[A microdialysis study of excitatory amino acid levels of the monkeys' caudate nucleus during the delayed go/no-go task].

Using in vivo microdialysis coupled with HPLC-fluorescent detection chemical analysis method, levels of excitatory amino acid were monitored in the caudate nucleus of rhesus monkeys (Macaca mulatta) during performance of a delayed go/no-go task in which movement or no-movement responses were executed depending on the position of a cue light. It was found that the levels of glutamate and aspartate in caudate microdialysates decreased by (31.68 +/- 3.85)% (n = 10, t9 = 6.51, P < 0.001) and (26.25 +/- 5.95)% (n = 10, t9 = 3.39, P < 0.01) respectively during the delayed go/no-go task performance as compared to their basal levels before the task performance. Glutamine and asparagine levels were also found decreased significantly (P < 0.05). In contrast, no such decreases were seen when the monkey performing a non-delayed go/no-go task or performing the task composed of delayed go-trials only. The results suggest that the excitatory amino acid transmission in the caudate nucleus may be involved in the delayed go/no-go task performance, and thereby provide a direct evidence for the modulation of motor working memory by glutamatergic transmission in caudate nucleus.