title: Antidepressants differentially affect striatal amphetamine-stimulated dopamine and serotonin release in rats with high and low novelty-oriented behaviour.
abstract: In the studies of depression pathogenesis and antidepressant action, the monoaminergic hypothesis of depression has mainly focused on the serotonergic and noradrenergic mechanisms. However, dopaminergic neurotransmission is also linked to both depressive symptomatology as well as antidepressant effects. We have previously shown that persistent inter-individual differences in the rat behavioural activity in novel environments is associated with differences in the striatal extracellular levels of dopamine and serotonin, depressive-like behaviour and the expression of several depression-related genes. The aim of the current study was to investigate the relative potency of the tricyclic antidepressant imipramine, the selective serotonin re-uptake inhibitor fluoxetine, and the selective noradrenaline re-uptake inhibitor reboxetine (all drugs administered in the dose of 10mg/kg, i.p.) to enhance amphetamine-stimulated dopamine and serotonin release in the striatum using in vivo microdialysis in awake, freely-moving rats, categorized into high explorers (HE) and low explorers (LE) based on their spontaneous novelty-oriented behaviour. The basal extracellular dopamine and serotonin concentration in the striatum did not differ between the LE- and HE-rats. None of the antidepressants alone were able to modify baseline striatal dopamine levels, but the amphetamine-stimulated dopamine release was significantly higher in the HE-rats after acute and chronic imipramine (but not fluoxetine or reboxetine). Acute imipramine and fluoxetine, but not reboxetine, increased both the basal and amphetamine-stimulated levels of serotonin in the striatum. Again, the HE-rats had higher amphetamine-stimulated serotonin release after fluoxetine administration. These findings suggest that rats with depressive-like phenotype are less sensitive to the neurochemical effects of antidepressants in the striatum. These results may have relevance in understanding the neurobiological bases for inter-individual differences in antidepressant treatment response in humans and development of novel medicines.
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, University of Tartu, Ravila 14a, 50411 Tartu, Estonia.
authors.forename: Aet
authors.initials: A
authors.lastname: O'Leary
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, University of Tartu, Ravila 14a, 50411 Tartu, Estonia.
authors.forename: Kadri
authors.initials: K
authors.lastname: Kõiv
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, University of Tartu, Ravila 14a, 50411 Tartu, Estonia.
authors.forename: Karita
authors.initials: K
authors.lastname: Raudkivi
authors.affiliation: Division of Neuropsychopharmacology, Department of Psychology, University of Tartu, Ravila 14a, 50411 Tartu, Estonia. Electronic address: jaanus.harro@ut.ee.
authors.forename: Jaanus
authors.initials: J
authors.lastname: Harro
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D000928:Antidepressive Agents / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects*; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D005473:Fluoxetine / Q000494:pharmacology; D007099:Imipramine / Q000494:pharmacology; D008297:Male; D017551:Microdialysis / Q000379:methods; D009025:Morpholines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D000077593:Reboxetine; D012701:Serotonin / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology
chemical_list: D000661:Amphetamine; D000928:Antidepressive Agents; D004298:Dopamine; D005473:Fluoxetine; D007099:Imipramine; D009025:Morpholines; D000077593:Reboxetine; D012701:Serotonin; D017367:Selective Serotonin Reuptake Inhibitors
keywords: Amphetamine; Antidepressant; Dopamine; Individual differences; Serotonin; Striatum