The effect of diabetes and centrally administered insulin on anterior hypothalamic estrogen receptor α immunoreactivity

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Diabetic rats have characteristic reproductive deficits. Peripheral and central (intra-cerebro-ventricular [ICV]) insulin restores the reproductive phenotype to control levels. In this experiment, we evaluated a possible defect in steroid feedback by evaluating hypothalamic estrogen receptor (ER) α availability using ERα immunocytochemistry. Animals were ovariectomised and given estradiol and progesterone. Diabetic and control animals were given ICV insulin or saline. Nuclear and/or cytoplasmic ERα immunoreactivity was evaluated in the paraventricular nucleus (PVN) and the organum vasculosum laminae terminalis (OVLT). In the PVN, nuclear immunoreactivity was increased among diabetic, ICV insulin-treated animals. Diabetic saline-treated and nondiabetic animals had similar ERα immunoreactivity. The OVLT had lower numbers of immunoreactive neurons compared to the PVN; no differences among the treatment groups were found in the OVLT. Central insulin treatment increased the number of PVN nuclear ERα immunoreactive neurons among diabetic animals. However, there was no reduction in ERα when comparing saline-treated diabetic animals to non-diabetic rats, suggesting that decreases in hypothalamic ERα in the regions studied do not account for diabetes-induced reproductive deficits.

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