Animal radioisotope Rats 174 rat 162 Support, Non-U.S. Gov't 160 nonhuman 134 animal experiment 122 endocrine system 110 animal cell 104 Female 102 Male 98 Rats, Inbred Strains 96 central nervous system 64 in vitro study 60 priority journal 58 article 52 pharmacokinetics 52 In Vitro 48 Pineal Gland 48 pineal body 48 Kinetics 44 animal 40 drug receptor binding 40 metabolism 38 drug efficacy 36 estradiol 36 Castration 34 Estradiol 34 prolactin 34 Norepinephrine 32