Torii M, Kubo K, Sasaki T
Department of Human Sciences, Kyushu Institute of Technology, Kitakyushu, 804, Japan.
Horm Behav. 1999 Jun;35(3):271-8. doi: 10.1006/hbeh.1999.1526.
The purpose of the present study was to investigate the effect of time of beta-endorphin (beta-EP) administration on lordosis in ovariectomized female rats injected subcutaneously (sc) with estradiol benzoate (EB) and progesterone (Prog). Intracerebroventricular (icv) injections of beta-EP and naloxone (NLX), an opioid receptor antagonist, were administered at the various stages of sc steroid hormone priming. Facilitation of lordosis induced by 10 microg beta-EP was observed exclusively within the initial 6 h of estrogen action, after which inhibition of lordosis occurred. At 12 h after EB priming, at the time of sc Prog treatment (or 43 h after EB priming), icv injection of 10 microg beta-EP significantly inhibited lordosis. Lordosis was significantly facilitated by icv injections of 1 and 10 microg beta-EP at the time of sc EB priming, but not by 0.1 microg beta-EP. A dose-response relationship was identified for lordosis in experimental animals receiving icv injection of beta-EP. Lordosis was inhibited by icv injections of 1 and 10 microg beta-EP at 1 h before the test (or 47 h after EB priming). Lordosis was significantly inhibited by icv injection of NLX at all stages. From the present results, it seems that two different mechanisms are involved in endorphinergic modulation of rats' sexual receptivity: (a) the endorphinergic system at the initial stages of estrogen action facilitates the estrogen activation of lordosis; (b) the endorphinergic system at the final stages of steroid action inhibits lordosis. Moreover, there exists a critical time between 6 and 12 h after estrogen priming for endorphinergic mediation to modulate estrogen action.
本研究的目的是调查在皮下注射苯甲酸雌二醇（EB）和孕酮（Prog）的去卵巢雌性大鼠中，β-内啡肽（β-EP）给药时间对脊柱前凸的影响。在皮下给予类固醇激素的不同阶段，进行脑室内（icv）注射β-EP和阿片受体拮抗剂纳洛酮（NLX）。仅在雌激素作用的最初6小时内观察到10微克β-EP诱导的脊柱前凸促进作用，之后出现脊柱前凸抑制。在EB预处理12小时后，即皮下注射Prog时（或EB预处理43小时后），脑室内注射10微克β-EP可显著抑制脊柱前凸。在皮下注射EB时，脑室内注射1微克和10微克β-EP可显著促进脊柱前凸，但0.1微克β-EP则无此作用。在接受脑室内注射β-EP的实验动物中，确定了脊柱前凸的剂量反应关系。在测试前1小时（或EB预处理47小时后），脑室内注射1微克和10微克β-EP可抑制脊柱前凸。在所有阶段，脑室内注射NLX均可显著抑制脊柱前凸。从目前的结果来看，内啡肽能调节大鼠性接受能力似乎涉及两种不同机制：（a）雌激素作用初始阶段的内啡肽能系统促进雌激素对脊柱前凸的激活；（b）类固醇作用最终阶段的内啡肽能系统抑制脊柱前凸。此外，在雌激素预处理后6至12小时之间存在一个关键时间，内啡肽能介导可调节雌激素作用。
