The effect of extracellular sodium ion concentration on the action of opiates to inhibit potassium-evoked release of [3H]noradrenaline from the mouse vas deferens.
Opiates depress the potassium-induced efflux of [3H]noradrenaline from the mouse vas deferens in a concentration-dependent (the IC50 for normorphine was 1.5 microM), stereospecific and naloxone-reversible manner. As the concentration of sodium in the extracellular fluid was reduced, the inhibitory action of opiates was also reduced. This attenuation of opiate action is the converse of that predicted by the 'sodium-shift' observed in opiate binding studies in which lowering the sodium concentration potentiates opiate agonist binding. The relevance of sodium to the pharmacological actions of opiates is discussed.
D000320:Adrenergic Fibers / Q000187:drug effects*; D000818:Animals; D008297:Male; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology*; D014649:Vas Deferens / Q000294:innervation* / Q000378:metabolism
D009294:Narcotics; D009270:Naloxone; D012964:Sodium; D011188:Potassium; D009638:Norepinephrine