雄激素对成年雄性斑胸草雀前脑高级发声中枢-弓状皮质栎核通路长时程压抑的影响

雄激素可通过调控鸣唱控制系统改变鸣禽的鸣唱行为。本研究以成年雄性斑胸草雀为实验动物,采用在体电生理实验方法,观察雄激素对高级发声中枢(high vocal center,HVC)-弓状皮质栎核(robust nucleus of the arcopallium,RA)通路突触可塑性的影响,以期阐明雄激素对成年鸣禽鸣唱稳定性维持的神经生理机制。将实验动物分为对照组、去势组与去势+埋植睾酮组,分别记录高频刺激(400 Hz,2 s)HVC后,HVC-RA通路长时程压抑(long-term depression,LTD)的变化以及双脉冲易化效应。结果显示,高频刺激HVC,在对照组可以记录到LTD现象;去势组中仅有短时程压抑(short-term depression,STD)现象;去势+埋植睾酮组中LTD现象则恢复。双脉冲易化现象在去势组不明显,而对照组和去势+埋植睾酮组易化率明显高于去势组。以上结果提示,雄激素可能通过影响成年雄性斑胸草雀HVC-RA通路的LTD水平来维持鸣曲稳定性,并对该通路的短时程突触可塑性有一定的调节作用。     

电刺激大鼠坐骨神经诱发海马齿状回突触可塑性研究

观察电刺激大鼠坐骨神经引起海马齿状回诱发场电位的变化,探讨外周传入信息在海马的可塑性以及海马在痛觉调制中的作用。共记录了28只大鼠海马齿状回诱发场电位,平均幅度(23.73±1.12)μV,潜伏期(198.46±5.91)ms。不同条件刺激引起的反应包括:高频条件刺激使海马齿状回诱发场电位幅度降低;低频条件刺激使海马齿状回诱发场电位幅度增大。结果提示,电刺激坐骨神经可在海马齿状回记录到诱发场电位,不同的条件刺激可引起诱发场电位的不同变化,表现为突触传递效能增强或降低,海马对外周传入信息及痛觉起一定的调制作用。     

大鼠丘脑侧后核到初级视皮层突触传递的短时程可塑性

大鼠丘脑侧后核(lateral posterior thalamic nucleus,LP nucleus)到初级视皮层的突触连接是膝体外视觉通路的重要组成部分.运用场电位记录和电泳的方法在位研究了该视觉回路突触传递的短时程可塑性.结果表明,无论是运用双脉冲刺激还是串刺激都能观察到明显的短时程抑制特性.电泳荷包牡丹碱(bicuculline)和2-hydroxy-saclofen使该抑制作用减弱,电泳钙离子使抑制加强,电泳APV对抑制作用没有明显影响.所以突触前递质释放水平的改变,和γ-氨基丁酸(GABA)能受体（尤其是GABA_B受体）的活动都会影响该回路突触传递的短时程可塑性,而N-甲基-D-天冬氨酸(NMDA)受体则几乎没有作用.该回路很强的短时程抑制特性可能与LP核在视觉注意中的作用有关.     

新纹状体巨细胞核外侧部（LMAN）与鸣禽鸣唱学习可塑性

鸣禽鸣唱控制系统的前端脑通路（anterior forebrain pathway, AFP）在鸣唱学习中发挥着重要作用。新纹状体巨细胞核外侧部（lateral magnocellular nucleus of the anterior neostriatum, LMAN）是AFP的最后一级输出核团,AFP中的信号通过LMAN传导到弓状皮质栎核（robust nucleus of the arcopallium, RA）,与高级发声中枢（high vocal centre,HVC）共同调节RA的活动,从而影响鸣禽的发声行为。LMAN可能通过其与RA的单突触连接来影响鸣唱可塑性。文章对近年来LMAN在鸣唱学习可塑性方面的研究进行综述。     

