| 1996 |
mGluR8 is localized presynaptically in axon terminals of projection neurons of the main olfactory bulb (rhinencephalon), as demonstrated by loss of immunoreactivity in layer Ia of piriform cortex after lateral olfactory tract transection and electron microscopic visualization of immunoreactivity in axon terminals making asymmetric synapses. |
Immunohistochemistry, electron microscopy, and lesion/tract-transection experiment |
Neuroscience letters |
High |
8710211
|
| 1998 |
mGluR8a and mGluR8b splice variants, which differ only in their C-terminal domains (last 16 amino acids replaced by 16 different amino acids via out-of-frame insertion), display identical pharmacological profiles when expressed heterologously, with rank order of potency DL-AP4 > L-SOP > glutamate and higher agonist potencies than mGluR7. In Xenopus oocytes co-expressed with Kir3.1/3.4, mGluR8 couples to GIRK currents, blocked by the group II/III antagonist CPPG. |
Reverse transcription-PCR, transient transfection in HEK293 cells with chimeric Gαqi9, Xenopus oocyte electrophysiology |
The European journal of neuroscience |
High |
9875342
|
| 2002 |
The mGlu8 receptor Venus flytrap module (VFTM) closure is required for receptor activation. Antagonists ACPT-II and MAP4 prevent VFTM closure via ionic (Asp-309) and steric (Tyr-227) hindrance respectively; alanine substitution of these residues converts the antagonists into full agonists, demonstrating that VFTM closure is necessary for family 3 GPCR activation. |
Site-directed mutagenesis, molecular modeling, functional assay in heterologous expression system |
Proceedings of the National Academy of Sciences of the United States of America |
High |
12151600
|
| 2002 |
mGlu8 receptors function as presynaptic autoreceptors selectively on lateral perforant path (LPP) afferents to the dentate gyrus. L-AP4 and the selective mGlu8 agonist DCPG suppress LPP-evoked fEPSPs in wild-type but not in mGlu8 knockout hippocampal slices; medial perforant path fEPSPs were unaffected by mGlu8 deletion. |
Field EPSP recording in hippocampal slices from wild-type and mGlu8 knockout mice, pharmacological dissection |
Neuropharmacology |
High |
12213276
|
| 2002 |
mGlu8 receptor-deficient mice show increased anxiety-related behavior in the elevated plus maze (increased open arm avoidance and risk assessment), indicating mGlu8 plays a role in modulating responses to novel stressful environments. |
Behavioral phenotyping of mGlu8 knockout mice generated by homologous recombination |
Neuropharmacology |
Medium |
12213278 12213279
|
| 2002 |
Selective activation of mGlu8 receptors by DCPG reduces excitatory synaptic transmission (fEPSPs evoked by optic tract stimulation) in the superficial superior colliculus, antagonized by LY341495 at concentrations selective for mGlu8, indicating mGlu8 modulates glutamate release in the retino-collicular pathway. |
Field EPSP recording in rat superior colliculus in vitro slice preparation with pharmacological antagonism |
Neuropharmacology |
Medium |
12213277
|
| 2003 |
Systemic administration of the mGlu8 agonist (S)-3,4-DCPG induces c-Fos expression in stress-related brain regions (paraventricular hypothalamus, central amygdala, lateral parabrachial nucleus, locus coeruleus) in wild-type but not mGlu8 knockout mice; over 92% of c-Fos positive neurons in the central amygdala were GABAergic, indicating mGlu8 activation modulates inhibitory neuronal activity in stress circuits. |
c-Fos immunohistochemistry, pharmacological challenge in wild-type vs. mGlu8 knockout mice, GABAergic neuron co-localization |
Neuropharmacology |
High |
12907308
|
| 2003 |
In a pilocarpine model of limbic epilepsy, mGluR8 function at lateral perforant path terminals is downregulated in rats with spontaneous recurrent seizures (SRS): maximal L-AP4- and PPG-mediated inhibition of fEPSPs is significantly reduced (50% to 26% for L-AP4), without change in EC50, indicating loss of mGluR8 receptor number/efficacy rather than affinity. |
Field EPSP recording in hippocampal slices, concentration-response curves, pharmacological antagonism |
Synapse |
Medium |
12539201
|
| 2005 |
