Amino acid release into the knee joint: key role in nociception and inflammation

This study examined the release of several amino acids after induction of k nee joint inflammation in rats using kaolin and carrageenan. During the ini tial 10-min collection after knee joint injection with the irritants, the c oncentration of glutamate and the nitric oxide metabolites, arginine and ci trulline, doubled. This increase persisted for at least two hours. During t he same time period aspartate concentrations remained unchanged. Direct kne e joint administration of lidocaine prevented the increases in amino acid c oncentration measurable by microdialysis probe inserted into the joint. The se data suggest the possibility that glutamate may be released by neuronal endings in the joint. (C) 2000 International Association for the Study of P ain. Published by Elsevier Science B.V. All rights reserved.