Ovariectomy and Estradiol Implant Protocol

Unless otherwise stated, females were ovariectomized in adulthood. Anesthesia was induced by an intraperitoneal injection of a mixture of ketamine (Nimatek, 80 mg/kg) and medetomidine (Domitor, Pfizer, 1 mg/kg). Then, both ovaries were removed, and an estradiol implant was placed subcutaneously in the back. The implant consisted of a 5 mm long capsule (outer diameter 2.41 mm, inner diameter 1.57 mm) filled with a 1:1 mixture of 17beta-estradiol (ICN biomedicals Inc., 101565) and cholesterol (Sigma, C8667). At the end of the surgery, all mice received a subcutaneous injection of atipamezole (Nacrostop, 4 mg/kg) to accelerate recovery by antagonizing medetomidine-induced effect. All animals were allowed to recover on a heating pad and were returned subsequently to their home cage^{19 (link),20 (link)}. In order to induce sexual receptivity at the day of testing, females received a subcutaneous injection of progesterone (500 µg, P0130, Sigma) 2 to 3 h before the test.