Functional group I metabotropic glutamate receptors in submucous plexus ofguinea-pig ileum

Intracellular recording methods and immunostaining revealed the existence o f functional group I metabotropic glutamate receptors (mGluRs) in submucous plexus neurons of guinea-pig ileum. Selective group I, but not groups II o r III metabotropic glutamate receptor agonists induced concentration-depend ent, slowly-activating depolarizing responses. Group I metabotropic glutama te receptor antagonism observed with (S)-4-carboxyphenylglycine (S-4-CPG) ( 100-600 mu 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 1 alpha and 5 receptors wer e found to locate exclusively in neurons in the submucous plexus of guinea- pig ileum with the highest density around the cell bodies. The results sugg est that group I metabotropic glutamate receptors are functionally expresse d in the submucous plexus of guinea-pig small intestine.