在新型成年大鼠纵切脊髓片上骶髓后连合核神经元的盲膜片钳全细胞 …

本文介绍了一种新型的成年大鼠（５－８周龄）纵切脊髓片模型。此模型与传统的横切脊髓片的不同之处是可带有多条长达１０ｍｍ的后根。在体视显微镜下骶髓后连合核（ＤＣＮ）为一条透明的灰质带，极易与后角其它部位区分，因此最适合于对ＤＣＮ神经元的研究。应用盲膜片钳全细胞记录法，在此模型上研究了ＤＣＮ神经元自发的和后根刺激诱发的兴奋性突触后电位（ＥＰ－ＳＰｓ）。自发的和后根刺激诱发的快ＥＰＳＰｓ主要由非ＮＭＤＡ谷     

成年大鼠骶髓后连合核神经元对与伤害性信息传递和抑制有关的神经递质的反应──脊髓片盲膜片钳全细胞记录法研究(英文)

以成年大鼠脊髓片骶髓后连合核（DCN）为模型，应用盲膜片钳全细胞记录法，研究了DCN神经元对与伤害性信息传递和抑制有关的递质的反应。证明：谷氨酸在DCN神经元引起了由NMDA和非NMDA受体介导的内向电流；P物质激发的内向电流可被spantide或CP－99994阻断；GABA激发的外向电流由GABAA和GABAB受体介导；甘氨酸激发的外向电流可被士的宁完全阻断。本研究结果提示DCN神经元既表达兴奋性神经递质受体又表达抑制性神经递质受体，即谷氨酸和P物质介导的外用伤害性信息与GABA和甘氨酸介导的抑制性信息可能在DCN神经元水平进行整合，从而起到了抑制伤害性信息传入的作用。本研究为进一步探索DCN参与伤害性信息的传递和镇痛作用的机理提供了电生理学基础。     

小鼠盆神经初级传入在脊髓的局部调控及与上级神经元的纤维联系

目的:利用重组伪狂犬病毒介导的逆行跨多突触追踪技术,观察小鼠盆神经初级传入在脊髓突触前神经元的形态特征及其与上级神经元的纤维联系。方法:在成年雄性C57小鼠一侧盆神经注射伪狂犬病毒,动物存活一周后灌注取材,在激光共聚焦显微镜下观察全脑的突触前神经元的分布;利用免疫荧光组织化学技术特异性标记脊髓神经元,观察盆神经初级传入的突触前神经元与痛相关神经元的共存情况。结果:将伪狂犬病毒介导的逆行跨多突触病毒注入盆神经后,脊髓和脑内大量核团,如下丘脑、运动皮质、中脑导水管周围灰质、臂旁核和腰骶髓后连合核(DCN)都可观察到密集分布的突触前神经元。利用免疫荧光组织化学染色技术,观察到DCN内存在大量SP受体(SPR)阳性神经元,且SPR阳性神经元与盆神经跨突触标记的突触前神经元不共存,这些突触前神经元主要呈GABA阳性。结论:DCN是盆神经初级传入在脊髓的关键中继部位,内脏伤害性信息可能在DCN处进行初级调控后向上逐级传导。     

NMDA受体介导的eEPSC在皮质发育障碍动物模型海马CA1区的改变

目的：研究皮质发育障碍（DCD）大鼠模型海马CA1区N-甲基-D-门冬氨酸（NMDA）受体及α-氨基-3-羧基5甲基异恶唑-4-丙酸（AmPA）受体介导的兴奋性突触后电流（eEPSC）的变化，探讨DCD大鼠模型的致痫机制。方法：选取出生10～20dDCD幼鼠模型和正常对照组，应用可视法脑片膜片钳记录方法，记录大鼠海马CA1区锥体神经元的NMDA受体及AmPA受体介导的eEPSC幅度及衰减时间常数。结果：DCD模型组与正常对照组相比，NMDA受体介导的eEPSC的幅度有明显增高r（119．54±10．97）pAVS（83．69±10．23）pA；P〈0．053；衰减时间常数明显延长[（154．59±3．92）VS（117．18±4．04）；P〈0．05]。而AmPA受体介导的eEPSC的幅度[（139．99±23．41）pAVS（135．50±26．44）pA；P〉0．05]及衰减时间常数[（47．23±2．28）VS（48．68±2．20）；P〉0．053无明显改变。结论：NMDA受体介导的异常突触后反应在DCD的致痫机制方面起到重要的作用。     

