Effects of dithiothreitol and glutathione on the release of [3H]GABA from hippocampal slices

Bll

Yth Meeting of the ESN

42

41

EFFECTS OF DITRIOTRREITOL THIONE ON THE RELEABE OF HIPPOCARPAL SLICES S.S.

Oja,

JanBky,

It.

V.

AND QLUTA[%]aABA FROM

Varga

and

Pirjo

Saransaari Tampere Brain Research Ctr, Dept. Biomedical University of Tamper-e, Finland Sciences, release

The

of

agonists glutamate studied slices was dithiothreitol (DTT)

[)H]GABA

from in

evoked

by

hippocampal rat presence of the

or reduced (GSH) and oxidized (GSSG) forms of glutathione. DTT, GSH and GSSG (1 mM) had no effect on the release of GABA. Neither did they basal affect the magnitude of initial stimulation of GABA release by 0.1 mM glutamate, kainate, N-methyl-D-aspartate quisqualate, (NMDA), NMDA applied with glycine. glycine or the presence of DTT the in However, stimulation was significantly more prolonged. The prolongation was concentration-dependent, the non-NMDA slightly inhibited by only 6-cyano-7-nitroquinoxaline-2,3antagonist dione (CNQX) and abolished by the NMDA (+)-S-methyl-lO,ll-dihydro-SHantagonist dibenzo(a,d)cyclohept-5,10-imine hydrogen and GSSG (W-801). Both GSH maleate attenuated the effect of DTT. The results imply that the stimulated release of GABA in by the redox the hippocampus is affected state of NUDA receptors possibly controlled by endogenous glutathione. (Supported by the Emil Aaltonen Foundation, Finland.) 43

INFLUENCE OF LIPID PEROXIDATlON ONGABARELEASE A COMPARATIVE STUDY IN SYNAPTOSOMES AND CIILTP RED RETINA CELLS 1'. Agostinho, P. Caseiro, C. R. Oliveica Center for Neurosciences,University nfC&lmbra, 3049 Coimbra Codex, Portugal Uptake and release of neurotransmitters havebeen studied in the central nervous system and incell cultures.GABA is an ubiquitous neurotransndtter in the CNS and Glutamate and GABAarealso found in retina cells where a high affinity Na ' dependent glutamate/GABA exchange was shown.In this study we compare the mechanisms ofrelease of 3H-accumulated GABA by synaptosomes and cultured chick retina cells and the influence of membrane lipid peroxidation on the releaseof GABA is also eva1uated.A Ca2+ dependent (exocytotic) and a Cazf-independent (cytoplasmir) release of 3H - GABA are characterized in synaP tosomes and in cultured retina cells.Ascorbate/ Fe'+'inducedmembranelipidperoxidationinhibits the exocytoticandthe cytoplasmicrelease of 3H-GABAinduced by K+-depolarization in synoptoso mes,while an increase in the release of GABAinduced by K+ and glutamateoccurs inretina cells. The involvement of changes inmembrane ursaturated fatty acid (20:4 and 22:6)and the influence of lipid peroxidation on the Na+-dependent&W carrier are discussed. 44

PHOSPHATE ACTIVATED GLUTAMINASE (PAG) AND MITOCHONDRIAL KETODICARBOXYLATE CARRIER (KDC): KEY POINTS FOR THE BIOSYNTHESIS NEUROTRANSMITTER GLUTAMATE IN RA%EREBRAL CORTEX. G. Palaiologos, A. Georgopoulos Lab. Biol. Chem. Medical School, 11527 Athens, Greece

and R. Svarna. Univ. of Athens,

Rat cerebral cortex slices were preloaded with D-TH]aspartate and superfused with Krebs-Ringer-HEPES-glucose medium with or without glutamine (ImM), in the presence or absence of Ca2+. or ketone

Phenylsuccinate (5mM) or NH4+ (4mM) bodies (3mM) were added to the superfusion

medium and

the

Ca2+

release of D-[‘HI-aspattate the control with glutamine. presence of NH4+ the

release

dependent

K+(45mM)

stimulated

was calculated and compared to The absence of glutamrne, the

or phenylsuccinata significantly increased

of D-[‘HI-aspartate

that means a decrease of

exogenously supplted neurotransmitter glutamate. Ketone bodies had no effect, Because the absence of glutamine deprives PAG from its substrate, NH4* rnhibiis PAG, phenylsuccinate

inhibits KDC

and

ketone

bodies

inhibit

glycolysis the present results indicate that in rat cerebral cortex, PAG and KDC, but not glycolysi- supply neurotransmitter glutamate.

PLASNA

QREA

AND

ALCOHOLIER

F. Petty, G.L. Kramer, C. Gullion, and M. Fulton Veterans Affairs Medical Center and UT Southwestern Medical School, Dallas, TX, U.S.A.

Free and total levels of GABA were healthy alcoholics and measured in Soon controls at several points in time. alcoholics after cessation of drinking, had low levels of free pGABA, but only correction for other statistical after Three weeks later, free pGABA variables. and was dropped in alcoholics had significantly lower than controls without confounding variables. for correction Total pGABA was lower than control at both Alcoholics who remained abstinent points. for 3-6 months continued to have low free those who resumed drinking pGABA while Drinking on returned to control values. could be predicted from free follow-up These ~GABA levels after 3 week sobriety. data are in agreement with other clinical and laboratory work which suggests that increases GABA consumption alcohol function measured by free pGABA, and that some alcoholics may have a GABA deficit.