Mu opioid control of the N-methyl-D-aspartate-evoked release of [3H]-acetylcholine in the limbic territory of the rat striatum in vitro: diurnal variations and implication of a dopamine link.

Using an in vitro microsuperfusion procedure, the release of newly synthesized [(3)H]-acetylcholine (ACh), evoked by N-methyl-D-aspartate (NMDA) receptor stimulation, was investigated in striosome-enriched areas and matrix of the rat striatum. The role of micro-opioid receptors, activated by endogenously released enkephalin, on the NMDA-evoked release of ACh was studied using the selective micro-opioid receptor antagonist, beta-funaltrexamine. Experiments were performed 2 (morning) or 8 (afternoon) h after light onset, in either the presence or absence (alpha-methyl-p-tyrosine, an inhibitor of dopamine synthesis) of dopaminergic transmission. As expected, based on the presence of micro-opioid receptors in striosomes, beta-funaltrexamine (0.1 nM, 10 nM and 1 microM) enhanced the NMDA (1 mM+10 microM D-serine)-evoked release of ACh in striosome-enriched areas but not in the matrix. Interestingly, these responses were significantly more pronounced in afternoon than in morning experiments. In the presence of alpha-methyl-p-tyrosine, the NMDA-evoked release of ACh was increased with similar amplitude in morning and afternoon experiments. However, in this condition (without dopamine transmission), the facilitatory effects of beta-funaltrexamine on the NMDA-evoked release of ACh were suppressed totally in the morning and only partially in the afternoon. The selective micro-opiate agonist, [D-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (1 microM, coapplied with NMDA), was without effect on the NMDA-evoked release of ACh but abolished both dopamine-dependent (morning) and dopamine-independent (afternoon) responses of beta-funaltrexamine (10 nM and 1 microM).Therefore, in the limbic territory of the striatum enriched in striosomes, the micro-opioid-inhibitory regulation of ACh release follows diurnal rhythms. While dopamine is required for this regulation in the morning and the afternoon, an additional dopamine-independent process is present only in the afternoon.

Control by GABA and tachykinins of the evoked release of acetylcholine in striatal compartments under different modalities of NMDA receptor stimulation.

The contribution of endogenously released dopamine, GABA and its co-transmitters, substance P (SP) and neurokinin A (NKA), to the control of the evoked release of acetylcholine was investigated in vitro in the striosomes and the matrix of the rat striatum under various modalities of NMDA receptor stimulation (NMDA 50 microM or 1 mM without or with 10 microM D-serine). Sulpiride, bicuculline, SR140333 and SR48968, the antagonists of D(2), GABA A, NK(1) and NK(2) tachykinin receptors, respectively, were used for this purpose. (1) In both striatal compartments, the dopamine-mediated inhibitory regulation of the evoked release of acetylcholine only occurred when D-serine was co-applied with 50 microM or 1 mM NMDA. (2) In striosomes, the dopamine-dependent inhibitory effects of SP and NKA on the evoked release of acetylcholine only occurred when D-serine was co-applied with 50 microM or 1 mM NMDA. (3) A similar inhibitory regulation by NKA, but not SP, was found in the matrix when 1 mM NMDA was co-applied with D-serine. (4) In contrast, the dopamine-dependent facilitatory effect of GABA on the evoked release of acetylcholine did not require added D-serine and was more important with 1 mM than 50 microM NMDA. In the presence of D-serine, and depending on the NMDA concentration, the facilitatory regulation of GABA was reduced (matrix) or suppressed (striosomes). This latter effect was partially restored in the presence of SR48968. Therefore, the dopamine-dependent inhibitory effects of tachykinins on the evoked release of acetylcholine only occurred when NMDA receptors were stimulated in the presence of saturating concentrations of D-serine.

Role of arachidonic acid in the regulation of the NMDA-evoked release of acetylcholine in striatal compartments.