大鼠脊髓背角CGRP、IB4阳性终末与GABA能神经元之间的联系及GABABR1阳性终末的超微结构观察

背根神经节小型神经元初级传入末梢上的GABAB受体在脊髓背角接受中间神经元的突触前抑制,是脊髓水平痛觉调节的途径之一。为研究大鼠脊髓背角胶状质中背根神经节神经元传入纤维末梢同脊髓背角GABA能中间神经元之间的联系,本实验用免疫组织化学法,通过激光共聚焦显微镜观察了正常大鼠CGRP阳性和IB4阳性背根节神经元的中枢突同脊髓背角GA-BA能中间神经元之间的联系。同时,用免疫电镜(IEM)技术研究了脊髓背角GABABR1阳性的背根神经节神经元中枢突末梢形成突触的特点。结果显示:CGRP阳性和IB4阳性背根节神经元的中枢突和脊髓背角GABA能中间神经元之间形成密切联系;电镜下许多脊髓背角胶状质中突触小球的中央末梢为GABABR1免疫阳性,并作为突触前或突触后成分与周围末梢之间形成对称性和非对称性突触。提示脊髓背角GABA能中间神经元可能通过分布在背根节神经元初级传入末梢上的GABAB受体产生突触前抑制,参与脊髓水平的痛觉调制。     

CABAA和GABAB受体介导的成年动物背根神经节神经元的电活动

许多药理学研究表明，哺乳动力的脊髓背角中的ＧＡＢ受体亚型参与介导脊髓初级传入末梢的突触前抑制。本研究应用细胞内记录技术探讨ＧＡＢＡＢ受体激活对背根神经节细胞膜电特性的作用。实际标本取自ＳＤ成年大鼠Ｌ４－６后根节和猫后根节。当灌流加入ＧＡＢＡＢ受体激动剂ｂａｃｌｏｆｅｎ时，后根节的９８个细胞中，约５８％的细胞无反应。部分Ａ类和Ｃ类细胞的膜电位出现超极化和去极化反应。Ａ传动（ｎ＝７１）和Ｃ传入（ｎ＝２     

卢非酰胺选择性抑制大鼠C纤维介导的伤害性初级传入发挥镇痛作用

目的:探讨抗癫痫药物卢非酰胺(rufinamide,RUF)对脊髓背角II层胶状质(substantia gelatinosa,SG)神经元兴奋性和突触传递的影响及其在神经病理性疼痛动物模型上的镇痛作用。方法:利用膜片钳技术,对SG神经元进行全细胞记录,观察卢非酰胺对神经元动作电位(action potentials,AP)发放频率及后根刺激诱发的兴奋性突触后电流(evoked excitatory postsynaptic currents,e EPSC)幅度及自发性兴奋性突触后电流(spontaneous excitatory postsynaptic currents,s EPSC)的影响。制备大鼠腰5脊神经结扎模型(spinal nerve ligation,SNL),观察腹腔注射卢非酰胺对机械性缩足反射阈值(paw withdrawal mechanical threshold,PWMT)的影响。结果:电生理结果显示:灌注卢非酰胺可明显抑制由C纤维介导的单突触e EPSC幅值,这一作用经洗脱可恢复至加药前,但对Aδ纤维介导的e EPSC幅度的抑制作用无统计学意义。卢非酰胺还可减少II层胶状质神经元动作电位的发放频率,减弱神经元的兴奋性,同时降低s EPSC的频率,但对其幅度没有影响。在大鼠SNL模型上,卢非酰胺能有效缓解由神经结扎引起的病理性疼痛,且镇痛作用具有浓度依赖性。结论:卢非酰胺可以通过减少SG神经元动作电位的发放频率,选择性的抑制脊髓背角浅层C纤维介导的伤害性初级传入而发挥镇痛作用。     

