Concentration of Norepinephrine in the Hypothalamus of the Rat in Relation to the Estrous Cycle

Norepinephrine (NE) concentrations in the hypothalamus of female Sprague-Dawley rats with normal estrous cycles averaged about 2.2 μg/g of wet tissue and these values were similar at the 3 phases of the estrous cycle. Comparison of NE levels in the hypothalamus of the rat at the 3 different time periods on proestrous day—preceding, following and coincidingcoinciding with the presumed time of the release of the ovulatory quota of gonadotropins—did not reveal measurable changes in hypothalamic concentrations of the neurohumor. Similarly, no measurable changes in NE levels were found as a result of castration. {Endocrinology83: 1383,