Hyperactive mTORC1 in striatum dysregulates dopamine receptor expression and odor preference behavior.

Mechanistic target of rapamycin (mTOR) plays an important role in brain development and synaptic plasticity. Dysregulation of the mTOR pathway is observed in various human central nervous system diseases, including tuberous sclerosis complex, autism spectrum disorder (ASD), and neurodegenerative diseases, including Parkinson's disease and Huntington's disease. Numerous studies focused on the effects of hyperactivation of mTOR on cortical excitatory neurons, while only a few studies focused on inhibitory neurons. Here we generated transgenic mice in which mTORC1 signaling is hyperactivated in inhibitory neurons in the striatum, while cortical neurons left unaffected. The hyperactivation of mTORC1 signaling increased GABAergic inhibitory neurons in the striatum. The transgenic mice exhibited the upregulation of dopamine receptor D1 and the downregulation of dopamine receptor D2 in medium spiny neurons in the ventral striatum. Finally, the transgenic mice demonstrated impaired motor learning and dysregulated olfactory preference behavior, though the basic function of olfaction was preserved. These findings reveal that the mTORC1 signaling pathway plays an essential role in the development and function of the striatal inhibitory neurons and suggest the critical involvement of the mTORC1 pathway in the locomotor abnormalities in neurodegenerative diseases and the sensory defects in ASD.