Rats drug comparison 68 rat 66 Animal 52 animal experiment 44 Male 38 Rats, Inbred Strains 38 nonhuman 38 Support, Non-U.S. Gov't 36 endocrine system 36 animal cell 30 drug response 30 radioisotope 30 dose response 28 drug efficacy 28 in vitro study 28 Female 26 Norepinephrine 18 central nervous system 18 Animals 16 In Vitro 16 priority journal 16 Pineal Gland 14 corticosterone 14 drug administration 14 drug mechanism 14 female genital system 14 methodology 14 noradrenalin 14 pineal body 14