The Discovery And Pharmacological Characterization Of Negative Allosteric Modulators For GABA_B Receptor

y-aminobutyric acid (GABA) is a major neurotransmitter in the mammalian brain that controls neuronal excitability by activating ionotropic GAB AA and GAB Ac receptors and metabotropic GABAB receptors. GABAB receptors belongs to class C G protein coupled receptors (GPCR), composed of two subunits:GABAB1 (GB1) and GABAB2 (GB2). GABAB receptors have been shown to play a key role in regulating synaptic transmission and membrane excitability in the brain. The dysregulation of GABAB receptor may lead to multiple diseases, such as epilepsy, depression, spastic, anxiety, drug addiction, and cognitive disorder.One agonist of GABAB receptor, baclofen, has been used for the treatment of spasticity, is muscle relaxation. With the development of the drug discovery technology, some allosteric modulators(PAMs) have been discovered,which show the effect in treating the diseases such as anxiety, drug addiction. The antagonists of GABAB receptor have also been developed, exhibiting the possibility to treat Absence Epilepsy and cognitive disorder. However, until now, no negative allosteric modulators have been reported.In order to find PAMs of GABAB receptor with better activity, we have been devoted to the structure optimization of CGP7930 and obtained an unexpected compound(CLH304a) with show negative allosteric effect,which is the first negative allosteric modulator of GABAB receptor reported. Then overall assessment to the effect of the negative allosteric modulator has been carried out in cultured CGNs or cells overexpressed different mutants of GABAB receptor. We also demonstrate the NAM modulates GABAB receptor signalling through HD domain of GB2. Finally, based on the NAMs, we develop an active activity-based probe targeting on GABAB receptor,which is a tool to study the mechanism of GABAB receptors.