Neuropharmacology
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Metabotropic glutamate receptors (mGluR) are classified into groups I (excitatory), II and III (inhibitory) mGluR. Activation of peripheral group III mGluR (mGluR4, mGluR6, mGluR7, mGluR8), particularly mGluR8, inhibits vagal afferent mechanosensitivity in vitro which translates into reduced triggering of transient lower oesophageal sphincter relaxations and gastroesophageal reflux in vivo. However, the expression and function of group III mGluR in central gastrointestinal vagal reflex pathways is not known. ⋯ The effects of DCPG were significantly reversed by the group III mGluR antagonist MAP4 (10 nmol, i.c.v.). In contrast, 4/4 NTS neurons inhibited by gastric distension were unaffected by DCPG. We conclude that group III mGluR are expressed in peripheral and central vagal pathways, and that mGluR8 within the NTS selectively reduce excitatory transmission along gastric vagal pathways.