title: Activation of dorsal raphe serotonin neurons is necessary for waiting for delayed rewards.
abstract: The forebrain serotonergic system is a crucial component in the control of impulsive behaviors. We previously reported that the activity of serotonin neurons in the midbrain dorsal raphe nucleus increased when rats performed a task that required them to wait for delayed rewards. However, the causal relationship between serotonin neural activity and the tolerance for the delayed reward remained unclear. Here, we test whether the inhibition of serotonin neural activity by the local application of the 5-HT(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin in the dorsal raphe nucleus impairs rats' tolerance for delayed rewards. Rats performed a sequential food-water navigation task that required them to visit food and water sites alternately via a tone site to get rewards at both sites after delays. During the short (2 s) delayed reward condition, the inhibition of serotonin neural activity did not significantly influence the numbers of reward choice errors (nosepoke at an incorrect reward site following a conditioned reinforcer tone), reward wait errors (failure to wait for the delayed rewards), or total trials (sum of reward choice errors, reward wait errors, and acquired rewards). By contrast, during the long (7-11 s) delayed reward condition, the number of wait errors significantly increased while the numbers of total trials and choice errors did not significantly change. These results indicate that the activation of dorsal raphe serotonin neurons is necessary for waiting for long delayed rewards and suggest that elevated serotonin activity facilitates waiting behavior when there is the prospect of forthcoming rewards.
authors.affiliation: Neural Computation Unit, Okinawa Institute of Science and Technology, Okinawa 904-0412, Japan. kmiyazaki@oist.jp
authors.forename: Kayoko W
authors.initials: KW
authors.lastname: Miyazaki
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Kenji
authors.initials: K
authors.lastname: Doya
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D002755:Choice Behavior / Q000187:drug effects; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D008297:Male; D017551:Microdialysis; D011903:Raphe Nuclei / Q000166:cytology* / Q000187:drug effects; D051381:Rats; D020318:Rats, Long-Evans; D012201:Reward; D059326:Serotonergic Neurons / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013997:Time Factors
chemical_list: D017366:Serotonin Receptor Agonists; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin