Journal
BEHAVIOURAL BRAIN RESEARCH
Volume 204, Issue 1, Pages 112-116Publisher
ELSEVIER
DOI: 10.1016/j.bbr.2009.05.029
Keywords
Median raphe nucleus; Estradiol; Anxiety; Contextual conditioning; Serotonin; 5-HT1A receptor
Categories
Funding
- FAPESP (Brazil)
- CNPq
- FAEPA
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Estrogen deficiency has been associated with stress, anxiety and depression. Estrogen receptors have been identified in the median raphe nucleus (MRN). This structure is the main source of serotonergic projections to the hippocampus, a forebrain area implicated in the regulation of defensive responses and in the resistance to chronic stress. There is reported evidence indicating that estrogen modulates 5-HT1A receptor function. In the MRN, somatodendritic 5-HT1A receptors control the activity of serotonergic neurones by negative feedback. The present study has evaluated the effect of intra-MRN injection of estradiol benzoate (EB, 600 or 1200 ng/0.2 mu l) on the performance of ovariectormized rats submitted to contextual conditioning. Additionally, the same treatment was given after intra-MRN injection of Way 100635 (100 ng/0.2 mu l). a 5-HT1A receptor antagonist. Both doses of EB decreased freezing and increased rearing, indicating an anxiolytic effect. Pretreatment with Way 100635 antagonized the anxiolytic effect of estradiol. On the basis of these results, it may be suggested that estrogens modulate anxiety by acting on 5-HT1A receptors localized in the MRN. (C) 2009 Elsevier B.V. All rights reserved.
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