The role of endogenously released arachidonic acid in the control of the NMDA (50 microM)-evoked release of [3H]-acetylcholine previously formed from [3H]-choline was investigated in striosome-enriched areas and in the matrix of the rat striatum using a microsuperfusion procedure in vitro. Experiments were performed with either mepacrine (0.2 microM) or bovine serum albumin (BSA, 0.02%) which inhibits phospholipase A2 activity or binds endogenously released arachidonic acid, respectively. Both treatments similarly reduce the NMDA-evoked release of [3H]-acetylcholine, this effect being more pronounced in striosomes than in the matrix. These reductions result from a facilitation of dopamine release, since they were not observed in the presence of (-)sulpiride, the D2 dopamine receptor antagonist. Moreover, the superfusion with BSA was shown to enhance the release of [3H]-dopamine (formed from [3H]-tyrosine), this effect being of larger amplitude in striosomes than in the matrix. In control conditions, due to the blockade of the presynaptic inhibitory effect of GABA on dopamine release, bicuculline (GABA(A) receptor antagonist) reduces the NMDA-evoked release of [3H]-acetylcholine in both striatal compartments. Bicuculline was no longer effective following superfusions with either mepacrine or BSA, suggesting that these treatments eliminate the GABAergic presynaptic inhibitory control on dopamine transmission and thus lead to the dopamine-mediated inhibition of [3H]-acetylcholine release. These results indicate that arachidonic acid endogenously formed under weak stimulation of NMDA receptors contributes to the regulation of the evoked release of [3H]-acetylcholine by facilitating GABAergic transmission and that this process is more important in striosomes than in the matrix.

Distinct modifications by neurokinin1 (SR140333) and neurokinin2 (SR48968) tachykinin receptor antagonists of the N-methyl-D-aspartate-evoked release of acetylcholine in striosomes and matrix of the rat striatum.

The effects of SR140333 and SR48968 (neurokinin1 and neurokinin2 tachykinin receptor antagonists, respectively) on the N-methyl-D-aspartate-evoked release of [3H]acetylcholine (previously formed from [3H]choline) were investigated in striosome-enriched areas and in the matrix of the rat striatum using an in vitro microsuperfusion method. In both striatal compartments, SR140333 and SR48968 did not modify the 50 microM N-methyl-D-aspartate-evoked release of [3H]acetylcholine. However, in low concentrations, both SR140333 (0.1 microM to 1 pM) and SR48968 (0.1 microM to 0.1 nM) markedly enhanced the 1 mM N-methyl-D-aspartate (+10 microM D-serine)-evoked release of [3H]acetylcholine in striosome-enriched areas. These responses were dopamine-dependent since they were not observed any more following the local blockade of D2 receptors by sulpiride or of dopamine synthesis by alpha-methyl-p-tyrosine. A dopamine-dependent disinhibitory effect (of lower amplitude) on the 1 mM N-methyl-D-aspartate (+10 microM D-serine)-evoked release of [3H]acetylcholine was also induced by SR48968 (0.1 microM to 0.1 nM) (but not by SR140333) in the matrix. In addition, in the matrix, as shown only in the presence of alpha-methyl-p-tyrosine, both SR140333 and SR48968 reduced the 1 mM N-methyl-D-aspartate (+10 microM D-serine)-evoked response and these non-dopamine-mediated inhibitory effects only occurred at the highest tested concentration (0.1 microM) of the antagonists. Indicating the specificity of these responses, the effects of SR140333 were reproduced by RP67580, another neurokinin1 receptor antagonist and, as expected from previous binding studies, corresponding SR140333 and SR48968 enantiomers were without effect. These results suggest that under potent stimulation of N-methyl-D-aspartate receptors, endogenously released substance P and neurokinin A (or related tachykinins) regulate differently the N-methyl-D-aspartate-evoked release of [3H]acetylcholine in striosomes and in the matrix. The inhibitory effects of these tachykinins on the evoked release of [3H]acetylcholine are mediated by dopamine. On the contrary, their facilitatory responses are only observed in the matrix under blockade of dopamine transmission.

N-methyl-D-aspartate-evoked release of [3H]acetylcholine in striatal compartments of the rat: regulatory roles of dopamine and GABA.

