[Effects of iontophoretically-applied LHRH, TRH, estrogen and clomiphene on thermo-sensitive neurons in the rat hypothalamus].

Studies were performed on the correlation between the hypothalamic temperature-sensitive neurons and hypothalamic neurons sensitive to LHRH, TRH, conjugated estrogen and clomiphene in 103 castrated matured female rats by the technique of microiontophoresis using a multi-barrel glass microelectrode. Out of 348 neurons in the hypothalamus, 24 neurons were found to be LHRH-sensitive, 20 TRH-sensitive, 41 estrogen-sensitive, and 18 clomiphene-sensitive. There were 19(28.8%) warm-sensitive and 11(16.7%) cold-sensitive neurons located in the preoptic area. From among the 19 warm-sensitive neurons, 14 neurons showed excitation by estrogen and 4 showed suppression by LHRH. Out of the 11 cold-sensitive neurons, estrogen, LHRH, and TRH excited 4, 3, and 3 neurons, respectively. It is suggested from these studies that LHRH mainly exhibits its thermo-regulatory functions by exciting warm-sensitive neurons and it is for this reason that exogenous estrogens are effective in alleviating hot flushes in natural as well as post-operative menopause which are thought to be caused by LHRH.