Re-examining the role of ventral tegmental area dopaminergic neurons in motor activity and reinforcement by chemogenetic and optogenetic manipulation in mice

• Published in: Metabolic brain disease 2019-10, Vol.34 (5), p.1421-1430
• Main Authors: Jing, Man-Yi, Han, Xiao, Zhao, Tai-Yun, Wang, Zhi-Yuan, Lu, Guan-Yi, Wu, Ning, Song, Rui, Li, Jin
• Format: Article
• Language: English
• Subjects: Animals; Behavior; Behavior, Animal - drug effects; Behavior, Animal - physiology; Biochemistry; Biomedical and Life Sciences; Biomedicine; Clozapine; Clozapine - analogs & derivatives; Clozapine - pharmacology; Dopamine; Dopamine D1 receptors; Dopamine Plasma Membrane Transport Proteins - genetics; Dopamine Plasma Membrane Transport Proteins - metabolism; Dopamine transporter; Dopaminergic Neurons - drug effects; Dopaminergic Neurons - metabolism; Injection; Intracranial self-stimulation; Locomotion; Locomotor activity; Medical treatment; Mental disorders; Metabolic Diseases; Mice; Mice, Transgenic; Microdialysis; Motor activity; Motor Activity - drug effects; Motor Activity - physiology; Neurology; Neurons; Neurosciences; Nucleus accumbens; Oncology; Optogenetics; Original Article; Pulse duration; Reinforcement; Reward; Self Stimulation; Transfection; Transgenic mice; Ventral Tegmental Area - drug effects; Ventral Tegmental Area - metabolism; Ventral tegmentum
• ISSN: 0885-7490; 1573-7365
• DOI: 10.1007/s11011-019-00442-z

The precise contributions of ventral tegmental area (VTA) dopaminergic (DAergic) neurons to reward-related behaviors are a longstanding hot topic of debate. Whether the activity of VTA DAergic neurons directly modulates rewarding behaviors remains uncertain. In the present study, we investigated the fundamental role of VTA DAergic neurons in reward-related movement and reinforcement by employing dopamine transporter (DAT)-Cre transgenic mice expressing hM3Dq, hM4Di or channelrhodopsin 2 (ChR2) in VTA DAergic neurons through Cre-inducible adeno-associated viral vector transfection. On the one hand, locomotion was tested in an open field to examine motor activity when VTA DAergic neurons were stimulated or inhibited by injection of the hM3Dq or hM4Di ligand clozapine-N-oxide (CNO), respectively. CNO injection to selectively activate or inhibit VTA DAergic neurons significantly increased or decreased locomotor activity, respectively, compared with vehicle injection, indicating that VTA DAergic neuron stimulation is directly involved in the regulation of motor activity. On the other hand, we used the optical intracranial self-stimulation (oICSS) model to investigate the causal link between reinforcement and VTA DAergic neurons. Active poking behavior but not inactive poking behavior was significantly escalated in a frequency- and pulse duration-dependent manner. In addition, microdialysis revealed that the concentration of dopamine (DA) in the nucleus accumbens (NAc) was enhanced by selective optogenetic activation of VTA DAergic neurons. Furthermore, systemic administration of a DA D1 receptor antagonist significantly decreased oICSS reinforcement. Our research profoundly demonstrates a direct regulatory role of VTA DAergic neurons in movement and reinforcement and provides meaningful guidance for the development of novel treatment strategies for neuropsychiatric diseases related to the malfunction of the reward system.