title: Short duration testosterone infusions maintain male sex behavior in Syrian hamsters.
abstract: In most mammalian species, reduced androgen availability is associated with marked reductions in male sexuality; conversely, androgen replacement in castrated males restores sex behavior within a few weeks. Testosterone (T) pulse duration, amplitude, frequency, and inter-pulse interval may be as important as total amount of hormone in determining target tissue responsiveness. We remain ignorant of the number and duration of daily T pulses necessary and sufficient to sustain male mating behavior. An in-dwelling infusion system was employed to vary T-pulse frequencies and durations. Daily 4 h infusions of aqueous T (100 microg/0.064 ml) and twice daily 4 h pulses of T (each 50 microg/0.064 ml) were sufficient to maintain ejaculatory behavior of sexually experienced castrated hamsters for 11 weeks post-castration; castrated hamsters infused with vehicle ceased to display the ejaculatory pattern 3 weeks after gonadectomy. Circulating T concentrations of hormone-infused hamsters declined markedly 7 h after the termination of each infusion. These results establish that male sex behavior can be sustained with infusions of relatively low T concentrations for 4 h/day and suggests that the basal concentrations of T sustained by the gonad during inter-pulse intervals may not be necessary for maintenance of sex behavior. 4 h T infusions were sufficient to maintain penile and seminal vesicles weights, but not ventral prostate weights or flank gland dimensions; the threshold for maintaining male sex behavior is lower than that for some androgen-dependent peripheral structures. Development of effective androgen replacement regimens that sustain sex behavior in castrated animals may be useful in the design of androgen replacement therapy for hypogonadal men.
authors.affiliation: Department of Biochemistry and Molecular Genetics, School of Medicine, University of Virginia, 1300 Jefferson Park Ave., Charlottesville, VA 22908, USA. jinhopark@virginia.edu
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Park
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Paul
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Butler
authors.forename: Philip
authors.initials: P
authors.lastname: Villa
authors.forename: Morgan
authors.initials: M
authors.lastname: Burke
authors.forename: Dennis P
authors.initials: DP
authors.lastname: Kim
authors.forename: David M
authors.initials: DM
authors.lastname: Routman
authors.forename: Elanor E
authors.initials: EE
authors.lastname: Schoomer
authors.forename: Irving
authors.initials: I
authors.lastname: Zucker
mesh_terms: D000818:Animals; D006224:Cricetinae; D004334:Drug Administration Schedule; D020249:Hormone Replacement Therapy; D007260:Infusion Pumps; D008297:Male; D008647:Mesocricetus; D009919:Orchiectomy; D009929:Organ Size / Q000187:drug effects; D010413:Penis / Q000033:anatomy & histology / Q000187:drug effects; D011467:Prostate / Q000033:anatomy & histology / Q000187:drug effects; D012669:Seminal Vesicles / Q000033:anatomy & histology / Q000187:drug effects; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D013739:Testosterone / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D013739:Testosterone