Improving and utilizing functional in vitro cAMP assay in pursuit to discover allosteric modulators of the GABAB receptor

Abstract

The GABAergic system is the main inhibitory neuronal system utilized within the central nervous system (CNS). γ-aminobutyric acid (GABA) is the fundamental neurotransmitter which transmit inhibitory signals through GABA receptors, the ionotropic GABAA and GABAC receptors; and the metabotropic G-protein coupled receptor GABAB receptor. Disruption of this system is associated with a range of psychiatric disorders such as depression, anxiety, addiction, and schizophrenia, among others. The efficacy of common antidepressants is dependent on their ability to restore conventional GABAergic function. As of 2021, the agonist baclofen is currently the only approved clinical drug targeting the metabotropic GABAB receptor. However, due to its limitations it was not originally applicable for use on receptors within the brain. A large magnitude of GABA and baclofen analogues have been discovered, though none have shown promise for application towards clinical use within the brain in vivo. Which has led to the investigation of allosteric modulation of the receptor. In the present study, in vitro cAMP accumulation assay and radioligand binding assay were used in combination to thoroughly test compounds discovered through virtual screening in pursuit to discover pharmacologically active allosteric modulators. Several compounds were found to increase or decrease effects of GABA, RB-490 and TI400 were the most promising candidates.