Cellular and Molecular NeuroscienceResearch PaperOverexpression or knockdown of rat tryptophan hyroxylase-2 has opposing effects on anxiety behavior in an estrogen-dependent manner
Research highlights
▶We examine the role of TpH2 in caudal DRN in estrogen-induced anxiolysis. ▶Estrogen-induced increase in DRN TpH2 mRNA is associated with decreased anxiety. ▶TpH2 overexpression mimics, while knockdown reduces anxiolytic effects of estrogen.
Section snippets
Subjects
A total of 114 female Sprague–Dawley rats between the ages of 60 and 90 days were used for behavioral experiments and 55 male Sprague–Dawley rats around the age of 60–77 days were used for biochemical verification of morpholino antisense oligonucleotide knockdown and virus-mediated gene transfer. Rats were group-housed with three animals per cage on a 12-h light/dark cycle (lights on at 06:00 am), and all behavioral measures were performed during the light period. Animals were acclimated to the
TpH2 antisense PMO infusion decreased TpH protein levels in a discrete subregion of DRN without causing toxicity
PMOs were efficiently taken up by cells without transfection agent as indicated by intense cytoplasmic fluorescence (Fig. 1). There was no histological indication of cytotoxicity and no caspase-3 immunoreactivity was detectable in any of the groups studied (data not shown), suggesting that there was no overt toxicity, including apoptosis, associated with the PMO injections. Scrambled control PMO had no apparent effect on TpH protein levels, as demonstrated by colocalization of PMO label with
Discussion
We previously reported that estrogen increased TpH2 expression selectively in the caudal DRN and that TpH2 expression in caudal DRN was inversely associated with anxiety (Hiroi et al., 2006). In the present study, we investigated the hypothesis that increased TpH2 in caudal DRN is involved in modulating estrogen's anxiolytic effects. To this end, we explored the roles of in-vivo TpH2 knockdown and overexpression selectively in the caudal DRN on the anxiolytic effects of estrogen. Our results
Conclusion
In summary, the present work highlights the role of the DRN serotonergic system in the regulation of anxiety by estrogen. Estrogen differentially activates TpH2 in select subregions of the DRN (Hiroi et al., 2006), which in turn supplies serotonin innervation to specific brain areas that regulate different aspects of anxiety behavior. The results from our study do not imply that the anxiolytic effect of estrogen is mediated solely through the caudal DRN 5-HT system, thus further studies
Acknowledgments
This work was supported by the National Institute of Mental Health (NIMH) grants MH63303 and MH75279. The authors would like to thank the following for their technical assistance and expert advice: Dr. Michele Kelly and William Brennan for vector packaging, Dr. Susan Ferguson with western blot, and Dr. Catherine Hagan with RT-PCR.
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Estrogen receptor β activation within dorsal raphe nucleus reverses anxiety-like behavior induced by food restriction in female rats
2019, Behavioural Brain ResearchCitation Excerpt :Moreover, it has been reported that estrogen increases TPH2 mRNA, raising 5-HT synthesis. These changes, in specific DRN areas, mainly the caudal part, are closed related to the control of anxiety-like behaviors [15,47,48]. However, no differences were observed in the behavior associated to anxiety responses on the OF paradigm after E2 treatment.
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2017, Vitamins and HormonesCitation Excerpt :One way in which ERβ may influence anxiety-like behavior through the serotonergic system is by mediating expression of tryptophan hydroxylase, the rate-limiting enzyme required for the synthesis of serotonin. Knockdown of this enzyme within the caudal dorsal raphe nucleus of OVX rats removes the anxiolytic-like effects of estradiol in the open field test (Hiroi, McDevitt, Morcos, Clark, & Neumaier, 2011). Correspondingly, both male and female ERβ-null mice have decreased expression of tryptophan hydroxylase.
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2016, Progress in Neuro-Psychopharmacology and Biological PsychiatryCitation Excerpt :Their effects on anxiety are more controversial even in animal models. Conflicting results seem be linked to the type of estrogen evaluated, but more importantly to the regimen (Hiroi et al., 2011; Kalandakanond-Thongsong et al., 2012). Considering the advantages of ERTs, there continues to be interest in finding new estrogenic molecules with an adequate balance between benefits and risks.
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2013, Biochemical PharmacologyUse of vivo-morpholinos for control of protein expression in the adult rat brain
2012, Journal of Neuroscience MethodsCitation Excerpt :While vivo-morpholinos are superior to non-conjugated morpholinos for achieving suppression following i.v. administration, brain tissue is not significantly accessed following systemic delivery (Li and Morcos, 2008; Morcos et al., 2008; Parra et al., 2011). A few examples of successful knockdown with non-conjugated morpholinos administered directly in the brain have been reported (Hiroi et al., 2011; Oh et al., 2006). However, evidence is not available on the efficacy or toxicity of vivo-morpholinos administered intracranially.
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Present address: Department of Basic Medical Sciences, University of Arizona College of Medicine in Phoenix, Phoenix, AZ 85004, USA.