Abstract:
Estradiol affects many aspects of the nervous system, including learning, memory, pain perception, mood, and neural plasticity. Estradiol signaling is highly complex, with multiple receptors initiating signaling cascades from the plasma membrane or transcription at estrogen response elements. Additional complexity is added at the level estrogen receptor expression through alternative promoters and splice variations. The aims of this study were to determine which estrogen receptor splice variants are expressed by sympathetic ganglia, how expression of these splice variants is regulated by estradiol, and whether there are differences in uterus-projecting and non-uterus-projecting neurons. We focused on estrogen receptor α (ERα), because it shows increased expression in uterine-projecting neurons and we analyzed variations at exons 3 and 4, because ERα Σ4 and ERα Σ3 are considered constitutively active and dominant negative isoforms respectively. Ovariectomized Sprague Dawley rats were subcutaneously injected with either 10μg of β estradiol benzoate per kg of body weight or a vehicle control and tissue was harvested 24 hours later. RT-PCR was performed using primers designed on either side of exons 3 and 4. Non-uterus-projecting neurons predominantly expressed the constitutively active ERα Σ4 isoform, while uterus-projecting neurons expressed both full length and ERα Σ4 isoforms, with enhanced ERα Σ4 expression after estradiol treatment. Increased amplification using nested primers indicated that ERα Σ3 and ERα Σ3, Σ4 may also be present at low levels. Differences in expression of ERα splice variants indicate that uterus-projecting sympathetic neurons may be differentially regulated by hormone changes.
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