The N-methyl-D-aspartate-evoked release of [3H]acetylcholine previously formed from [3H]choline was estimated in striosome- (identified by [3H]naloxone binding) or matrix-enriched areas of the rat striatum using an in vitro microsuperfusion procedure. Experiments were performed in either the absence or the presence of dopaminergic and/or GABAergic receptor antagonists. Although the cell bodies of the cholinergic interneurons were mainly found in the matrix, in the absence of magnesium, N-methyl-D-aspartate (50 microM) stimulated the release of [3H]acetylcholine in both striatal compartments. These responses were blocked by either magnesium, dizocilpine maleate, 7-chlorokynurenate or tetrodotoxin. N-Methyl-D-aspartate responses were concentration-dependent, but the 1 mM N-methyl-D-aspartate response was higher in striosomes than in the matrix. The co-application of D-serine (10 microM) enhanced the 10 microM N-methyl-D-aspartate response in both compartments, but reduced those induced by 1 mM N-methyl-D-aspartate, this reduction being higher in striosomes. The blockade of dopaminergic transmission with the D2 and D1 dopaminergic receptor antagonists, (-)-sulpiride (1 microM) and SCH23390 (1 microM), was without effect on the 50 microM N-methyl-D-aspartate-evoked release of [3H]acetylcholine, but markedly enhanced the 1 mM N-methyl-D-aspartate+D-serine-evoked response in striosomes and to a lesser extent in the matrix. Disinhibitory responses of similar amplitude were observed not only in striosomes but also in the matrix when (-)-sulpiride was used alone, while SCH23390 alone enhanced the 1 mM N-methyl-D-aspartate+D-serine response only in striosomes and to a lower extent than (-)-sulpiride. These results indicate that D2 receptors are mainly involved in the inhibitory effect of dopamine on the 1 mM N-methyl-D-aspartate+D-serine-evoked release of [3H]acetylcholine. They also show that the stimulation of D1 receptors can either reduce (striosomes) or enhance (matrix) this response, since in the latter case the effect induced by the combined application of the D1 and D2 receptor antagonists was smaller than that observed with the D2 receptor antagonist alone. Indicating that released GABA facilitates N-methyl-D-aspartate responses, the blockade of GABAA receptors with bicuculline (5 microM) reduced the 50 microM N-methyl-D-aspartate-evoked release of [3H]acetylcholine in both striatal compartments and the 1 mM N-methyl-D-aspartate+D-serine response in the matrix. These effects result from an inhibition by GABA of the evoked release of dopamine, since the reducing effects of bicuculline on N-methyl-D-aspartate responses were not observed under the complete blockade of dopaminergic transmission by the D1 and D2 receptor antagonists. Further demonstrating a facilitatory role of GABA in the control of N-methyl-D-aspartate-evoked release of [3H]acetylcholine, in the presence of bicuculline, (-)-sulpiride and SCH23390 alone or in combination enhanced, in both compartments, the responses induced not only by 1 mM N-methyl-D-aspartate+D-serine, but also by 50 microM N-methyl-D-aspartate.

Distinct regulations by septide and the neurokinin-1 tachykinin receptor agonist [pro9]substance P of the N-methyl-D-aspartate-evoked release of dopamine in striosome- and matrix-enriched areas of the rat striatum.

