Bicknell R J, Chapman C, Leng G
Exp Brain Res. 1985;60(1):192-6. doi: 10.1007/BF00237032.
When electrical stimuli are applied to the neural stalk of the pituitary, oxytocin, vasopressin, and probably several opioid peptides also contained in nerve terminals in the gland are released: one action of the released opioids appears to be to inhibit oxytocin release by an action that has been likened to pre-synaptic inhibition. Thus, when Clarke et al. (1979) stimulated the neural stalk following intravenous injection of the opioid antagonist naloxone, they observed that the evoked oxytocin release was potentiated. In the present study we confirm this result and show that oxytocin release evoked by stimulation of the supraoptic nucleus is similarly potentiated by naloxone. This finding is consistent with the hypothesis that the opioid responsible for inhibition of oxytocin release coexists with either oxytocin or vasopressin. We further report that the specific delta-receptor antagonist ICI 174864 does not potentiate oxytocin release either in vivo or in vitro. Thus, it seems unlikely that the enkephalins, putative delta-receptor agonists present in neurohypophysial fibres, are the opioids responsible for the observed inhibition of oxytocin release.
当对垂体神经柄施加电刺激时，催产素、血管加压素以及可能也存在于腺体内神经末梢中的几种阿片肽会被释放出来：所释放的阿片类物质的一种作用似乎是通过一种类似于突触前抑制的作用来抑制催产素的释放。因此，当克拉克等人（1979年）在静脉注射阿片拮抗剂纳洛酮后刺激神经柄时，他们观察到诱发的催产素释放增强了。在本研究中，我们证实了这一结果，并表明刺激视上核诱发的催产素释放在纳洛酮作用下同样增强。这一发现与负责抑制催产素释放的阿片类物质与催产素或血管加压素共存的假说相符。我们进一步报告，特异性δ受体拮抗剂ICI 174864在体内或体外均不能增强催产素的释放。因此，存在于神经垂体纤维中的假定δ受体激动剂脑啡肽似乎不太可能是导致观察到的催产素释放受抑制的阿片类物质。
