Title: [<sup>3</sup>H]Tryptamine Binding Sites Are Not Identical to Monoamine Oxidase in Rat Brain
Abstract: Abstract: Competition binding studies, subcellular distribution, and in vitro autoradiography were employed to compare the binding in rat brain of [ 3 H]tryptamine with two radio‐ligands for monoamine oxidase (MAO), [ 3 H]pargyline, and [ 3 H] 1 ‐methyl‐4‐phenyl‐1,2,5,6‐tetrahydropyridine ([ 3 H]MPTP). The MAO inhibitors pargyline, clorgyline, and deprenyl all yielded biphasic competition curves versus [ 3 H]tryptamine. At low concentrations, these drugs stimulated binding by protecting the radioligand from MAO oxidation; at considerably higher concentrations, they inhibited binding by direct competition at the [ 3 H]tryptamine binding site. In subcellular distribution studies, [ 3 H]tryptamine was localized preferentially to the synaptosomal fraction, whereas [ 3 H]pargyline showed greater binding to the mitochondrial fraction. Equilibrium binding studies revealed that the potencies of a series of seven compounds at inhibiting [ 3 H]tryptamine binding were completely different from their potencies at inhibiting [ 3 H]MPTP binding. Finally, the au‐toradiographic distribution of [ 3 H]tryptamine binding in rat brain v/as different from that of [ 3 H]MPTP and [ 3 H]pargyline. We conclude that the [ 3 H]tryptamine binding site in rat brain is not equivalent to MAO.
Publication Year: 1988
Publication Date: 1988-11-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 8
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