2 Hz与100 Hz刺激在诱导大鼠视皮层长持续长时程增强中的不同作用

在哺乳动物的视皮层,多种不同参数的刺激可诱导出长时程增强(long-term potentiation,LTP)现象。但关于刺激参数与持续时间长于3h的长持续LTP(long lasting LTP,L-LTP)之间关系的研究较少。本研究用3周龄的大鼠视皮层脑片标本,在Ⅳ层刺激而在Ⅱ／Ⅲ层记录场电位,待场电位稳定后施加强直刺激诱导LTP,探讨2Hz与100Hz的强直刺激在诱发持续时间长于3h的L-LTP中的作用。结果表明,多于300个脉冲不同频率的刺激可稳定地诱导出L-LTP;2Hz与100Hz的刺激诱发的L-LTP有明显不同的表达形式,100Hz刺激可诱导出较大的L-LTP;频率相同而脉冲数不同的强直刺激诱发的L-LTP有相同的表达形式。以上结果提示,不同频率的强直刺激诱发的L-LTP机制可能不同;相同频率的刺激(脉冲数不同)诱发的L-LTP可能有相同的机制。     

新纹状体巨细胞核外侧部与鸣禽鸣唱学习可塑性

鸣禽鸣唱控制系统的前端脑通路(anterior forebrain pathway,AFP)在呜唱学习中发挥着重要作用.新纹状体巨细胞核外侧部(lateral magnocellular nucleus of the anterior neostriatum,LMAN)是AFP的最后一级输出核团,AFP中的信号通过LMAN传导到弓状皮质栎核(robust nucleus of the arcopallium,RA),与高级发声中枢(high vocal centre,HVC)共同调节RA的活动,从而影响鸣禽的发声行为.LMAN可能通过其与RA的单突触连接来影响鸣唱可塑性.文章对近年来LMAN在呜唱学习可塑性方面的研究进行综述.     

强直电刺激嗅内皮质—海马环路诱发CAI神经元的癫痫同步性膜电位振？…

目的和方法：４００－５００μｍ大鼠水平脑切片吸封闭的ＥＣ－海马环路。强直电刺激（６０Ｈｚ,２ｓ）海马Ｓｃｈａｅｆｆｅｒ侧支诱发癫痫放电,全细胞记录ＣＡ１胞体层单个神经元电活动,同步记录相应树突外场电位,探讨单个神经元膜电位振荡特性和细胞外癫痫电活动之间的关系。结果：（１）强直电刺激诱发ＣＡ１神经元膜电位后放性振呈宽频特征（３－１００ＨＺ）。以θ节律多见,跟随在刺激引起的膜电位去极化或超极化偏移之后     

皮质醇对离体牛蛙交感神经节B细胞胆碱能突触传递的快速作用

在离体灌流的牛蛙交感神经节标本上,电刺激节前纤维,细胞内记录Ｂ细胞的电活动,观察给予皮质醇对Ｂ细胞突触传递作用。主要结果有：（１）电刺激节前纤维,细胞内记录１７０个Ｂ细胞的动作电位,给予皮质醇后０．５￣３ｍｉｎ内,５２个Ｂ细胞的突触传递发生脱漏甚至完全阻断,有明显的量效关系。甾体激素胞内受体阻断剂ＲＵ３８４８６可部分阻断这种作用。（２）蛋白合成抑制剂放线菌酮不能阻断皮质醇的快速阻断作用。（３）阿托     

猫中·间脑结合部神经元与眼球下斜肌运动神经元的直接突触联系

本文应用神经元自发放电触发的迭加平均法,研究了猫中·间脑结合部内侧区神经元与眼球下斜肌运动神经元（inferiorobliquemotoneurons,IOMNs）之间的突触联系。电刺激同侧或对侧中·间脑结合部的Forel'sfieldeH（FFH）的内侧区（A7～Ag）,在IOMN池内记录到兴奋性单突触电场电位。应用FFH神经元的自发放电作为触发信号,将此放电引起的IOMNs的电位变化进行迭加平均,结果亦获得一兴奋性单突触电场电位。这些结果表明,中·间脑结合部内侧区神经元与IOMNs之间存在兴奋性单突触联系,其作用为启动眼球的垂直运动。     

燕雀丘间复合体背内侧核对叫声的调控模式

鸣禽鸟的基本发声中枢——丘间复合体背内侧核(nucleus dorsalis medialis of the intercollicular complex,DM)对叫声的调控模式是诱发单次叫声。应用电生理与声学分析相结合的方法研究鸣禽鸟燕雀(Fringilla montifringilla)DM核团对声音调控的模式。经语图和频谱图分析,结果显示：燕雀左侧DM诱发单次叫声的声长和主能量区的带宽分别为右侧DM诱发叫声的2倍和1．7～3．1倍,提示燕雀DM对叫声声长和声强的调控能力,均呈明显的左侧优势。这与高级发声中枢(high vocal center,HVC)和古纹状体粗核(nucleus robustus archistriatalis,RA)等发声控制核团在控声模式中具有左侧优势的特征相似,从而为鸣禽发声控制通路高、低级中枢具有内源投射关系提供了声学上的证据。     

