Brain stem projections to lobule VII of the posterior vermis in the squirrel monkey: as demonstrated by the retrograde axonal transport of tritiated horseradish peroxidase.

In streptozotocin-diabetic female rats acute (24 h) withdrawal of insulin significantly impairs both estradiol+progesterone-induced sexual receptivity and cell nuclear concentration of [³H]estradiol in hypothalamus, preoptic area, and pituitary gland. Omission of insulin treatment for the first 24 h of a 30-h or 54-h estradiol benzoate-conditioning period significantly reduced mean lordosis ratings of ovariectomized-diabetic rats. Insulin withdrawal at the time of progesterone treatment and behavioral testing did not diminish sexual receptivity. One-half or 2 h after an intravenous injection of [³H]estradiol-17β diabetic rats without insulin exhibited reduced cell nuclear [³H]estradiol concentrations (2 h) and/or diminished cell nuclear/whole homogenate concentration ratios (0.5 and 2 h). Twenty-four hour insulin withdrawal affected neither whole tissue [³H]estradiol uptake nor hypothalamus-preoptic area cytoplasmic estrogen-receptor content. These results: (1) suggest that diminished estradiol binding by target tissue cell nuclei may contribute to the well-known reproductive failures of female diabetics, and (2) support the concept that estradiol acts at the level of brain cell nuclei to induce female sexual behavior.