Meek L R, Romeo R D, Novak C M, Sisk C L
Department of Psychology, Neuroscience Program, Michigan State University, East Lansing 48824, USA.
Horm Behav. 1997 Feb;31(1):75-88. doi: 10.1006/hbeh.1997.1371.
This study was conducted to determine whether there is a increase in responsiveness to the activating effects of testosterone on male reproductive behavior during puberty in male golden hamsters and whether responsiveness to behavioral actions of testosterone is correlated with the ability of testosterone to upregulate brain androgen receptor immunoreactivity (AR-ir). Sexually naive male hamsters were castrated at 21 or 42 days of age and implanted subcutaneously with a pellet containing 0, 2.5, or 5 mg of testosterone. One week later, males were given a 10-min mating test with a receptive female. Animals were euthanized 1 hr after the behavioral test, and blood samples and brains were collected. Plasma testosterone levels were equivalent in prepubertal and adult males that had been administered the same dose of testosterone. However, adult males exhibited more mounts, intromissions, and ejaculations than prepubertal males, demonstrating that postpubertal males are more responsive than prepubertal males to the effects of testosterone on sexual behavior. In both age groups, testosterone increased the number of AR-ir cells per unit area in several brain regions involved in male sexual behavior, including the medial preoptic nucleus (MPN), medial amygdala, posteromedial bed nucleus of the stria terminalis, and magnocellular preoptic nucleus (MPNmag). Surprisingly, testosterone increased AR-ir in the latter three regions to a greater extent in prepubertal males than in adults. Thus, prepubertal males are more responsive to the effects of testosterone on AR-ir in these regions. In a separate experiment, a pubertal increase in the number of AR-ir cells per unit area was found in both the MPN and MPNmag of intact male hamsters. These results indicate that a testosterone-dependent increase in brain AR during puberty may be necessary, but is not sufficient, to induce an increase in behavioral responsiveness to testosterone.
本研究旨在确定雄性金黄仓鼠在青春期对睾酮对雄性生殖行为激活作用的反应性是否增加，以及对睾酮行为作用的反应性是否与睾酮上调脑雄激素受体免疫反应性（AR-ir）的能力相关。性未成熟的雄性仓鼠在21或42日龄时被阉割，并皮下植入含0、2.5或5毫克睾酮的药丸。一周后，让雄性仓鼠与一只处于接受状态的雌性仓鼠进行10分钟的交配测试。行为测试1小时后对动物实施安乐死，并采集血样和大脑样本。给予相同剂量睾酮的青春期前雄性和成年雄性的血浆睾酮水平相当。然而，成年雄性比青春期前雄性表现出更多的爬跨、插入和射精行为，表明青春期后的雄性比青春期前的雄性对睾酮对性行为的影响更敏感。在两个年龄组中，睾酮均增加了参与雄性性行为的几个脑区每单位面积的AR-ir细胞数量，包括内侧视前核（MPN）、内侧杏仁核、终纹床核后内侧核和视前大细胞核（MPNmag）。令人惊讶的是，睾酮使青春期前雄性的后三个区域的AR-ir增加的程度比成年雄性更大。因此，青春期前雄性对睾酮对这些区域AR-ir的影响更敏感。在另一个实验中，在完整雄性仓鼠的MPN和MPNmag中均发现每单位面积的AR-ir细胞数量在青春期有所增加。这些结果表明，青春期期间脑AR的睾酮依赖性增加可能是诱导对睾酮行为反应性增加所必需的，但并不充分。
