Portal de Periódicos da CAPES

Intrahypothalamic Implants of Testosterone or Estradiol and Resumption of Masculine Sexual Behavior in Long-term Castrated Male Rats

1974; Oxford University Press; Volume: 95; Issue: 4 Linguagem: Inglês

10.1210/endo-95-4-984

1945-7170

L. W. CHRISTENSEN, Lynwood G. Clemens,

Neuroendocrine regulation and behavior

Intracerebral applications of cholesterol, testosterone or estradiol were evaluated as to their ability to induce masculine sexual behavior in long-term castrated male rats. Thirty castrated male rats that had exhibited no ejaculatory response in three consecutive weekly tests were bilaterally implanted with stainless steel cannulae in the preoptic area (POA) (20 animals) or in the posterior hypothalamic area (PHA) (10 animals). The animals implanted with cannulae in the PHA and 10 animals implanted in the POA received applications of testosterone (15 µg/cannula every 3 days) for 12 days. The 10 remaining animals with cannulae placed in the POA received cholesterol applications (15 µg/cannula every 3 days) for 12 days. When tested for masculine sexual behavior 7, 10 and 13 days after the start of steroid treatment, animals receiving testosterone applications in the POA exhibited significantly more mounts, intromissions and ejaculations than the animals receiving testosterone in the PHA or cholesterol in the POA. An additional 20 long-term castrated male rats, screened for loss of sexual behavior, were bilaterally implanted with cannulae in the POA (10 animals) or in the PHA (10 animals). All animals then receivedintracerebral applications of estradiol (10 µg/cannula every 3 days) for 12 days. When tested for masculine sexual behavior 7, 10 and 13 days after the start of treatment, animals receiving estradiol applications to the POA exhibited significantly more mounts, intromissions and ejaculations than animals receiving estradiol in the PHA or cholesterol controls in the POA. In both experiments, applications of testosterone or estradiol to the PHA were not effective in significantly increasing any component of sexual behavior above the cholesterol (POA) control levels. Further comparisons revealed that applications of estradiol to the POA, were more effective than testosterone in inducing mount and intromission behavior. Histological examination of implant sites revealed no differences in the site of application among the POA-treated groups or among the PHA treated groups. These data show that estradiol, when applied directly to the brain, is more effective than testosterone in activating masculine sexual behavior. In addition, these data support the hypothesis that testosterone is aromatized at a central neural site to an estrogen, before activatingmasculine copulatory behavior. (Endocrinology95: 984, 1974)