3016189

Comparative stereostructure-activity studies on GABAA and GABAB receptor sites and GABA uptake using rat brain membrane preparations.

Article date: 1986/9/1

PubMed ID: 3016189

Journal name: Journal of neurochemistry (ISSN: 0022-3042)

ABSTRACT

The affinities of a number of analogues of gamma-aminobutyric acid (GABA) for GABAA and GABAB receptor sites and GABA uptake were studied using rat brain membrane preparations. Studies on the (S)-(+)- and (R)-(-)-isomers of baclofen, 3-hydroxy-4-aminobutyric acid (3-OH-GABA), and 4,5-dihydromuscimol (DHM) revealed different stereoselectivities of these synaptic mechanisms in vitro. Although (S)-3-OH-GABA and, in particular, (S)-DHM were more potent than the corresponding (R)-isomers as inhibitors of GABAA binding, the opposite stereoselectivity was demonstrated for the GABAB binding sites. Thus, (R)-3-OH-GABA and (R)-baclofen were more potent than the (S)-isomers as inhibitors of GABAB binding, (R)-baclofen being some five times more potent than (R)-3-OH-GABA. These two (R)-isomers actually have opposite orientation of the substituents on the GABA backbones, suggesting that the lipophilic substituent of (R)-baclofen interacts with a structural element of the GABAB receptor site different from that that binds the very polar hydroxy group of (R)-3-OH-GABA. The O-methylated analogue of 3-OH-GABA, 3-methoxy-4-aminobutyric acid (3-OCH3-GABA), did not interact significantly with GABAB sites. The homologues of GABA, trans-4-aminocrotonic acid (trans-ACA), muscimol, and 3-OH-GABA, that is, 5-aminovaleric acid (DAVA), trans-5-aminopent-2-enoic acid, homomuscimol, and 3-hydroxy-5-aminovaleric acid (3-OH-DAVA), respectively, were generally much weaker than the parent compounds, whereas 2-hydroxy-5-aminovaleric acid (2-OH-DAVA) showed a significantly higher affinity for GABAB sites than the corresponding GABA analogue.(ABSTRACT TRUNCATED AT 250 WORDS)

This document is available from: http://directlinks.cc/files/muscimol/3016189.pdf

Author List: Falch E, Hedegaard A, Nielsen L, Jensen B R, Hjeds H, Krogsgaard-Larsen P

Publication Types: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Substances mentioned in the article: Receptors, GABA-A; gamma-Aminobutyric Acid;

Mesh terms: Animals; Brain/metabolism; Chemical Phenomena; Chemistry; Female; Male; Rats; Receptors, GABA-A/metabolism; Stereoisomerism; Structure-Activity Relationship; Synaptic Membranes/metabolism; gamma-Aminobutyric Acid/analogs & derivatives;

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