Metabotropic and ionotropic glutamate receptors as neurobiological targets in anxiety and stress-related disorders: focus on pharmacology and preclinical translational models

Abstract

Anxiety disorders are amongst the most common and disabling of psychiatric illnesses and have severe health and socio-economic implications. Despite the availability of a number of treatment options there is still a strong medical need for novel and improved pharmacological approaches in treating these disorders. New developments at the forefront of preclinical research have begun to identify the therapeutic potential of molecular entities integral to the biological response to adversity, particularly molecules and processes that may pre-determine vulnerability or resilience, and those that may act to switch off or "unlearn" a response to an aversive event. The glutamate system is an interesting target in this respect, especially given the impact anxiety disorders have on neuroplasticity, cognition and affective function. These areas of research demonstrate expanding and improved evidence-based options for treating disorders where stress in various guises plays an important etiological role. The current review will discuss how these pathways are involved in fear circuitry of the brain and compare the strength of therapeutic rationale as well as progress towards pharmacological validation of the glutamate pathway towards the treatment of anxiety disorders, with a particular focus on metabotropic and ionotropic glutamate receptors. Specific reference to their anxiolytic actions and efficacy in translational disease models of posttraumatic stress disorder, obsessive-compulsive disorder, panic disorder and phobia will be made. In addition, the availability of ligands necessary to assist clinical proof of concept studies will be discussed.