DEPOLARIZATION-EVOKED RELEASE OF GLUTAMATE, ASPARTATE AND GAMMA-AMINOBUTYRIC-ACID FROM RAT DORSAL SPINAL-CORD SLICES DOES NOT ORIGINATE FROM CAPSAICIN-SENSITIVE NEURONS

A release of endogenous glutamate (Glu), aspartate (Asp) and gamma-aminobutyric acid (GABA) from rat dorsal spinal cord slices was evoked by a 60 mM K+-depolarization (calcium dependent) and by 50-mu-M veratridine (tetrodotoxin sensitive) indicating a neuronal exocytosis mechanism. No release of the 3 amino acids investigated was obtained with the selective C-fiber excitant capsaicin (1-mu-M) and after impairment of afferent C-fibers the amount of amino acids released by K+-depolarization or veratridine was not reduced. These results suggest that amino acids may be exclusively transmitters of capsaicin-insensitive nerve structures in the rat dorsal spinal cord.