title: Local GABAergic regulation of the N-methyl-D-aspartate-evoked release of dopamine is more prominent in striosomes than in matrix of the rat striatum.
abstract: Using an in vitro microsuperfusion device we have previously demonstrated that in the absence of magnesium, the N-methyl-D-aspartate-evoked release of [3H]dopamine (continuously synthesized from [3H]tyrosine) is more prominent in matrix- than in striosome-enriched areas of the rat striatum and that in the matrix, the response is partially tetrodotoxin-sensitive. Since the medium-sized GABAergic neurons are the main targets of the corticostriatal glutamatergic fibers, the involvement of local GABAergic regulation in the N-methyl-D-aspartate-evoked release of [3H]dopamine was investigated in both striatal compartments using the same experimental approach. Firstly, bicuculline alone (5 microM, 25-min application) was shown to enhance the release of [3H]dopamine similarly in both compartments revealing the existence of a tonic GABAergic control of the spontaneous release of [3H]dopamine. Secondly, the N-methyl-D-aspartate (50 microM, 25-min application)-evoked release of [3H]dopamine was markedly amplified in the presence of bicuculline (5 microM, continuous delivery). This effect being more important in striosome- than in matrix-enriched areas (5.5- and two-times the N-methyl-D-aspartate-evoked response observed in the absence of the GABAA antagonist, respectively). Thirdly, the tetrodotoxin (1 microM, continuous delivery)-resistant N-methyl-D-aspartate-evoked responses were also enhanced in the presence of bicuculline, but in this case, the amplification of the N-methyl-D-aspartate-evoked release of [3H]dopamine was less marked than in the absence of tetrodotoxin and identical in both compartments (about two-times the tetrodotoxin-resistant N-methyl-D-aspartate-evoked responses observed in the absence of bicuculline). Altogether, these results indicate that GABAergic neurons exert locally an important inhibitory regulation of the N-methyl-D-aspartate-evoked release of dopamine and that this effect is more prominent in the striosome-enriched area. Both tetrodotoxin-sensitive (striosome) and tetrodotoxin-resistant (striosome and matrix) processes intervene in this inhibitory GABAergic presynaptic regulation of dopamine release.
authors.affiliation: Chaire de Neuropharmacologie, INSERM U114, Collège de France, Paris.
authors.forename: M O
authors.initials: MO
authors.lastname: Krebs
authors.forename: M L
authors.initials: ML
authors.lastname: Kemel
authors.forename: C
authors.initials: C
authors.lastname: Gauchy
authors.forename: M
authors.initials: M
authors.lastname: Desban
authors.forename: J
authors.initials: J
authors.lastname: Glowinski
mesh_terms: D000818:Animals; D001345:Autoradiography; D001640:Bicuculline / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology*; D017072:Neostriatum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013779:Tetrodotoxin / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D013779:Tetrodotoxin; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D004298:Dopamine; D001640:Bicuculline