剥夺性弱视猫外侧膝状体c-fos基因及Fos蛋白表达

为研究生后关键期内,正常猫及剥夺性弱视猫外侧膝状体神经元功能形态的变化规律,对正常视发育敏感期的幼猫行左眼睑缝合术,造成剥夺性弱视模型,采用Nissl染色法及电镜观察正常猫及剥夺性弱视猫外侧膝状体神经元的形态改变,并用免疫组化和原位杂交技术检测Fos蛋白及cfos基因的表达情况。结果显示:(1)剥夺猫剥夺层外侧膝状体神经元的截面积比非剥夺层及正常猫的明显变小,差异有显著性(P<0.05);(2)超微结构显示:剥夺性弱视猫的剥夺层出现大量变性的细胞,剥夺4周时最为显著;(3)正常猫外侧膝状体神经元Fos蛋白和cfos原位杂交的阳性细胞数及OD值随着时间的延长而降低。同龄猫剥夺层外侧膝状体Fos蛋白和cfos原位杂交阳性细胞数及OD值较正常猫减少(P<0.05)。结果提示:猫视觉的可塑性敏感期为生后4周到8周。剥夺性弱视猫外侧膝状体剥夺层及非剥夺层神经元形态及功能与正常猫相比较均发生改变。Fos法可以成为衡量弱视猫外侧膝状体兴奋性状态与形态学定位相结合的实验方法,但必须注意神经可塑性对其的影响。     

切割穹窿海马伞大鼠海马IGF2及其受体IGF2R蛋白的表达变化

目的:观察穹窿海马伞切割后不同时间点海马胰岛素样生长因子2(insulin-like growth factor,IGF2)及其受体IGF2R蛋白的表达变化及定位。方法:应用ELISA、Western blot和免疫荧光组织化学方法检测海马内IGF2及其受体IGF2R蛋白,以及齿状回门区和颗粒下层中IGF2/Hoechst和IGF2R/Hoechst阳性细胞的数量及形态学变化。结果:(1)ELASA结果显示:IGF2在切割后7 d表达开始上升,14 d达最高水平,随后缓慢下降,28 d时降至正常水平。(2)Western blot结果显示:IGF2R也存在一个相应的表达升高与消退的过程,说明两者具有明显的相关性。(3)免疫荧光染色结果显示:正常组海马齿状回门区和颗粒下层IGF2及其受体IGF2R阳性细胞的数量较少,切割穹窿海马伞后第3 d数量稍有增多,但差异不明显;7 d时阳性细胞明显增多;14 d时阳性细胞继续增多,并达到最高水平;21 d后阳性细胞的数量开始下降,28 d时接近正常组水平。结论:切割穹窿海马伞后IGF2及其受体IGF2R的高表达可能与海马神经再生中抑制神经干细胞和放射状胶质细胞增殖,从而启动其向神经元等分化有关。     

磷酸化PKCγ在正常小鼠脑内的免疫组织化学定位

为了研究磷酸化的蛋白激酶Cγ(pPKCγ)在小鼠脑内的区域分布,为进一步了解其在脑内的功能提供线索。我们将BALB/c小鼠脱臼处死,灌流取脑,行免疫组织化学染色,观察pPKCγ阳性反应产物在脑内的分布。观察到pPKCγ阳性产物主要见于神经元的胞浆和突起中,在正常小鼠脑内表达广泛。仅很少量胶质细胞被染色,着色浅淡。海马CA1区锥体细胞,小脑的浦肯野氏细胞,大脑新皮质V层细胞,边缘前皮质、岛皮质的深层细胞以及前梨皮质的颗粒层细胞,外侧嗅束核、杏仁基底外侧核和杏仁外侧核的神经元,以及穹窿、锥体束纤维等均有强或较强的pPKCγ表达;吻侧丘脑大多数核团,尾侧丘脑的内侧膝状体核及外侧膝状体的背侧核,脑干耳蜗背侧核的表浅部位,三叉神经感觉核簇及巨细胞网状结构神经元中均有弱阳性表达。本实验研究揭示正常状态下小鼠脑内pPKCγ表达广泛,但有区域特异性,提示PKCγ可能参与正常状态下脑内部分脑区/核团神经元的功能活动。     

