GLUTAMATE PARTICIPATES IN THE PERIPHERAL MODULATION OF THERMAL HYPERALGESIA IN RATS

While the effects of excitatory amino acids have been well characteriz ed in the central nervous system, relatively little is known about the ir possible modulation of elements responsible for hyperalgesia within peripheral tissue. The presented experiments demonstrate that the int raplantar (i.pl.) injection of L-glutamate (30 nmol) evokes a thermal hyperalgesic response in the paw withdrawal latencies of normal rats w hich is stereospecific. In addition, the i.pl. injection of either the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist MK-80 1 (10 nmol) or the competitive lpha-amino-3-hydroxy-4-methyl-5-isoxazo lepropionic acid (AMPA)/kainate receptor antagonist 6-cyano-7-nitroqui noxaline-2,3-dione (CNQX) (100 nmol) into hind paws inflamed with carr ageenan significantly reduced the thermal hyperalgesic response in rat s. Collectively, these results suggest that excitatory amino acids act ivate a peripheral target which facilitates a hyperalgesic behavioral response to thermal stimulation via a receptor mediated process.