急性神经损伤引起脊髓背角C-纤维诱发电位长时程增强

神经损伤引起神经病性疼痛,表现为持续性痛超敏和痛觉过敏。目前对神经病性疼痛的机制尚缺乏了解。我们以往的工作表明强直电刺激坐骨神经可引起脊髓背角C-纤维诱发电位的长时程增强(long-term potentiation,LTP),该LTP被认为是病理性疼痛的突触模型。本研究的目的在于探讨急性神经损伤是否能在完整动物的脊髓背角诱发出C-纤维诱发电位LTP。在以测试刺激(10～20V,0．5ms)电刺激坐骨神经的同时在脊髓背角用微电极记录C一纤维诱发电位。分别用强直刺激、剪断或夹捏坐骨神经诱导LTP。结果发现：(1)剪断或夹捏坐骨神经都可以诱导脊髓背角C-纤维诱发电位的LTP,该LTP可持续到实验结束(3～9h),在剪断神经前10min用利多卡因局部阻滞坐骨神经则可完全阻断LTP的产生;(2)神经损伤诱导的LTP可被NMDA受体阻断剂AP5所阻断;(3)用单次强直刺激引起LTP后,切断坐骨神经可使LTP的幅度进一步增大,而用多次强直电刺激使LTP饱和后,损伤神经则不能使LTP进一步增大。切断神经引起LTP后,强直电刺激也不能使LTP进一步增大。这些结果表明,急性神经损伤可以诱导脊髓背角C纤维诱发电位LTP,且切断神经能更有效地诱导LTP。该试验进一步支持我们的设想,即脊髓背角C-纤维诱发电位LTP可能在病理性疼痛的形成中起重要作用。     

HVC microlesions do not destabilize the vocal patterns of adult male zebra finches with prior ablation of LMAN

The songs of adult male zebra finches (Taeniopygia guttata) arise by an integration of activity from two neural pathways that emanate from the telencephalic nucleus HVC (proper name). One pathway descends directly from HVC to the vocal premotor nucleus RA (the robust nucleus of the arcopallium) whereas a second pathway descends from HVC into a basal ganglia circuit (the anterior forebrain pathway, AFP) that also terminates in RA. Although HVC neurons that project directly to RA outnumber those that contribute to the AFP, both populations are distributed throughout HVC. Thus, partial ablation (microlesion) of HVC should damage both pathways in a proportional manner. We report here that bilateral HVC microlesions in adult male zebra finches produce an immediate loss of song stereotypy from which birds recover, in some cases within 3 days. The contribution of the AFP to the onset of song destabilization was tested by ablating the output nucleus of this circuit (LMAN, the lateral magnocellular nucleus of the anterior nidopallium) prior to bilateral HVC microlesions. Song stereotypy was largely unaffected. Together, our findings suggest that adult vocal production involves nonproportional integration of two streams of neural activity with opposing effects on song--HVC's direct projection to RA underlies production of stereotyped song whereas the AFP seems to facilitate vocal variation. However, the rapid recovery of song in birds with HVC microlesions alone suggests the presence of dynamic corrective mechanisms that favor vocal stereotypy.     

Temporal patterning of song production: Participation of nucleus uvaeformis of the thalamus

Birdsong is a learned vocal behavior used in intraspecific communication. The motor pathway serving learned vocalizations includes the forebrain nuclei NIf, HVC, and RA; RA projects to midbrain and brain stem areas that control the temporal and acoustic features of song. Nucleus Uvaeformis of the thalamus (Uva) sends input to two of these forebrain nuclei (NIf and HVC) but has not been thought to be important for song production. We used three experimental approaches to reexamine Uva's function in adult male zebra finches. (1) Electrical stimulation applied to Uva activated HVC and the vocal motor pathway, including tracheosyringeal motor neurons that innervate the bird's vocal organ. (2) Bilateral lesions of Uva including the dorso-medial portion of the nucleus affected the normal temporal organization of song. (3) Chronic multiunit recordings from Uva during normal song and calls show bursts of premotor activity that lead the onset of some song components, and also larger bursts that mark the end of complete song motifs. These results implicate Uva in the production of learned vocalizations, and further suggest that Uva contributes more to the temporal structure than to the acoustic characteristics of song. © 1993 John Wiley & Sons, Inc.     

