Testosterone decreases the potential for song plasticity in adult male zebra finches

Zebra finches are age-limited learners; males crystallize their songs at 90 days and do not subsequently alter those songs. However, a variety of interventions, including deafening and syringeal denervation, result in long-term changes to the crystallized song. These changes can be prevented by lesioning nucleus LMAN. As different social contexts for song production result in differential activation of LMAN, we asked whether the social context experienced by adult males would affect their ability to alter their songs in response to syringeal denervation. Males able to see and direct their songs to females made fewer changes to their songs than did males that could hear but not see females, but this trend was not significant. The volume of a male's HVc, a forebrain song control nucleus, also failed to predict the degree to which a male would change his song. However, testis mass was significantly correlated with the number of changes made to the song, indicating that variations in testosterone modulate adult song plasticity. We directly tested the effect of circulating testosterone on adult song plasticity by implanting adult males with either testosterone or flutamide, a testosterone receptor blocker, and tracking song changes triggered by ts nerve injury. As predicted, males implanted with testosterone changed their songs less than did males that received flutamide implants. These results suggest that the high testosterone concentrations associated with sexual maturity and song crystallization in zebra finches continue to act in adult males to reduce the potential for vocal plasticity.     

Vasotocin treatment inhibits courtship in male zebra finches; concomitant androgen treatment inhibits this effect

Zebra finches evolved in arid areas of Australia. Their reproduction is stimulated by water availability, which is unpredictable. Cheng (Poult. Sci. Rev. 5 (1993) 37) hypothesized that the primary mechanism controlling reproduction in species relying on unpredictable cues should be inhibitory. The onset of stimulatory environmental conditions terminates the inhibition, allowing rapid initiation of reproduction. As the primary hormone regulating water balance in birds, arginine vasotocin (AVT) appears a likely candidate to modulate reproduction in finches. Drought conditions cause sustained AVT release, which in other species inhibits androgen production. To determine whether increased AVT inhibits reproductive behavior, intact males were tested with females and divided into three groups matched for courtship behavior. Osmotic minipumps containing (a) saline, (b) 264 ng AVT, or (c) 1320 ng AVT in saline were implanted subcutaneously and males tested 48 h later. AVT-treated males socialized with females, but the high dose significantly reduced singing and courtship displays. To determine whether AVT acted by depressing androgen secretion, additional males were given subcutaneous androgen implants and divided into two groups matched for courtship behavior. Males were then implanted with minipumps containing (a) saline or (b) the high AVT dose. Males treated with AVT plus androgen showed no deficits in courtship behavior. These data suggest that AVT secretion during periods of drought may inhibit reproduction by inhibiting androgen production. Inhibition of reproductive behavior by AVT may be a more general phenomenon. Large quantities of AVT or, in mammals the closely-related peptide vasopressin (VP), are released when animals are stressed, and high levels of AVT/VP may inhibit reproductive behavior. The extremely short half-life of these peptides means that once proximal factors become more favorable, the gonads should rapidly be released from the peptides' inhibitory actions.     

Sexual preferences for songs in female domestic canaries (<Emphasis Type="Italic">Serinus canaria</Emphasis>): can late song exposure,without social reinforcement,influence the effects of early tutoring?

We studied the relative effects of early and late song exposure without social reinforcement on female sexual preferences in the domestic canary (Serinus canaria). Young female canaries were tape-tutored during their first 4 months of life with songs of either domestic or wild male canaries (DT and WT conditions). When they reached sexual maturity, these females were placed in breeding conditions and some of them were re-exposed to songs. During this late exposure the females, according to their experimental group, were either presented with new domestic or wild songs (DL and WL conditions) over 40 days, or were kept without song stimulation (– condition). Afterwards, we assessed the sexual preferences of all the females for domestic or wild songs using the copulation solicitation display assay. The results showed that both DT/– and DT/DL females showed a clear preference for domestic songs. However, whereas WT/WL females preferred wild songs; WT/– females did not show any preference. Finally, DT/WL and WT/DL females failed to show any preference. It appeared that a second song experience at the beginning of their first breeding season, without any social reinforcement, allowed the emergence or stabilisation of early preferences, or interfered with these early preferences depending on whether the song category used during the late exposure phase matched or not the song category used during the early tutoring phase, and also depending on which category was used during the first tutoring phase. This behavioural plasticity could help young adult females to adjust the standard they built during infancy to new environmental conditions.Communicated by P.K. McGregor     

