Neuronal efflux of noradrenaline induced by tris or lithium as substitutes for extracellular sodium.
Vasa deferentia of either untreated or reserpine (R) and/or pargyline (P) pretreated rats were incubated with 3H-noradrenaline and then washed with amine- and Ca2+-free solution until (after 100 min) the efflux of radioactivity largely originated from adrenergic nerve endings; COMT was inhibited by U-0521 (U). After 110 min of wash out, the sodium chloride in the wash-out solution was replaced by an equimolar concentration of either Tris-HCl or LiCl. This caused a desipramine-sensitive (i.e., carrier-mediated) efflux of tritiated noradrenaline. The initial increase of the "low Na+"-induced efflux dependent on the experimental conditions: it was most pronounced when the axoplasmic concentration of noradrenaline was high (RPU) and relatively small when MAO and vesicular storage were intact (U). The effects of Li+ and Tris+ differed with regard to the time course of the efflux of tritium: under all three experimental conditions (RPU, PU, U), Tris+ caused the rate of efflux of tritium to increase gradually within the 30 min period of observation, while Li+ either had a "peak-effect" (RPU, PU) or a "plateau-effect" (U). Under "U-conditions" Tris+ caused a slowly increasing, pronounced increase with time of the efflux of both, 3H-noradrenaline and 3H-DOPEG; whereas Li+ caused only a small and sustained increase of the efflux of 3H-noradrenaline and a decrease in the efflux of 3H-DOPEG.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002712:Chlorides / Q000494:pharmacology*; D003891:Desipramine / Q000494:pharmacology; D066298:In Vitro Techniques; D008094:Lithium / Q000494:pharmacology*; D018021:Lithium Chloride; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D010293:Pargyline / Q000494:pharmacology; D011427:Propiophenones / Q000494:pharmacology; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D012964:Sodium / Q000502:physiology*; D013936:Thymidine / Q000378:metabolism; D014325:Tromethamine / Q000494:pharmacology*; D014649:Vas Deferens / Q000294:innervation
D002712:Chlorides; D011427:Propiophenones; D014325:Tromethamine; D008734:Methoxyhydroxyphenylglycol; C006104:U 0521; D012110:Reserpine; D008094:Lithium; D010293:Pargyline; D012964:Sodium; D018021:Lithium Chloride; D003891:Desipramine; C010117:3,4-dihydroxyphenylglycol; D013936:Thymidine; D009638:Norepinephrine