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Long-term treatment with fluoxetine induces desensitization of 5-HT4 receptor-dependent signalling and functionality

Rebeca Vidal1, Elsa M Valdizán, Ricardo Mostany

  • 1Departamento de Fisiología y Farmacología, Universidad de Cantabria and Instituto de Biomedicina y Biotecnología (IBBTEC) (UC-CSIC-IDICAN), Santander, Cantabria, Spain.

Journal of Neurochemistry
|June 16, 2009
PubMed

Insights

Chronic treatment with fluoxetine, a selective serotonin reuptake inhibitor (SSRI), decreases serotonin 5-HT(4) receptor signaling in rat brains. This adaptation may explain how SSRIs achieve their antidepressant effects.

Area of Science:

  • Neuroscience
  • Pharmacology

Background:

  • The efficacy of antidepressant drugs is potentially linked to monoamine receptor adaptation.
  • Serotonin 5-HT(4) receptor subtypes are implicated in these adaptive mechanisms.

Purpose of the Study:

  • To investigate the impact of chronic fluoxetine treatment on serotonin 5-HT(4) receptor sensitivity in the rat brain.
  • To explore the potential role of 5-HT(4) receptor pathway changes in antidepressant drug action.

Main Methods:

  • Repeated administration of fluoxetine (5 and 10 mg/kg) to rats for 21 days.
  • Utilized receptor autoradiography to quantify 5-HT(4) receptor binding density.
  • Employed adenylate cyclase assays and extracellular recordings to assess receptor activity.

Main Results:

  • Fluoxetine treatment significantly reduced 5-HT(4) receptor binding density in the hippocampus (CA1) and striatum.
  • A notable decrease in zacopride-stimulated adenylate cyclase activity was observed in rats treated with 10 mg/kg/day fluoxetine.
  • Post-synaptic 5-HT(4) receptor activity in the hippocampus was attenuated by both doses of fluoxetine.

Conclusions:

  • Chronic selective serotonin reuptake inhibitor (SSRI) treatment leads to a net decrease in the serotonin 5-HT(4) receptor signaling pathway.
  • This adaptive downregulation of 5-HT(4) receptor function may contribute to the therapeutic benefits of SSRI antidepressants.

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