The influence of wind conditions in Europe on the advance in timing of the spring migration of the song thrush (<Emphasis Type="Italic">Turdus philomelos</Emphasis>) in the south-east Baltic region

Some of the factors that could influence changes in phenology of the song thrush (Turdus philomelos) during spring migration have been analyzed in relation to the timing of their return to the south-east Baltic region over the last 40 years. These include wind direction and velocity, temperature and precipitation in the wintering areas and along the migratory route. In March, a significant correlation was found between the timing of passage in the Baltic region and both the air temperatures in wintering area and winds over the migratory route. In April, when mass migration of thrushes occurs, the timing of passage was correlated with temperature, winds and, partly, precipitation over the route of migration. In this month, the frequency of tailwinds increased significantly along the route of migration from south-west France to the Baltic region over the last 40 years. The tailwind frequency was correlated with the beginning, middle and end of spring passage, accounting for 51% of the variance of median dates of the passage. The higher ambient temperatures over the migratory route explain nearly 20% of the variance in the timing of passage. Our results suggest that the advance in the timing of spring migration is primarily due to (1) the increased frequency of tailwinds favorable for migratory flights over the migratory route, and (2) the earlier emergence of the conditions enhancing migration due to higher spring temperatures in the winter quarters and on the migratory route.     

驿路视角下的古代城湖分布探析

研究中国的历史名城常会发现一个有趣的现象,多数历史名城往往会有湖泊相伴,如杭州西湖、南宁南湖、肇庆星湖等。这些城市湖泊与古代城市发展密切相关,但其与古代城市在历史发展之间的共振关系,还处在开放的研究之中。对其分布的结构性特征还未有结论。根据唐代以来逐渐形成的正南线和东南线2条古代驿路结构主线,同时比对历史文献记载中中国古代的“城市—湖泊”系统的分布,进而初步形成一个结构性的认识。中国古代“城湖”体系的形成,与自唐宋起始的大规模地方州府城市的建设密切相关,同时亦是适应中国胡焕庸线以东南,以丘陵地貌为主的自然山水本底。这对于揭示中国古代城市近郊基于自然山水本底而营造的山水风景的历史形成,具有重要意义。     

武汉地区大山雀（Parus major minor）对major与minor亚种组鸣唱回放的差别反应

分析鸟类鸣声能为研究鸟类系统学和生物地理学提供重要信息。鸟类鸣声的地理变异能影响鸟类的性选择,进而导致不同地理种群间的生殖隔离,从而促进地方种群(或亚种)的分化,乃至新种的形成。在鸟类系统学研究中,鸣声回放实验是研究物种分化并衡量分类地位的一项重要研究手段。本实验以武汉地区大山雀(Parus major minor,隶属于minor亚种组)为实验对象进行鸣唱回放实验,观测其对来自欧亚大陆西部及北部各地的major亚种组和来自我国各地的minor亚种组大山雀鸣唱回放的反应,探讨实验对象能否区分来自上述两个不同亚种组的鸣唱,从而推断两亚种组之间是否存在足以导致识别障碍的鸣声分化,以致产生行为上的生殖隔离。本实验共测试了24只雄性大山雀,每个亚种组的鸣唱各回放给12只个体,通过记录不同行为反应指标来衡量每只受试个体的反应程度。统计分析结果显示,受试大山雀对major和minor亚种组鸣唱的反应有显著差异,对同为minor亚种组的鸣唱反应程度激烈,而对major亚种组鸣唱的反应微弱甚至大多无反应。由此认为,大山雀major和minor亚种组之间存在显著的鸣声分化,已达到能形成配对前生殖隔离的程度,从而一定程度上支持将大山雀拆分成不同种的说法。     

四种草螽雄性鸣声的研究

对分布于我国的长瓣草螽Conocephalus(Anisoptera)gladiatus,中华草螽C.(Amurocephalus)chinensis,悦鸣草螽 C.(Anisoptera)melaenus和斑翅草螽C.(Anisoptera)maculatus雄性鸣声进行了分析.研究结果表明,这4种草螽雄性鸣声的时域波形较简单,鸣声均由1种类型的脉冲组序列构成.长瓣草螽雄性鸣声每个脉冲组持续时间约0.13 s,脉冲组间隔约0.12 s,每个脉冲组通常由8脉冲构成,鸣声的频率范围5～20 kHz.中华草螽雄性的鸣声脉冲组由2个脉冲构成,每次鸣叫持续时间约为3.3 s,两次连续鸣叫间隔约10.5 s,鸣声频率范围为20 Hz～20 kHz.斑翅草螽雄性鸣声的脉冲组由10～13个脉冲构成,脉冲组持续时间2.1～2.5 s,两次连续鸣叫间隔时间约为3 s;鸣声频率从5.5 kHz到高于20 kHz.悦鸣草螽雄性鸣声由单一规则的重复脉冲组序列构成,每个鸣声脉冲组持续时间约0.035 s,脉冲组间隔约0.023 s,每个脉冲组由3个脉冲构成,脉冲组重复率20/s,鸣声频率6.0～20.0 kHz.     