内脏和躯体初级传入冲动在猫骶髓后连合核的汇聚

用玻璃微电极细胞外记录的方法，观察了在电刺激猪盆神经和胫神经或机械性刺激会阴部时骶髓后连合核神经元自发放电频率的变化．共记录了80个单位放电神经元，其中13个为无关单位．电反应类型有3种：长潜伏期长串反应，短潜伏期长串反应，抑制性反应．在所观察的对刺激呈有效反应的67个单位中，30个（44．78％）对躯体和内脏刺激均起反应，其中，12个对盆神经和胫神经传入冲动都起反应；18个对盆神经和会阴部躯体感受野的传入呈汇聚性反应．对会阴部感受野施加各种机械性刺激，鉴定此汇聚神经元为WDR神经元．67个有效反应单位中还有5个（7.46％）只对内脏传入冲动，32个（47.76％）仅对躯体传入冲动做出反应．本研究从电生理学上验证了本教研室在形态学上发现的盆腔内脏（膀胱）初级传入和坐骨神经躯体初级传入在骶髓后连合核神经元的汇聚，并对汇聚的类型和意义进行了观察和讨论．     

哺乳动物脊髓内沉默性谷氨酸能突触与痛

人们已在哺乳动物中枢神经系统的许多部位（如海马、丘脑以及大脑皮层的某些区域）发现沉默性谷氨酸能突触的存在。本文作者用全细胞电压钳记录方法,在出生后２～１７天的带后根的大鼠脊髓（骶髓）薄片上发现大鼠脊髓后角浅层的某些神经元上也存在沉默性谷氨酸能突触,并对其特点和功能进行了分析和研究。作者首先通过改变细胞膜的钳制电位观察了神经元对后根刺激的突触反应。观察到有些突触只在钳制电位由７０ｍＶ升到＋４０ｍＶ时才对后根刺激起反应,即可记录到由后根刺激引起的兴奋性突触后电流（ＥＰＳＣ）;并观察到此反应由ＮＭＤ…     

内源性大麻素类似物NAGly对大鼠脊髓胶状质神经元的突触传递的抑制作用

目的:探讨内源性大麻素类似物N-花生四烯酰甘氨酸(N-arachidonylglycine,NAGly)对脊髓后角II层胶状质(SG)神经元突触兴奋性的影响。方法:选用生后4~6周雄性SD大鼠,深麻醉后蔗糖人工脑脊液快速心脏灌注处死,取脊髓腰膨大段,制备保留脊髓腰膨大处一侧后根的脊髓矢状切片。利用膜片钳技术,对脊髓后角II层SG神经元进行全细胞记录,通过分析后根刺激诱发的兴奋性突触后电流(eEPSC)的变化情况,观察NAGly(20μmol/L)对SG神经元突触传递兴奋性的影响,以及对自发性兴奋性突触后电流(sEPSC)的发放频率及幅度的影响。结果:通过诱发刺激的强度、潜伏期以及纤维传导速度我们将记录到的SG神经元分为Aδ纤维/C纤维投射神经元,NAGly对Aδ纤维和C纤维介导的eEPSC的幅度都有明显的抑制作用(P0.001),并且这种作用可以被洗脱。NAGly对SG神经元的sEPSC的频率有明显的抑制,但不明显改变其幅度,提示其作用部位在突触前。结论:内源性大麻素类似物NAGly可以抑制脊髓后角浅层Aδ纤维及C纤维介导的突触传递,并通过突触前机制抑制SG神经元的兴奋性。提示内源性大麻素类似物NAGly可通过抑制伤害性C和A纤维介导的突触传递发挥镇痛作用。     

Excitatory transmission in the dorsal horn is in part mediated through APV-sensitive NMDA receptors

The role of subtypes of excitatory amino acid receptor in synaptic transmission in the spinal dorsal horn has been studied in an in vitro slice preparation with well-preserved afferent inputs to the dorsal horn. Intracellular recordings were made from 30 dorsal horn neurons in laminae I-III of 18-28 day old rats. Superfusion of the slice with a Mg2+ zero solution resulted in an increase in the amplitude and duration of dorsal root-evoked excitatory postsynaptic potentials (EPSP) recorded intracellularly from dorsal horn neurons. Bath application of D-2-amino-5-phosphonovalerate (10(-5) M to 2.5 x 10(-5) M) or DL-2-amino-5-phosphonovalerate (10(-4) M to 2.5 x 10(-4) M) rapidly and reversibly abolished the later component of the EPSP evoked by activation of either group of primary afferents and selectively antagonized the N-methyl-D-aspartate-induced depolarization.     