大鼠束缚后脑内Fos蛋白的表达

目的探讨大鼠束缚后对大鼠脑内Fos蛋白表达的影响。方法将大鼠束缚于小的塑料桶内1、3或6h,于解束后30min处死,脑组织进行Fos蛋白免疫组织化学染色。结果Fos阳性神经元表达于1．前脑：扣带回、新皮质(尤其是第3和5层)、外侧隔核、杏仁中央核;2．间脑：下丘脑视前区、下丘脑外侧区、视上核、室旁核、第三脑室室周区、弓状核、丘脑室旁核、外侧膝状体、内侧膝状体;3．脑干：中脑的上丘视性层、中脑导水管周围灰质、下丘的皮质部;脑桥的臂旁外侧核、蓝斑、A5区;延髓的耳蜗核、延髓内脏带(MVZ)等处。Fos表达的时问规律是束缚1h最高,3h次之,6h最少。结论大鼠被束缚后全脑多处核团的神经元发生不同程度的Fos反应,随着束缚时间的延长,动物产生适应性,Fos表达减少。     

视神经切断诱导金黄地鼠脑内视觉通路小热休克蛋白27的表达

目的 观察成年金黄地鼠左侧视神经眶内切断术后，视交叉、视束、外侧膝状体以及上丘内小热休克蛋白27(small heat shock protein，HSP27)表达的变化。方法 免疫组织化学染色法及光密度测定。结果 在正常对照和手术对照组，双侧视交叉、视束、外侧膝状体和上丘未见明显免疫反应物，光密度值之间亦无显著差异。而在实验组，与左侧相比，右侧视交叉、视束、外侧膝状体和上丘免疫组织化学染色明显增强。术后1周，右侧脑内视觉通路可见免疫反应物明显沉着的阳性细胞，形态类似星形胶质细胞。统计学分析显示，视交叉、外侧膝状体和上丘左、右两侧的光密度差值在术后1周时最大，至术后第2周迅速降低，以后下降趋势减缓，到术后8周仍可见右侧光密度值高于左侧。结论 一侧视神经切断后，对侧视交叉、视束、外侧膝状体和上丘等区域均有HSP27表达的增强，并可持续至术后8周之久。提示上述区域HSP27表达增强与视觉通路的损伤有关，但其发生机理及生物学意义尚待进一步研究。     

小鼠生后不同发育阶段海马和丘脑组织中三叶因子3的表达

目的:了解小鼠生后不同时相海马以及丘脑组织中三叶因子3(TFF3)的表达。方法:取生后P0、P1、P3、P5、P7、P9、P11、P13、P15、P17、P19、P21、P23、P25、P27及成年昆明种小鼠全脑,参照小鼠脑图谱,进行石蜡包埋、切片厚6μm、H-E染色和TFF3免疫组织化学显色。另取不同时相小鼠海马组织液氮冻存,提取组织总RNA,RT-PCR检测TFF3 mRNA的转录水平。结果:TFF3在海马CA1、CA2、CA3、CA4及齿状回神经元的胞质与胞核中均有表达,随生后发育,胞质阳性信号增强,P15开始胞核呈阴性表达,且CA1~CA4区阳性神经元减少;丘脑内侧背核、外侧背核、缰内侧核、外侧膝状体背核、丘脑后核、丘脑腹后内侧核、外侧核、中央内侧核等也呈TFF3免疫反应阳性,且表达趋势与海马相似。随着个体的发育,P15后海马组织中TFF3 mRNA的表达量与P1~P13相比逐渐减少;海马CA2、CA3区TFF3平均光密度在P1~P15水平较高,P15最高,P15之后逐渐下降,成年最低。结论:小鼠海马和丘脑TFF3生后发育的变化,提示TFF3可能参与海马和丘脑各核团的发育。     

