Visualisation and characterisation of oestrogen receptor α‐positive neurons expressing green fluorescent protein under the control of the oestrogen receptor α promoter

Oestrogen receptor ( ER )α plays important roles in the development and function of various neuronal systems through activation by its ligands, oestrogens. To visualise ER α‐positive neurons, we generated transgenic (tg) mice expressing green fluorescent protein ( GFP ) under the control of the ER α promoter. In three independent tg lines, GFP ‐positive neurons were observed in areas previously reported to express ER α mRNA , including the lateral septum, bed nucleus of the stria terminalis, medial preoptic nucleus ( MPO ), hypothalamus, and amygdala. In these areas, GFP signals mostly overlapped with ER α immunoreactivity. GFP fluorescence was seen in neurites and cell bodies of neurons. In addition, the network and detailed structure of neurites were visible in dissociated and slice cultures of hypothalamic neurons. We examined the effect of oestrogen deprivation by ovariectomy on the structure of the GFP ‐positive neurons. The area of ER α‐positive cell bodies in the bed nucleus of the stria terminalis and MPO was measured by capturing the GFP signal and was found to be significantly smaller in ovariectomy mice than in control mice. When neurons in the MPO were infected with an adeno‐associated virus that expressed small hairpin RNA targeting the ER α gene, an apparent induction of GFP was observed in this area, suggesting a negative feedback mechanism in which ER α controls expression of the ER α gene itself. Thus, the ER α promoter– GFP tg mice will be useful to analyse the development and plastic changes of the structure of ER α‐expressing neurons and oestrogen and its receptor‐mediated neuronal responses.