大鼠三叉神经中脑核神经元中枢突在脑干内投射的光、电镜观察(中脑核-丘脑投射通路研究之一)

为了进一步搞清三叉神经中脑核(Vine)向丘脑的投射通路,本文首先用HRP跨节追踪技术在大鼠研究了接受咬肌本体觉传入的Vme神经元中枢突在脑干内的终止情况。结果证明它除终止于三叉运动核及三叉上核外,主要终止于面神经核水平的三叉神经脊束核吻侧亚核背内侧部(Vodm)及邻接的外侧网状结构(LRF)。在电镜观察到Vme神经元中枢突终末在Vodm区主要和该区内的树突形成突触。并观察到这些终末接受另外来源的神经终末的突触前控制。     

GAD67-GFP基因敲入小鼠三叉上核内向三叉神经运动核投射的GFP阳性神经元表达c-fos的研究

本文综合应用逆行束路追踪(将四甲基罗达明-TMR注入一侧三叉神经运动核)和免疫荧光组织化学三重标记技术,在激光共聚焦显微镜下对谷氨酸脱羧酶67-绿色荧光蛋白(GAD67-GFP)基因敲入小鼠在口周部给予伤害性刺激时,三叉上核(Vsup)内向对侧三叉神经运动核(Vmo)投射的呈GFP阳性的GABA能神经元表达c-fos的情况进行了研究。结果显示:(1)Vsup内可观察到许多GFP阳性神经元,细胞较小;(2)也可观察到许多TMR或c-fos单标神经元较密集地分布于Vsup内,其中c-fos阳性产物只见于神经元的胞核,在胞浆内未见表达;(3)在激光共聚焦显微镜下可进一步观察到部分神经元同时呈GFP/TMR、TMR/c-fos、GFP/c-fos双重标记或GFP/TMR/c-fos三重标记。其中GFP/TMR双标神经元分别占GFP或TMR阳性神经元的17.8%和19.2%;TMR/c-fos双标神经元分别占TMR或c-fos阳性神经元的34.9%和31.3%;GFP/c-fos双标神经元分别占GFP或c-fos阳性神经元的21.2%和20.5%;而GFP/TMR/c-fos三标神经元分别占GFP、TMR或c-fos阳性神经元的11.1%、12%和10.8%。以上结果表明小鼠Vsup内部分GABA能神经元可接受来自同侧的口面部伤害性信息,并对这些信息进行整合后,直接发出投射纤维至Vmo;故Vsup内部分GABA能运动前神经元可能参与口面部伤害性反射局部环路的构成。     

大鼠三叉神经脊束核吻侧亚核背内侧部及邻接的外侧网状结构的传出投射——WGA-HRP顺行追踪研究(中脑核—丘脑投射通路研究之二)

在已探明三叉神经中脑核神经元中枢突向三叉神经脊束核吻侧亚核的背内侧部(Vodm)及邻接的网状结构(LRF)投射的基础上,本文作者用WGA—HRP顺行标记法追踪了Vodm和其邻接的LRF传出投射的终止部位,以期探索Vme—丘脑通路中第三级神经元的所在。结果发现Vodm及邻接的LRF除投射到一些脑神经运动核、臂旁核、下橄榄主核腹肢内端外,还发现了前人未曾注意到的沿三叉神经感觉主核内缘存在且向腹侧伸延的一个带状区内有浓密的标记终末终止。此标记终末带区在上橄榄核背侧,三叉神经运动核腹侧以及三叉神经感觉主核的背内侧部等处增大,而上橄榄核背侧及三叉运动核腹侧的终末区以往并无人注意到在此有与之相应的核团。     

大鼠沿三叉神经感觉主核内缘的带状区向丘脑的投射—HRP法研究(中脑核—丘脑投射通路研究之三)

本文作者在系统地探索三叉神经本体觉传递的中枢通路工作中,曾证明做为初级传入神经元的三叉神经中脑核(Vme)神经元的中枢突主要投射于三叉神经脊束核吻侧亚核背内侧部及邻接的网状结构(Vodm-LRF)区。而此区的传出纤维又向沿三叉神经感觉主核(Vp)内缘伸延的一个带状区投射。此带状区腹侧达上橄榄核背侧,背侧达三叉上核及臂旁核,形成浓密的标记终末带。为了追踪此带状终末区的神经元向何处投射以及它在Vme—丘脑投射通路中的地位,本实验将HRP溶液注入于丘脑腹后核的不同部位进行了逆行追踪。结果表明,上述带状区的神经元主要投射到丘脑腹后内侧核的腹内侧部。结合本研究的一、二两篇的结果,作者推论传递面、口部本体觉刺激的中枢通路可能是由Vme,Vodm—LRF,沿Vp内侧延伸的带状区和丘脑等四级神经元组成。本文并根据实验结果进行了有关问题的讨论。     

