Tetrodotoxin-resistant release of 3H-noradrenaline from the mouse vas deferens by high intensity electrical stimulation.
Vasa deferentia of mice were preincubated with 3H-noradrenaline and then superfused with a medium containing cocaine 10 microM and phentolamine 30 microM. The tetrodotoxin-resistant outflow of tritium evoked by high intensity electrical field stimulation (0.5 Hz, 200 mA current strength, 2 ms pulse width) was studied and, in some experiments, compared with the tetrodotoxin-sensitive outflow evoked by low intensity electrical field stimulation (0.5 Hz, 50 mA, 1 ms). In contrast to the outflow evoked by low intensity stimulation, the outflow evoked by high intensity stimulation was increased in Na+-free medium, and was only partly dependent on the external Ca2+ concentration. The Ca2+-dependent fraction consisted mainly of 3H-noradrenaline. Again, in contrast to the outflow caused by stimulation at low intensity, that caused by stimulation at high intensity was not reduced by Mg2+ 20 mM, Co2+ 5 mM or normorphine 40 or 100 microM, and was not enhanced by tetraethylammonium 5 mM or 4-aminopyridine 1 mM. It is concluded that high intensity electrical stimulation elicits a tetrodotoxin-resistant, calcium-dependent release of noradrenaline which differs in mechanism from the release elicited by action potentials.
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D004351:Drug Resistance; D004558:Electric Stimulation; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009294:Narcotics / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D012964:Sodium / Q000502:physiology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology*; D014316:Tritium; D014649:Vas Deferens / Q000378:metabolism*
D000631:Aminopyridines; D002413:Cations, Divalent; D009294:Narcotics; D013757:Tetraethylammonium Compounds; D014316:Tritium; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D012964:Sodium; D015761:4-Aminopyridine; D009638:Norepinephrine