Pineal Gland pineal body 82 Rats 74 Animal 70 rat 66 endocrine system 62 animal experiment 58 central nervous system 56 radioisotope 56 Support, Non-U.S. Gov't 54 Male 50 Rats, Inbred Strains 44 nonhuman 40 Female 36 melatonin 34 Melatonin 30 Norepinephrine 30 superior cervical ganglion 28 autonomic nervous system 26 noradrenalin 26 Ganglia, Sympathetic 24 pineal gland 24 Pineal gland 22 animal cell 22 estradiol 22 Animals 18 Serotonin 18 in vitro study 18 In Vitro 16 Kinetics 16