Serotonin modulates the dehydration-induced changes in tolerance for bitter water.
Drinking behavior is regulated by endogenous factors such as the hydration condition of animals and exogenous factors such as the taste of ingested fluids. These factors have been suggested to interact with each other via serotonergic (5-HT) signaling to regulate drinking behavior. In the present study, we examined how dehydration affects the intake of bitter water, which suppresses drinking behavior, via 5-HT signaling. Water deprivation increased water intake for 1h, depending on the duration of water deprivation. The intake of 1mM quinine, which is a bitter tastant, was lower than that of water in mice deprived of water for 24h but not 48 h. We next examined the involvement of the dorsal raphe nucleus (DRN) and median raphe nucleus (MRN), which contain a large population of 5-HT neurons, in changing tolerance for quinine intake after water deprivation. The intake of quinine following water deprivation for 24h, but not 48 h, increased the number of tryptophan hydroxylase-positive neurons expressing c-Fos in the DRN, but not in the MRN. Moreover, administration of paroxetine, a selective serotonin reuptake inhibitor, decreased the intake of quinine solution, but not water, in mice deprived of water for 48 h, indicating that paroxetine treatment restored the aversion to quinine. These results suggest that unresponsiveness of 5-HT neurons in the DRN may be involved in the dehydration-induced increase in tolerance for bitter water.
Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan. Electronic address: muroyoc@hotmail.co.jp.
Masaki
M
Iwai
Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan. Electronic address: muroi@obihiro.ac.jp.
Yoshikage
Y
Muroi
Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan. Electronic address: ken_ichi@yahoo.co.jp.
Ken-ichi
K
Kinoshita
Department of Basic Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan. Electronic address: Ishii@obihiro.ac.jp.
Toshiaki
T
Ishii
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000818:Animals; D003681:Dehydration / Q000188:drug therapy / Q000503:physiopathology*; D004326:Drinking / Q000187:drug effects / Q000502:physiology; D004327:Drinking Behavior / Q000187:drug effects / Q000502:physiology*; D060766:Drinking Water; D005518:Food Preferences / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008807:Mice, Inbred BALB C; D023421:Models, Animal; D017374:Paroxetine / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D011803:Quinine; D011903:Raphe Nuclei / Q000187:drug effects / Q000503:physiopathology; D059326:Serotonergic Neurons / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D013997:Time Factors; D014365:Tryptophan Hydroxylase / Q000378:metabolism; D014868:Water Deprivation / Q000502:physiology
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D060766:Drinking Water; D017374:Paroxetine; D016760:Proto-Oncogene Proteins c-fos; D011803:Quinine; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors; D014365:Tryptophan Hydroxylase
Bitter water tolerance; Dehydration; Quinine; Serotonin