Effects of Activation of NMDA and AMPA Glutamate Receptors on the Extracellular Concentrations of Dopamine, Acetylcholine, and GABA in Striatum of the Awake Rat: A Microdialysis Study

The effects of activation of the AMPA and NMDA ionotropic glutamate receptors on the extracellular concentration of dopamine, acetylcholine, (ACh) and GABA in striatum of the awake rat was investigated. Also the levels of DOPAC, HVA, and choline (Ch) were included in this study. Seven to eight days after stereotaxical implantation of a guide-cannulae assembly, microdialysis experiments were performed. The dopamine and ACh content of samples were measured by HPLC coupled to electrochemical detection. GABA was measured using fluorometric detection. Perfusion of AMPA (1, 20, 100 mM) produced a dose-related increase of dopamine and a dose-related decrease of DOPAC and HVA. AMPA 100 M decreased extracellular concentrations of ACh and increased the extracellular concentration of Ch and GABA. Perfusion of NMDA 500 M increased the concentration of dopamine and decreased DOPAC and HVA. Also, NMDA 100 M decreased DOPAC. NMDA 500 M decreased the extracellular concentrations of ACh and increased the concentrations of Ch and GABA. Perfusion of the AMPA/kainate-antagonist DNQX (100 M) blocked the effects of AMPA (100 M) on dopamine, DOPAC, HVA, ACh, and GABA concentrations. Perfusion of the NMDA-antagonist CPP (100 M) blocked the effects of NMDA 500 M on dopamine, DOPAC, HVA, ACh, Ch, and GABA concentrations. These results suggest an interaction between glutamate-dopamine-ACh-GABA in striatum of the awake rat.