Male Support, Non-U.S. Gov't endocrine system Animal 68 Rats 64 rat 60 animal experiment 52 Rats, Inbred Strains 50 nonhuman 40 radioisotope 32 drug efficacy 28 male genital system 24 Female 22 central nervous system 22 Pineal Gland 20 Testosterone 20 pineal body 20 superior cervical ganglion 18 Castration 16 Prolactin 16 animal cell 16 autonomic nervous system 16 in vitro study 14 priority journal 14 Epididymis 12 Ganglia, Sympathetic 12 epididymis 12 hypophysis 12 Circadian Rhythm 10 Luteinizing Hormone 10