TY - JOUR
T1 - Activation of presynaptic group III metabotropic receptors enhances glutamate release in rat entorhinal cortex
AU - Evans, D. Ieuan
AU - Jones, Roland S.G.
AU - Woodhall, Gavin
PY - 2000/6/1
Y1 - 2000/6/1
N2 - The role of group III metabotropic glutamate receptors (mGluRs) in modulating excitatory synaptic transmission was investigated in the rat entorhinal cortex (EC) in vitro. AMPA receptor-mediated excitatory postsynaptic currents (EPSCs) were recorded in the whole cell configuration of the patch-clamp technique from visually identified neurons in layers V and II. In layer V, bath application of the specific group lII mGluR agonist L(+)-2-amino-4-phosphonobutyric acid (L-AP4, 500 μM) resulted in a marked facilitation of both spontaneous and activity-independent 'miniature' (s/mEPSC) event frequency. The facilitatory effect of L-AP4 (100 μM) on sEPSC frequency prevailed in the presence of DL - 2-amino-5- phosphonopentanoic acid (100 μM) but was abolished by the group III antagonist (RS)-cyclopropyl-4-phosphonophenylglycine (20 μM). These data confirmed that group III mGluRs, and not N-methyl-D-aspartate (NMDA) receptors were involved in the response to L-AP4. Bath application of the specific mGluR4a agonist (1S,3R,4S)-1-aminocyclopentane-1,2,4-tricarboxylic acid (20 μM) also had a facilitatory effect on sEPSC frequency, suggesting involvement of mGluR4a. In layer II neurons, L-AP4 caused a reduction in sEPSC frequency but did not affect mEPSCs recorded in the presence of tetrodotoxin. These findings suggest that a group III mGluR with mGluR4a-like pharmacology is involved in modulating synaptic transmission in layer V cells of the EC. The effect on mEPSCs suggests that this receptor is located presynaptically and that its activation results in a direct facilitation of glutamate release. This novel facilitatory effect is specific to layer V and, to our knowledge, is the first report of a direct facilitatory action of group III mGluRs on synaptic transmission, in layer II, L-AP4 had an inhibitory effect on glutamate release similar to that reported in other brain regions.
AB - The role of group III metabotropic glutamate receptors (mGluRs) in modulating excitatory synaptic transmission was investigated in the rat entorhinal cortex (EC) in vitro. AMPA receptor-mediated excitatory postsynaptic currents (EPSCs) were recorded in the whole cell configuration of the patch-clamp technique from visually identified neurons in layers V and II. In layer V, bath application of the specific group lII mGluR agonist L(+)-2-amino-4-phosphonobutyric acid (L-AP4, 500 μM) resulted in a marked facilitation of both spontaneous and activity-independent 'miniature' (s/mEPSC) event frequency. The facilitatory effect of L-AP4 (100 μM) on sEPSC frequency prevailed in the presence of DL - 2-amino-5- phosphonopentanoic acid (100 μM) but was abolished by the group III antagonist (RS)-cyclopropyl-4-phosphonophenylglycine (20 μM). These data confirmed that group III mGluRs, and not N-methyl-D-aspartate (NMDA) receptors were involved in the response to L-AP4. Bath application of the specific mGluR4a agonist (1S,3R,4S)-1-aminocyclopentane-1,2,4-tricarboxylic acid (20 μM) also had a facilitatory effect on sEPSC frequency, suggesting involvement of mGluR4a. In layer II neurons, L-AP4 caused a reduction in sEPSC frequency but did not affect mEPSCs recorded in the presence of tetrodotoxin. These findings suggest that a group III mGluR with mGluR4a-like pharmacology is involved in modulating synaptic transmission in layer V cells of the EC. The effect on mEPSCs suggests that this receptor is located presynaptically and that its activation results in a direct facilitation of glutamate release. This novel facilitatory effect is specific to layer V and, to our knowledge, is the first report of a direct facilitatory action of group III mGluRs on synaptic transmission, in layer II, L-AP4 had an inhibitory effect on glutamate release similar to that reported in other brain regions.
UR - http://www.scopus.com/inward/record.url?scp=0034033016&partnerID=8YFLogxK
UR - https://www.physiology.org/doi/full/10.1152/jn.2000.83.5.2519?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed
U2 - 10.1152/jn.2000.83.5.2519
DO - 10.1152/jn.2000.83.5.2519
M3 - Article
C2 - 10805653
AN - SCOPUS:0034033016
SN - 0022-3077
VL - 83
SP - 2519
EP - 2525
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
IS - 5
ER -