Shin S H, Obonsawin M C, Stirling R
Department of Physiology, Queen's University, Kingston, Ontario, Canada.
Acta Endocrinol (Copenh). 1989 Sep;121(3):411-6. doi: 10.1530/acta.0.1210411.
Neurophysins have been considered to be physiologically inert carrier proteins for the neurohypophysial hormones, oxytocin and vasopressin. We have observed that bovine neurophysin-II indirectly stimulates prolactin release in estradiol-primed male rats. The release of prolactin is regulated by a dual hypothalamic control system, the prolactin-release-inhibiting factor and the prolactin-releasing factor. We have tried to clarify whether neurophysin-II is acting through stimulation of prolactin-releasing factor by eliminating the possibility of dopaminergic prolactin release-inhibiting factor release. Male rats were primed with estradiol and functional dopaminergic prolactin release-inhibiting factor receptors were completely blocked by pretreatment with a large dose of pimozide (3 mg/kg), a dopaminergic receptor blocking agent. The neurophysin-II stimulated prolactin release in the rats which did not have any functional dopaminergic prolactin release-inhibiting factor receptors suggesting that neurophysin-II likely initiates a chain of events which eventually stimulates prolactin-releasing factor release since the possibility of involvement of the dopaminergic prolactin release-inhibiting factor system is eliminated. Opioids are known to be one of a chain of events which transmit external stress into a stimulation of prolactin release. Naloxone, a mu-receptor antagonist, was injected 20 min before neurophysin-II administration into rats which were primed with estradiol and pretreated with pimozide (3 mg/kg), but the naloxone administration did not block the prolactin release stimulated by neurophysin-II injection. This result indicates that opioids are not one of the chain of events between initiation of stimulation by neurophysin-II and prolactin release.
神经垂体素一直被认为是神经垂体激素（催产素和加压素）的生理惰性载体蛋白。我们观察到，牛神经垂体素II可间接刺激经雌二醇预处理的雄性大鼠释放催乳素。催乳素的释放受下丘脑双重控制系统调节，即催乳素释放抑制因子和催乳素释放因子。我们试图通过排除多巴胺能催乳素释放抑制因子释放的可能性，来阐明神经垂体素II是否通过刺激催乳素释放因子起作用。用雌二醇对雄性大鼠进行预处理，并用大剂量多巴胺能受体阻断剂匹莫齐特（3毫克/千克）进行预处理，完全阻断功能性多巴胺能催乳素释放抑制因子受体。神经垂体素II刺激了那些没有任何功能性多巴胺能催乳素释放抑制因子受体的大鼠释放催乳素，这表明神经垂体素II可能引发一系列事件，最终刺激催乳素释放因子释放，因为多巴胺能催乳素释放抑制因子系统参与的可能性已被排除。已知阿片类物质是将外部应激转化为催乳素释放刺激的一系列事件之一。在给经雌二醇预处理并用匹莫齐特（3毫克/千克）处理的大鼠注射神经垂体素II前20分钟，注射μ受体拮抗剂纳洛酮，但纳洛酮的注射并未阻断神经垂体素II注射刺激的催乳素释放。这一结果表明，阿片类物质不是神经垂体素II引发刺激与催乳素释放之间一系列事件的一部分。
