Restoration of nNOS Expression Rescues Autistic-Like Phenotypes Through Normalization of AMPA Receptor-Mediated Neurotransmission.

Autism spectrum disorder (ASD) is associated with a range of abnormalities characterized by deficits in socialization, communication, repetitive behaviors, and restricted interests. We have recently shown that neuronal nitric oxide synthase (nNOS) expression was decreased in the basolateral amygdala (BLA) of mice after postnatal valproic acid exposure. Neuronal activity-regulated pentraxin (Narp) could contribute to the regulation of the GluA4 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl) propanoic acid (AMPA) subunits which are predominantly expressed in interneurons. However, the specific role of nNOS re-expression on excitatory neurotransmitter with relevance to ASD core symptoms in VPA-treated animals remains to be elucidated. Herein, nNOS overexpression using a lentiviral vector and L-arginine-activating PI3K-Akt-mTOR signaling can restore nNOS expression in the BLA induced by VPA. Restoration of nNOS expression in these mice was sufficient to reduce the severity of ASD-like behavioral patterns such that animals exhibited decreases in abnormal social interactions and communication, stereotyped/repetitive behaviors, and anxiety-like traits. Most strikingly, re-expression of nNOS upregulated surface expression of Narp and GluA4 in nNOS-positive interneuron as shown by immunoprecipitation and Western blotting. Whole-cell patch-clamp recordings demonstrated that restoration of nNOS had a significant enhancing effect on AMPA receptor-mediated excitatory glutamatergic synaptic neurotransmission, which was inhibited by disturbing the interaction between Narp and GluA4 in acutely dissociated BLA slices. Overall, these data offer a scientific basis for the additional study of nNOS re-expression as a promising therapeutic target by correcting AMPA receptor-mediated synaptic function in ASD and related neurodevelopmental disorders.