发育早期和成年大鼠背侧纹状体内CRF轴突终末的分布和变化

目的:探讨背侧纹状体(dorsal striatum)内促肾上腺皮质激素释放因子(CRF)阳性轴突终末和CRF表达的分布特征及年龄变化。方法:采用免疫组织化学、原位杂交、免疫印迹和体视学分析方法,观察分析出生后第1~21日龄(P1-21)及成年(P90)大鼠背侧纹状体内的CRF轴突终末及CRF蛋白含量。结果:背内、背外侧纹状体内含大量CRF轴突终末,背外侧纹状体内的CRF轴突终末更为丰富。这些终末集中位于纹状体的尾部区域,与纹状体主要神经元形成典型的环胞体支配。和成年比较,发育早期(P1-14)背侧纹状体内CRF轴突终末的密度较高(P0.05),CRF蛋白表达量以P7组相对最高(P0.05)。结论:发育早期背侧纹状体内富含CRF轴突终末,提示CRF是影响纹状体神经元生长发育的因子之一。     

金黄地鼠丘脑网状核视部的纤维联系

本实验采用顺行、逆行及跨神经元追踪技术,对金黄地鼠丘脑网状核视部的纤维联系进行了实验观察。一、正常金黄地鼠4只,制成尼氏和Loyez染色的连续切片各4套,观察丘脑网状核(RT)的正常位置形态和范围。二、将 ~3H-Proline和~3H-Fucose注人动物一侧眼球2只,存活期分别为10、15天)后,可见跨神经元标记于双侧RT的背尾侧部,但同侧标记甚少。三、将HRP分别注入丘脑后外侧核(LP)、外侧膝状体背核(LGd)和外侧膝状体腹核(LGv)(8只,存活期1天)后,分别在同侧RT的背尾侧份的背侧区、中份和腹侧区见有HRP标记神经元。四、将~3H-Proline和~3H-Leucine混合导入视皮质17区不同部位(3只,存活期1天)后,可见在各例的同侧RT的背尾侧部的整个吻尾范围内都有长形的标记点。当注射17区尾侧时,标记部位靠背侧,而注射区越近吻侧时,标记点亦越靠腹侧。五、将HRP注入上丘(6例)时,见RT有极少量标记。本文认为,RT的背尾侧部为核的视部,因为它与视皮质及一些已知的与视觉有关的核团,如后外侧丘脑核、外侧膝状体背核和腹核等都有联系;同时,由于它们之间有局部点对点的定位关系,故此核可能与特定的、有局部定位的视信息的调节有关。     

缝隙连接蛋白43和黄体生成素受体在小鼠卵巢中的表达

目的 观察小鼠卵泡发育过程中缝隙连接蛋白43（Cx43）和黄体生成素受体（LHR）在小鼠卵巢中的表达以及黄体生成素(LH)对卵巢Cx43表达的影响,为这两种分子与卵泡发育的关系提供实验依据。 方法 选择出生后1d、4d、7d、2周、3周、4周、6周、8周龄雌性C57小鼠共8组,每组10只,取卵巢。HE染色观察卵巢形态、卵泡发育并测量颗粒细胞体积分数。免疫组织化学和Western blotting观察卵巢组织中Cx43及LHR的表达,Western blotting检测不同浓度黄体生成素（LH）孵育后对卵巢Cx43表达的影响。 结果 HE染色显示,出生1d小鼠卵巢中见原始卵泡,出生7d卵巢内出现初级卵泡,2周时出现窦前卵泡和少量窦卵泡,3周、4周时,出现较多大的窦卵泡,6～8周时出现黄体。卵泡颗粒细胞体积分数在2周后的卵巢中明显增加。Cx43表达在各阶段卵泡的颗粒细胞胞膜上,LHR表达在卵泡膜细胞、颗粒细胞及卵母细胞胞质中。Cx43和LHR出生后2周卵巢中的表达开始明显增加,并随卵泡发育表达逐渐增强,在3周、4周、6周和8周维持相对较高水平。LH体外干预可增加卵巢组织Cx43的表达。 结论 Cx43和LHR在卵泡发育中发挥重要作用,LH可能通过LHR促进卵巢卵泡颗粒细胞Cx43的表达。     

