Mechanism of efflux of noradrenaline from adrenergic nerves in rabbit atria.
1. The mechanism of efflux of (-)-[(3)H]-noradrenaline was examined in rabbit atria, which were pretreated with reserpine and pargyline.2. Between 40 and 100 min, efflux occurred predominantly from a single intraneuronal compartment.3. Efflux was rapidy increased by (-)- and (+)-noradrenaline, tyramine and (+/-)-metaraminol, but not by (+/-)-isopropylnoradrenaline or (+/-)-normetanephrine. The increase in efflux produced by (-)-noradrenaline was inhibited by cocaine and desipramine but not by lidocaine.4. Spontaneous effluxes, and those accelerated by (-)-noradrenaline, were temperature-sensitive.5. Efflux was increased by ouabain, omission of K(+), metabolic inhibition and lowering of the external Na(+) concentration. These effects were significantly reduced by cocaine and desipramine but not by lidocaine.6. These findings provide evidence that the efflux of [(3)H]-noradrenaline from adrenergic nerves occurs by a cocaine-sensitive, carrier-mediated process. The characteristics of the efflux process are compatible with, but not conclusive proof for, the Na(+)-gradient hypothesis.
D000818:Animals; D003042:Cocaine / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D006321:Heart / Q000294:innervation*; D006325:Heart Atria / Q000294:innervation / Q000378:metabolism; D066298:In Vitro Techniques; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008680:Metaraminol / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D009647:Normetanephrine / Q000494:pharmacology; D010293:Pargyline / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011292:Premedication; D011817:Rabbits; D012110:Reserpine / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors; D014316:Tritium; D014439:Tyramine / Q000494:pharmacology
D009647:Normetanephrine; D014316:Tritium; D008680:Metaraminol; D012110:Reserpine; D008012:Lidocaine; D010293:Pargyline; D012964:Sodium; D003042:Cocaine; D011188:Potassium; D003891:Desipramine; D009638:Norepinephrine; D014439:Tyramine