The central projections of primary afferent neurons of greater splanchnic and intercostal nerves in the rat

Summary The central projections of primary afferent fibers of the greater splanchnic nerve of the rat were investigated using the transganglionic horseradish peroxidase transport technique. In addition, the corresponding spinal ganglion cells and the preganglionic sympathetic neurons were demonstrated. For comparing visceral and somatic afferents, intercostal nerve afferents were labelled by the same technique.Splanchnic afferent dorsal root ganglion cells were found at segments T3 to T13 ipsilaterally, with the greatest density at T8 to T12. Labelled cells represented about 10%–15% of all neurons in the ganglia at maximal projection levels. They were randomly distributed within individual ganglia. The great majority were medium to small sized and round to slightly oval in shape.In the spinal cord, labelled visceral afferent axons were found maximally at T8 to T11, but could be detected in decreasing density up to T1 and down to L1. They were distributed over Lissauer's tract and the dorsal funiculus to a medial and lateral collateral pathway (MCP and LCP, respectively). The MCP, somewhat more prominent than the LCP, was destined primarily to clustered presumptive terminal fields in medial lamina I and outermost lamina IIa. Only a few axons continued further to laminae V and X. Splanchnic afferent axons, most likely derived from the MCP, formed a longitudinal bundle ventral to the central canal. The LCP consisted of more or less well-defined axon bundles emanating from the lateral Lissauer's tract and curving round the lateral edge of the dorsal horn and through the dorsolateral funiculus. Presumptive terminal sites of LCP axons are the lateral laminae I and IIa, the nucleus of the dorsolateral funiculus and the dorsal part of lamina V. A few LCP axons were seen in the vicinity of lateral dendrites of preganglionic sympathetic axons. Visceroafferent terminals were absent from laminae IIb–IV and VII. The possible consequences of the MCP/LCP duality for the central connections of splanchnic afferents are discussed. Some splanchnic afferents ascended to the gracile and cuneate nuclei, and rarely to the spinal trigeminal nucleus.These results fit into the general concept of visceroafferent terminal organization that has emerged during the last few years. Differences to other reports in the detailed arrangement of fibers and terminals are discussed.Somatoafferent cell bodies represented the vast majority of neurons in the respective spinal ganglia. Cell sizes encompassed the whole range from very small to very large without a clear predominance of one particular size class. Cell shapes of somatic neurons were more variable than those of visceral afferent neurons. Somatic afferent fibers and presumptive terminals in the spinal cord are distributed ipsilaterally to dorsal horn laminae I–V, most heavily II–IV, to the nucleus dorsalis Clarke, to the ventral horn, and also sparsely to the dorsal horn contralaterally.Labelled preganglionic sympathetic neurons were found in segments T3–T13. The vast majority was located in the intermediolateral nucleus. Fewer neurons occurred in the intercalated nucleus, and occasionally a neuron was labelled in the dorsal grey commissure.Parts of this study have been presented in abstract form at the 8th ENA meeting in Den Haag, September 1984Dedicated to Prof. Dr. W. Zenker on occasion of his 60th birthday     

内脏大神经初级传入神经元向中枢投射的光镜和电镜研究——CT-HRP跨神经节运送法

用猫20只,于内脏大神经注射CT—HRP,对初级传入在中枢内的投射进行了光、电镜观察。光镜下,内脏初级传入神经元的中枢投射纤维主要经Lissauer's束到脊髓后角边缘,部分可能终止于Ⅰ层,大部分分为内、外侧束包绕灰质后角边缘由浅部板层向深部板层进入Ⅴ、Ⅶ、Ⅹ层。内侧束可能有部分上升到薄束核。电镜观察,在Ⅰ、Ⅴ、Ⅶ、Ⅹ层看到标记的轴突末梢且可直接与交感节前神经元形成突触。本文还对内脏传入通路进行了讨论并认为交感传入纤维可能经脊髓后角神经元中继上传至孤束核。     

