تقويت سيناپسي القايي توسط S)- 3,5- DIHYDROXYPHENYLGLYCINE) (آگونيست گيرنده هاي گروه I متابوتروپيك) در سيناپس هاي تحريكي نرون هاي گابائرژيك سريع در قشر بينايي

(S)- 3,5-Dihydroxyphenylglycine, an agonist for group I metabotropic glutamate receptors, induces synaptic potentiation at the excitatory synapses of the fast spiking GABAergic cells in the visual cortex

Introduction: (S)- 3,5-Dihydroxyphenylglycine (DHPG) is an agonist for group I metabotropic glutamate receptors. DHPG-induced synaptic depression of excitatory synapses of the hippocampal pyramidal neurons is a well known model for synaptic plasticity studies. The aim of the present study was to examine the effects of DHPG superfusion on the excitatory synapses of the pyramidal and fast-spiking GABAergic cells (FS-GABA) of layer II/III of mice visual cortex. Methods: Effects of DHPG was examined in visual cortical slices of GAD67-GFP knock-in mice using whole-cell recordings of excitatory postsynaptic potentials (EPSPs) in layer II/III cells evoked by layer IV stimulation. Experiments also included long term potentiation (LTP) induction by theta burst stimulation (TBS) paired with postsynaptic depolarization. Results: DHPG induced potentiation of EPSPs of the FS-GABA neurons in dose- and use-dependent manners but it had no effect on the pyramidal cell excitatory synapses. An antagonist for type 5 metabotropic glutamate receptors (mGluR5) blocked DHPG-induced LTP, while an antagonist for mGluRl was not effective. This potentiation and TBS- induced LTP blocked each other. Conclusion: Since FS-GABA cells have an important role in the cortical neuronal circuits, mGlur5-dependent LTP may play a role in the enhancement or maintenance of synchronized activity of cortical pyramidal neurons.