mGluRs Modulate Strength and Timing of Excitatory Transmission in Hippocampal Area CA3

Abstract

Excitatory transmission within hippocampal area CA3 stems from three major glutamatergic pathways: the perforant path formed by axons of layer II stellate cells in the entorhinal cortex, the mossy fiber axons originating from the dentate gyrus granule cells, and the recurrent axon collaterals of CA3 pyramidal cells. The synaptic communication of each of these pathways is modulated by metabotropic glutamate receptors that fine-tune the signal by affecting both the timing and strength of the connection. Within area CA3 of the hippocampus, group I mGluRs (mGluR1 and mGluR5) are expressed postsynaptically, whereas group II (mGluR2 and mGluR3) and III mGluRs (mGluR4, mGluR7, and mGluR8) are expressed presynaptically. Receptors from each group have been demonstrated to be required for different forms of pre- and postsynaptic long-term plasticity and also have been implicated in regulating short-term plasticity. A recent observation has demonstrated that a presynaptically expressed mGluR can affect the timing of action potentials elicited in the postsynaptic target. Interestingly, mGluRs can be distributed in a target-specific manner, such that synaptic input from one presynaptic neuron can be modulated by different receptors at each of its postsynaptic targets. Consequently, mGluRs provide a mechanism for synaptic specialization of glutamatergic transmission in the hippocampus. This review will highlight the variability in mGluR modulation of excitatory transmission within area CA3 with an emphasis on how these receptors contribute to the strength and timing of network activity within pyramidal cells and interneurons.

Evolution and functional diversity of the Calcium Binding Proteins (CaBPs)

“…The biochemical characteristics reported in this paper are, however, consistent with documented CaM/CaBP1 in vivo interactions (Lee et al, 2002; Few et al, 2005, 2011) and this work remains of great potential interest as Ca 2+ -influx downstream of mGluR activation is known to influence short term facilitation and higher level neuronal function (Cosgrove et al, 2011; Fioravante and Regehr, 2011). …”

Regulation of neuronal pH by the metabotropic Zn2+‐sensing Gq‐coupled receptor, mZnR/GPR39

“…Synaptic release of glutamate and activation of postsynaptic metabotropic mGluRs have also been associated with changes in postsynaptic intracellular Ca 2+ (Cosgrove et al 2011). We thus examined whether changes in pHe would also affect glutamate-dependent Ca 2+ responses in hippocampal neurons.…”

Increased prion protein processing and expression of metabotropic glutamate receptor 1 in a mouse model of Alzheimer's disease

“…For example, mGluRs are involved in regulating synaptic plasticity (Luscher and Huber ; Cosgrove et al . ), which is affected in AD. Particular roles of group I mGluRs in AD are somewhat controversial as they have been shown to have both excitotoxic and neuroprotective effects under stress conditions.…”