drug comparison 92 rat 74 Rats 68 animal experiment 60 Animal 58 Support, Non-U.S. Gov't 44 in vitro study 44 nonhuman 44 endocrine system 42 radioisotope 42 drug response 40 Male 38 Rats, Inbred Strains 38 dose response 38 animal cell 32 drug efficacy 30 Female 28 central nervous system 26 priority journal 20 Norepinephrine 18 corticosterone 18 female genital system 18 noradrenalin 18 Animals 16 In Vitro 16 Pineal Gland 16 drug mechanism 16 methodology 16 pineal body 16 preliminary communication 16