Department of Animal Science, University of California, Davis, USA.
Physiol Behav. 2010 Aug 4;101(1):13-21. doi: 10.1016/j.physbeh.2010.04.002. Epub 2010 Apr 10.
Previous studies show that post-hatch oral exposure of zebra finches to estradiol benzoate compromises male fertility, but the basis of the infertility is not clear. In this study, zebra finch nestlings were orally dosed with estradiol benzoate (at 1, 10, or 100 nmol/g BW per day, post-hatch days 5 to 11 [EB1, EB10, and EB100, respectively]). EB10 and EB100 males exhibited no significant differences in the frequency of mounting behavior (compared to canola oil [vehicle]-treated controls), when observed for six weeks as adults in communal breeding cages with similarly treated females; EB1 males showed reduced mounting behavior compared to controls (p<0.05). EB- and control-treated adult pairs were subsequently co-housed in a communal breeding trial to determine the extent of parentage outside the established pair-bond. Microsatellite analysis was consistent with EB-treated males having lower success than controls in obtaining paternity outside the established pair-bond. Histological examination of testes revealed dose-related disruption of normal morphology: disrupted basal-to-lumen laminarity of spermatogenesis stages, increased vacuolization within seminiferous tubules, decreased sperm aggregation and decreased spermatid density. Additionally, EB100 and control males were housed individually, implanted with testosterone propionate (TP) and presented with a female 3, 5, 9, and 11 days post-implantation for assessment of male sexual behavior. EB-treated, TP-implanted birds showed a slight decrease in mounting and singing behavior on day 5 after implantation; other male courtship behaviors (display, solicitation) were unaffected. Taken together, these results suggest that infertility in male zebra finches resulting from early oral estrogen exposure is more likely due to disrupted testicular morphology than altered sexual behavior.
先前的研究表明，斑胸草雀在孵化后通过口服苯甲酸雌二醇（E2B）会损害其雄性生殖能力，但导致不育的原因尚不清楚。在这项研究中，研究人员用 E2B（孵化后第 5 至 11 天，每天 1、10 或 100nmol/gBW，分别为 EB1、EB10 和 EB100）对斑胸草雀雏鸟进行口服处理。在与用菜籽油（vehicle，对照）处理的对照组相比，当观察 6 周龄的成年雄性在有同样处理的雌性的共养繁殖笼中时，EB10 和 EB100 雄性在交配行为的频率上没有显著差异；EB1 雄性与对照组相比，交配行为减少（p<0.05）。随后，将用 EB 和对照处理的成年对共同饲养在一个共养繁殖试验中，以确定在已建立的配对关系之外获得亲代的程度。微卫星分析结果与用 EB 处理的雄性在已建立的配对关系之外获得亲代的成功率低于对照组的结果一致。睾丸组织学检查显示，正常形态学受到与剂量相关的破坏：生精阶段的基底到管腔分层紊乱，精小管内空泡化增加，精子聚集减少，精子密度降低。此外，将 EB100 和对照组雄性单独饲养，植入丙酸睾酮（TP），并在植入后 3、5、9 和 11 天分别与一只雌性接触，以评估雄性性行为。用 EB 处理、植入 TP 的鸟类在植入后第 5 天表现出交配和鸣叫行为略有减少；其他雄性求偶行为（展示、求爱）未受影响。综上所述，这些结果表明，早期口服雌激素暴露导致雄性斑胸草雀不育，更可能是由于睾丸形态破坏，而不是性行为改变。
