Dunlap K D, Sridaran R
Department of Physiology, Morehouse School of Medicine, Atlanta, GA 30310.
Physiol Behav. 1988;42(2):199-202. doi: 10.1016/0031-9384(88)90298-3.
Exogenously administered dihydrotestosterone (DHT) is a potent inhibitor of sexual behavior in ovariectomized, estrogen-primed rats and endogenous DHT has been implicated as an inhibitor of sexual behavior in cycling rats. To determine the temporal relationship between DHT levels and the expression of sexual behavior, females were tested at midnight of each day of the 4-day estrous cycle for lordosis response to male mounts and subsequently bled. Plasma DHT levels were highest (177 +/- 10 pg/ml) at proestrus (P), when lordosis was fully expressed, fell to significantly lower levels (136 +/- 8, p less than 0.025) at estrus (E), and rose at diestrus I and diestrus II (DII) (152 +/- 8 and 154 +/- 10 respectively). Other female rats were bled from a jugular cannula at 4-hr intervals between midnight of DII and midnight of E. Plasma DHT was elevated from 1200 of P to 0400 of E and fell rapidly through 0800 of E. This elevation of endogenous DHT coincides with the expression of lordosis behavior, and the magnitude of this peak is many times lower than the concentrations reached by the minimal exogenous dose that inhibits lordosis behavior. This suggests that cyclic changes of DHT in the peripheral circulation do not inhibit lordosis behavior during the estrous cycle.
外源性给予的二氢睾酮（DHT）是去卵巢并用雌激素预处理的大鼠性行为的强效抑制剂，内源性DHT被认为是性周期中大鼠性行为的抑制剂。为了确定DHT水平与性行为表达之间的时间关系，在4天发情周期的每一天午夜对雌性大鼠进行测试，观察其对雄性爬跨的脊柱前凸反应，随后取血。在动情前期（P），脊柱前凸充分表达时，血浆DHT水平最高（177±10 pg/ml），在发情期（E）降至显著较低水平（136±8，p＜0.025），并在间情期I和间情期II（DII）升高（分别为152±8和154±10）。其他雌性大鼠在DII午夜至E午夜期间每隔4小时从颈静脉插管取血。血浆DHT从P的12:00升高至E的04:00，并在E的08:00迅速下降。内源性DHT的这种升高与脊柱前凸行为的表达一致，且该峰值的幅度比抑制脊柱前凸行为的最小外源性剂量所达到的浓度低很多倍。这表明发情周期中外周循环中DHT的周期性变化并不抑制脊柱前凸行为。
