Detection of amino acids in human nasal mucosa using microdialysis technique: increased glutamate in allergic rhinitis.

Amino acids, the smaller basic biochemical units of neuropeptides, have not been evaluated in the nasal cavity. The purpose of this study was to measure the concentration of neurotransmitting amino acids of the central nervous system, glutamate, aspartate, serine, taurine (2-aminoethane sulfonic acid; a conditionally essential amino acids), and GABA (gamma-amino-butyric acid; an amino acid produced in the brain), in nasal mucosa of allergic rhinitis patients and normal controls using a microdialysis technique. A microdialysis probe appropriate for use on human nasal mucosa was developed using Cuprophan hollow fiber. Glutamate concentration in allergy group was significantly higher (p = 0.004) than in control group, while the concentrations of the other four amino acids showed no significant difference between the two groups. Our findings and review of the literature suggest that glutamate is one of the most potent neurotransmitters associated with the parasympathetic nerve in the nasal cavity, and that the microdialysis technique is useful in studying the pharmacokinetics in situ and local organ chemistry of the nasal cavity.