subcutaneous drug administration animal experiment 74 nonhuman 70 rat 70 Rats 58 article 52 Animal 48 Female 46 priority journal 46 Support, Non-U.S. Gov't 42 controlled study 42 female 32 endocrine system 30 Estradiol 28 Rats, Inbred Strains 28 animal cell 28 estradiol 28 Male 26 Animalia 24 radioisotope 22 Animals 20 central nervous system 20 male 20 Rats, Sprague-Dawley 18 animal tissue 18 drug mechanism 18 ovariectomy 18 unclassified drug 18 animal model 16 intraperitoneal drug administration 16