Shank3b deficiency drives anxiety-like behaviors via impaired GABAergic inhibition and enhanced intrinsic excitability in the basolateral amygdala.

Abstract

Anxiety is a highly prevalent and disabling comorbidity in autism spectrum disorder (ASD), but its neurobiological mechanisms remain poorly understood. The basolateral amygdala (BLA) is critically involved in anxiety processing, yet the synaptic substrates linking ASD gene mutations to BLA dysfunction are not fully defined. Here, we evaluated anxiety-like behaviors in male Shank3b knockout (Shank3b-/-) mice using open field, elevated plus maze, and light-dark transition tests. Molecular alterations in the BLA were assessed by qPCR and Western blotting, and whole-cell patch-clamp recordings were performed to examine synaptic transmission and intrinsic excitability of BLA pyramidal neurons. Shank3b-/- mice exhibited robust anxiety-like behaviors across multiple behavioral paradigms. In the BLA, expression of the GABAA receptor α2 subunit (GABRA2) was significantly reduced, accompanied by decreased levels of NMDA receptor subunits (GluN2A and GluN2B). Electrophysiological recordings revealed a marked reduction in inhibitory synaptic transmission, as evidenced by decreased frequency and amplitude of spontaneous inhibitory postsynaptic currents, whereas excitatory transmission remained largely unchanged, resulting in a significantly elevated excitation/inhibition (E/I) ratio. In addition, BLA pyramidal neurons displayed increased intrinsic excitability, characterized by a depolarized resting membrane potential and enhanced action potential firing. Collectively, these findings identify impaired GABAergic transmission associated with reduced GABRA2 expression as a key mechanism underlying E/I imbalance and heightened neuronal excitability in the BLA of Shank3b-deficient mice, which likely contributes to ASD-related anxiety-like behaviors. These results identify GABAA receptor signaling as a promising therapeutic target for pharmacological intervention in ASD-related anxiety.