No abstract

Japanese women can experience a sensation of cold feet in daily life. It is possible that this sensation of coldness in feet may be associated with female hormones, but to date the effect of menstrual cycle phase on the skin temperature (T) of the foot during local cooling is unknown. We therefore examined T and partial cutaneous blood flow in the foot during the follicular (F) and luteal (L) phases of the menstrual cycle in women experiencing local cooling. T was measured in the toes and the dorsum of the left foot using infrared thermography, while cutaneous blood flow was evaluated in the big toe of the left foot using laser Doppler flowmetry (LDF), both at 28 °C. Mild local cooling (24.7 °C) was then applied for 30 min to the right foot. During cooling of the right foot, no significant differences in T were observed between the F and L phases in either the toes of the left foot or the dorsum of the left foot of all subjects. However, cutaneous blood flow determined by LDF in the big toe of the left foot was greater in the F phase than in the L phase. These results suggest that the menstrual cycle phase did not affect T in the foot, but it did affect cutaneous blood flow in the big toe during mild local cooling.

No abstract

Estradiol (E2) modulates the central and peripheral thermoregulatory responses to cold. Menthol is an agonist of transient receptor potential melastatin type 8 (TRPM8), which is a peripheral cold receptor. E2 suppresses menthol-induced elevation of body temperature (Tb) in ovariectomized rats, but the mechanism is unknown. The aim of the present study is to investigate the effect of E2 on uncoupling protein 1 (UCP1), a thermogenic gene, and TRPM8 mRNA levels in ovariectomized rats applied menthol. A silastic tube was implanted in ovariectomized rats with and without E2 underneath the dorsal skin (E2(1) and E2(2) groups), and data loggers for Tb measurement into peritoneal cavity. After application of 10% l-menthol or vehicle to the skin of the whole trunk of rats, Tb was measured for 2 h. The interscapular brown adipose tissue (BAT) and spinal ganglia of cervical, thoracic, and lumbar parts were obtained for RT-qPCR assay. In the menthol application, Tb in the E2(1) group was lower than that in the E2(2) group. The UCP1 mRNA in the BAT, TRPM8 mRNA in the BAT and spinal ganglia in all areas did not differ between the E2(1) and E2(2) groups. In conclusion, the UCP1 and TRPM8 expression in the brown fat did not affect the restriction of the menthol-induced hyperthermia by estradiol in ovariectomized rats.