PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 11578600

Decrease in GABA synthesis rate in rat cortex following GABA-transaminase inhibition correlates with the decrease in GAD(67) protein.

G F Mason·D L Martin·S B Martin·D Manor·N R Sibson·A Patel·D L Rothman·K L Behar
View original source ↗Export metadata ↓

Abstract

gamma-Aminobutyric acid (GABA) synthesis in the brain is mediated by two major isoforms of glutamic acid decarboxylase, GAD(65) and GAD(67). The contribution of these isoforms to GABA synthesis flux (V(GAD)) is not known quantitatively. In the present study we compared V(GAD) in cortex of control and vigabatrin-treated rats under alpha-chloralose/70% nitrous oxide anesthesia, with total GAD activity and GAD isoform composition (GAD(65) and GAD(67)) measured by enzymatic assay and quantitative immunoblotting. V(GAD) was determined by re-analysis of 13C NMR data obtained ex vivo and in vivo during infusions of [1-13C]glucose using an extension of a model of glutamate-glutamine cycling that included a discrete GABAergic neuronal compartment with relevant interconnecting fluxes. V(GAD) was significantly lower in vigabatrin-treated rats (0.030-0.05 micromol/min per g, P<0.003) compared to the non-treated control group (0.10-0.15 micromol/min per g). The 67-70% decrease in V(GAD) was associated with a 13% decrease in total GAD activity (P=0.01) and a selective 44+/-15% decrease in GAD(67) protein (from 0.63+/-0.10 to 0.35+/-0.08 microg protein/mg tissue, P<0.05); GAD(65) protein was unchanged. The reduction in GAD(67) protein could account for a maximum of approximately 65% of the decrease in V(GAD) in vigabatrin-treated animals suggesting that inhibition of GAD(65) must have also occurred in these experiments, although product inhibition of GAD(67) by increased GABA could play a role. GAD(67) could account for 56-85% of cortical GABA synthesis flux under basal conditions and the entire flux after vigabatrin treatment.

Explore related subjects

4-Aminobutyrate TransaminaseAnimalsAstrocytesCarbon RadioisotopesCerebral CortexDown-RegulationEnzyme InhibitorsGlutamate DecarboxylaseGlutamic AcidGlutamineIsoenzymesKineticsMaleNeuronsProtein IsoformsRatsRats, Sprague-DawleyVigabatringamma-Aminobutyric AcidJournal ArticleResearch Support, Non-U.S. Gov'tResearch Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

G F Mason, D L Martin, S B Martin, D Manor, N R Sibson, A Patel, D L Rothman, K L Behar. 2001-09-28. Decrease in GABA synthesis rate in rat cortex following GABA-transaminase inhibition correlates with the decrease in GAD(67) protein.. https://doi.org/10.1016/s0006-8993(01)02778-0

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2002

Gamma-vinyl GABA, an irreversible inhibitor of GABA transaminase, alters the acquisition and expression of cocaine-induced sensitization in male rats.

We examined the effect of (+/-)-gamma-vinyl GABA (GVG, Vigabatrin), an irreversible inhibitor of the enzyme GABA transaminase, on the acquisition and expression of cocaine-induced sensitization in albino male Sprague-Dawley rats. Animals received a single injection of 1 ml/kg i.p. of 0.9% saline or 15 mg/kg i.p. of (-)-cocaine and locomotor activity was assessed using automated locomotor cages and stereotyped behaviors were scored using a 4-point rating scale (Day 1). Subsequently, animals were given 15 mg/kg i.p. of cocaine every 48 h in their home cage for 1 week (Days 3, 5, and 7) and then given no treatment for 1 week. A challenge injection of 15 mg/kg i.p. of cocaine, but not vehicle, produced a significant increase in locomotor activity and stereotyped behaviors on Day 15 compared to animals that received cocaine on Day 1. Administration of 75 mg/kg i.p. of GVG 2.5 h before the cocaine injections did not significantly alter the acquisition of cocaine-induced locomotor sensitization. However, 150 mg/kg i.p. of GVG significantly attenuated the acquisition of cocaine-induced locomotor sensitization. Administration of 150 mg/kg i.p. of GVG 2.5 h before the cocaine challenge injection on Day 15 significantly attenuated the expression of cocaine-induced locomotor sensitization. Acquisition and expression of cocaine-induced sensitization of stereotypy was also significantly attenuated by 150 mg/kg i.p. of GVG. Since sensitization may be one of the factors involved in relapse to drug use, the present results, in combination with previous findings that GVG blocks the rewarding and incentive motivating effects of cocaine, suggest that GVG might prove useful in the treatment of cocaine addiction.

4-Aminobutyrate Transaminase↗
PubMed2002

Inactivation and inhibition of gamma-aminobutyric acid aminotransferase by conformationally restricted vigabatrin analogues.

Four cyclohexene analogues of gamma-aminobutyric acid (GABA) and beta-alanine were designed as conformationally rigid analogues of the epilepsy and drug addiction drug vigabatrin and as potential mechanism-based inactivators of gamma-aminobutyric acid aminotransferase (GABA-AT). The corresponding cyclopentene analogues were previously reported to be inhibitors, but not inactivators, of GABA-AT (Qiu, J.; Pingsterhaus, J.; Silverman, R. B. J. Med. Chem. 1999, 42, 4725-4728). cis-3-Aminocyclohex-4-ene-1-carboxylic acid (3) and cis-2-aminocyclohex-3-ene-1-carboxylic acid (5) showed time- and concentration-dependent, irreversible inactivation of GABA-AT. In both cases, the inactivations are protected by substrate, indicating that they are active site-directed. trans-3-Aminocyclohex-4-ene-1-carboxylic acid (4) and trans-2-aminocyclohex-3-ene-1-carboxylic acid (6) are not inactivators but are competitive reversible inhibitors of GABA-AT. Unlike the cyclopentene analogues, there appears to be sufficient ring flexibility to allow inactivation to occur. The orientation of the carboxylic and amino groups of these analogues is important for their binding to GABA-AT. Molecular modeling of GABA-AT with 3-6 and molecular dynamics simulations with vigabatrin bound provide rationalizations for the inhibitory properties of these compounds.

4-Aminobutyrate Transaminase↗
PubMed2002

Detection of molecules related to the GABAergic system in a single-cell eukaryote, Paramecium primaurelia.

Gamma-aminobutyric acid (GABA)-related molecules were identified in Paramecium primaurelia by immunocytochemical methods, and GABA(A) receptors by their histochemical BODIPY-binding sites. Confocal microscope analysis showed different localizations according to the stages of the developmental cycle. A comparison was made with the cholinergic molecules, such as the acetylcholine biosynthetic enzyme (choline acetyltransferase), in double-labelled cells by confocal microscopy. In vivo experiments suggested the involvement of GABA-related molecules in cell-cell interaction.

4-Aminobutyrate Transaminase↗