AMPA- and kainate-receptors differentially mediate excitatory amino acid-induced dopamine and acetylcholine release from rat striatal slices.

Rat striatal slices, preincubated with [3H]dopamine (DA) and [14C]choline, were superfused continuously. Detection of radioactivity was used to monitor the release of the neurotransmitters DA and acetylcholine (ACh). 6-Cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)quinoxaline (NBQX) caused a concentration-dependent decrease in 100 microM alpha-amino-3-hydroxy-5-methylisoxazol-4-propionate (AMPA)-, 100 microM kainate- or 100 mM glutamate-induced release of DA and ACh. The IC50 of NBQX is 3-fold higher (for ACh release) and is 2-fold lower (for DA release) than that of CNQX. This is in agreement with the IC50 ratio of NBQX and CNQX on kainate- and AMPA-receptor binding. These two antagonists, at doses that produce an equivalent blockade of kainate-receptor binding (5 microM for NBQX and 1.56 microM for CNQX), caused an approximately equal decrease in ACh- but not DA-release induced by 100 microM kainate or AMPA. At doses that produce an equivalent blockade of AMPA-receptor binding (5 microM for NBQX and 10 microM for CNQX), they caused an approximately equal decrease in DA but not ACh release induced by 100 microM AMPA or kainate. Moreover, concanavalin A (0.3 and 0.5 mg/ml), which selectively potentiates kainate-receptor responses, markedly enhanced 100 microM kainate-induced release of ACh but not DA. Cyclothiazide (10 microM), which selectively potentiates AMPA-receptor responses, significantly increased 100 microM AMPA- or kainate-induced release of DA but not ACh. In summary, these results indicate that AMPA-and kainate-receptor activation, respectively, are predominantly involved in excitatory amino acid (EAA)-induced DA and ACh release in the striatum.