CHANGES IN BRAIN GNRH ASSOCIATED WITH PHOTOREFRACTORINESS IN-HOUSE SPARROWS (PASSER-DOMESTICUS)
CHANGES IN BRAIN GNRH ASSOCIATED WITH PHOTOREFRACTORINESS IN-HOUSE SPARROWS (PASSER-DOMESTICUS)
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DOI：
10.1006/gcen.1995.1119
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发表时间：
1995-09-01
影响因子：
2.7
通讯作者：
BALL, GF
中科院分区：
文献类型：
--
作者：
HAHN, TP;BALL, GF
温带的鸟类在变得不耐光时就终止了繁殖。在许多物种中，难治性是“绝对的”，因为性腺衰退发生在白昼长度下降之前，个体甚至对连续的光线也没有生殖反应。根据对少数物种的研究，这种形式的难治性似乎与（与繁殖和/或光敏鸟类相比）下丘脑细胞和纤维数量的减少有关，这些细胞和纤维对促性腺激素释放激素（GnRH）具有免疫反应。一些物种表现出“相对的”耐受性，在性腺退化发生之前，白天的长度必须下降，个体永远不会失去对很长时间的反应能力。一些报告表明，在相对难治的鸟类中，大脑中的GnRH水平没有变化。家雀（Passer domesticus）在夏季白昼长度下降时，性腺的退化速度比夏至后不允许光周期下降时要快（即，它们似乎“相对”难以恢复）。然而，如果长时间服用，它们最终会使性腺退化，尽管光周期没有下降（它们似乎是“绝对”难治的）。在本实验中，我们测试了性腺退化是否与成年雄性家雀下丘脑GnRH的变化有关。我们使用免疫细胞化学（对两种形式的鸟类GnRH都敏感的一抗）来比较在长日繁殖活跃的个体、长日“绝对”难反应的个体和短日诱导退化的可能“相对”难反应的个体中GnRH免疫反应细胞和纤维的分布和数量。与仍处于繁殖状态的鸟类相比，两组难治性鸟类的ir-GnRH细胞数量和细胞大小都出现了类似的减少。性腺退化也与细胞体染色强度降低和纤维染色减少相关，但这些降低在“绝对”比“相对”难治鸟中更为明显。我们将这些结果与其他鸟类GnRH随生殖阶段变化的研究结合起来讨论。我们的结果与家麻雀变得绝对耐火的想法是一致的，无论是否暴露在光周期的下降。然而，研究结果还表明，相对难治性可能通过停止GnRH分泌诱导性腺功能衰退，而绝对难治性也涉及肽生成的下调。(C) 1995学术出版社，Inc。
Temperate zone birds terminate reproduction when they become photorefractory. In many species, refractoriness is ''absolute'' in that gonadal regression occurs before day length declines, and individuals are reproductively unresponsive even to continuous light. Based on studies of a few species, this form of refractoriness appears to be associated with a reduction (compared with breeding and/or photosensitive birds) in numbers of hypothalamic cells and fibers that are immunoreactive for gonadotropin releasing hormone (GnRH). Some species display ''relative'' refractoriness, in that day length must decline before gonadal regression occurs, and individuals never lose the capacity to respond to very long days. A few reports suggest that GnRH levels in the brain do not change in relatively refractory birds. House sparrows (Passer domesticus) regress their gonads sooner when day length declines during summer than they do if photoperiod is not permitted to decline after the summer solstice (i.e., they appear to be ''relatively'' refractory). However, if held on long days they eventually regress the gonads despite no decline in photoperiod (they appear to be ''absolutely'' refractory). In this experiment, we tested whether gonadal regression was associated with changes in hypothalamic GnRH in adult male house sparrows. We used immunocytochemistry (primary antibody sensitive to both forms of avian GnRH) to compare the distribution and number of GnRH-immunoreactive cells and fibers among reproductively active individuals on long days, ''absolutely'' refractory individuals on long days, and presumably ''relatively'' refractory individuals induced to regress by shortened days. Similar reductions in ir-GnRH cell number and cell size occurred in both groups of refractory birds compared with birds still in breeding condition. Gonadal regression also was correlated with reduced staining intensity of cell bodies and reduced fiber staining, but these reductions were somewhat more pronounced in the ''absolutely'' than the ''relatively'' refractory birds. We discuss these results in light of other studies of avian GnRH changes with reproductive stage. Our results are consistent with the idea that house sparrows become absolutely refractory, regardless of whether exposed to a decline in photoperiod. However, the results also suggest that relative refractoriness may induce gonadal regression through a cessation of GnRH secretion, whereas absolute refractoriness involves down-regulation of peptide production as well. (C) 1995 Academic Press, Inc.