人外侧膝状体的血液供应及其临床意义

目的：为外侧膝状体（LGB）缺血所致的视野缺损提供形态学依据。方法：手术显微镜下观察成人和胎儿脑的LGB动脉的来源和微血管构筑,部分脑标本用组织切片方法观察营养LGB动脉的粥样硬化病理改变。结果：LGB营养动脉第一级来自颈内动脉和大脑后动脉,二级为脉络丛前动脉、脉络丛后外动脉和丘脑膝状体动脉,三级构成LGB的小动脉。50岁以上的标本,LGB的一、二级动脉有硬化改变的占88％,二级小动脉被阻塞占10％。结论：二级动脉在LGB内有各自的供血区,脉络丛前动脉是供应LGB前部和外侧部的唯一动脉,大脑后动脉营养LGB的其余部分。不同动脉的阻塞可导致不同种类的视野改变,是视野缺损的原因之一。     

Transient expression of somatostatin receptors in the rat visual system during development.

The ontogeny of somatostatin receptors in the rat visual system was studied by auto-radiography, using [125I-Tyr0,DTrp8]S14 as a radioligand. The binding sites showed high affinity for somatostatin and somatostatin analogues, and were regulated by GTP as early as day 16 of fetal life (E16), indicating that they represent functional somatostatin receptors. The density of somatostatin receptors was quantified by computerized image-analysis of film autoradiograms, and by grain counting on emulsion-coated slides. During fetal life, somatostatin receptors were observed in the retina, optic nerve, optic chiasma, optic tract, and lateral geniculate nucleus. The highest densities of somatostatin receptors were measured from E16 to E18 in the retina and primary optic pathways. During the first postnatal days, the density of somatostatin receptors decreased dramatically in the retina. In both the optic pathways and dorsal lateral geniculate nucleus, somatostatin receptors gradually disappeared, and the levels of somatostatin receptors were almost undetectable at postnatal day 21 (P21). Conversely, the density of somatostatin receptors remained stable in the ventral lateral geniculate nucleus during the early postnatal life (P0-P7). The timing of expression and the localization of somatostatin receptors in the developing visual system suggest that the immature ganglion cells are responsible for the expression of these evanescent somatostatin receptors. After eye opening, the distribution patterns of somatostatin receptors in the retina and the lateral geniculate nucleus were similar to those observed in adults. In particular, from P14 onwards, somatostatin receptors were concentrated in the inner plexiform layer and, to a lesser extent, in the ganglion cell and photoreceptor layers. In the ventral lateral geniculate nucleus, a heterogeneous distribution of somatostatin receptors was noted, the highest densities being found in the intergeniculate leaflet and the medial zone limiting the parvo-magnocellular interface. The distribution of somatostatin receptors in the retina and the ventral lateral geniculate nucleus after the second postnatal week, together with the presence of somatostatin-like immunoreactive elements in these structures, provide support for the involvement of somatostatin as a neurotransmitter or neuromodulator in the visual system of the adult rat. Conversely, the transient expression of somatostatin receptors observed before maturation and complete organization of the optic pathways suggests that somatostatin plays a trophic role during development of the visual system.     

Some aspects of the modular organization of the primary visual cortex of the cat: Patterns of cytochrome oxidase activity

The distribution of the enzyme cytochrome oxidase (CO) in continuous series of parasagittal sections from field 17 and frontal sections of the dorsal nucleus of the lateral geniculate body (LGB) from normal kittens and adult cats was studied. In all cats apart from neonates, layer IV showed regularly alternating areas with above-background levels of CO activity (“spots”). There was a significant increase in the contrast of the “spots” from days 13 to 21, which was followed by a significant decrease from days 48 to 93. These changes coincided with ontogenetic changes in the level of visual system plasticity. There were no differences in CO activity between layers A and A1 of the dorsal nucleus of the LGB. It is suggested that the non-uniform distribution of the level of functional activity of neurons in field 17 reflects the formation of columnar cortical structures during the critical period of postnatal ontogenesis. __________ Translated from Morfologiya, Vol. 132, No. 5, pp. 28–33, September–October, 2007.     

