Bernard D J, Ball G F
Department of Psychology, Johns Hopkins University, Baltimore, Maryland 21218-2686, USA.
J Comp Neurol. 1995 Oct 2;360(4):726-34. doi: 10.1002/cne.903600415.
Most studies of seasonal changes in the avian song control system have used Nissl stains to characterize the nuclei. More recent work has indicated that changes in nucleus volume evident in Nissl-stained tissue are not always apparent when investigated with other histochemical criteria. In this experiment, we used two different markers (Nissl stain and alpha 2-adrenergic receptor autoradiography) to characterize changes in the song system of European starlings (Sturnus vulgaris). Fluctuating levels of circulating testosterone (T) appear to be causally related to seasonal changes in the song system. Therefore, we used photoperiod manipulations to place male starlings into different physiological conditions. Photosensitive male starlings were placed on 11L:13D or 16L:8D photoperiods for at least 5 months. Birds on 11L:13D have enlarged gonads and circulating T. In contrast, starlings maintained on 16L:8D initially show marked gonadal growth. However, after about 6-8 weeks the birds are photorefractory (i.e., the gonads are regressed and T falls to undetectable levels). The volume of the high vocal center (HVC) was 44% larger in the 11L:13D than in 16L;8D birds in Nissl-stained tissue. The density of alpha 2-adrenergic receptors as determined by in vitro receptor autoradiography with [3H]p-amino-clonidine (PAC) is higher in HVC than in the surrounding neostriatum, clearly delineating the boundaries of the nucleus. We reconstructed the volume of HVC using PAC stained tissue. Thus, two histochemical markers indicate a photoperiodic difference in HVC volume of male starlings.
大多数关于鸟类鸣叫控制系统季节性变化的研究都使用尼氏染色来表征细胞核。最近的研究表明，用其他组织化学标准进行研究时，尼氏染色组织中明显的细胞核体积变化并不总是显而易见的。在本实验中，我们使用了两种不同的标记物（尼氏染色和α2-肾上腺素能受体放射自显影）来表征欧洲椋鸟（Sturnus vulgaris）鸣叫系统的变化。循环睾酮（T）水平的波动似乎与鸣叫系统的季节性变化存在因果关系。因此，我们通过光周期调控使雄性椋鸟处于不同的生理状态。将光敏雄性椋鸟置于11小时光照：13小时黑暗或16小时光照：8小时黑暗的光周期下至少5个月。处于11小时光照：13小时黑暗光周期的鸟类性腺增大且循环T水平升高。相比之下，处于16小时光照：8小时黑暗光周期的椋鸟最初性腺显著生长。然而，大约6 - 8周后，这些鸟类进入光不应期（即性腺退化且T降至无法检测的水平）。在尼氏染色组织中，处于11小时光照：13小时黑暗光周期的鸟类的高发声中枢（HVC）体积比处于16小时光照：8小时黑暗光周期的鸟类大44%。用[3H]对氨基可乐定（PAC）进行体外受体放射自显影测定的α2-肾上腺素能受体密度在HVC中高于周围的新纹状体，清晰地勾勒出了细胞核的边界。我们使用PAC染色组织重建了HVC的体积。因此，两种组织化学标记物表明雄性椋鸟的HVC体积存在光周期差异。
