Biochemical effects of the antidepressant paroxetine, a specific 5-hydroxytryptamine uptake inhibitor

Psychopharmacology (Berl). 1987;93(2):193-200. doi: 10.1007/BF00179933.

Abstract

Paroxetine was shown to be a potent (Ki = 1.1 nM) and specific inhibitor of [3H]-5-hydroxytryptamine (5-HT) uptake into rat cortical and hypothalamic synaptosomes in vitro. Lineweaver-Burk kinetic analysis determined that this inhibition was competitive in nature, implying a direct interaction with the 5-HT uptake transporter complex. Oral administration of paroxetine produced a dose-related inhibition of [3H]-5-HT uptake (ED50 = 1.9 mg/kg) into rat hypothalamic synaptosomes ex vivo with little effect on [3H]-l-noradrenaline (NA) uptake (ED50 greater than 30 mg/kg). This selectivity for 5-HT uptake was maintained after oral dosing for 14 days. Paroxetine (ED50 1-3 mg/kg PO) prevented the 5-HT depleting effect of p-chloroamphetamine (PCA) in rat brain, demonstrating 5-HT uptake blockade in vivo. Radioligand binding techniques in rat brain in vitro showed that paroxetine has little affinity for alpha 1, alpha 2 or beta adrenoceptors, dopamine (D2), 5-HT1, 5-HT2 or histamine (H1) receptors at concentrations below 1000 nM. Paroxetine demonstrated weak affinity for muscarinic receptors (Ki = 89 nM) but was at least 15 fold weaker than amitriptyline (Ki = 5.1 nM). Paroxetine, therefore, provides a useful pharmacological tool for investigating 5-HT systems and furthermore should be an antidepressant with reduced tricyclic-like side-effects.

MeSH terms

  • Animals
  • Antidepressive Agents / pharmacology
  • Biological Transport, Active / drug effects
  • Brain / drug effects
  • Brain / metabolism
  • In Vitro Techniques
  • Kinetics
  • Male
  • Norepinephrine / metabolism
  • Paroxetine
  • Piperidines / pharmacology*
  • Rats
  • Serotonin / metabolism*
  • Serotonin Antagonists / pharmacology
  • Synaptosomes / drug effects
  • Synaptosomes / metabolism
  • p-Chloroamphetamine / pharmacology

Substances

  • Antidepressive Agents
  • Piperidines
  • Serotonin Antagonists
  • Serotonin
  • Paroxetine
  • p-Chloroamphetamine
  • Norepinephrine