Of note, Group I mGluRs (mGluR1 and mGluR5) expressed on glutamatergic synapses localized in the spinal cord of SOD1G93A ALS mice resulted in overexpression and enhanced sensitivity to the agonist present in the synaptic cleft; this phenomenon triggers increased activation of these receptors, mobilization of Ca2+ from the intracellular stores and further glutamate release [201]. The gene discussed is GRM1; the disease is amyotrophic lateral sclerosis.