The effects of septide (a short substance P C-terminal analogue) and of the neurokinin-1 receptor agonist [Pro9]substance P on the N-methyl-D-aspartate (50 microM)-evoked release of [3H]dopamine (continuously synthesized from [3H]tyrosine) were investigated in the absence or the presence of the selective neurokinin-1 receptor antagonist RP 67580 in selected striosome- and matrix-enriched areas of the rat striatum. Experiments were performed in vitro using a microsuperfusion procedure described previously. At a concentration of 0.1 microM, septide and [Pro9]substance P stimulated the spontaneous release of [3H]dopamine in striosome-enriched areas similarly. However, in this compartment, these peptides induced larger and opposite effects on the N-methyl-D-aspartate (50 microM)-evoked release of [3H]dopamine (estimated in the absence of magnesium). Indeed, septide markedly enhanced the N-methyl-D-aspartate response, while [Pro9]substance P largely reduced the N-methyl-D-aspartate-evoked release of [3H]dopamine. Septide also enhanced the N-methyl-D-aspartate response in the matrix, but [Pro9]substance P was without effect. When used alone, at 0.1 or 1 microM, RP 67580 reduced by about 33% the N-methyl-D-aspartate-evoked release of [3H]dopamine in striosome-enriched areas. In contrast, in the matrix, the N-methyl-D-aspartate response was enhanced in the presence of a low concentration of the antagonist, while the higher concentration was ineffective. In striosomes, the reducing effect of [Pro9]substance P and the enhancing action of septide on the N-methyl-D-aspartate response were respectively blocked in the presence of low and high concentrations of RP 67580, while the stimulatory effect of septide on the N-methyl-D-aspartate response in the matrix was prevented with both concentrations of the neurokinin-1 receptor antagonist. Finally, the co-application of [Pro9]substance P (0.1 microM) with septide (0.1 microM) abolished the enhancing effect of septide on the N-methyl-D-aspartate-evoked release of [3H]dopamine in both striatal compartments. Altogether, these results suggest that substance P and eventually one of its metabolites, substance P(6-11) or another endogenous tachykinin released under the action of N-methyl-D-aspartate, contribute to the regulation of [3H]dopamine release in both striatal compartments. They also extend previous observations which allowed us to demonstrate that the local circuits contributing to the presynaptic regulation of [3H]dopamine release differ in striosome- and matrix-enriched areas. Furthermore, in agreement with observations made in some peripheral tissues, the present results support the existence of "septide-sensitive" tachykinin receptors in the rat striatum or alternatively of septide sensitive sites on tachykinin neurokinin-1 receptors distinct from those sensitive to neurokinin-1 receptor agonists, coupled to distinct transducing systems, and thus leading to biological responses which differ from those evoked by neurokinin-1 receptor agonists.

Heterogeneous topographical distribution of the striatonigral and striatopallidal neurons in the matrix compartment of the cat caudate nucleus.

The topographical organization of the striatonigral projection was investigated in the cat by comparing the localization and the intensity of labelling of retrogradely labelled cells in the caudate nucleus following one or multiple injections of horseradish peroxidase-wheat germ agglutinin into the center or along the rostrocaudal axis of the substantia nigra pars reticulata. Second, the localizations of retrogradely labelled striatopallidal neurons and of clusters of aggregated striatonigral neurons (as outlined by the transport of 14C-material) were compared in cats that received four horseradish peroxidase-wheat germ agglutinin injections into the internal segment of the globus pallidus and three nigral injections of 14C-amino acids into the substantia nigra pars reticulata. Two types of striatonigral neurons located predominantly within the matrix compartment were identified: poorly collateralized aggregated cells distributed in clusters and more numerous collateralized cells distributed outside the clusters. In addition, two cell types were distinguished within each cluster of aggregated neurons. Those innervating the center of the substantia nigra pars reticulata were observed after a single nigral injection of the tracer, whereas those projecting to distinct sites of the substantia nigra pars reticulata along a rostrocaudal axis were observed only after multiple injections. Striatal neurons innervating the internal segment of the globus pallidus were heterogeneously distributed predominantly within the matrix but outside the clusters of aggregated striatonigral neurons. Together, these results provide further evidence for the heterogeneity of the matrix and for the complexity of matrix striatonigral connections that send both diverging and converging signals to the substantia nigra pars reticulata.

Role of dynorphin and GABA in the inhibitory regulation of NMDA-induced dopamine release in striosome- and matrix-enriched areas of the rat striatum.

