NMDA AND CARBACHOL BUT NOT AMPA AFFECT DIFFERENTLY THE RELEASE OF [H-3] GABA IN STRIOSOME-ENRICHED AND MATRIX-ENRICHED AREAS OF THE RAT STRIATUM

The effects of pha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMP A; 10(-3) M), N-methyl-D-aspartate (10(-3) M, in the absence of magnes ium or presence of AMPA) and carbachol (10(-3) M) on the release of pr eloaded [H-3]gamma-aminobutyric acid ([H-3]GABA) from microdiscs of ti ssue punched out from sagittal brain slices in striosome- or matrix-en riched areas of the rat striatum have been compared. Although AMPA sti mulated similarly the release of [H-3]GABA in both striatal compartmen ts, the release of [H-3]GABA evoked by either N-methyl-D-aspartate (in the presence of AMPA) or carbachol was more pronounced in matrix- tha n in striosome-enriched areas. AMPA- and N-methyl-D-aspartate- (in the absence of magnesium) evoked responses were reduced but not abolished in the presence of tetrodotoxin (10(-6) M) in both compartments while the carbachol-evoked release of [H-3]GABA was decreased by tetrodotox in only in the matrix. The interruption of cholinergic transmission by the combined application of atropine (10(-5) M) and pempidine (10(-4) M) was without effect on the AMPA-evoked release of [H-3]GABA, but it reduced the N-methyl-D-aspartate- (in the absence of magnesium or pre sence of AMPA) evoked release of [H-3]GABA in both compartments, these reductions being of similar amplitude than those observed with tetrod otoxin.