Estrogen enhances light-induced activation of dorsal raphe serotonergic neurons

Alfonso Abizaid, Gabor Mezei, Gita Thanarajasingam, Tamas L. Horvath

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

The serotonergic system has been implicated in the modulation of physiological processes including circadian rhythms, learning, memory, mood and food intake. In females, cessation of ovarian function produces deleterious changes in all of these processes and estrogen treatment often ameliorates these conditions. Estrogen may produce these effects by acting on the midbrain raphe, an estrogen-sensitive region that receives direct projections from sensory systems. Here we examined the ability of estradiol to modulate neuronal responses of neurons within raphe nuclei to photic stimulation. Ovariectomized rats treated with estradiol or cholesterol were killed 1 h after the normal onset of light (Zeitgeber time 0) or after a 2-h phase advance (Zeitgeber time 22). In a second study, estradiol-treated ovariectomized rats under constant dark conditions were exposed to light 2 h before the subjective onset of circadian time [(CT)22] and killed 1 h later (CT23). The brains from all animals were processed for Fos and/or serotonin (5-HT) immunocytochemistry. Comparisons showed that the phase shift increased Fos immunoreactivity in all dorsal raphe nucleus (DRN) regions. Although estradiol did not alter the overall number of Fos-positive nuclei, it significantly increased the number of Fos/5-HT double-labelled cells in the medial and lateral DRN. In contrast, neither a phase shift nor estradiol altered the number of Fos-immunoreactive cells or the proportion of Fos-positive 5-HT cells in the median raphe nucleus. Results reveal that the DRN 5-HT system responds to changes in the light: dark cycle and that these responses are modulated by estrogen.

Original languageEnglish (US)
Pages (from-to)1536-1546
Number of pages11
JournalEuropean Journal of Neuroscience
Volume21
Issue number6
DOIs
StatePublished - Mar 1 2005
Externally publishedYes

Fingerprint

Serotonergic Neurons
Estradiol
Serotonin
Estrogens
Light
Raphe Nuclei
Physiological Phenomena
Lateral Thalamic Nuclei
Photic Stimulation
Aptitude
Photoperiod
Circadian Rhythm
Eating
Immunohistochemistry
Cholesterol
Dorsal Raphe Nucleus
Learning
Neurons
Brain

Keywords

  • Circadian rhythms
  • Dorsal raphe
  • Fos
  • Median raphe
  • Rat
  • Serotonin

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Estrogen enhances light-induced activation of dorsal raphe serotonergic neurons. / Abizaid, Alfonso; Mezei, Gabor; Thanarajasingam, Gita; Horvath, Tamas L.

In: European Journal of Neuroscience, Vol. 21, No. 6, 01.03.2005, p. 1536-1546.

Research output: Contribution to journalArticle

Abizaid, Alfonso ; Mezei, Gabor ; Thanarajasingam, Gita ; Horvath, Tamas L. / Estrogen enhances light-induced activation of dorsal raphe serotonergic neurons. In: European Journal of Neuroscience. 2005 ; Vol. 21, No. 6. pp. 1536-1546.
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