Temporal expression of estrogen receptor α in the hypothalamus and medulla oblongata during fasting: a role of noradrenergic neurons

Abstract

Fasting-induced LH suppression is augmented by estrogen in female rats. We investigated the temporal changes in the number of estrogen receptor a (ERa)-immunoreactive (ir) cells in various brain regions in ovariectomized rats fasted for 6, 24, 30, and 48 h, commencing at 1300 h. We also determined the anatomical relationship of ERa immunoreactivity and dopamine-b-hydroxylase (DBH) neurons in the A2 region of the nucleus of the solitary tract (NTS) and the paraventricular nucleus (PVN). The number of ERa-ir cells significantly increased after 30 h from the onset of fasting in the PVN and NTS compared with the unfasted controls and was sustained until 48 h. In the A2 region of 48-h fasted rats, 46$75% DBH-ir cells expressed ERa, and this was significantly higher than in unfasted controls (8$16% DBH-ir cells expressed ERa). In the PVN, most ERa-ir neurons were juxtaposed with DBH-ir varicosities. These results suggest that ERa is expressed in specific brain regions at a defined time from the onset of fasting. In addition, the anatomical relationship of noradrenergic and ERa-ir neurons in the A2 region and PVN may suggest a role for estrogen in increasing the activity of noradrenergic neurons in the A2 region and enhancing sensitivity of the PVN to noradrenergic input arising from the lower brainstem and thereby augmenting the suppression of LH secretion during fasting.

Estrogen replacement regimen and brain infusion of lipopolysaccharide differentially alter steroid receptor expression in the uterus and hypothalamus

“…While all rats showed LPS-induced increases in activated microglia, we were surprised to find that only intact rats showed LPS effects on ERa and HSP90 expression. Fasting has been shown to alter ERa expression [53], but no correlation was observed between body weight and any of the steroid proteins measured in the current study (data not shown). ERa plays a role in modulating inflammatory processes [13][14][15]54] and, in response to the inflammatory cytokine, TNFa, can be recruited to the Tnf promoter with HSP90 as part of a transcriptional complex [55].…”

Oestrogen receptors in the central nervous system and evidence for their role in the control of cardiovascular function

“…As mentioned above, ERa immunoreactivity colocalises extensively with tyrosine hydroxylase (TH) and dopamine b-hydroxylase (DBH) immunoreactivities in the NTS (Simonian and Herbison, 1997b;Simonian et al, 1998Simonian et al, , 1999Haywood et al, 1999;Lee et al, 2000;Vanderhorst et al, 2005;Reyes et al, 2006) (see Fig. 1A).…”

“…Both ERa and ERb immunoreactivities have been detected in the rat periventricular hypothalamic dopamine neurones of the A12/A14 groups (Hou et al, 2003). ERa expression is prominent in the A1/A2 noradrenergic (Simonian and Herbison, 1997b;Simonian et al, 1998;Haywood et al, 1999;Lu et al, 2003;Vanderhorst et al, 2005;Reyes et al, 2006) and C1/C2/C3 adrenergic (Lee et al, 2000) groups of the brainstem in different species. Our own data using antibodies to ERa (Table 1) supports these findings (Fig.…”

Effects of the Estrous Cycle and Ovarian Hormones on Central Expression of Interleukin-1 Evoked by Stress in Female Rats

“…However, the present data showed that ER-α, but not ER-β, mRNA expression up-regulated following ovariectomy. It has been reported that ER-α expression is minimal in the PVN of rats under normal conditions, while fasting significantly increases the number of ER-α-immunoreactive cells in the PVN [58,81]. Interestingly, binding of estrogen to ER-α results in stimulation of TNF-α and IL-1 gene expression [82,83], and augments HPA reactivity [57].…”