Physiological roles of endogenous neurosteroids at extrasynaptic GABAARs (360G-Wellcome-105206_Z_14_A)

The role of GABA and GABAA receptors in providing synaptic and tonic inhibition of neurons is an important aspect of normal brain function. This is evident when inhibition becomes dysfunctional, resulting in neurological and psychiatric diseases. GABA receptors are also subject to modulation by endogenous compounds. Paramount amongst these are the neurosteroids that regulate inhibition, but their physiological role and how they are involved in brain diseases is largely unexplored. Having discovered the binding site for neurosteroids on GABAA receptors, revealing a highly conserved site on receptor alpha subunits, we can now dissect both their physiological and pathophysiological roles by adopting a genetic-based approach. The main aim of this proposal is to characterise the GABA receptor alpha4 subunit in a mouse knock-in line that has been rendered insensitive to neurosteroids by mutation of its binding site. This subunit is involved in the assembly of extrasynaptic GABAA receptors. By investigating inhibitory transmission, using brain slice preparations and dissociated neuronal cell cultures, in conjunction with biochemical, chemical, electrophysiological, imaging (single particle tracking), pharmacological and molecular approaches, we will uncover the role(s) of neurosteroids at this highly sensitive extrasynaptic GABAA receptor that underpins tonic inhibition in the brain.