VGluT1样阳性终末在大鼠三叉神经本体觉中枢通路的第三级核团-“带状区”内的分布及来源

本文综合运用免疫组织化学、逆行束路追踪和免疫荧光组织化学双标技术,对Ⅰ型囊泡膜谷氨酸转运体(VGluT1)样阳性终末在大鼠三叉神经本体觉中枢通路的第三级核团-“带状区”内的分布和来源、以及与向丘脑腹后内侧核(VPM)投射的神经元之间的联系进行了研究。结果显示:(1)在组成“带状区”的四个核团,即三叉神经感觉主核背内侧部(Vpdm)、三叉上核尾外侧部(Vsup-CL)、三叉神经运动核腹侧区(AVM)和上橄榄核背侧区(ADO)内,均可观察到大量的VGluT1样阳性终末呈密集分布;(2)将逆行追踪剂四甲基罗达明(TMR-DA)注入丘脑VPM后,在上述核团内均可观察到大量的TMR逆标神经元的胞体和突起;(3)在激光共聚焦显微镜下可观察到部分VGluT1样阳性终末包绕在TMR逆标神经元的胞体或树突周围,并与之形成密切接触;(4)当切断三叉神经感觉根7d后,光学显微镜下可观察到手术侧Vpdm内的VGluT1样阳性产物明显下降,其他三个核团内无明显变化,但当切断三叉神经运动根8周后,则在手术侧Vsup内观察到VGluT1样阳性产物几乎完全消失,而Vpdm、AVM和ADO内并无变化。以上结果提示:(1)大鼠三叉神经本体觉中枢通路的第三级核团-“带状区”的四个核团内均有大量的VGluT1样阳性终末分布,但它们的来源有所不同,其中Vpdm内的VGluT1样阳性终末来自于外周的三叉神经节细胞,Vsup内的VGluT1样阳性终末来自于三叉神经中脑核神经元,而AVM和ADO内的VGluT1样阳性终末可能来自于中枢其他核团;(2)口面部本体感觉信息从“带状区”向丘脑VPM传递的过程中,谷氨酸发挥着重要作用。     

NEURAL PATHWAYS OF TRIGEMINAL PROPRIOCEPTIVE AFFERENTS COORDINATE ORAL MOTOR BEHAVIORS

Neural pathways and synaptic connections from the trigeminal mesencephalic nucleus (Vme) neurons to the cranial motor nuclei were studied in the rat using double labelling methodologies of intracellular Neurobiotin staining combined with retrograde horseradish peroxidase (HRP) transport, anterograde biotinylated dextran amine (BDA) tracing combined with retrograde HRP transport, and a dual fluorescent labelling of BDA anterograde combined tracing with Cholera Toxin B (CTB) retrograde transport. Direct projections and synapses were demonstrated from Vme neuronal boutons to motoneurons (MNs) of the trigeminal motor nucleus (Vmo), the hypoglossal nucleus (XⅡ) and the ambiguus nucleus (Amb). Indirect projections and pathways from Vme neurons to the cranial motor nuclei including Vmo, XⅡ, the facial nucleus (VⅡ) and the cervical spinal cord (C1～5) were seen to relay on their premotor neurons. The premotor neurons of above cranial motor nuclei were overlapped in bilateral premotor neuronal pool including the parvocellular reticular formation (PCRt) and its alpha division (PCRtA), the dorsomedial part of the spinal trigeminal nucleus oralis (Vodm), and interpolaris (Vidm), the medullary reticular nucleus dorsal division (MdD), the supratrigeminal region (Vsup) and the dorsomedial part of the principal trigeminal sensory nucleus (Vpdm). Synapses between Vme neuronal boutons and Vmo and XⅡ MNs and XII premotor neurons were predominantly asymmetric. There were four types of synaptic organizations, i.e. synaptic convergence; synaptic divergence presynaptic inhibition and afferent feedforward inhibition seen between Vme boutons and Vmo, XⅡ MNs and between Vme boutons and XⅡ premotor neurons. The results of present studies have demonstrated direct pathways from the trigeminal proprioceptive afferents to Vmo, XⅡ and Amb MNs, and indirect pathways from the trigeminal proprioceptive afferents to bilateral Vmo, XⅡ, VⅡ and C1～5 via their premotor neurons. It provides neuroanatomical network to elucidate trigeminal proprioceptive afferents coordinate oral motor behaviors.     

