central nervous system animal experiment 71 nonhuman 71 rat 68 Rats 62 Animal 60 Male 44 endocrine system 44 radioisotope 43 Support, Non-U.S. Gov't 40 priority journal 40 Animals 39 Female 34 animal cell 30 article 29 Pineal Gland 28 pineal body 28 Rats, Inbred Strains 26 Brain 22 hypothalamus 22 drug receptor binding 18 human 18 unclassified drug 18 Humans 17 Hypothalamus 17 animal 17 controlled study 16 noradrenalin 16 Cerebral Cortex 15 melatonin 15