抄録
Recent studies have shown that multiple glutamate receptors are expressed on peripheral primary afferent terminals, and they may contribute to peripheral nociceptive signaling. However, little is known about the action of subcutaneous glutamate on the nociceptors in humans. Thus, glutamate was injected subcutaneously into the forearms of healthy volunteers with or without Lidocaine Patch in order to investigate whether the subcutaneous glutamate induces neurogenic inflammation following the excitation of nociceptors. Glutamate caused severe pain immediately after the injection on the subjects without Lidocaine Patch. The intensity of pain expressed by VAS peaked within 5 minute, and gradually decreased, but slight pain was maintained for 30 minutes. Skin temperature on fingers, monitored by thermography, led to a temporary decrease immediately after the injection. On the other hand, skin temperature around the injection site, started to increase about 3 min after injection, reached a peak in 20-25 min and then decayed gradually. Pretreatment with Lidocaine Patch for 60 minutes did not alleviate glutamate-evoked pain sensation, but attenuated skin temperature increase around the injection site. These data demonstrate that subcutaneous injection of glutamate activates nociceptors, and that Lidocaine Patch blocks glutamate-evoked neurogenic inflammation in humans. [Jpn J Physiol 55 Suppl:S165 (2005)]
