caa a22 4500 469078979 CHVBK 20180323132944.0 cr unu---uuuuu 170328e19920101xx s 000 0 eng 10.1007/BF00175464 doi (NATIONALLICENCE)springer-10.1007/BF00175464 Palatý Vladimir Department of Anatomy, The University of British Columbia, 2177 Wesbrook Mall, V6T 1W5, Vancouver, B.C., Canada aut The cocaine-insensitive component of non-exocytotic efflux of noradrenaline from adrenergic axons in the isolated rat tail artery [Elektronische Daten] [Vladimir Palatý] Summary: The working hypothesis was that the cocaine-insensitive component of non-exocytotic efflux of noradrenaline represents diffusion of the unprotonated amine across the axonal membrane. It was tested by examination of the effect of changing axoplasmic pH —and thus the fraction of extravesicular noradrenaline in the unprotonated form — on the overflows of endogenous noradrenaline and 3,4-dihydroxyphenylethylene glycol from rat tail arteries. The catechols were assayed by liquid chromatography with amperometric detection. To dissipate the H+ gradient across the axonal membrane, the tissues were incubated in media of different pH, in which Na+ was completely replaced with K+ and which were HCO3 − - (and Ca2+-)free. Exposure of the tissues to these media produced substantial, but reversible increases in the overflow of noradrenaline. Subsequently, the overflows of both noradrenaline and the glycol kept rising, but their ratio did not change. Cocaine (0.1 mmol/1) lowered the (noradrenaline overflow: glycol overflow) ratio significantly. The ratio observed in its presence increased steeply with decreasing external and, presumably, axoplasmic pH. Addition of valinomycin and carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (1 μmol/1 each) to the cocaine-containing media more than doubled the overflows without altering significantly the ratio. Under identical conditions, the overflow of noradrenaline from preparations with inactive neuronal monoamine oxidase did not decrease with decreasing pH. Since, in the presence of cocaine, the overflow ratio increased — rather than decreased — with decreasing pH, and because the overflow or noradrenaline from preparations with inactive monoamine oxidase did not decline with pH, the cocaine-insensitive component of noradrenaline efflux does not seem proportional to the axoplasmic concentration of the unprotonated amine. The data can, however, be accounted for by postulating that the component reflects the concentration of the protonated form of noradrenaline. Springer-Verlag, 1992 Adrenergic nerves nationallicence Noradrenaline efflux nationallicence Cocaine nationallicence 3,4-Dihydroxyphenylethylene glycol nationallicence pH Dependence nationallicence Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 345/1(1992-01-01), 21-24 0028-1298 345:1<21 1992 345 210 https://doi.org/10.1007/BF00175464 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00175464 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Palatý Vladimir Department of Anatomy, The University of British Columbia, 2177 Wesbrook Mall, V6T 1W5, Vancouver, B.C., Canada aut NATIONALLICENCE 773 0- Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 345/1(1992-01-01), 21-24 0028-1298 345:1<21 1992 345 210 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer