Cyclic AMP-mediated regulation of striatal glutamate release: interactions of presynaptic ligand- and voltage-gated ion channels and G-protein-coupled receptors.
The presynaptic regulation of striatal glutamate transmission was investigated using D-[3H]aspartate and mouse striatal slices. Functional changes in voltage-dependent and glutamate receptor-gated ion channels were elicited by pharmacologically modifying intracellular cyclic AMP formation via G-protein-coupled receptor stimulation. The kainate (KA)-evoked release was potentiated by the stimulatory G-protein (G(s))-coupled beta-adrenoceptor agonist isoproterenol (ISO) in a concentration-dependent manner. This effect was mimicked by the specific calmodulin (CaM) antagonists trifluoperazine and calmidazolium. Tetrodotoxin (TTX), a blocker of Na(+) channels, did not affect the basal release but inhibited to the same degree the releases evoked by kainate alone and by kainate and isoproterenol together. Vinpocetine, a blocker of voltage-dependent Na(+) channels, did not alter the basal or the evoked release. The Na(+) channel activator veratridine enhanced the basal release in a concentration-dependent manner and isoproterenol attenuated this effect. The opposite effects of isoproterenol on the kainate- and veratridine-evoked releases may reflect prevention of the cyclic AMP-protein kinase A (PKA) phosphorylation cascade in striatal glutamatergic signal transduction. In addition, the calmidazolium-induced potentiation of kainate-evoked release was thwarted by LY354740 and L-2-amino-4-phosphonobutanoate, agonists of the inhibitory G-protein (G(i))-coupled metabotropic group II and III glutamate receptors (mGluRs). Vinpocetine, which inhibits the CaM-dependent phosphodiesterase (PDE1), was likewise inhibitory. In turn, selective agonists and antagonists of the G(q)-protein-coupled group I mGluRs and (S)-3,5-dihydroxyphenylglycine (3,5-DHPG) and (RS)-1-aminoindan-1,5-dicarboxylate (AIDA), which modulate the intracellular Ca(2+) levels, did not alter the kainate-evoked release. The beta-adrenoceptor-mediated cyclic AMP accumulation seems to downregulate Na(+) channels but to enhance glutamate release by means of upregulation of kainate receptors. This regulation of presynaptic ligand- and voltage-gated ion channels is affected by the cAMP-protein kinase A-dependent phosphorylation cascade and controlled by G(i)-protein-coupled mGluRs.
Dohovics
Róbert
R
Tampere Brain Research Center, Medical School, University of Tampere, FIN-33014 Tampere, Finland. lorodo@uta.fi
Janáky
Réka
R
Varga
Vince
V
Saransaari
Pirjo
P
Oja
Simo S
SS
D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects* / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology*; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D007093:Imidazoles / Q000494:pharmacology; D015640:Ion Channel Gating; D007608:Kainic Acid / Q000494:pharmacology; D008024:Ligands; D008297:Male; D051379:Mice; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors; D014701:Veratridine / Q000494:pharmacology; D014748:Vinca Alkaloids / Q000494:pharmacology
D007093:Imidazoles; D008024:Ligands; D011956:Receptors, Cell Surface; D018094:Receptors, Metabotropic Glutamate; D014748:Vinca Alkaloids; D018698:Glutamic Acid; C031938:calmidazolium; C013983:vinpocetine; D014701:Veratridine; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D007608:Kainic Acid