Using a new superfusion procedure in vitro, we have previously reported that the NMDA-evoked release of newly synthesized 3H-dopamine (DA) was higher in matrix- than in striosome-enriched areas of the rat striatum. In addition, GABAergic medium-sized spiny neurons were shown to be indirectly involved in this regulation. Since dynorphin and GABA are colocalized in a population of medium-sized spiny neurons, the role of dynorphin-containing neurons in the NMDA-evoked release of 3H-DA has been investigated using the same superfusion procedure on rat striatal slices. (1) The NMDA (50 microM, 25 min application)-evoked release of 3H-DA was increased in the presence of naloxone (1 microM, continuously delivered) in both striatal compartments, the overall response being more elevated in the striosome-enriched area. (2) The TTX (1 microM, continuously delivered)-resistant NMDA-evoked responses were also enhanced in the presence of naloxone, but in this case, the disinhibitory effects of naloxone were similar in striosome- and matrix-enriched areas. (3) The selective kappa-agonist U-50488 (1 microM) totally reversed the naloxone-disinhibitory effect on the NMDA-evoked response in the matrix-enriched area, but only partially in the striosome-enriched area. It also completely prevented the disinhibitory effect of naloxone on the TTX-resistant NMDA-evoked release of 3H-DA in both compartments. (4) The bicuculline (5 microM)- and naloxone (1 microM)-disinhibitory effects on the NMDA-evoked release of 3H-DA were additive in the matrix- but not in the striosome-enriched areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Does bicuculline antagonize NMDA receptors? Further evidence in the rat striatum.

In two areas of the rat striatum, the in vitro N-methyl-D-aspartate (NMDA, 50 microM)-evoked release of [3H]dopamine was studied in the presence of bicuculline (5 and 50 microM), an antagonist of GABAA receptors. The responses observed with the higher concentration (50 microM) is compatible with an antagonistic activity of bicuculline on NMDA receptor, as recently reported by Wright and Nowak.

NMDA regulation of dopamine release from proximal and distal dendrites in the cat substantia nigra.

The NMDA regulation of the dendritic release of [3H]dopamine ([3H]DA) synthesized from [3H]tyrosine was investigated in vitro using a microsuperfusion procedure in the pars compacta (SNC) and the pars reticulata (SNR) of the cat substantia nigra. The spontaneous release of [3H]DA was threefold higher in the SNC than in the SNR and amphetamine (1 microM) enhanced similarly [3H]DA release in both nigral areas. In the absence of magnesium, NMDA (50 microM) stimulated markedly the release of [3H]DA in the SNC and SNR, these effects being completely prevented by MK 801 (1 microM), the NMDA receptor antagonist. The DA uptake inhibitor, nomifensine (5 microM), increased the amount of [3H]DA recovered in SNC (x2) and SNR (x3) superfusates but did not significantly modify the NMDA-evoked responses. The effects of NMDA seen in the absence or presence of nomifensine persisted when the two nigral areas were continuously superfused with tetrodotoxin (1 microM). These results are in favor of the presence of NMDA receptors on dopaminergic dendritic arborizations and indicate that the stimulation of these receptors facilitates in a similar way the release of DA from proximal and distal dendrites.

Spatial organization of patch and matrix compartments in the rat striatum.

The visualization of mu opiate receptors by [3H]naloxone binding was used to determine precisely the spatial organization of the patch compartment in the rat striatum and its reproducibility in different animals. Three-dimensional reconstruction of the patch network was made using maps of autoradiographic data obtained from successive coronal, sagittal or horizontal sections. The extreme rostral pole of the striatum (A 11) was characterized by a large patch territory exhibiting complex and tortuous fields with several extensions. In the intermediate part of the structure (A 9.0-10.0), about 20 serial parallel continuous patch channels running in a mediolateral axis, obliquely oriented and displaying in some cases connecting branches, could be observed. However, no channels could be distinguished in the rostrocaudal direction. More caudally, patches were rare and of small size. In addition, the laterocaudal region of the striatum was almost exclusively represented by a large matrix field. Finally, a fine discontinuous band of [3H]naloxone binding was seen in all sections, bordering and limiting the dorsolateral part of the striatum. The topographical and spatial distribution of the patch compartment was similar in all animals investigated. However, due to the tortuous shape and the labyrinthine organization of the patches, the precise degree of reproducibility from one animal to another could not be established. Nevertheless, the prominent patch compartment observed in the rostral pole of the striatum, the patch channels, oriented in the mediolateral axis as well as the large laterocaudal matrix field were observed in all cases. These results were compared with previous data obtained in the cat in which patch (striosome) channels oriented along a rostrocaudal axis are also observed.