Postnatal development of 3H-rauwolscine binding sites in the dorsal lateral geniculate nucleus and the striate cortex of the tree shrew (Tupaia belangeri)

Summary Noradrenaline has been shown to play an important role within the visual system of the brain. To analyze the postnatal development of alpha₂-noradrenergic receptors in the visual system of tree shrews, we localized and quantified binding sites for the antagonist [³H]-rauwolscine by in vitro-autoradiography in the dorsal lateral geniculate nucleus and the striate cortex at different postnatal ages. At birth, the dorsal lateral geniculate nucleus is only slightly labeled by [³H]-rauwolscine. During the postnatal period, the number of binding sites increases to reach a maximum around postnatal day 20. Since the young tree shrews open their eyes at approximately day 19, it appears that this high concentration of alpha₂-adrenoceptors is related to eye opening. In the adult animal, [³H]-rauwolscine labeling shows a laminated pattern in the dorsal lateral geniculate nucleus. Laminae 1, 2, and 3 are more strongly labeled than laminae 4, 5, and 6. In the striate cortex, the pattern of [³H]-rauwolscine-binding sites changes dramatically during the early postnatal period. Immediately after birth, there is only one layer, located within the subplate zone, which is labeled. From postnatal day 5 onwards, all cortical layers which can be distinguished on histologically stained sections reveal [³H]-rauwolscine-binding sites, but in layer IV, which is known to receive major inputs from the dorsal lateral geniculate nucleus, there is very little labeling during the first two postnatal weeks. In this layer, a large number of [³H]-rauwolscine-binding sites occurs between postnatal day 15 and 20, that is slightly before and around the time of eye opening. From this time onwards, the pattern of [³H]-rauwolscine binding in the striate cortex is very similar to that in the adult, where all layers are labeled although to different degrees. Since around postnatal day 20, maximal numbers of [³H]-rauwolscine binding sites are present in the dorsal lateral geniculate nucleus and a large number of these binding sites also emerges in layer IV of the striate cortex, alpha₂-noradrenergic receptors are probably important for processes related to the opening of the eye and/or for the visual system to function.     

Subcortical projections to the lateral geniculate body in the rat

Summary The subcortical projections to the lateral geniculate body (LGB) in the rat were studied by means of discrete HRP iontophoretic deposits in the dorsal or the ventral LGB; the labelling was compared to that resulting from HRP deposits in neighboring nuclei.After injecting HRP in the dorsal LGB, labelled cells appeared bilaterally in the ventral LGB, pretectum, superior colliculus, lateral groups of the dorsal raphe nucleus and locus coeruleus. Ipsilaterally, labelled cells were found in the lateral posterior thalamus, nucleus of the posterior commissure and deep mesencephalic reticular nucleus.After injecting HRP into the ventral LGB, labelled cells were observed bilaterally in the pretectum, superior colliculus and dorsal raphe nucleus (lateral groups). Contralateral labelling appeared in the ventral LGB and parabigeminal nucleus. Ipsilateral labelling was found in the zona incerta, lateral posterior thalamus, lateral and medial mesencephalic reticular formation, vestibular and dorsal tegmental nuclei.These findings provide evidence of subcortical projections to the LGB arising in visually-related areas as well as extravisual areas, which might be related to the LGB boutons that survive complete cortical and retinal ablations.     