P2X purinoceptors and sensory transmission

The involvement of P2X purinoreceptors (P2X receptors) in somatosensory transmission is herein reviewed with a focus on those receptors that are expressed on sensory neurons to elucidate their roles in the initiation of sensory excitation from primary afferent neurons, in modulating synaptic transmission at the first sensory synapses formed between primary afferent central terminals and dorsal horn neurons, in directly mediating sensory synaptic transmission to the spinal cord dorsal horn, and in modulating synaptic transmission among spinal cord dorsal horn neurons. Research on P2X receptors has indicated that these receptors play a significant role in both physiological and pathological pain states. As a result, P2X receptors may serve as therapeutic targets for the treatment of pathological pain conditions associated with nerve injury, tissue inflammation, cancer, and other diseases.     

Morphology and synaptic relationships of physiologically identified low-threshold dorsal root axons stained with intra-axonal horseradish peroxidase in the cat and monkey

The arborizations and synaptic relationships of intra-axonally stained horseradish peroxidase- (HRP) labeled primary afferent fibers to the dorsal horn of the cat and monkey spinal cord have been studied by light and electron microscopic methods. The light microscopic arborizations of the afferent fiber types (hair follicle afferents, pacinian corpuscle afferents, type I and type II slowly adapting afferents) are similar to those described by Brown and his colleagues (1) in the cat. The synaptic profiles formed by labeled afferents contain rounded synaptic vesicles. In serial thin sections, it was found that single dorsal root axons may make hundreds or thousands of synapses with neuronal structures of the dorsal horn. The vast majority of synaptic contacts are on the dendritic trees of dorsal horn neurons. The synapses made by these low-threshold afferent axons are almost all in the deeper laminae (III-VI) of the dorsal horn. The hair follicle afferent axons and the pacinian corpuscle afferents have numerous vesicle-containing structures that synapse on them to form either axoaxonal synapses or dendroaxonal synapses. The slowly adapting afferent axons are less often found to be postsynaptic to axons or dendrites. It is concluded that different physiological classes of primary afferent axons have different morphological characteristics, both at the light and electron microscopic level.     

ULTRASTRUCTURAL LOCALIZATION OF SUBSTANCE PRECEPTOR AND ITS SYNAPTIC RELATIONSHIP WITH THE PRIMARY AFFERENTS IN THE SUPERFICIAL DORSAL HORN OF THE RAT SPINAL CORD

ＵＬＴＲＡＳＴＲＵＣＴＵＲＡＬＬＯＣＡＬＩＺＡＴＩＯＮＯＦＳＵＢＳＴＡＮＣＥＰＲＥＣＥＰＴＯＲＡＮＤＩＴＳＳＹＮＡＰＴＩＣＲＥＬＡＴＩＯＮＳＨＩＰＷＩＴＨＴＨＥＰＲＩＭＡＲＹＡＦＦＥＲＥＮＴＳＩＮＴＨＥＳＵＰＥＲＦＩＣＩＡＬＤＯＲＳＡＬＨＯＲＮＯＦＴ...     

Bicuculline and strychnine suppress the mesencephalic locomotor region-induced inhibition of group III muscle afferent input to the dorsal horn