Afferent influences on cell death and birth during development of a cortical nucleus necessary for learned vocal behavior in zebra finches

Forebrain nuclei that control learned vocal behavior in zebra finches are anatomically distinct and interconnected by a simple pattern of axonal pathways. In the present study, we examined afferent regulation of neuronal survival during development of the robust nucleus of the archistriatum (RA). RA projection neurons form the descending motor pathway of cortical vocal-control regions and are believed to be directly involved in vocal production.RA receives afferent inputs from two other cortical regions, the lateral magnocellular nucleus of the anterior neostriatum (lMAN) and the higher vocal center (HVC).However, because the ingrowth of HVC afferent input is delayed, lMAN projection neurons provide the majority of afferent input to RA during early vocal learning. lMAN afferent input to RA is of particular interest because lMAN is necessary for vocal learning only during a restricted period of development. By making lesions of lMAN in male zebra finches at various stages of vocal development (20-60 days of age) and in adults (>90-days old), we asked whether the survival of RA neurons depends on lMAN afferent input, and if so whether such dependence changes over the course of vocal learning. The results showed that removal of lMAN afferent input induced the loss of over 40% of RA neurons among birds in early stages of vocal development(20 days of age). However, lMAN lesions lost the ability to induce RA neuron death among birds in later stages of vocal development (40 days of age and older). These findings indicate that many RA neurons require lMAN afferent input for their survival during early vocal learning, whereas the inability of lMAN lesions to induce RA neuron death in older birds may indicate a reduced requirement for afferent input or perhaps the delayed ingrowth of HVC afferent input (at approx. 35 days of age)provides an alternate source of afferent support. Removal of lMAN afferent input also dramatically increased the incidence of mitotic figures in RA, but only among 20-day-old birds at 2 days post-lesion. The early, acute nature of the mitotic events raises the possibility that cell division in RA may be regulated by lMAN afferent input.     

间歇性低氧对大鼠海巴长时程增强电位的影响

目的：研究间歇性低氧对大鼠海马神经元突触可塑性的影响。方法：大鼠受间歇性低氧处理后,用脑立体定位仪定位,观察海马时程增强电位（LTP）的变化。结果：间歇性低氧大鼠LTP幅值显著低于对照组。结论：间歇性低氯可影响LTP幅值,提示间歇性低氧可能使大鼠海马神经元的突触可塑性发生变化。     

Adenosine (A2) antagonist inhibits induction of long-term potentiation of evoked synaptic potentials but not of the population spike in hippocampal CA1 neurons.

The effects of adenosine A2 receptor antagonist (CP-66713) on long-term potentiation were studied using guinea pig hippocampal slices in a perfusion system. Tetanic stimulation of Schaffer collateral input which was applied during perfusion of CP-66713 (10 microM), did not induce long-term potentiation but rather long-term depression of evoked synaptic potentials (field EPSP), but induced long-term potentiation of the population spike in CA1 neurons. Thus, adenosine derivatives which accumulate in the synaptic cleft during the tetanic stimulation may be involved in induction of the long-term potentiation via A2 receptors at the synapse. The clear discrimination between long-term depression of the field EPSP and long-term potentiation of the population spike suggests EPSP-spike potentiation at the postsynaptic sites.     

Differential estrogen accumulation among populations of projection neurons in the higher vocal center of male canaries

The higher vocal center (HVC) of adult male canries undergoes a seasonal change in volume that corresponds to seasonal modifications of vocal behavior: HVC is large when birds produce stereotyped song (spring) and is small when birds produce plastic song and add new song syllables into their vocal repertoires (fall). We reported previously that systemic exposure to testosterone (T) produces an increase in the volume of HVC similar to that observed with long-day photoperiods. T-induced growth of HVC occured regardless of wheter the borders of HVC were defined by Nissl-staining, the distribution of androgen-concentrating cells, or the distribution of projection neurons [separate neuronal populations within HVC project to the robust nucleus of the archistriatum (RA) and to Area X of the avian striatum (X)]. In the present study we used steroid autoradiography to determine whether T can influence the distribution of HVC cells that bind estrogen, and we combined estrogen autoradiography with retrograde labeling to determine whether HVC neurons that project to RA versus X differ in their ability to accumulate estrogen. Results showed that T increased the volume of Nissl-defined HVC and although HVC contained a low density of estrogen-concentrating cells, T increased the spatial distribution of these cells to match the Nissl borders of HVC. We also identified a region containing a high density of estrogenconcentrating cells located medial to HVC [we call this region paraHVC (pHVC)], and T also increased the volume of pHVC. pHVC also contained numerous X-projecting neurons, but few if any RA-projecting neurons. Double-labeling analysis revealed the RA-projecting neurons did not accumulate estrogen, a small percentage of X-projecting neurons in HVC accumulated estrogen, and the majority of X-projecting neurons in pHVC showed heavy accumulation of estrogen. The data reported here and in our previous article suggest distinct roles for gonadal steroids within the HVC-pHVC complex: estrogens are concentrated by neurons that project to a striatal region that influences vocal production during song learning (X), whereas androgens are concentrated primarily by neurons that project to a motor region that is involved in vocal production during both song learning and the recitation of already-learned song (RA). © 1995 John Wiley & Sons, Inc.     

