Effects of repeated fluoxetine on anxiety-related behaviours, central serotonergic systems, and the corticotropic axis in SHR and WKY rats

• Published in: Neuropharmacology Vol. 38; no. 6; pp. 893 - 907
• Main Authors: Durand, M., Berton, O., Aguerre, S., Edno, L., Combourieu, I., Mormède, P., Chaouloff, F.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-06-1999; Elsevier
• Subjects: 5-HT receptors/transporters; Anxiety; Biological and medical sciences; Body weight; Corticosteroid receptors; Corticosterone; Fluoxetine; Life Sciences; Medical sciences; Neuropharmacology; Pharmacology. Drug treatments; Psycholeptics: tranquillizer, neuroleptic; Psychology. Psychoanalysis. Psychiatry; Psychopharmacology; SHR rats; WKY rats; 5-HT receptors/transporters; Fluoxetine; Corticosterone; SHR rats; Body weight; Corticosteroid receptors; WKY rats; Anxiety; Intraperitoneal administration; Rat; Mineralocorticoid; Psychotropic; Anxiety disorder; Strain specificity; Reuptake inhibitor; Glucocorticoid; Multiple dose; Genetics; Mechanism of action; Serotonin; Steroid hormone; Treatment efficiency; Rodentia; Vertebrata; Chemotherapy; Mammalia; Tranquillizer; Animal; Adrenal hormone; Hormonal receptor; RAT; SURRENALE
• ISSN: 0028-3908; 1873-7064
• DOI: 10.1016/S0028-3908(99)00009-X

In keeping with the anxiolytic property of selective serotonin reuptake inhibitors (SSRIs) in humans, we have examined in the spontaneously hypertensive rat (SHR) and the Wistar–Kyoto (WKY) rat, which display low and high anxiety, respectively, some psychoneuroendocrine effects of a repeated treatment with the SSRI fluoxetine (5 or 10 mg/kg daily, for 3 weeks). Two days after the last injection, plasma levels of fluoxetine were not detectable whereas those of its metabolite, norfluoxetine, were present to similar extents in both strains. By means of the elevated plus-maze test (29–30 h after the 13th administration of fluoxetine) and an open field test (48 h after the last injection of fluoxetine), it was observed that fluoxetine pretreatment did not yield anxiolysis; hence, some, but not all, behaviours were indicative of anxiety and hypolocomotion (as assessed through principal component analyses and acute diazepam studies). In both strains, the 10 mg/kg dose of fluoxetine decreased hypothalamus 5-HT and 5-HIAA levels, and reduced midbrain and/or hippocampus [
3H]citalopram binding at 5-HT transporters, but did not affect [
3H]8-hydroxy-2-(di-
N-propylamino)tetralin binding at hippocampal 5-HT
1A receptors. However, the fluoxetine-elicited reduction in hippocampal 5-HT transporter binding was much more important in WKY than in SHR rats, this strain-dependent effect being associated in WKY rats with a reduction in cortical [
3H]ketanserin binding at 5-HT
2A receptors. Lastly, in WKY rats, repeated fluoxetine administration increased adrenal weights and the plasma corticosterone response to open field exposure, but did not affect the binding capacities of hippocampal mineralocorticoid and glucocorticoid receptors. These data show that key psychoneuroendocrine responses to repeated fluoxetine administration may be strain-dependent, and that repeated fluoxetine administration does not yield anxiolysis, as assessed by two standard tests of emotivity.