Acosta-Martinez Maricedes, Etgen Anne M
Department of Neuroscience, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Forchheimer 113, Bronx, New York 10461, USA.
Horm Behav. 2002 Feb;41(1):88-100. doi: 10.1006/hbeh.2001.1741.
The present study investigated the effect of highly selective mu-opioid receptor (OR) agonists on lordosis behavior in ovariectomized rats treated with 3 microg of estradiol benzoate followed 48 h later by 200 microg of progesterone. Ventricular infusion of the endogenous mu-OR agonists endomorphin-1 and -2 suppressed receptive behavior in a time- and dose-dependent fashion. At 6 microg, both endomorphin-1 and -2 inhibited lordosis behavior within 30 min. However, while the effect of endomorphin-1 lasted 60 min, endomorphin-2 inhibition lasted up to 120 min after infusion. Pretreatment with naloxone (5 mg/kg sc) was able to block both endomorphin-1 and endomorphin-2 effects on lordosis. Site-specific infusions of endomorphin-1 or endomorphin-2 into the medial preoptic area (mPOA), the ventromedial nucleus of the hypothalamus (VMH), or into the mesencephalic central gray did not affect receptivity. In contrast, infusion of 1 mug of either compound into the medial septum/horizontal diagonal band of Broca inhibited lordosis in a pattern very similar to that seen after intraventricular infusions. Infusion of the potent synthetic mu-OR agonist [D-Ala(2),N-Me-Phe(4),Gly-ol(5)]-enkephalin (0.08 microg) into the VMH and mPOA inhibited lordosis behavior for at least 60 min after infusion. The nonspecific opioid receptor antagonist naloxone was able to facilitate lordosis in partially receptive female rats when infused into the mPOA but not when infused into the VMH. The behavioral effects of the agonists and antagonist used in this study suggest that the endogenous mu-opioid system modulates estrogen and progesterone-induced lordosis behavior.
本研究调查了高选择性μ-阿片受体（OR）激动剂对去卵巢大鼠脊柱前凸行为的影响，这些大鼠先接受3微克苯甲酸雌二醇治疗，48小时后再接受200微克孕酮治疗。脑室内注入内源性μ-OR激动剂内吗啡肽-1和-2可抑制接受行为，呈现出时间和剂量依赖性。在注入6微克时，内吗啡肽-1和-2在30分钟内均抑制了脊柱前凸行为。然而，内吗啡肽-1的作用持续60分钟，而内吗啡肽-2的抑制作用在注入后可持续长达120分钟。用纳洛酮（5毫克/千克，皮下注射）预处理能够阻断内吗啡肽-1和内吗啡肽-2对脊柱前凸行为的影响。将内吗啡肽-1或内吗啡肽-2特异性注入内侧视前区（mPOA）、下丘脑腹内侧核（VMH）或中脑中央灰质，均不影响接受性。相反，将1微克的这两种化合物之一注入内侧隔/布罗卡水平斜带，抑制脊柱前凸的模式与脑室内注入后所见非常相似。将强效合成μ-OR激动剂[D-Ala(2),N-Me-Phe(4),Gly-ol(5)]-脑啡肽（0.08微克）注入VMH和mPOA后，至少60分钟内抑制了脊柱前凸行为。非特异性阿片受体拮抗剂纳洛酮注入mPOA时能够促进部分接受性雌性大鼠的脊柱前凸行为，但注入VMH时则不能。本研究中使用的激动剂和拮抗剂的行为学效应表明，内源性μ-阿片系统调节雌激素和孕酮诱导的脊柱前凸行为。
