ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
The hydroxylated phenylethylamines p-tyramine, m-tyramine, octopamine, metaraminol and norepinephrine were accumulated by homogenates of rat brain much more vigorously than β-phenethylamine or amphetamine. The affinity concentrations (Km) for initial (5-min) uptake by homogenates of whole brain were 0.5, 3 and 6 μM for DL-norepine-phrine, p-tyramine and DL-octopamine, respectively. The uptake of these three hydroxylated compounds was much more vigorous in striatal tissue than in cortical tissue, and in both tissues the rate of uptake decreased in the sequence: norepinephrine 〉 tyramine 〉 octopamine. The uptake of these three substances was inhibited by reduced temperature, by lack of glucose, by CN- and DNP, and by desmethylimipramine, cocaine and ouabain. The uptake of norepinephrine and octopamine appeared to require Na+. Pretreatment of rats with reserpine or 6-hydroxydopamine decreased the ability of brain to take up norepinephrine or octopamine. Previously accumulated labelled phenylethylamines migrated in sucrose density gradients with a peak of radioactivity corresponding to an equilibrium position of catecholamine-containing nerve endings. The magnitude of the retention of [3H]amine in this synaptosornal peak decreased in the order: norepinephrine 〉 octopamine 〉 tyramine. The accumulated amines were released by sonic, osmotic and thermal stresses which disrupt neuronal membranes. The presence of a β-hydroxyl group appeared to protect amines from destruction by monoamine oxidase, presumably by virtue of uptake in presynaptic storage vesicles. During superfusion, tyramine and metaraminol appeared to displace [3H]norepinephrine from binding sites in brain slices.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1971.tb00208.x
Permalink
