Animal Support, Non-U.S. Gov't nonhuman radioisotope Rats 90 animal cell 86 rat 84 Rats, Inbred Strains 64 endocrine system 50 Female 48 animal experiment 46 Male 44 priority journal 44 drug receptor binding 36 drug efficacy 32 pharmacokinetics 32 central nervous system 30 In Vitro 24 article 24 Pineal Gland 22 female genital system 22 Progesterone 20 pineal body 20 Kinetics 18 methodology 18 progesterone 18 prolactin 16 Prolactin 14 drug comparison 14 estradiol 14