The serotonin transporter and nonselective transporters are involved in peripheral serotonin uptake in the gulf toadfish, opsanus beta

Molly H.B. Amador, Danielle M Mcdonald

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Abstract

In mammals, circulating serotonin [5-hydroxytryptamine (5-HT)] is sequestered by platelets via the 5-HT transporter (SERT) to prevent unintended signaling by this potent signaling molecule. Teleost fish appear to lack a similar circulating storage pool, although the diverse effects of 5-HT in teleosts likely necessitate an alternative method of tight regulation, such as uptake by peripheral tissues. Here, a 5-HT radiotracer was used to explore the 5-HT uptake capacity of peripheral tissues in the Gulf toadfish, Opsanus beta, and to elucidate the primary excretion routes of 5-HT and its metabolites. Pharmacological inhibition of SERT and other transporters enabled assessment of the SERT dependence of peripheral 5-HT uptake and excretion. The results indicated a rapid and substantial uptake of 5-HT by the heart atrium, heart ventricle, and gill that was at least partly SERT dependent. The results also supported the presence of a partial blood-brain barrier that prevented rapid changes in brain 5-HT content despite fluctuating plasma 5-HT concentrations. The renal pathway appeared to be the dominant excretory route for 5-HT and its metabolites over shorter time frames (up to ~30 min), but hepatic excretion was substantial over several hours. SERT inhibition ultimately reduced the excretion of 5-HT and its metabolites by urinary, biliary, and/or intestinal pathways. In addition, branchial excretion of 5-HT and its metabolites could not be ruled out. In summary, this study reveals that the toadfish heart and gill play active roles in regulating circulating 5-HT and yields important insights into the control of peripheral 5-HT in this teleost fish.

Original languageEnglish (US)
Pages (from-to)R1154-R1166
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume315
Issue number6
DOIs
StatePublished - Dec 1 2018

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Keywords

  • 5-hydroxytryptamine
  • Bupropion
  • Decynium-22
  • Fluoxetine
  • Serotonin transport

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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