NMDA and Non-NMDA Ionotropic Glutamate Receptors Modulate Striatal Acetylcholine Release via Pre- and Postsynaptic Mechanisms

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The effects of NMDA and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) on endogenous acetylcholine release from rat striatal slices and synaptosomes were investigated. Both agonists (1-300 μM) facilitated acetylcholine release from slices in a dose-dependent manner. NMDA (100-300 μM) and AMPA (30-300 μM), however, subsequently inhibited acetylcholine release. NMDA (100 μM)-induced facilitation was antagonized by 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) and dizocilpine (both 1-10 μM), whereas the 10 μM AMPA effect was antagonized by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 1-30 μM). NMDA (100 μM)-induced inhibition was counteracted by CPP, but not dizocilpine, and by the nitric oxide synthase inhibitor L-nitroarginine (1-100 μM). Tetrodotoxin (0.5 μM) prevented the facilitatory effect of 3 μM NMDA and AMPA, but left unchanged that of 30 μM NMDA and 100 μM AMPA. Acetylcholine release from synaptosomes was stimulated by KCl (7.5-100 mM) in a dose-dependent manner. NMDA and AMPA maximally potentiated the 20 mM KCl effect at 1 μM and 0.01 μM, but were ineffective at 100 μM and 10 μM, respectively. Inhibition of acetylcholine release was never found in synaptosomes. The effects of 1 μM NMDA and 0.01 μM AMPA were antagonized by CPP (0.0001-1 μM) or dizocilpine (0.0001-10 μM) and by CNQX (0.001-1 μM), respectively. These data suggest that glutamatergic control of striatal acetylcholine release is mediated via both pre- and post-synaptic NMDA and non-NMDA ionotropic receptors.

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