Further studies on α2-adrenoceptor subtypes involved in the modulation of [3H]noradrenaline and [3H]5-hydroxytryptamine release from rat brain cortex synaptosomes

M. Gobbi, E. Frittoli, T. Mennini

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14 Citations (Scopus)

Abstract

Three selective α(2A)- or α(2B)-adrenergic antagonists (BRL-44408, BRL-41992 and imiloxan) were used in the present study designed to classify the presynaptic α2-auto- and heteroreceptors in the rat brain cortex. The rank order of potency in antagonizing the inhibitory effect of (-)-noradrenaline or clonidine on the K+-induced [3H]noradrenaline and [3H]5-hydroxytryptamine (5-HT) release from superfused synaptosomes was BRL-44408 ≥ BRL-41992 >> imiloxan. The same rank order was found for the affinities of these compounds for [3H]yohimbine binding in human platelet membranes, containing only α(2A)-adrenoceptors, but does not correlate with the known affinities for α(2B)-adrenoceptors (BRL-41992 ≥ imiloxan > BRL-44408). These data support the conclusion that presynaptic α2-auto- and heteroreceptors in rat brain cortex do not belong to the α(2B)-subtype and suggest that the modulation of noradrenaline and 5-HT release may be mediated by the α(2A)-subtype.

Original languageEnglish
Pages (from-to)811-814
Number of pages4
JournalJournal of Pharmacy and Pharmacology
Volume45
Issue number9
Publication statusPublished - 1993

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Synaptosomes
Adrenergic Receptors
Autoreceptors
Serotonin
Norepinephrine
Brain
Adrenergic Antagonists
Yohimbine
Clonidine
Blood Platelets
Membranes
BRL 44408
BRL 41992
Imiloxan

ASJC Scopus subject areas

  • Pharmaceutical Science
  • Pharmacology

Cite this

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title = "Further studies on α2-adrenoceptor subtypes involved in the modulation of [3H]noradrenaline and [3H]5-hydroxytryptamine release from rat brain cortex synaptosomes",
abstract = "Three selective α(2A)- or α(2B)-adrenergic antagonists (BRL-44408, BRL-41992 and imiloxan) were used in the present study designed to classify the presynaptic α2-auto- and heteroreceptors in the rat brain cortex. The rank order of potency in antagonizing the inhibitory effect of (-)-noradrenaline or clonidine on the K+-induced [3H]noradrenaline and [3H]5-hydroxytryptamine (5-HT) release from superfused synaptosomes was BRL-44408 ≥ BRL-41992 >> imiloxan. The same rank order was found for the affinities of these compounds for [3H]yohimbine binding in human platelet membranes, containing only α(2A)-adrenoceptors, but does not correlate with the known affinities for α(2B)-adrenoceptors (BRL-41992 ≥ imiloxan > BRL-44408). These data support the conclusion that presynaptic α2-auto- and heteroreceptors in rat brain cortex do not belong to the α(2B)-subtype and suggest that the modulation of noradrenaline and 5-HT release may be mediated by the α(2A)-subtype.",
author = "M. Gobbi and E. Frittoli and T. Mennini",
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journal = "Journal of Pharmacy and Pharmacology",
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AU - Frittoli, E.

AU - Mennini, T.

PY - 1993

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AB - Three selective α(2A)- or α(2B)-adrenergic antagonists (BRL-44408, BRL-41992 and imiloxan) were used in the present study designed to classify the presynaptic α2-auto- and heteroreceptors in the rat brain cortex. The rank order of potency in antagonizing the inhibitory effect of (-)-noradrenaline or clonidine on the K+-induced [3H]noradrenaline and [3H]5-hydroxytryptamine (5-HT) release from superfused synaptosomes was BRL-44408 ≥ BRL-41992 >> imiloxan. The same rank order was found for the affinities of these compounds for [3H]yohimbine binding in human platelet membranes, containing only α(2A)-adrenoceptors, but does not correlate with the known affinities for α(2B)-adrenoceptors (BRL-41992 ≥ imiloxan > BRL-44408). These data support the conclusion that presynaptic α2-auto- and heteroreceptors in rat brain cortex do not belong to the α(2B)-subtype and suggest that the modulation of noradrenaline and 5-HT release may be mediated by the α(2A)-subtype.

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