Simultaneous treatment with an aromatase inhibitor and an anti-androgen decreases the likelihood of dawn song in free-living male great tits, Parus major

Gonadal steroids, most importantly testosterone (T), are considered to be a major factor in the expression of adult song behavior in temperate-zone songbirds. The action of T within specific brain regions involved in the regulation of song may occur either directly, or through its androgenic or estrogenic metabolites. In the present study, we tested steroid-dependence of great tit dawn song by blocking both known pathways of T action by simultaneous implantation of flutamide, an anti-androgen, and ATD, an aromatase inhibitor. By our knowledge, this is the first study investigating the effects of androgen inhibitors on dawn song in free-living birds. Male great tits were implanted during their mate's egg laying stage, being the time of maximal male song activity at dawn. Treatment with ATD and flutamide significantly increased plasma T levels, probably because feedback mechanisms on T secretion were inhibited. The treatment decreased the likelihood of showing dawn song, which is in line with the hypothesis that sex steroids are involved in the endocrine control of song behavior. In males that did show dawn song, we found no evidence for a treatment effect on song quality. Although the implants were present for the larger part of the breeding season, males were able to maintain control of a territory and mate and to complete their brood cycle as successful as control males.     

Neuroanatomical evidence for indirect connections between the medial preoptic nucleus and the song control system: possible neural substrates for sexually motivated song

In European starlings (Sturnus vulgaris) as in other seasonally breeding songbirds, a major function of song during the breeding season is mate attraction, and song in this context is highly sexually motivated. Song learning, perception, and production are regulated by nuclei of the song control system, but there is no evidence that these nuclei participate in the motivation to sing. Evidence suggests that the medial preoptic nucleus (POM), a diencephalic nucleus outside of the song control system, might regulate the motivation to sing, at least in a sexual context. If the POM is involved in the regulation of sexually motivated song, then this structure must interact with the song control system. To examine possible neuroanatomical connections between the POM and song control nuclei a tract-tracing study was performed in male starlings using the antero- and retrograde tract tracer, biotinylated dextran amine (BDA). No direct connections were identified between the POM and song control nuclei; however, labeled fibers were found to terminate in a region bordering dorsal-medial portions of the robust nucleus of the archistriatum (RA). Additionally, several indirect routes via which the POM might communicate with the song control system were identified. Specifically, POM projected to dorsomedial nucleus intercollicularis (DM), mesencephalic central gray (GCt), area ventralis of Tsai (AVT), and locus ceruleus (LoC), structures projecting directly to nuclei involved in song production (DM vocal-patterning and respiratory nuclei; GCt, AVT, LoC RA and HVC, and the context in which song is sung (AVT area X). These results are consistent with the possibility that the POM regulates sexually motivated song through interactions with brain regions involved in vocal production.We gratefully acknowledge grant sponsors NIMH (R01-MH 65645) to LVR and NSF for a graduate research fellowship to SJA     

Synucleins and their relationship to Parkinson’s disease

Parkinsons disease (PD) is one of the most common neurodegenerative motor disorders, marked by chronic progressive loss of neurons in the substantia nigra. It has long been believed that PD is caused by environmental factors. The discovery of genetic factors involved in PD has improved the understanding of the pathology of the disease. The first gene found to be mutated in PD encodes for the presynaptic protein -synuclein. -Synuclein is a major component of Lewy bodies and Lewy neurites, which represent the morphological hallmarks of the disease. The mechanisms by which -synuclein is involved in nigral cell death remain poorly understood. Moreover, the factors triggering the formation of -synuclein-positive inclusion bodies remain enigmatic. Indeed, even the normal cellular functions of -synuclein and of the other synucleins (-synuclein and -synuclein) are still unknown. Several lines of evidence suggest that they play a role in the regulation of vesicular turnover under normal nonpathological conditions.The work of O. von Bohlen und Halbach is supported by the DFG (Forschergruppe FOR 302 and SFB 636)