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.

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.

Distinct presynaptic control of dopamine release in striosomal- and matrix-enriched areas of the rat striatum by selective agonists of NK1, NK2, and NK3 tachykinin receptors.

Using a sensitive in vitro microperfusion method, the effects of selective and potent agonists of NK1, NK2, and NK3 tachykinin receptors ([Pro9]SP, ([Lys5,MeLeu9,Nle10]NKA-(4-10), and [Pro7]NKB, respectively) on the presynaptic control of dopamine release were investigated in striosomal-enriched (area rich in [3H]naloxone binding sites) and matrix-enriched areas of the rat striatum. Marked differences could be demonstrated as follows: (i) when used at 0.1 microM, the NK1 agonist stimulated the release of [3H]dopamine continuously synthesized from [3H]tyrosine in both compartments, while the NK2 and NK3 agonists enhanced the release of [3H]dopamine only in the matrix; (ii) the stimulatory effect of the NK3 agonist was less pronounced than those of the NK1 and NK2 agonists; (iii) the NK1 agonist-evoked responses were tetrodotoxin (1 microM) sensitive, while those of the NK2 and NK3 agonists were, respectively, partially and totally tetrodotoxin resistant; (iv) specific receptors are involved in these responses since the stimulatory effects of the NK1 and NK2 agonists were, respectively, blocked by potent antagonists of NK1 (RP-67580; 1 microM) and NK2 (SR-48968; 1 microM) receptors, while these antagonists did not affect the NK3 agonist-evoked response; (v) the indirect stimulatory effect of the NK1 agonist was partially reduced under local blockade of cholinergic transmission in the matrix but not in the striosomal-enriched area. Interestingly, this study also revealed mismatches between autoradiographic data and receptor-mediated responses, since NK2 binding sites could not be observed in the striatum while NK3 but not NK1 binding sites were visualized in the striosomal-enriched area.

Functional heterogeneity of the matrix compartment in the cat caudate nucleus as demonstrated by the cholinergic presynaptic regulation of dopamine release.

Previously, using a new in vitro microsuperfusion procedure, we have demonstrated marked differences in the cholinergic presynaptic regulation of the release of [3H]dopamine continuously synthesized from [3H]tyrosine in two close striosomal- and matrix-enriched areas of the cat caudate nucleus. A tetrodotoxin-resistant stimulatory effect of acetylcholine mediated by muscarinic receptors was observed in both compartments. However, in addition, two opposing types of tetrodotoxin-sensitive acetylcholine-evoked regulation of [3H]dopamine release were only seen in the matrix: one facilitatory, involving nicotinic receptors located on as yet unidentified neurons, and the other inhibitory, mediated by muscarinic receptors located on dynorphin-containing neurons. In the present study, using the same approach, a functional heterogeneity was demonstrated in the matrix. Indeed, in various conditions the effects of acetylcholine (50 microM) on the release of [3H]dopamine were different in a matrix-enriched area (matrix 2) distinct from that previously investigated (matrix 1); these areas being characterized by the presence or absence of islands of striatonigral cells, respectively. As in matrix 1, acetylcholine induced a short-lasting stimulation of [3H]dopamine release in matrix 2 but, in contrast to that observed in matrix 1, the acetylcholine-evoked response in matrix 2 was not modified in the presence of tetrodotoxin (1 microM). Experiments made in the presence of the tetrodotoxin and atropine (1 microM) indicated that both muscarinic and nicotinic receptors are located on dopaminergic nerve terminals in matrix 2 while muscarinic receptors are only present in matrix 1. In the absence of tetrodotoxin, the short-lasting stimulation of [3H]dopamine release was transformed into a long-lasting response in the presence of pempidine (50 microM), in matrix 2 but not in matrix 1 while prolonged responses were seen in both matrix areas in the presence of atropine. Finally, the acetylcholine short stimulatory effect on [3H]dopamine release was transformed into a long stimulatory response in the presence of bicuculline (50 microM) but not naloxone (1 microM) in matrix 2 while the reverse was observed in matrix 1. By providing further evidence for a functional heterogeneity of the matrix, our results suggest that depending on the matrix area investigated, dynorphin- or GABA-containing neurons are involved in the indirect cholinergic inhibitory control of dopamine release.

