incidence of hot flashes.

Conclusions:

• Ovariectomy in ewes induces body temperature changes interpretable as hot flashes.
• Estradiol administration mitigates the occurrence and severity of these temperature fluctuations.
• This study reports periodic hot flashes in a species other than rats, suggesting the ewe as a potential model for menopausal vasomotor symptoms.