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Endogenous GABA released into the fourth ventricle of the rat brain in vivo is enhanced by noxious stimuli
1Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
Abstract:
In vivo release of endogenous gamma-aminobutyric acid (GABA) and glutamic acid into the 4th ventricle of the rat brain in response to noxious stimuli was examined. Both these compounds were dansylated and the concentrations determined, using high-performance liquid chromatography (HPLC) combined with an UV detector. Following noxious stimuli (subcutaneous injection of diluted formalin into the hind-paw or noxious pinch of the hind-paws), there was a remarkable release of GABA, but not of glutamic acid. Basal on our heretofore obtained data that bicuculline methiodide, a GABAA antagonist, produces a potent analgesia in mice, the present results suggest that the GABAergic system in the brain stem may promote nociceptive transmission in rats.