Modulation of GABA release by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate and N-methyl-D-aspartate receptors in matrix-enriched areas of the rat striatum.

Using a new in vitro superfusion device, the release of preloaded [3H]GABA was examined in microdiscs of tissues taken from sagittal slices in matrix-enriched areas of the rat striatum. Potassium (9 mM, 15 mM) stimulated the release of [3H]GABA in a concentration- and calcium-dependent manner and the veratridine (1 microM)-evoked release of [3H]GABA was completely abolished in the presence of tetrodotoxin (1 microM). The selective glutamatergic agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (1 mM) enhanced the potassium-evoked release of [3H]GABA as well as the basal outflow of [3H]GABA. This latter effect was found to be calcium-dependent, partially diminished by tetrodotoxin (1 microM), completely blocked by 6,7-dinitro-quinoxaline-2,3-dione (0.1 mM), which is generally used as an antagonist of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors, but not affected by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK801, 10 microM), a specific antagonist of N-methyl-D-aspartate receptors. Similarly, N-methyl-D-aspartate (1 mM) enhanced both the potassium (9 mM) and the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (1 mM)-evoked release of [3H]GABA but when used alone, due to the presence of magnesium in the superfusion medium, was ineffective on the basal efflux of [3H]GABA. A stimulatory effect of N-methyl-D-aspartate (1 mM) on the basal outflow of [3H]GABA was observed, however, when magnesium was omitted from the superfusion medium. The stimulatory effect of N-methyl-D-aspartate (1 mM) observed in the presence of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate was not potentiated by glycine (1 microM, in the presence of strychnine 1 microM) and the N-methyl-D-aspartate-evoked response seen in the absence of magnesium was not enhanced by D-serine (1 mM), suggesting that endogenous glycine is already acting on N-methyl-D-aspartate receptors. In fact, in the absence of magnesium, 7-chloro-kynurenate (1 mM) completely abolished the stimulatory effect of N-methyl-D-aspartate on the release of [3H]GABA confirming that under our conditions, the glycine site of the N-methyl-D-aspartate receptor is saturated. N-methyl-D-aspartate-evoked responses were all blocked by MK801 (10 microM). Finally, the N-methyl-D-aspartate-evoked response seen in the absence of magnesium was markedly reduced in the presence of tetrodotoxin (1 microM).(ABSTRACT TRUNCATED AT 400 WORDS)

Distinct presynaptic regulation of dopamine release through NMDA receptors in striosome- and matrix-enriched areas of the rat striatum.

Striosome- and matrix-enriched striatal zones were defined in coronal and sagittal brain sections of the rat, on the basis of 3H-naloxone binding to mu-opiate receptors (a striosome-specific marker). Then, using a new in vitro microsuperfusion device, the NMDA (50 microM)-evoked release of newly synthesized 3H-dopamine (3H-DA) was examined in these four striatal areas under Mg(2+)-free conditions. The amplitudes of the responses were different in striosomal (171 +/- 6% and 161 +/- 5% of the spontaneous release) than in matrix areas (223 +/- 6% and 248 +/- 12%), even when glycine (1 or 100 microM) was coapplied (in the presence of 1 microM strychnine). In the four areas, the NMDA-evoked release of 3H-DA was blocked completely by Mg2+ (1 mM) or (+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5,10-imine maleate (MK-801; 1 microM) and almost totally abolished by kynurenate (100 microM). Because the tetrodotoxin (TTX)-resistant NMDA-evoked release of 3H-DA was similar in striosome- (148 +/- 5% and 152 +/- 6%) or matrix-enriched (161 +/- 5% and 156 +/- 7%) areas, the indirect (TTX-sensitive) component of NMDA-evoked responses, which involves striatal neurons and/or afferent fibers, seems more important in the matrix- than in the striosome-enriched areas. The modulation of DA release by cortical glutamate and/or aspartate-containing inputs through NMDA receptors in the matrix appears thus to be partly distinct from that observed in the striosomes, providing some functional basis for the histochemical striatal heterogeneity.

