Presynaptic group II mGluR inhibition of short-term depression in the medial perforant path of the dentate gyrus in vitro.
Inhibition of short-term plasticity by activation of presynaptic group II metabotropic glutamate receptors (group II mGluR) was investigated in the medial perforant path of the dentate gyrus in the hippocampus in vitro. Brief trains of stimulation (10 stimuli at 1--200 Hz) evoked short-term depression of field excitatory postsynaptic potentials (EPSPs). The steady-state level of depression, measured after 10 stimuli, was frequency dependent, increasing between 1 and 200 Hz. Activation of group II mGluR by the selective agonist LY354740 did not alter short-term depression evoked by frequencies up to 10 Hz, but did inhibit short-term depression evoked at higher frequencies in a frequency- and concentration-dependent manner. The time-averaged postsynaptic response (EPSP per unit time) was found to increase linearly with frequency up to approximately 20 Hz. At higher frequencies, the response plateaued, thereby becoming independent of frequency. Frequencies above this were differentiated only during the transient postsynaptic response that accompanies changes in firing rates. Activation of presynaptically located group II mGluR increased the frequency at which the EPSP per unit time plateaued up to 30-50 Hz.
Kilbride
J
J
Department of Physiology, Trinity College, Dublin 2, Ireland.
Rush
A M
AM
Rowan
M J
MJ
Anwyl
R
R
D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology; D003521:Cyclopropanes / Q000494:pharmacology; D018891:Dentate Gyrus / Q000502:physiology*; D004558:Electric Stimulation; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D019580:Perforant Pathway / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D000927:Anticonvulsants; D001643:Bridged Bicyclo Compounds; D003521:Cyclopropanes; D018690:Excitatory Amino Acid Agonists; D018094:Receptors, Metabotropic Glutamate; C108822:metabotropic glutamate receptor 2; C082313:2-(2,3-dicarboxycyclopropyl)glycine; C104753:eglumetad; D005998:Glycine