大鼠三叉神经本体觉中枢通路上第三级核团内PV样阳性终末与丘脑投射神经元的突触联系

目的 观察大鼠三叉神经本体觉中枢通路上第三级核团内Paralbumin样阳性轴突终末与丘脑投射神经元之间是否存在突触联系。方法 用HRP逆行追踪和包埋前免疫电镜相结合的双重标记法。将WGA-HRP注入丘脑腹后内侧核逆行标记投射神经元。结果 WGA-HRP注入丘脑腹后内侧核(VPM)后，WGA-HRP标记神经元主要分布在感觉主核背内侧部(Vpdm)、三叉上核尾外侧部(Vsup-CL)以及三叉神经运动核腹侧区(AVM)和上橄榄核背侧区(ADO)。电镜下可见PV样阳性神经元的轴突终末与WGA-HRP标记的胞体或者树突形成突触联系。另外PV阴性神经元的轴突终末也与WGA-HRP标记的胞体或树突形成突触联系，这些胞体或树突偶尔为PV阳性。结论 在三叉神经本体感觉信息从第三级神经元向丘脑腹后内侧核(VPM)传递的过程中，PV样阳性神经元可能通过突触传递机制而发挥作用。     

大鼠三叉神经脊束核吻侧亚核背内侧部向三叉神经中脑核的回返投射

既往的研究证明,由支配咬肌的三叉神经中脑核神经元到丘脑腹后内侧核存在着一条由四级神经元组成的传递本体觉信号的中枢通路．此通路的第二级神经元位于三叉神经脊束核吻测亚核背内侧部和邻接的小细胞网状核的一部分,第三级神经元存在于沿三又神经感觉主核内缘伸延的“带状区”。本研究将ＰＨＡ－Ｌ注入第二级神经元所在区域,不仅在“带状区”发现有很多标记终末,而且在三叉神经中脑核区域内也发现较密集的ＰＨＡ－Ｌ阳性终末,许多终末与中脑核神经无形成密切接触．对这种材料又向咬肌神经内注入ＨＲＰ,观察到有一些ＨＲＰ标记的中脑核神经元与ＰＨＡ－Ｌ标记终末接触．本研究结果提示,在三叉神经本体感觉通路中,由第二级神经元的核区向初级传入神经元发出有回返投射,并对其机能意义进行了讨论．     

大鼠三叉神经中脑核神经元细胞内HRP标记的研究

本文用电生理方法对大鼠三叉神经中脑核进行定位后将微电极插入该核的神经元,进行细胞内HRP注射。对53个标记神经元的形态、突起的行径、投射范围及其终末分支的特点和终止模式进行了研究。结果表明:(1)三叉神经中脑核神经元有单极、假单极、双极和多极神经元等四种类型,这些神经元有大有小,形状也多样;(2)单极和假单极神经元的突起行程长,投射广泛,侧支极其丰富。它们投射到中间神经元核团(三叉上核、三叉间核,桥延网状结构小细胞网状核等),运动核团(三叉运动核、外展神经副核、面神经副核等)和感觉核团(感觉主核背肉侧部、三叉脊束核吻侧亚核背内侧部等)。此外,还有个别突起投射到动眼神经核、滑车神经核和孤束中。(3)本文首次注意到,这些神经元在性质不同的核群其终末特点和终止模式不同,而在同类核群的各核中其终末特点和终止模式相似。(4)本文还观察到中脑核神经元的周围轴突发出侧支分布到三叉运动核。(5)本文首次提供了三叉神经中脑核神经元向感觉主核背内侧部、外展神经副核和面神经副核投射的资料。此外,本文还就三叉神经本体觉脑内传递通路进行了讨论。     

