Noxious stimulation increases glutamate and arginine in the periaqueductal gray matter in rats: a microdialysis study

Abstract
N microdialysis in freely moving rats and capillary zone electrophoresis with laser induced-fluorescence detection allowed us to detect short lasting changes of excitatory amino acid in dialysates. A formalin injection in the hindpaw of the rat increased glutamate, arginine and aspartate concentration in PAG dialysates. This increase was calcium and nerve impulse-dependent, suggesting neuronal and glial origin of glutamate and arginine, respectively. Handling, pinching or saline injection in the hind paw did not increase glutamate showing that this neurochemical phenomenon is related to painful and persistent noxious stimulation. The results suggest that a rapid excitation of the PAG occurs during noxious stimulation. The role of glutamate and arginine in analgesia is discussed....

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