Tetraethylammonium ions and 4-aminopyridine prevent opioid inhibition of neurohypophysial oxytocin release.
Naloxone increased the electrically (15 Hz, 1 min) evoked release of oxytocin from isolated neural lobes of rats 3-4-fold. In the presence of 4-aminopyridine or tetraethylammonium ions the evoked release of oxytocin was increased 8-9-fold and remained unaffected by naloxone. Increasing the calcium concentration in the medium from 1.2 to 3 mM caused only a marginal increase of the evoked oxytocin release. In conclusion, blockade of potassium channels and/or the resulting prolongation of the action potential can surmount the opioid inhibition of oxytocin release.
Racké
K
K
Department of Pharmacology, University of Mainz, F.R.G.
Altes
U
U
Baur
A M
AM
Jost
D
D
Schäfer
J
J
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D004558:Electric Stimulation; D005048:Etorphine / Q000494:pharmacology; D005260:Female; D009270:Naloxone / Q000494:pharmacology*; D010121:Oxytocin / Q000378:metabolism*; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*
D000631:Aminopyridines; D013757:Tetraethylammonium Compounds; D009270:Naloxone; D005048:Etorphine; D010121:Oxytocin; D015761:4-Aminopyridine