3H-catecholamine binding to α-receptors in rat brain: Enhancement by reserpine

David C. U'Prichard, Solomon H. Snyder

Research output: Contribution to journalArticle

Abstract

(±)-3H-Epinephrine and (-)-3H-norepinephrine bind to rat cortex membranes in a saturable manner with dissociation constants of 16.7 and 27 nM0 respectively. The maximum number f 3H-catecholamine binding sites, 10-12 pmoles/g tissue, and the pharmacological characteristics of (±)-3H-epinephrine binding, indicate that the catecholamines label the same α-noradrenergic receptor in the rat as does 3H-clonidine. At 25°, (±)-3H-epinephrine binding associates rapidly to equilibrium, and dissociates in a biphasic manner. The affinities of α-agonists at the 3H-catecholamine binding site are 2-4 fold weaker in the rat than in the calf cortex under the same experimental conditions. Ergot alkaloids and phenoxybenzamine have similar affinities in the two tissues, whereas phentolamine and WB-4101 are 8-10 times weaker in the rat. Reserpine (0.25 mg/kg s.c. per day for 3 weeks) causes 25 and 46% increases in the numbers of (±)-3H-epinephrine and 3H-WB-4101 α-receptor binding sites respectively, and a 51% increase in the number of 3H-dihydroalprenolol β-receptor sites, in rat forebrain. Reserpine pretreatment does not alter the affinities of either α-or β-receptor 3H-ligands.

Original languageEnglish (US)
Pages (from-to)145-155
Number of pages11
JournalEuropean Journal of Pharmacology
Volume51
Issue number2
DOIs
StatePublished - Sep 15 1978

Keywords

  • Adrenoceptor binding
  • Catecholamines
  • Rat brain
  • Reserpine

ASJC Scopus subject areas

  • Pharmacology

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