Molecular mechanisms of neuronal death in the dorsal lateral geniculate nucleus following visual cortical lesions

We investigated the molecular mechanisms of cell death in the dorsal lateral geniculate nucleus of the rat, following suction lesion of the visual cortex at birth or in the third postnatal week, using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) technique and immunohistochemistry for caspase-3, -7, -8, and cleaved poly(ADP-ribose) polymerase.Following lesion at birth, TUNEL-positive neurons were found in the dorsal lateral geniculate nucleus between 24 h and 3 days after lesion, with a peak on the second day. Shorter survival times (12-18 h) resulted in labeling of very few neurons in dorsal lateral geniculate nucleus and of several neurons in the perilesional cortex. Activated caspase-3 was expressed from the first to the third days after lesion, whereas cleaved poly(ADP-ribose) polymerase and activated caspase-8 were expressed on the second and third day. Activated caspase-7 was expressed mainly in pretectal nuclei. Caspase-3 activation coincided with the appearance of TUNEL-positive profiles, but decreased earlier than TUNEL. In the ipsi- and contralateral cerebral cortex, all parameters were unchanged. In animals lesioned in the third week, rare apoptotic thalamic neurons were detected as TUNEL- and activated caspase-3-positive profiles 2 days after cortical ablation, and were still present 1 week after lesion.Thus, early target ablation has dramatic effects on neonatal thalamic neurons, which die following activation of caspases 3 and 8. In contrast, cortical neurons are relatively unaffected by target deprivation. Compared with early lesions, late lesions induce a limited thalamic cell death, that persists over time.     

Lack of 5-HT(1B) receptor and of serotonin transporter have different effects on the segregation of retinal axons in the lateral geniculate nucleus compared to the superior colliculus

We have shown previously that raised levels of serotonin (5-hydroxytryptamine or 5-HT) during development prevent retinal ganglion cell axons from segregating into eye-specific regions in their principal targets: the superior colliculus and the dorsal lateral geniculate nucleus. Possible mediators of 5-HT in this system include its plasma membrane transporter, which is transiently expressed by a sub-population of retinal ganglion cells, and the presynaptic 5-HT(1B) receptor carried on retinal ganglion cell axons. We analysed the retinal projections of 5-HT(1B) knockout (n=15), serotonin transporter knockout (n=14), serotonin transporter/5-HT(1B) double knockout (n=4) and monoamine oxidase A/5-HT(1B) double knockout (n=3) mice.In all four different knockout mice, the ipsilateral retinal projection to the superior colliculus was more diffuse and lost its characteristic patchy distribution. The alterations were most severe in the serotonin transporter knockout mice, where the ipsilateral retinal fibres covered the entire rostrocaudal and mediolateral extent of the superior colliculus, whereas in the 5-HT(1B) and double knockout mice, fibres retracted from the caudal and lateral superior colliculus. Abnormalities in the 5-HT(1B) knockout mice appeared only after postnatal day (P) 4. Treatment with parachlorophenylalanine (at P1-P12) to decrease serotonin levels caused an exuberance of the ipsilateral retinal fibres throughout the superior colliculus (n=9). In the dorsal lateral geniculate nucleus in contrast, the distribution and size of the ipsilateral retinal projection was normal in all four knockout mice. In the serotonin transporter knockout mice however, the contralateral retinal fibres failed to retract from the mediodorsal dorsal lateral geniculate nucleus, an abnormality that was reversed by early treatment with parachlorophenylalanine and in the serotonin transporter/5-HT(1B) double knockout.OUR OBSERVATIONS INDICATE: (1) that the lack of 5-HT transporter and the associated changes in 5-HT levels impair the segregation of retinal axons in both the superior colliculus and the dorsal lateral geniculate nucleus; (2) that 5-HT and 5-HT(1B) receptors are necessary for the normal refinement of the ipsilateral retinal fibres in the superior colliculus, but are not essential for the establishment of eye-specific segregation in the thalamus. Thus, both an excess and a lack of 5-HT affect the refinement of the superior colliculus retinal projection, while the establishment of eye-specific patterns in the dorsal lateral geniculate nucleus appears not to be sensitive to the lack of 5-HT or 5-HT(1B) receptors.     

Does the development of the perigeniculate nucleus support the notion of a hierarchical progression within the visual pathway?