Auditory-vocal cholinergic pathway in the songbird brain

Male zebra finches learn to imitate a tutor's song through auditory and motor learning. The two main song control nuclei in the zebra finch forebrain, the higher vocal center (HVC) and the robust nucleus of the archistriatum (RA), receive cholinergic innervation from the ventral paleostriatum (VP) of the basal forebrain which may play a key role in song learning. By injecting neuroanatomical tracers, we found a topographically segregated pathway from nucleus ovoidalis (Ov) to VP that in turn projects in a topographic fashion to HVC and RA. Ov is a major relay in the main ascending auditory pathway. The results suggest that the cholinergic neurons in the VP responsible for song learning are regulated by auditory information from the Ov.     

An in vitro study of long-term potentiation in the carp (Cyprinus carpio L.) olfactory bulb

Long-term potentiation (LTP) of synaptic transmission is considered a cellular mechanism for neural plasticity and memory formation. Previously, we showed that in the carp olfactory bulb, LTP occurs at the dendrodendritic mitral-to-granule cell synapse following tetanic electrical stimulation applied to the olfactory tract, and suggested that it is involved in the process of olfactory memory formation. As a first step towards understanding mechanisms underlying plasticity at this synapse, we examined the effects of various drugs (glutamate and GABA receptor agonists and antagonists, noradrenaline, and drugs affecting cAMP signaling) on dendrodendritic mitral-to-granule cell synaptic transmission in an in vitro preparation. Two forms of LTP are involved: a postsynaptic form (tetanus-evoked LTP) and a presynaptic form. The postsynaptic form is evoked at the granule cell dendrite following tetanic olfactory tract stimulation and is suppressed by the NMDA receptor antagonist, D-AP5, enhanced by noradrenaline, and occluded by the metabotropic glutamate receptor agonist, trans-ACPD. The presynaptic form occurs at the mitral cell dendrite following blockade of the GABA_A receptor by picrotoxin and bicuculline, or via activation of cAMP signaling by forskolin and 8-Br-cAMP.     

Song-selective auditory input to a forebrain vocal control nucleus in the zebra finch

Neurons in nuclei on the motor pathway for vocalizations in songbirds are known to responses in one such nucleus, robustus archistriatalis (RA), were characterized by making multi-unit recordings in awake and anesthetized adult male zebra finches and in birds that had received lesions of the input to RA from the lateral part of the magnocellular nucleus of the anterior neostriatum (LMAN) or the Higher Vocal Center (HVC). In awake birds, RA neurons have a high level of spontaneous activity and vigorous auditory responses to song stimuli. Significantly greater responses are seen to the bird's own song (BOS) than to BOS played in reverse (REV) or to the songs of conspecifics (CON). Under ketamine-xylazine anesthesia, spontaneous activity is reduced, response latency increases and responses to BOS, REV and CON are indistinguishable. Responses obtained under urethane anesthesia are similar to those seen in awake birds. Thus, the pattern and selectivity of auditory responses in RA depend on the animal's state. Auditory responses in RA are qualitatively unchanged following lesion of the input to RA from LMAN, indicating that this pathway is not required for the sensory processing that underlies the preference for BOS on the vocal production pathway. Our results show that an input other than that from LMAN must be primarily responsible for auditory responses in RA. The direct projection form HVC is the most likely pathway by which song selective auditory information arrives in RA, since lesioning HVC abolished auditory responses in RA. © 1993 John Wiley & Sons, Inc.