Kotegawa T, Abe T, Tsutsui K
Laboratory of Brain Science, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima, Japan.
J Exp Zool. 1997 Feb 1;277(2):146-54. doi: 10.1002/(sici)1097-010x(19970201)277:2<146::aid-jez6>3.0.co;2-p.
We have recently isolated three opioid peptides, i.e., Met- and Leu-enkephalins and Met-enkephalin-Arg6-Phe7, from the avian brain. Furthermore, electrophysiological studies have shown that the dominant effect of these enkephalins on preoptic and hypothalamic neurons is an inhibition of neuronal activities in the male Japanese quail. The hypothalamus and preoptic area are known to be involved in the control of male reproductive behaviors, such as aggressive and sexual behaviors. To determine the functional role of opioid peptides in these reproductive behaviors, therefore, the present study was undertaken using adult males of the Japanese quail. We examined behavioral changes following an injection of naloxone (0.2, 2.0, and 20.0 nmol), a nonselective opioid receptor antagonist, or D-Ala2-Met5-enkephalinamide (DALA; 0.2, 2.0, and 20.0 nmol), a selective delta opioid receptor agonist, into the preoptic and anterior hypothalamic regions. Naloxone treatment showed a significant increase in the frequency of several aggressive actions and the effect was dose dependent. In contrast, DALA treatment significantly decreased the frequency of aggressive actions in a dose-dependent manner. Similar significant effects of these two drugs were observed in the sexual behavior. These findings provide the first evidence for the role of opioid peptides in the reproductive behaviors in the bird and suggest an inhibitory action of opioid to evoke the behaviors.
我们最近从禽脑中分离出了三种阿片肽，即甲硫氨酸脑啡肽和亮氨酸脑啡肽以及甲硫氨酸脑啡肽-精氨酸6-苯丙氨酸7。此外，电生理研究表明，这些脑啡肽对视前区和下丘脑神经元的主要作用是抑制雄性日本鹌鹑的神经元活动。已知下丘脑和视前区参与雄性生殖行为的控制，如攻击行为和性行为。因此，为了确定阿片肽在这些生殖行为中的功能作用，本研究使用成年雄性日本鹌鹑进行。我们检查了在视前区和下丘脑前部区域注射非选择性阿片受体拮抗剂纳洛酮（0.2、2.0和20.0纳摩尔）或选择性δ阿片受体激动剂D-丙氨酸2-甲硫氨酸5-脑啡肽酰胺（DALA；0.2、2.0和20.0纳摩尔）后行为的变化。纳洛酮处理显示几种攻击行为的频率显著增加，且效果呈剂量依赖性。相比之下，DALA处理以剂量依赖性方式显著降低了攻击行为的频率。在性行为中也观察到了这两种药物的类似显著效果。这些发现首次证明了阿片肽在鸟类生殖行为中的作用，并表明阿片类物质对引发这些行为具有抑制作用。
