Premium
Glutamate receptors in the enteric nervous system: ionotropic or metabotropic?
Author(s) -
Ren J.,
Hu HZ.,
Liu S.,
Xia Y.,
Wood J. D.
Publication year - 2000
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1046/j.1365-2982.2000.00207.x
Subject(s) - metabotropic glutamate receptor , kainate receptor , dnqx , glutamate receptor , depolarization , metabotropic glutamate receptor 5 , metabotropic glutamate receptor 6 , neuroscience , metabotropic glutamate receptor 2 , biology , ampa receptor , metabotropic receptor , enteric nervous system , excitatory postsynaptic potential , long term depression , chemistry , inhibitory postsynaptic potential , biophysics , receptor , biochemistry
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 IC 50 of 357 μ M at 30 μ M 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 iGluRs 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 and 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 and 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.