Electrical stimulation of the vagus increases extracellular glutamate recovered from the nucleus tractus solitarii of the cat by in vivo microdialysis.

Release of glutamate into the extracellular space of the cat nucleus tractus solitarii (NTS) was measured by in vivo microdialysis and high performance liquid chromatography. Perfusion of the probe with 100 mM potassium increased glutamate release by 211% (P < 0.001), while electrical stimulation of the cervical vagus increased release by 53% (P < 0.01). These results are compatible with the hypothesis that glutamate is a neurotransmitter released by vagal afferent nerve terminals in the NTS.