title: Activation of dorsal raphe serotonergic neurons promotes waiting but is not reinforcing.
abstract: BACKGROUND
  The central neuromodulator serotonin (5-HT) has been implicated in a wide range of behaviors and affective disorders, but the principles underlying its function remain elusive. One influential line of research has implicated 5-HT in response inhibition and impulse control. Another has suggested a role in affective processing. However, whether and how these effects relate to each other is still unclear.
  
  
  RESULTS
  Here, we report that optogenetic activation of 5-HT neurons in the dorsal raphe nucleus (DRN) produces a dose-dependent increase in mice's ability to withhold premature responding in a task that requires them to wait several seconds for a randomly delayed tone. The 5-HT effect had a rapid onset and was maintained throughout the stimulation period. In addition, movement speed was slowed, but photostimulation did not affect reaction time or time spent at the reward port. Using similar photostimulation protocols in place preference and value-based choice tests, we found no evidence of either appetitive or aversive effects of DRN 5-HT neuron activation.
  
  
  CONCLUSIONS
  These results provide strong evidence that the efficacy of DRN 5-HT neurons in promoting waiting for delayed reward is independent of appetitive or aversive effects and support the importance of 5-HT in behavioral persistence and impulse control.
authors.affiliation: Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Avenida de Brasília, 1400-038 Lisbon, Portugal.
authors.forename: Madalena S
authors.initials: MS
authors.lastname: Fonseca
authors.affiliation: Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Avenida de Brasília, 1400-038 Lisbon, Portugal.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Murakami
authors.affiliation: Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Avenida de Brasília, 1400-038 Lisbon, Portugal. Electronic address: zmainen@neuro.fchampalimaud.org.
authors.forename: Zachary F
authors.initials: ZF
authors.lastname: Mainen
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D065786:Delay Discounting / Q000502:physiology*; D065847:Dorsal Raphe Nucleus / Q000166:cytology* / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D007175:Impulsive Behavior / Q000502:physiology*; D008027:Light; D051379:Mice; D062308:Optogenetics; D010775:Photic Stimulation; D059326:Serotonergic Neurons / Q000502:physiology* / Q000528:radiation effects; D012701:Serotonin / Q000378:metabolism; D013997:Time Factors
chemical_list: D012701:Serotonin