三叉神经初级传入纤维的中枢投射——HRP跨节追踪研究

分别向猫眶上神经、眶下神经和下牙槽神经的神经干内注射20％HRP(Toyobo,RZ 3.3)溶液,跨节追踪了三叉神经初级传入纤维在中枢内的分布。 1.三叉神经的初级传入纤维在中枢内都与三叉神经感觉核簇发生全面的联系。其中,眶上神经向三叉神经脊束核的尾侧亚核第Ⅰ～Ⅴ层都有大量的投射,而向吻侧,则标记终末只位于各亚核腹侧的极小范围内。眶下神经在三叉神经感觉核簇中的标记终末分布范围较大,以尾侧亚核的中央部和感觉主核腹侧2/3部的标记终末最为密集。下牙槽神经在尾侧亚核和吻侧亚核的标记终末数量和分布范围最大。 2.含有大量来自额部皮肤和上颌胡须的触觉传入纤维的眶上、眶下神经除向感觉主核投射外,也向其它各亚核特别是尾侧亚核有大量的投射。含有较大量痛觉传入纤维的下牙槽神经不仅向脊束核投射,在感觉主核的投射也是明显的。因而,确证了感觉主核接受触觉,脊束核接受痛温觉传入投射的传统看法是不符合实际的。 3.上述三神经都向尾侧亚核内侧相当于脊髄后角第Ⅴ层的区域有明显的投射。结合文献,本文作者支持此第Ⅴ层应归属于尾侧亚核的看法,并推论此区可能有三叉神经传入纤维和其它脑结构来源的纤维的汇聚。     

Serotonin-containing projections to the mesencephalic trigeminal nucleus of the cat

Background: It is well known that the mesencephalic trigeminal nucleus (MTN) neurons transmit somatosensory information from proprioceptors in the oral-facial region. Several mechanisms of sensory transduction in these specialized receptors have been proposed, but the neurotransmitters which are responsible for mediating proprioceptive information are still unknown. The current study concentrates on the distribution of one putative neurotransmitter system, serotonin (SER), in the cat MTN. A second objective was to clarify the location and sources of serotoninergic projections on the MTN neurons. Methods: To determine whether SER was localized in the MTN, the peroxidase-antiperoxidase (PAP) immunocytochemical technique was applied at light and electron microscopic levels in colchicine-treated animals. The origin of SER-containing fibers in the MTN was studied using a doublelabeling method combining retrograde transport with wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) and SER immunocytochemistry. Results: There were no SER-containing neurons in the MTN. The cell bodies of immunonegative MTN neurons were closely surrounded by fine SER-positive fibers and terminals. The labeled fibers were in most cases very thin and sometimes varicose. Ultrastructurally, direct synaptic contacts between SER-containing terminals and perikarya of MTN neurons of all sizes could be seen. The majority of SER-labeled structures were synaptic terminals in which the immunoreactive material was located within the small round clear as well as the small granular vesicles (diameter 50–80 nm) and a few large dense-cored vesicles (up to 150 nm). Retrograde tracing demonstrated that most of cells in the nuclei raphe dorsalis, pontis and magnus were WGA-HRP-labeled. Conclusions: These results indicated that MTN neurons received serotoninergic projections from the raphe nuclei of the brainstem. In light of these morphological data, it is concluded that the MTN of the cat is under the influence of SER-containing axons and this serotoninergic input may modulate MTN neuronal activity at the first synaptic relay. © 1995 Wiley-Liss, Inc.     

Neurons of the motor trigeminal nucleus project to the hypoglossal nucleus in the rat

Summary The hypoglossal nucleus (Mo12) contains motoneurons that innervate the tongue, while the motor trigeminal nucleus (Mo5) contains motoneurons that elevate or depress the mandible. Previous studies have revealed lateral and medial tegmental field neuronal afferents to the Mo12 adjacent to, but not within, the motor trigeminal nucleus (Mo5). The current studies demonstrate the presence of retrogradely labeled neuronal afférents to the Mo12 within the Mo5 produced by as little as 10 nl of Fast Blue (FB) injected into the Mo12. Retrograde labeling of Mo5 afferents to the Mo12 with injections of Diamidino Yellow (DY) combined with injections of FB into the lumbar spinal cord showed these neuronal afferents to the Mo12 are not part of the diffuse projections to motoneurons from the nucleus subcoeruleus. Retrograde labeling of Mo5 afferents to the Mo12 with DY combined with injections of FB into the masseter revealed these neuronal afferents to the Mo12 are not trigeminal motoneurons. These results indicate that Mo5 interneurons are part of the lateral tegmental field projections to the Mo12, and are likely to comprise part of the neural substrate coordinating the motor activity of the jaw and tongue.     

