首页 | 本学科首页   官方微博 | 高级检索  
检索        


Naloxone potentiates the release of oxytocin induced by systemic administration of cholecystokinin without enhancing the electrical activity of supraoptic oxytocin neurones
Authors:G Leng  R E J Dyball  S A Way
Institution:(1) AFRC Institute of Animal Physiology and Genetics Research, Babraham, CB2 4AT Cambridge, UK;(2) Department of Anatomy, University of Cambridge, Downing Street, Cambridge, UK;(3) Department of Neuroendocrinology, UK
Abstract:Summary Studies performed in conscious female rats confirmed that iv injection of cholecystokinin octapeptide (CCK; 20µ/kg) increased the circulating concentration of oxytocin but not that of vasopressin, and confirmed that the stimulation of oxytocin release was markedly facilitated after iv administration of naloxone (1mg/kg), indicating attenuation of oxytocin release by endogenous opioids. To investigate the site of action of the endogenous opioids, the electrical activity of putative oxytocin neurones in the supraoptic nucleus was recorded in urethaneanaesthetised female rats. Oxytocin neurones responded to CCK injection with an increase in firing rate lasting 5–15 min, but this response was not facilitated by prior injection of naloxone. The results suggest that the opioid influence upon CCK-induced oxytocin release operates at the level of the neurosecretory terminals in the neurohypophysis rather than centrally. Since CCK does not elevate vasopressin release, it appears unlikely that dynorphin, the opioid peptide co-existing with vasopressin, is responsible in these circumstances for the cross-inhibition of oxytocin release. It is suggested that products of proenkephalin A, the met-enkephalin precursor present in the supraoptic nucleus and in the neurohypophysis itself, may be active in the regulation of oxytocin release.
Keywords:Supraoptic nucleus  Dynorphin  Opioids  Neurohypophysis  Rat
本文献已被 SpringerLink 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号