Hsu H K, Hsu C, Yu J Y, Peng M T
Gerontology. 1986;32(1):10-7. doi: 10.1159/000212760.
Various parameters of copulatory behavior were examined in intact and castrated testosterone-(T-)treated male rats of various ages ranging from 3 to 27 months. Serum T levels were controlled by subcutaneous implantation of different sizes of T-filled Silastic capsules at the time of castration. In intact male rats, scores of various parameters of copulatory behavior declined gradually from middle age and no ejaculation was observed in any rats over 22 months of age. When serum T levels were maintained at 0.78-0.87 ng/ml for 6 months from 4 months of age, these rats showed the same copulatory activity as intact rats, except that fewer rats exhibited ejaculation at 8 and 10 months of age and showed decreased total mount frequency at 10 months of age. Even when serum T levels were maintained at 2.95-3.53 ng/ml for a period of 6 months from 18 months of age, copulatory activity still declined gradually and no rats over 22 months of age ejaculated. However, long-term elevation of serum T level could prevent further decline of intromission frequency in old age. These results indicate that the copulatory activity of male rats in response to circulatory T declined with advancing age and that prolonged low levels of serum T had only a minor role in the onset of decreased responsiveness of neural male sexual behavior.
在3至27个月龄的完整和阉割并经睾酮（T）处理的雄性大鼠中，研究了交配行为的各种参数。在阉割时，通过皮下植入不同大小的含T硅橡胶胶囊来控制血清T水平。在完整雄性大鼠中，交配行为的各种参数得分从中年开始逐渐下降，22个月龄以上的大鼠均未观察到射精。从4个月龄开始，当血清T水平维持在0.78 - 0.87 ng/ml达6个月时，这些大鼠表现出与完整大鼠相同的交配活动，只是在8和10个月龄时射精的大鼠较少，且在10个月龄时总爬跨频率降低。即使从18个月龄开始将血清T水平维持在2.95 - 3.53 ng/ml达6个月，交配活动仍逐渐下降，22个月龄以上的大鼠均未射精。然而，血清T水平的长期升高可防止老年时插入频率的进一步下降。这些结果表明，雄性大鼠对循环T的交配活动随年龄增长而下降，且血清T水平长期处于低水平在雄性神经性行为反应性降低的起始中仅起次要作用。
