Functional group I metabotropic glutamate receptors in submucous plexus of guinea‐pig ileum

Intracellular recording methods and immunostaining revealed the existence of functional group I metabotropic glutamate receptors (mGluRs) in submucous plexus neurons of guinea‐pig ileum. Selective group I, but not groups II or III metabotropic glutamate receptor agonists induced concentration‐dependent, slowly‐activating depolarizing responses. Group I metabotropic glutamate receptor antagonism observed with (S)‐4‐carboxyphenylglycine (S‐4‐CPG) (100–600 μ M ) was competitive as determined by Schild analysis (pA 2 =3.81±0.02). Neither the group II and III metabotropic nor ionotropic glutamate receptor antagonists altered responses evoked by group I receptor agonists. Immunoreactivities for metabotropic glutamate 1α and 5 receptors were found to locate exclusively in neurons in the submucous plexus of guinea‐pig ileum with the highest density around the cell bodies. The results suggest that group I metabotropic glutamate receptors are functionally expressed in the submucous plexus of guinea‐pig small intestine. British Journal of Pharmacology (1999) 128 , 1631–1635; doi: 10.1038/sj.bjp.0702980