animal experiment central nervous system 144 nonhuman 114 rat 112 Male 100 Rats 92 Animal 86 Animals 80 controlled study 70 Female 64 priority journal 64 article 62 endocrine system 60 mouse 54 radioisotope 54 Support, Non-U.S. Gov't 50 male 50 Mice 48 animal cell 46 animal tissue 46 animal 40 Rats, Inbred Strains 38 hypothalamus 36 metabolism 36 Brain 32 Pineal Gland 32 pineal body 32 Hypothalamus 28 Mice, Inbred C57BL 28 animal model 28