Effects of 5-hydroxytryptamine on defecation in open-field behavior in rats

Tsutomu Kameyama, Masahiko Suzuki, Toshitaka Nabeshima

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25 Citations (Scopus)


An attempt was made to elucidate the role of the serotonergic nervous system in defecation resulting from environmental stimulation in rats. The open-field (OF) test and shuttle box method were used to study the defecation. 5-Hydroxytryptophan (5-HTP) significantly decreased the number of fecal boluses excreted in both emotional situations, namely, in both OF and shuttle box. The fecal excretion was significantly reduced compared with the controls after intraventricular injection of 5-hydroxytryptamine (5-HT). Animals pretreated with p-chlorophenylalanine (pCPA) and 5,6-dihydroxytryptamine (5,6-DHT) tended to show a slight increase in the OF defecation. 5-HTP was equally effective in diminishing the OF performance of pCPA-treated rats. The inhibitory effects of 5-HTP on the defecation were also observed after depletion of biogenic amines by reserpine treatment. Home cage defecation was increased after 5-HTP administration, decreased under pretreatment with pCPA and not influenced by intraventricular injection of 5-HT. These results suggested that the defecation after environmental stimuli was due to a change in 5-HT levels in the brain.

Original languageEnglish
Pages (from-to)875-882
Number of pages8
JournalPharmacology, Biochemistry and Behavior
Issue number6
Publication statusPublished - 06-1980
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Toxicology
  • Pharmacology
  • Clinical Biochemistry
  • Biological Psychiatry
  • Behavioral Neuroscience


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