mGlu8 receptor activation via intra-PAG (periaqueductal gray) perfusion with (S)-3,4-DCPG increases extracellular glutamate and decreases GABA levels; these effects are blocked by the group III antagonist MSOP and by the PKA inhibitor H-89, implicating adenylate cyclase/PKA signaling downstream of mGlu8 in differential regulation of glutamate and GABA release at the PAG. |
In vivo microdialysis in rat PAG, pharmacological antagonism with MSOP, UBP1112, and PKA inhibitor H-89 |
Neuropharmacology |
Medium |
16084932
|
| 2005 |
mGlu8 receptor activation by (S)-3,4-DCPG in the lateral amygdala attenuates synaptic transmission from sensory afferents presynaptically (increased paired-pulse facilitation, no postsynaptic effect), and inhibits acquisition and expression of conditioned fear (fear-potentiated startle) in vivo; LTP by tetanic stimulation was also inhibited. |
In vivo fear-potentiated startle, patch-clamp recording in amygdala slices, paired-pulse protocol |
Neuropharmacology |
Medium |
16188284
|
| 2005 |
mGluR8 activation in rod photoreceptors (by L-AP4, L-SOP, or L-glutamate) decreases cytosolic Ca2+ influx via a pertussis toxin-sensitive Gi/o protein and via Gβγ subunit signaling; suramin (G protein uncoupler), pertussis toxin, and a Gβγ-inhibiting peptide all abolish this effect, while cholera toxin (Gs activator) has no effect, and the absence of Go and Gz proteins suggests Gi2 and/or transducin as the coupling G protein. |
Microspectrofluorimetry of cytosolic Ca2+ in isolated rod photoreceptors, pertussis toxin, cholera toxin, Gβγ-inhibiting peptide, suramin |
Investigative ophthalmology & visual science |
High |
15623786
|
| 2008 |
Both mGluR4 and mGluR8 contribute to presynaptic inhibition of synaptic transmission at the lateral olfactory tract–piriform cortex synapse; the selective mGluR8 agonist DCPG (300 nM) suppresses transmission, and the mGluR4 positive allosteric modulator PHCCC potentiates L-AP4 inhibition at this synapse. |
Whole-cell patch-clamp recordings in piriform cortex pyramidal cells, selective agonists and allosteric modulators |
Neuropharmacology |
Medium |
18625254
|
| 2011 |
mGluR8 mediates presynaptic depression of excitatory transmission in the bed nucleus of the stria terminalis (BNST): DCPG effects are absent in mGluR8 KO slices, associated with increased paired-pulse facilitation and decreased spontaneous EPSC frequency; this mGluR8-mediated suppression is disrupted by α1 adrenergic receptor activation and by both acute and chronic restraint stress in vivo, as well as in α2A AR KO mice. |
Electrophysiology in BNST slices from wild-type and mGlu8 KO mice, mGluR8 immunohistochemistry, pharmacological dissection with α1/α2 AR modulators, in vivo stress paradigms |
Neuropsychopharmacology |
High |
21451497
|
| 2011 |
mGluR8 achieves nearly complete inhibition of glutamate release at hippocampal lateral perforant path synapses without affecting presynaptic Ca2+ entry, diffusion, or buffering; instead, it acts by decreasing the apparent Ca2+ affinity of the release sensor and reducing maximal release rate. This action is resistant to inhibitors of adenylate cyclase and may represent a direct effect on the release machinery. |
Presynaptic Ca2+ imaging, miniature EPSC recording, quantitative Ca2+ dependence modeling, pharmacological blockade of adenylate cyclase and G-protein pathways |
Cerebral cortex |
High |
21903594
|
| 2013 |
mGlu8 but not mGlu7 ablation reduces contextual fear; mGlu8 agonist DCPG decreases synaptic transmission but not LTP at thalamo-lateral amygdala synapses, and intra-amygdala DCPG selectively reduces expression of contextual fear but not cued fear acquisition or expression, establishing distinct roles for mGlu7 and mGlu8 in amygdala synaptic physiology and fear behavior. |
Electrophysiology (LTP and synaptic transmission) in amygdala slices from mGlu7 and mGlu8 KO mice, intra-amygdala microinjection with behavioral fear testing |
Neuropharmacology |
High |
23664812
|
| 2016 |
mGluR8 negatively modulates TRPA1 activity on cutaneous nociceptors: DCPG (mGluR8 agonist) reduces TRPA1-mediated Ca2+ mobilization (co-localization of TRPA1 and mGluR8 confirmed), reverses mustard-oil-induced mechanical hypersensitivity in vivo, and reduces nociceptor firing at the single-fiber level; PKA inhibitor RpCAMPS mimics the DCPG effect, implicating the cAMP/PKA pathway. |
Ca2+ imaging in dorsal root ganglion neurons, in vivo paw withdrawal threshold testing, single-fiber electrophysiology, PKA inhibition |