Dynorphin-A immunoreactive terminals on the neuronal somata of rat mesencephalic trigeminal nucleus

Dynorphin-A-like immunoreactivity was investigated in the rat mesencephalic trigeminal nucleus (Mes 5) at the light and electron microscopic levels. Dynorphin-A immunoreactive fibers and puncta, likely representing nerve terminals, were observed throughout rostrocaudal extension of the Mes 5 at the light microscopic level. Within the rostrocaudal extension, more abundant fibers and puncta were localized in the midbrain–pontine junction and pontine areas than in the midbrain area. At the electron microscopic level, dynorphin-A immunoreactive synapses were observed on the somata of Mes 5. Dynorphin-A-like immunoreactivity tended to be restricted to dense-cored vesicles in the synapses. These results suggest that dynorphin-A-containing fiber systems affect mastication through the Mes 5.     

刺激三叉上核引起三叉神经中脑核神经元的突触反应(英文)

目的:旨在研究三叉上核(Su5)对三叉神经中脑核(Me5)神经元的活动是否发挥着重要的调节作用,从而参与对颌运动的调节。方法:本研究通过全细胞电流钳技术,刺激生后30～43d大鼠脑片上三叉上核并记录Me5神经元反应。结果:Me5神经元静息膜电位为(-53.5±0.5)mV;所有Me5神经元在超极化和去极化时分别显示为内向、外向整流;同时去极化引起神经元放电。刺激三叉上核引起4种类型的Me5神经元的反应,即逆向动作电位、GABAA、AMPA/kainate和NMDA等受体介导的反应,这些反应各占32%、36%、20%和12%。钳制电位在-60mV左右时,诱发的GABA能突触后电位为(1.08±0.45)mV,膜电位水平时;刺激引起的AMPA/Kainate受体介导的电流大小为(0.98±0.51)mV;钳制电位在-45mV左右时,NMDA受体介导的谷氨酸电流为(2.40±0.75)mV。结论:三叉上核神经元可通过突触由GABA和谷氨酸信号系统调节Me5神经元活动。     

The morphology of neurons in trigeminal nucleus oralis projecting to the medullary dorsal horn (trigeminal nucleus caudalis): a retrograde horseradish peroxidase and Golgi study

This study demonstrates that trigeminal nucleus oralis, the most rostral subdivision of the spinal trigeminal nucleus, contains four morphologically distinct types of small neurons which project to the medullary dorsal horn (trigeminal nucleus caudalis) via descending intratrigeminal pathways. Using the retrograde transport of horseradish peroxidase following injections in the medullary dorsal horn, labeled small neurons with cell bodies ranging from 8-15 microns in diameter are found principally in the ventrolateral portion of the trigeminal nucleus oralis. Most neurons are labeled ipsilaterally throughout the entire rostrocaudal extent of the ventrolateral portion of the trigeminal nucleus oralis, but a few cells are also labeled contralaterally. From this aspect of the present study it can be concluded that a specific portion of the trigeminal nucleus oralis, i.e. the ventrolateral part, contains numerous small neurons which send descending projections to the medullary dorsal horn that could affect synaptic activity there. Utilizing both the methods of Golgi and retrograde horseradish peroxidase labeling four distinct types of small descending medullary dorsal horn projection neurons can be distinguished in the ventrolateral portion of the trigeminal nucleus oralis on the basis of their morphology and the distribution of their axons and dendrites. All four neuronal cell types are present throughout the entire rostrocaudal extent of the trigeminal nucleus oralis. Type I neurons are the most frequently labeled descending medullary dorsal horn projection neurons. They are concentrated in the medial 500-550 microns of the ventrolateral portion of the trigeminal nucleus oralis and display dendritic trees which occupy spherical domains approaching 300 microns in diameter. The unmyelinated axons of many of these cells arise either directly from the cell body or a primary dendrite and give rise to a single collateral within 50 microns of their site of origin. This collateral generates a fine axonal plexus within a portion of the dendritic arbor of the parent cell while the parent axon, without branching further, travels a short distance in the ventrolateral portion of the trigeminal nucleus oralis and enters a deep axon bundle. Type II neurons are the second most frequently labeled descending medullary dorsal horn projection neuron. They generate medial and lateral dendritic arbors which together span nearly the entire medial 500-550 microns of the ventrolateral portion of the trigeminal nucleus oralis. An unmyelinated axon emerges from the cell body and within 10-30 microns of its origin gives rise to two collaterals.(ABSTRACT TRUNCATED AT 400 WORDS)     

