A Deep Mesencephalic Nucleus Circuit Regulates Licking Behavior

 Di Zheng1,2 • Jia-Yu Fu1,2 • Meng-Yu Tang1,2 • Xiao-Dan Yu1,2 • Yi Zhu1,2 • Chen-Jie Shen2 • Chun-Yue Li1,2 • Shi-Ze Xie1,2 • Shan Lin1,2 • Minmin Luo3,4,5 • Xiao-Ming Li1,2,6
1 Department of Neurobiology and Department of Neurology of Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310058, China 
2 NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brainmachine Integration, School of Brain Science and Brian Medicine, Zhejiang University, Hangzhou 310058, China 
3 National Institute of Biological Sciences (NIBS), Beijing 102206, China 
4 Chinese Institute for Brain Research, Beijing 102206, China 
5 School of Life Sciences, Tsinghua University, Beijing 100084, China 
6 Center for Brain Science and Brain-Inspired Intelligence, Research Units for Emotion and Emotion Disorders, Chinese Academy of Medical Sciences, China/Guangdong-Hong Kong-Macao Greater Bay Area, Joint Institute for Genetics and Genome Medicine Between Zhejiang University and University of Toronto, Hangzhou 310058, China
Licking behavior is important for water intake. The deep mesencephalic nucleus (DpMe) has been implicated in instinctive behaviors. However, whether the DpMe is involved in licking behavior and the precise neural circuit behind this behavior remains unknown. Here, we found that the activity of the DpMe decreased during water intake. Inhibition of vesicular glutamate transporter 2-positive (VGLUT2?) neurons in the DpMe resulted in increased water intake. Somatostatin-expressing (SST?), but not protein kinase C-d-expressing (PKC-d?), GABAergic neurons in the central amygdala (CeA) preferentially innervated DpMe VGLUT2? neurons. The SST? neurons in the CeA projecting to the DpMe were activated at the onset of licking behavior. Activation of these CeA SST? GABAergic neurons, but not PKC-d? GABAergic neurons, projecting to the DpMe was sufficient to induce licking behavior and promote water intake. These findings redefine the roles of the DpMe and reveal a novel CeASST– DpMeVGLUT2 circuit that regulates licking behavior and promotes water intake.
Midbrain; Amygdala; Licking; Neural;Circuit; Optogenetics