Male Rats Pineal Gland 48 pineal body 46 rat 46 Animal 42 animal experiment 38 Rats, Inbred Strains 36 Support, Non-U.S. Gov't 34 endocrine system 34 central nervous system 32 radioisotope 32 Melatonin 24 melatonin 22 Norepinephrine 20 autonomic nervous system 20 nonhuman 20 Ganglia, Sympathetic 18 superior cervical ganglion 18 Pineal gland 16 noradrenalin 16 pineal gland 14 Female 12 in vitro study 12 nervous system 12 Animals 10 Hypothalamus 10 Kinetics 10 animal cell 10 isoprenaline 10