Reward processing by the dorsal raphe nucleus: 5-HT and beyond.
The dorsal raphe nucleus (DRN) represents one of the most sensitive reward sites in the brain. However, the exact relationship between DRN neuronal activity and reward signaling has been elusive. In this review, we will summarize anatomical, pharmacological, optogenetics, and electrophysiological studies on the functions and circuit mechanisms of DRN neurons in reward processing. The DRN is commonly associated with serotonin (5-hydroxytryptamine; 5-HT), but this nucleus also contains neurons of the neurotransmitter phenotypes of glutamate, GABA and dopamine. Pharmacological studies indicate that 5-HT might be involved in modulating reward- or punishment-related behaviors. Recent optogenetic stimulations demonstrate that transient activation of DRN neurons produces strong reinforcement signals that are carried out primarily by glutamate. Moreover, activation of DRN 5-HT neurons enhances reward waiting. Electrophysiological recordings reveal that the activity of DRN neurons exhibits diverse behavioral correlates in reward-related tasks. Studies so far thus demonstrate the strong power of DRN neurons in reward signaling and at the same time invite additional efforts to dissect the roles and mechanisms of different DRN neuron types in various processes of reward-related behaviors.
National Institute of Biological Sciences, Beijing 102206, China School of Life Sciences, Tsinghua University, Beijing 100084, China luomm@tsinghua.edu.cn.
Minmin
M
Luo
National Institute of Biological Sciences, Beijing 102206, China.
Jingfeng
J
Zhou
National Institute of Biological Sciences, Beijing 102206, China.
Zhixiang
Z
Liu
D000818:Animals; D065847:Dorsal Raphe Nucleus / Q000166:cytology / Q000502:physiology*; D006801:Humans; D009474:Neurons / Q000166:cytology / Q000502:physiology; D012201:Reward; D012701:Serotonin / Q000378:metabolism
D012701:Serotonin