Reversal of an Unconditioned Behavioral Preference for Specific Food Pellets by Intervention of Whisker Sensory Inputs

Cortico-basal ganglia circuits underlying dysfunctional control of motor behaviors in neuropsychiatric disorders

Neuropsychiatric disorders often manifest with abnormal control of motor behavior. Common symptoms include restricted and repetitive patterns of behavior (RRBs). Cortico-basal ganglia circuits have been implicated in the etiology of RBBs. However, there is a vast range of behaviors encompassed in RRBs, from simple explosive motor tics to rather complex ritualized compulsions. In this review, we highlight how recent findings about the function of specific basal ganglia circuits can begin to shed light into defined motor symptoms associated with neuropsychiatric disorders. We discuss recent studies using genetic animal models that advocate that different aspects of motor repetition in neurodevelopmental disorders, like obsessive-compulsive disorder and autism spectrum disorder, emerge from particular dysregulations in distinct cortico-basal ganglia circuits.

Striatal Inhibition of MeCP2 or TSC1 Produces Sociability Deficits and Repetitive Behaviors

Autism spectrum disorder (ASD) is a heterogeneous group of neurobehavioral disorders characterized by the two core domains of behavioral deficits, including sociability deficits and stereotyped repetitive behaviors. It is not clear whether the core symptoms of ASD are produced by dysfunction of the overall neural network of the brain or that of a limited brain region. Recent studies reported that excessive glutamatergic or dopaminergic inputs in the dorsal striatum induced sociability deficits and repetitive behaviors. These findings suggest that the dorsal striatum plays a crucial role in autistic-like behaviors. The present study addresses whether functional deficits of well-known ASD-related genes in the dorsal striatum also produce ASD core symptoms. This study also examines whether these behavioral changes can be modulated by rebalancing glutamate and/or dopamine receptor activity in the dorsal striatum. First, we found that the siRNA-mediated inhibition of Shank3, Nlgn3, Fmr1, Mecp2, or Tsc1 in the dorsal striatum produced mild to severe behavioral changes in sociability, cognition, and/or repetitive behaviors. The knockdown effects of Mecp2 and Tsc1 on behavioral changes were the most prominent. Next, we demonstrated that behavioral changes induced by striatal inhibition of MeCP2 and TSC1 were rescued by D-cycloserine (an NMDA agonist), fenobam (an mGluR5 antagonist), SCH23390 (a D1 antagonist), and/or ecopipam (a D1 partial antagonist), pharmacological drugs that are known to regulate ASD-like symptoms in animal models. Collectively, these results suggest that the dorsal striatum is a critical brain region that, when dysfunctional, produces the core symptoms of ASD.

Excessive D1 Dopamine Receptor Activation in the Dorsal Striatum Promotes Autistic-Like Behaviors

The dopamine system has been characterized in motor function, goal-directed behaviors, and rewards. Recent studies recognize various dopamine system genes as being associated with autism spectrum disorder (ASD). However, how dopamine system dysfunction induces ASD pathophysiology remains unknown. In the present study, we demonstrated that mice with increased dopamine functions in the dorsal striatum via the suppression of dopamine transporter expression in substantia nigra neurons or the optogenetic stimulation of the nigro-striatal circuitry exhibited sociability deficits and repetitive behaviors relevant to ASD pathology in animal models, while these behavioral changes were blocked by a D1 receptor antagonist. Pharmacological activation of D1 dopamine receptors in normal mice or the genetic knockout (KO) of D2 dopamine receptors also produced typical autistic-like behaviors. Moreover, the siRNA-mediated inhibition of D2 dopamine receptors in the dorsal striatum was sufficient to replicate autistic-like phenotypes in D2 KO mice. Intervention of D1 dopamine receptor functions or the signaling pathways-related D1 receptors in D2 KO mice produced anti-autistic effects. Together, our results indicate that increased dopamine function in the dorsal striatum promotes autistic-like behaviors and that the dorsal striatum is the neural correlate of ASD core symptoms.

Loss of Adenylyl Cyclase Type-5 in the Dorsal Striatum Produces Autistic-Like Behaviors

Autism spectrum disorders (ASDs) are a heterogeneous group of psychiatric illness characterized by common core symptoms including sociability deficits and stereotyped behaviors. ASD is caused by various genetic and non-genetic factors. The genetic effects of autism-related genes are usually global and are presented with multiple symptoms, which hamper understanding of the mechanism through which the diverse causes of ASD produce common symptoms. In the present study, we demonstrate that genetic or molecular disruption of an array of molecular networks centered on adenylyl cyclase type-5 (AC5 or ADCY5) in the dorsal striatum produces autistic-like behaviors. AC5 knockout (KO) mice exhibit increased repetitive behaviors and sociability deficits, the two core domains of ASD, and that siRNA-mediated suppression of AC5 within the dorsal striatum is sufficient to replicate these behavioral phenotypes. Notably, the autistic-like behaviors of AC5 KO mice are rescued by blocking mGluR5 glutamate receptors within the dorsal striatum. Furthermore, pharmacological or siRNA-mediated inhibition of mGluR3, GluA and GluN glutamate receptors in the dorsal striatum in wildtype mice also induces autistic-like behaviors. Optogenetic inhibition of the prelimbic cortical neurons projecting to the dorsal striatum in AC5 KO mice rescues the deficits in social and object novelty preferences. Our results suggest that AC5 mutation produces autistic-like symptoms through the upregulation of mGluR5 functions in the dorsal striatum and that the dorsal striatum regulated by AC5 is a neural correlate responsible for core ASD symptoms.