Animals

Female virgin Sprague-Dawley rats (250–290 g; Charles River) were used for all experiments. Female rats were chosen for study because of the contribution of PVN NPY and α-MSH inputs to elevated basal SNA during pregnancy (14). The sympathoexcitatory effects of insulin do not vary during the estrous cycle (13); therefore, the cycle stage was not established before experimentation. Rats were housed in a room with a 12:12-h light-dark cycle with free access to food (LabDiet 5001, Richmond, IN) and water. All procedures were conducted in accordance with the National Institutes of Health's Guide for the Health and Use of Laboratory Animals and approved by the Institutional (Oregon Health & Science University) Animal Care and Use Committee.