Deficiency of serotonin in raphe neurons and altered behavioral responses in tryptophan hydroxylase 2-knockout medaka (oryzias latipes)

Satoshi Ansai, Hiroshi Hosokawa, Shingo Maegawa, Kiyoshi Naruse, Youhei Washio, Kenji Sato, Masato Kinoshita

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Serotonin (5-hydroxytryptamine [5-HT]) is a bioactive monoamine that acts as a neurotransmitter in the central and peripheral nervous system of animals. Teleost fish species have serotonergic neurons in the raphe nuclei of the brainstem; however, the role of 5-HT in the raphe neurons in teleost fish remains largely unknown. Here, we established a medaka (Oryzias latipes) strain with targeted disruption of tryptophan hydroxylase 2 (tph2) gene that is involved in the 5-HT synthesis in the raphe nuclei. Immunohistochemistry and mass spectrometry analysis revealed that the homozygous mutants (tph2Δ13/Δ13) lacked the ability to synthesize 5-HT in the raphe neurons. To investigate the effects of 5-HT deficiency in adult behaviors, the mutant fish were subjected to five behavioral paradigms (diving, open-field, light-dark transition, mirror-biting, and two-fish social interaction). The homozygous mutation caused a longer duration of freezing response in all examined paradigms and reduced the number of entries to the top area in the diving test. In addition, the mutants exhibited a decreased number of mirror-biting in the males and an increased contact time in direct social interaction between the females. These results indicate that this tph2-knockout medaka serves as a good model to analyze the effects of 5-HT deficiency in the raphe neurons.

Original languageEnglish
Pages (from-to)495-507
Number of pages13
JournalZebrafish
Volume14
Issue number6
DOIs
Publication statusPublished - 2017 Dec
Externally publishedYes

Keywords

  • behavior
  • knockout
  • medaka
  • serotonin
  • tryptophan hydroxylase

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Developmental Biology

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