Glutamatergic control of dopamine release in the rat striatum: evidence for presynaptic N-methyl-D-aspartate receptors on dopaminergic nerve terminals.

The N-methyl-D-aspartate (NMDA) receptor-mediated regulation of the release of newly synthesized [3H]dopamine [( 3H]DA) was studied in vitro, both on rat striatal slices using a new microsuperfusion device and on rat striatal synaptosomes. Under Mg2(+)-free medium conditions, the NMDA (5 X 10(-5) M)-evoked release of [3H]DA from slices was found to be partly insensitive to tetrodotoxin (TTX). This TTX-resistant stimulatory effect of NMDA was blocked by either Mg2+ (10(-3) M) or the noncompetitive antagonist MK-801 (10(-6) M). In addition, the TTX-resistant NMDA-evoked response could be potentiated by glycine (10(-6) M) in the presence of strychnine (10(-6) M). The coapplication of NMDA (5 X 10(-5) M) and glycine (10(-6) M) stimulated the release of [3H]DA from striatal synaptosomes. This effect was blocked by Mg2+ (10(-3) M) or MK-801 (10(-5) M). These results indicate that some of the NMDA receptors involved in the facilitation of DA release are located on DA nerve terminals. These presynaptic receptors exhibit pharmacological properties similar to those described in electrophysiological studies for postsynaptic NMDA receptors.

Role of dynorphin-containing neurons in the presynaptic inhibitory control of the acetylcholine-evoked release of dopamine in the striosomes and the matrix of the cat caudate nucleus.

The roles of acetylcholine and dynorphin (1-13) in the presynaptic control of the release of [3H]dopamine continuously synthesized from [3H]tyrosine were examined in a prominent striosomal enriched area and in an adjacent matrix enriched area of the cat caudate nucleus. This was achieved using microsuperfusion devices applied vertically onto coronal slices of cat brain. These devices were placed in a striosomal enriched area located in the core of the structure (acetylcholinesterase-poor zone) and in an adjacent matrix enriched area (acetylcholinesterase-rich zone). [3H]Tyrosine was delivered continuously to each microsuperfusion device and [3H]dopamine released was estimated in the superfusate. As previously shown, in the presence of tetrodotoxin (1 microM), acetylcholine (50 microM) induces a prolonged stimulation of [3H]dopamine release in both compartments through an interaction with muscarinic receptors. Our present study indicates that both dynorphin 1-13 (1 microM) and the selective kappa agonist trans-3,4-dichloro-N-methyl-N[2-(1-pyrrolidinyl)cyclohexyl]benzeneace tamine (U50488) (1 microM) inhibit the tetrodotoxin-resistant acetylcholine-evoked release of [3H]dopamine, these effects being slightly more pronounced in the matrix than in the striosomal enriched area. Naloxone (1 microM) reversed the inhibitory effect of U50488 in both areas. These results suggest that dynorphin exerts an inhibitory presynaptic control of dopamine release through kappa opioid receptors located on dopamine nerve terminals in the striosome as well as in the matrix. However, the presynaptic cholinergic control of dopamine release is much more complex in the matrix than in the striosomal enriched area. Besides its tetrodotoxin-resistant stimulatory effect, acetylcholine exerts two opposing tetrodotoxin-sensitive effects on [3H]dopamine release, one facilitatory and the other inhibitory. We demonstrate here that in the superfused matrix enriched area, the indirect acetylcholine inhibitory response is mediated by dynorphin-containing neurons. Indeed, the short-lasting stimulatory effect of acetylcholine on [3H]dopamine release was converted into a long-lasting response in the presence of naloxone (1 microM), and, in this latter condition, the co-application of dynorphin 1-13 (1 microM) restored the short-lasting stimulatory effect.