Metabotropic glutamate receptors (mGluR or mGlu) are G-protein coupled receptors activated by the binding of glutamate, the main classical neurotransmitter of the nervous system. Eight different mGluR subtypes (mGluR1-8) have been cloned and are classified in three groups based on their molecular, pharmacological and signaling properties. mGluRs mediate several physiological functions such as neuronal excitability and synaptic plasticity, but they have also been implicated in numerous pathological conditions including pain. The availability of new and more selective allosteric modulators together with the canonical orthosteric ligands and transgenic technologies has led to significant advances in our knowledge about the role of the specific mGluR subtypes in the pathophysiological mechanisms of various diseases. Although development of successful compounds acting on mGluRs for clinical use has been scarce, the subtype-specific-pharmacological manipulation might be a compelling approach for the treatment of several disorders in humans, including pain; this review aims to summarize and update on preclinical evidence for the roles of different mGluRs in the pain system and discusses knowledge gaps regarding mGluR-related sex differences and neuroimmune signaling in pain.

This case report describes a 73-year-old Caucasian male who contracted COVID-19 and struggled with chronic, severe pruritus after that. The patient's pruritus resisted numerous conventional and unconventional therapy modalities, highlighting the difficulty of treating post-COVID-19 dermatological symptoms. Pruritus in the patient was significantly alleviated due to therapy with Dupixent, a monoclonal antibody that inhibits interleukin-4 and interleukin-13 signaling. Treatment of the condition improved significantly with the use of Dupixent. The report describes the story of the patient's journey, from the first-time symptoms showed up after COVID-19 infection, through several treatments that was not effective, to when the patient's symptoms disappeared after starting Dupixent. The patient's recent SARS-CoV-2 infection may be connected to the immune-mediated process shown by the patient's histopathological results. Even though these results are based on a single instance, they highlight COVID-19's ability to cause chronic pruritus and recommend Dupixent as a possible treatment approach. More study is required to confirm these findings and investigate possible immunological connections between COVID-19 and chronic pruritus.