The development of the visual pathway has been extensively studied. However, despite of the importance of the perigeniculate nucleus within this pathway, there is a lack of information concerning its development. The present study examined the dendritic development of perigeniculate nucleus cells using single cell injections in 400-500 microm thick fixed brain slices from kittens of different ages between postnatal day 0 and postnatal day 125. A total of 189 perigeniculate nucleus cells were reconstructed from serial sections for qualitative and quantitative analysis. Cells during the first month were characterized by an abundance of branch points and appendages. There was a significant (P>0.05), albeit variable, increase in the number of branch points and appendages up to about postnatal day 12 after which the numbers were rapidly reduced over the next two weeks. Similarly, appendage numbers significantly increased over the first two weeks until postnatal day 17 and then fell to near adult levels by postnatal day 34. The majority of branch points and appendages occur within 100-200 microm of the soma (10-30% of the dendritic diameter). The data indicate that perigeniculate nucleus dendritic maturation lags shortly behind that of the retina but may precede that of its dorsal thalamic target, the lateral geniculate nucleus. Thus, it may be that the earlier maturation of the perigeniculate nucleus and its inhibitory input is a necessary requirement for the proper development of retinogeniculate and corticothalamic topographic maps within the dorsal lateral geniculate nucleus and perigeniculate nucleus.     

Nucleus- and species-specific properties of the slow (<1 Hz) sleep oscillation in thalamocortical neurons

The slow (<1 Hz) rhythm is an electroencephalogram hallmark of resting sleep. In thalamocortical neurons this rhythm correlates with a slow (<1 Hz) oscillation comprising recurring UP and DOWN membrane potential states. Recently, we showed that metabotropic glutamate receptor activation brings about an intrinsic slow oscillation in thalamocortical neurons of the cat dorsal lateral geniculate nucleus in vitro which is identical to that observed in vivo. The aim of this study was to further assess the properties of this oscillation and compare them with those observed in thalamocortical neurons of three other thalamic nuclei in the cat (ventrobasal complex, medial geniculate body; ventral lateral nucleus) and two thalamic nuclei in rats and mice (lateral geniculate nucleus and ventrobasal complex). Slow oscillations were evident in all of these additional structures and shared several basic properties including, i) the stereotypical, rhythmic alternation between distinct UP and DOWN states with the UP state always commencing with a low-threshold Ca2+ potential, and ii) an inverse relationship between frequency and injected current so that slow oscillations always increase in frequency with hyperpolarization, often culminating in delta (delta) activity at approximately 1-4 Hz. However, beyond these common properties there were important differences in expression between different nuclei. Most notably, 44% of slow oscillations in the cat lateral geniculate nucleus possessed UP states that comprised sustained tonic firing and/or high-threshold bursting. In contrast, slow oscillations in cat ventrobasal complex, medial geniculate body and ventral lateral nucleus thalamocortical neurons exhibited such UP states in only 16%, 11% and 10% of cases, respectively, whereas slow oscillations in the lateral geniculate nucleus and ventrobasal complex of rats and mice did so in <12% of cases. Thus, the slow oscillation is a common feature of thalamocortical neurons that displays clear species- and nuclei-related differences. The potential functional significance of these results is discussed.     

Developmental regulation of brain nitric oxide synthase expression in the ferret thalamic reticular nucleus

We have found that cells in the ferret thalamic reticular nucleus (TRN) express brain nitric oxide synthase (bNOS) in a transient pattern during early postnatal development. Similar to our previous findings in the lateral geniculate nucleus (LGN), bNOS expression in the TRN is first observed at postnatal day 7 (P7) and continues to P35. Quantitative measures show a significant change in the relative numbers of bNOS+ cells from P7–P35, and suggest there is a transition in morphology from a bipolar shape with two primary dendrites, to a more complex, multipolar arrangement. During TRN development, the pattern of bNOS expression shifts from the somatodendritic localization seen during the first postnatal month to expression within axon fibers in the adult. Expression of bNOS within TRN cells demonstrates an additional source of nitric oxide in the developing visual thalamus, perhaps indicating a common function for thalamic nitergic neurons as cellular mediators in the establishment of central topography both in the LGN and the TRN.