Neuroscience |
Medium |
27497709
|
| 2018 |
The crystal structure of the human mGlu8 amino terminal domain (ATD) bound to L-AP4 and to L-glutamate was solved, revealing that L-glutamate binds differently in mGlu8 compared to mGlu1, and that both the electronic and steric properties of the distal phosphate of L-AP4 account for its group III selectivity. |
X-ray crystallography of recombinant human mGlu8 ATD |
Bioorganic & medicinal chemistry letters |
High |
29402739
|
| 2018 |
Crystal structure of recombinant human mGlu8 ATD bound to (S)-DCPG was solved; the structure shows the largest lobe opening angle among known agonist-bound mGlu ATD structures, and the DCPG binding conformation differs substantially from homology-model predictions, rationalizing (S)-DCPG's high mGlu8 subtype selectivity. |
X-ray crystallography, homology modeling of other mGlu subtypes |
Journal of medicinal chemistry |
High |
30365309
|
| 2018 |
GRM8 transcriptional activation in squamous cell lung cancer promotes tumor cell survival by inhibiting the cAMP pathway and activating the MAPK pathway; the SNV A112G identified in GRM8 activates downstream signaling and induces cell proliferation, reversed by cAMP stimulator and MEK inhibitor. |
CRISPR-Cas9 genome editing in patient-derived xenograft cells, cAMP and MAPK pathway assays, pharmacological rescue |
Cancer letters |
Medium |
30391781
|
| 2018 |
mGluR8 downregulation in human neuroblastoma (SH-SY5Y) cells increases proliferation and chemoresistance (to staurosporine, doxorubicin, irinotecan, cisplatin) with decreased caspase, calpain, GSK-3β, Akt, and JNK activity; conversely, mGluR8 overexpression in glioma cells (U87-MG, LN18) decreases proliferation and increases apoptosis and chemosensitivity, identifying a tumor suppressor role. |
RNAi knockdown and cDNA overexpression, cell proliferation assays, caspase/calpain activity assays, kinase activity measurement |
Cancer letters |
Medium |
29885518
|
| 2010 |
Selective activation of mGluR8 by DCPG reversibly reduces Off-light responses of retinal ganglion cells in wild-type but not mGluR8-deficient retinas by suppressing both excitatory and inhibitory synaptic conductances, indicating mGluR8 reduces glutamate release from bipolar cell terminals and possibly inhibitory transmitter release from amacrine cells. |
Extracellular and whole-cell light-evoked recording in wild-type and mGluR8 KO mouse retina |
Neuroscience |
High |
20096339
|
| 2024 |
mGlu8 receptor activation (DCPG) in the dentate gyrus inhibits LTP in normal rats but enhances impaired LTP in VPA-exposed (autism model) rats at the perforant path–dentate gyrus synapse; intra-DG DCPG also reverses reduced social novelty preference in VPA-exposed rats, suggesting mGlu8 dysfunction contributes to impaired synaptic plasticity in this ASD model. |
In vivo hippocampal field recording with high-frequency stimulation, intra-DG microinjection, social behavior testing in VPA rat model |
Scientific reports |
Medium |
38849397
|
| 2024 |
In the thalamic reticular nucleus (TRN), mGlu8 (grm8) mRNA is expressed in parvalbumin-positive cells of both TRN core and shell matrices and in cortical layers involved in corticothalamic signaling. Constitutive parvalbumin-specific mGlu8 knockout increases spontaneous excitatory drive onto dorsal thalamus relay cells and impairs sensorimotor gating (paired-pulse inhibition); TRN-conditional AAV-mediated grm8 knockdown produces hyperlocomotion and anxiolytic effects in repeated open field testing. |
Fluorescent in situ hybridization, conditional (AAV-CRE) and cell-type-specific constitutive knockout, whole-cell patch-clamp, paired-pulse inhibition, open field behavioral testing |
The Journal of neuroscience |
High |
38918065
|
| 2012 |
DCPG at submicromolar concentrations selectively inhibits excitatory transmission in the lateral perforant path (LPP) via mGlu8; at concentrations >1 μM, DCPG produces additional non-selective effects in both LPP and medial perforant path (MPP) that are absent in mGlu8 KO but mediated primarily by mGlu2, as shown in mGlu2, mGlu4, and mGlu7 KO mice and an mGlu2-deficient rat substrain. |
Field EPSP recording in hippocampal slices from multiple receptor-specific knockout mice and a naturally mGlu2-deficient rat substrain |
Neuropharmacology |
High |
23220400
|