Journal
PSYCHOPHARMACOLOGY
Volume 225, Issue 1, Pages 61-74Publisher
SPRINGER
DOI: 10.1007/s00213-012-2795-9
Keywords
5-HT1A receptor; Antidepressant effects; Depression; RNA interference; Serotonin; Stress
Categories
Funding
- Spanish Ministry of Science and Innovation [SAF2007-62378]
- CDTI
- DENDRIA Consortium from Instituto de Salud Carlos III
- Centro de Investigacion Biomedica en Red de Salud Mental (CIBERSAM)
- CSIC-IDIBAPS
- NEDKEN, S.L.-nLife Therapeutics
- European Union [R+D+I 2008/11]
- Catalan Government [2009SGR220]
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Identifying the etiological factors in anxiety and depression is critical to develop more efficacious therapies. The inhibitory serotonin(1A) receptors (5-HT1AR) located on 5-HT neurons (autoreceptors) limit antidepressant responses and their expression may be increased in treatment-resistant depressed patients. Recently, we reported that intranasal administration of modified small interference RNA (siRNA) molecules targeting 5-HT1AR in serotonergic neurons evoked antidepressant-like effects. Here we extended this finding using marketed siRNAs against 5-HT1AR (1A-siRNA) to reduce directly the 5-HT1A autoreceptor expression and evaluate its biological consequences under basal conditions and in response to stressful situations. Adult mice were locally infused with vehicle, nonsense siRNA, and 1A-siRNA into dorsal raphe nucleus (DR). 5-HT1AR knockout mice (1A-KO) were also used. Histological approaches, in vivo microdialysis, and stress-related behaviors were performed to assess the effects of 5-HT1A autoreceptor knockdown. Intra-DR 1A-siRNA infusion selectively reduced 5-HT1AR mRNA and binding levels and canceled 8-OH-DPAT-induced hypothermia. Basal extracellular 5-HT in medial prefrontal cortex (mPFC) did not differ among treatments. However, 1A-siRNA-treated mice displayed less immobility in the tail suspension and forced swim tests, as did 1A-KO mice. This was accompanied by a greater increase in prefrontal 5-HT release during tail suspension test. Moreover, intra-DR 1A-siRNA infusion augmented the increase of extracellular 5-HT in mPFC evoked by fluoxetine, up to the level in 1A-KO mice. Together with our previous report, the present results indicate that acute suppression of 5-HT1A autoreceptor expression evokes robust antidepressant-like effects, likely mediated by an increased capacity of serotonergic neurons to release 5-HT in stressful conditions.
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