Dependence of electrical activity of neurons in rostral parts of spinal trigeminal nucleus on functional state of trigeminal Gasser ganglion

Unilateral injection of 100 μl 1% lidocaine into the trigeminal Gasser ganglion of narcotized rats produced a long-term moderation of the discharge rate of neurons in the ipsilateral (relative to the side of injection) rostral area of the spinal trigeminal nucleus. Activity of neurons in the contralateral rostral area of the spinal trigeminal nucleus was not blocked. Functional state of neurons in the trigeminal ganglion determines discharge activity of ipsilateral neurons of the spinal trigeminal nucleus. Activity of neurons in the contralateral rostral area of spinal trigeminal nucleus was not inhibited. Functional state of the cells in the trigeminal ganglion determines the character of electrical activity of neurons in the ipsilateral rostral area of spinal trigeminal nucleus. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 7, pp. 4–6, July, 2007     

A microiontophoretic study of the action of kainic acid and putative neurotransmitters in the rat mesencephalic trigeminal nucleus

The ‘excitotoxic’ hypothesis proposes that neurotoxic amino acids exert their effect through neuronal excitation (Olney, Ho &;Rhee, 1971).Colonnier, Steriade &;Landry (1979) have found that trigeminal mesencephalic neurons in the cat are resistant to the neurotoxic effect of kainic acid. In the present study it was found that the same neurons in the rat also resist the cytotoxic action of this amino acid. In addition, kainic acid, applied iontophoretically onto these neurons failed to alter their firing frequency. The resistance of these neurons to both neurotoxic and excitatory actions of kainic acid is consistent with the ‘excitotoxic’ hypothesis.Other putative neurotransmitters were applied by microiontophoresis on these neurons and none were found to alter their rate of discharge. Procaine however applied with relatively low ejecting currents consistently reduced their firing rates. The failure of the putative neurotransmitters tested to influence the rate of discharge of the trigeminal mesencephalic neurons suggests that the chemical synapses present on these neurons in the rat (Hinrichsen &;Larramendi, 1970) utilize another neurotransmitter from those tested. Alternatively the synapses might have a role other than the direct regulation of the firing frequency of these primary afferent neurons.     

Tyrosine kinase receptor immunoreactivity in trigeminal mesencephalic and motor neurons following transection of masseteric nerve of the rat

Neurotrophins are known to promote survival after neural injury. To determine the relative importance of tyrosine kinase receptors on the survival of axotomized trigeminal nuclear neurons, we examined the temporal expression profile of tyrosine kinase A, tyrosine kinase B and tyrosine kinase C receptors in the mesencephalic trigeminal nucleus and the motor trigeminal nucleus following transection of the masseteric nerve in rats. Axotomized neurons in these nuclei were retrogradely identified with FluoroGold. We found increase in tyrosine kinase A-immunoreactive mesencephalic trigeminal nucleus neurons in the second week after axotomy but no change in the number of tyrosine kinase A-immunoreactive motor trigeminal nucleus neurons. There was no change in the number of tyrosine kinase B-immunoreactive mesencephalic trigeminal nucleus neurons but the significant increase of tyrosine kinase B-immunoreactive motor trigeminal nucleus neurons throughout the period of observation (3 weeks) peaked at approximately 1 week after axotomy. There was no alteration in the number of tyrosine kinase C-immunoreactive mesencephalic trigeminal nucleus neurons but significant increase in tyrosine kinase C-immunoreactive motor trigeminal nucleus neurons observable by 4 days post-axotomy was followed by decline to levels lower than the control in 2 weeks. Temporal changes in the expression of individual tyrosine kinase receptors in mesencephalic trigeminal nucleus and motor trigeminal nucleus neurons following transection of the masseteric nerve suggest differential contribution of tyrosine kinase-specific neurotrophins to the survival of these neurons after axotomy.     

Radioautographic study of serotoninergic axon terminals in the rat trigeminal motor nucleus

The responses of center red ON and center red OFF ganglion cells of the isolated goldfish retina to a flickering stimulus light diminish by GABA. Without stimulation GABA blocks the maintained activity of the OFF cells. With a green flickering spot in the receptive field center, the green ON-response of the OFF cells becomes an OFF-response during GABA administration. It is concluded that, besides the common antagonistic green input, the receptive field center of these cells also has a synergistic green input, which is mediated by a pathway other than the center opponent red and green inputs.