rat 71 Rats 68 animal experiment 58 Animal 52 Female 51 Rats, Inbred Strains 43 in vitro study 42 female genital system 39 nonhuman 38 Support, Non-U.S. Gov't 33 Prostaglandins 31 Animals 30 Prostaglandins E 29 indometacin 29 In Vitro 28 Prostaglandins F 28 prostaglandin 28 Uterus 27 Male 26 animal cell 25 drug efficacy 25 endocrine system 25 noradrenalin 25 prostaglandin f2 alpha 25 article 24 radioisotope 24 acetylsalicylic acid 23 phentolamine 23 Norepinephrine 22 Uterine Contraction 22