38 Scopus citations

Abstract

Intracellular recording methods were used to investigate actions of glutamate on morphologically identified neurones in the myenteric and submucous plexuses of guinea-pig small intestine. Glutamate evoked a tetrodotoxin-resistant, slowly activating depolarizing response in most of the submucous neurones (86 of 125, 69%) and a smaller number of myenteric neurones (6 of 60, 10%). The depolarizing responses were restricted to S-type neurones with uniaxonal morphology. The group I metabotropic glutamate receptor (mGluRs) agonists quisqualate, 1S, 3R-ACPD and DHPG mimicked the depolarizing action of glutamate. A group I mGluRs antagonist, S-4-carboxyphenylglycine (S-4CPG), suppressed the glutamate responses with an IC50 Of 357 μM at 30 μM glutamate. Group II or III mGluRs agonists did not produce depolarizing responses and group II or III mGluRs antagonists did not alter glutamate-evoked depolarization. The ionotropic glutamate receptor (iGluRs) agonists NMDA, AMPA, or kainate did not evoke depolarizing responses and glutamate-evoked depolarization was unaffected by the iGIuRs antagonists D-APV, MK-801, or DNQX. No rapidly activating fast depolarizing responses reminiscent of fast excitatory postsynaptic potentials (EPSPs) were ever observed during application of glutamate or AMPA find stimulus-evoked fast EPSPs were unaffected by DNQX. The results suggest that the excitatory action of glutamate on enteric neurones is mediated by group I metabotropic glutamate receptors find that ionotropic glutamate receptors are not involved. The results also suggest that glutamate-mediated fast EPSPs may not be present in myenteric and submucous neurones in guinea-pig small bowel.

Original languageEnglish
Pages (from-to)257-264
Number of pages8
JournalNeurogastroenterology and Motility
Volume12
Issue number3
DOIs
StatePublished - 2000

Keywords

  • Enteric nervous system
  • Glutamate receptors
  • Myenteric plexus
  • Small intestine
  • Submucous plexus

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