central nervous system 123 nonhuman 103 animal experiment 91 rat 72 Animals 70 priority journal 66 Rats 65 Animal 60 Male 60 article 45 endocrine system 44 radioisotope 43 Female 42 Support, Non-U.S. Gov't 40 animal cell 40 controlled study 40 animal 31 animal tissue 30 human 30 Pineal Gland 28 male 28 pineal body 28 Humans 27 Mice 27 Rats, Inbred Strains 26 mouse 25 protein expression 24 Brain 23 hypothalamus 22 unclassified drug 22