Abstract
We investigated the functional significance of peripherally distributed glutamate, including N-methyl-D-aspartate (NMDA), receptors in humans. Magnesium sulfate (MG) and ketamine hydrochloride (KET), NMDA receptor antagonists, were injected into the skin of the medial region of forearm of healthy volunteers to investigate whether these substances are capable of changing the sensory transmission. We found that intracutaneous injections of MG and KET cause hypesthesia to noxious and innoxious mechanical stimulations. These results suggest that peripheral NMDA receptors are involved not only in sensory acceptance of noxious mechanical stimulation, but also in transmission of innoxious mechanical stimuli. The observation that the state of NMDA receptors in the skin may be affected by intracutaneous injection of their antagonists lays ground for possible clinical applications.