We examined the effect of iontophoretic application of bicuculline methiodide and strychnine hydrochloride on the mesencephalic locomotor region (MLR)-induced inhibition of dorsal horn cells in paralyzed cats. The activity of 60 dorsal horn cells was recorded extracellularly in laminae I, II, V-VII of spinal segments L7-S1. Each of the cells was shown to receive group III muscle afferent input as demonstrated by their responses to electrical stimulation of the tibial nerve (mean latency and threshold of activation: 20.1+/-6.4 ms and 15.2+/-1.4 times motor threshold, respectively). Electrical stimulation of the MLR suppressed transmission in group III muscle afferent pathways to dorsal horn cells. Specifically the average number of impulses generated by the dorsal horn neurons in response to a single pulse applied to the tibial nerve was decreased by 78+/-2.8% (n=60) during the MLR stimulation. Iontophoretic application (10-50 nA) of bicuculline and strychnine (5-10 mM) suppressed the MLR-induced inhibition of transmission of group III afferent input to laminae I and II cells by 69+/-5% (n=10) and 29+/-7% (n=7), respectively. Likewise, bicuculline and strychnine suppressed the MLR-induced inhibition of transmission of group III afferent input to lamina V cells by 59+/-13% (n=14) and 39+/-11% (n=10), respectively.Our findings raise the possibility that GABA and glycine release onto dorsal horn neurons in the spinal cord may play an important role in the suppression by central motor command of thin fiber muscle afferent-reflex pathways.     

Mu opiates inhibit long-term potentiation induction in the spinal cord slice

Long-term potentiation (LTP) involves a prolonged increase in neuronal excitability following repeated afferent input. This phenomenon has been extensively studied in the hippocampus as a model of learning and memory. Similar long-term increases in neuronal responses have been reported in the dorsal horn of the spinal cord following intense primary afferent stimulation. In these studies, we utilized the spinal cord slice preparation to examine effects of the potently antinociceptive mu opioids in modulating primary afferent/dorsal horn neurotransmission as well as LTP of such transmission. Transverse slices were made from the lumbar spinal cord of 10- to 17-day-old rats, placed in a recording chamber, and perfused with artificial cerebrospinal fluid also containing bicuculline (10 microM) and strychnine (1 microM). Primary afferent activation was achieved in the spinal slice by electrical stimulation of the dorsal root (DR) or the tract of Lissauer (LT) which is known to contain a high percentage of small diameter fibers likely to transmit nociception. Consistent with this anatomy, response latencies of LT-evoked field potentials in the dorsal horn were considerably slower than the response latencies of DR-evoked potentials. Only LT-evoked field potentials were found to be reliably inhibited by the mu opioid receptor agonist [D-Ala(2), N-Me-Phe(4), Gly(5)] enkephalin-ol (DAMGO, 1 microM), although evoked potentials from both DR and LT were blocked by the AMPA/kainate glutamate receptor antagonist 6-cyano-7-nitroquinoxalene-2,3-dione. Moreover repeated stimulation of LT produced LTP of LT- but not DR-evoked potentials. In contrast, repeated stimulation of DR showed no reliable LTP. LTP of LT-evoked potentials depended on N-methyl-D-aspartate (NMDA) receptor activity, in that it was attenuated by the NMDA antagonist APV. Moreover, such LTP was inhibited by DAMGO interfering with LTP induction mechanisms. Finally, in whole cell voltage-clamp studies of Lamina I neurons, DAMGO inhibited excitatory postsynaptic current (EPSC) response amplitudes from LT stimulation-evoked excitatory amino acid release but not from glutamate puffed onto the cell and increased paired-pulse facilitation of EPSCs evoked by LT stimulation. These studies suggest that mu opioids exert their inhibitory effects presynaptically, likely through the inhibition of glutamate release from primary afferent terminals, and thereby inhibit the induction of LTP in the spinal dorsal horn.     

Neurons in laminae III and IV of the rat spinal cord with the neurokinin-1 receptor receive few contacts from unmyelinated primary afferents which do not contain substance P

We have previously demonstrated that neurons in laminae III and IV of the spinal dorsal horn which possess the neurokinin-1 receptor and have long dorsal dendrites receive a major synaptic input from substance P-containing primary afferents and a more limited input from myelinated afferents. In the present study we have carried out a quantitative analysis of the contacts which cells of this type receive from two other classes of unmyelinated primary afferent: those which contain somatostatin and those without neuropeptides. We found that although boutons belonging to both of these types of afferent do form contacts with neurons of this type, the contacts are far less numerous than those formed by substance P-containing afferents. In laminae I and II, the density of contacts which dendrites of these cells received from somatostatin-containing afferents was 1.2/100 microm and that from non-peptidergic C afferents was 2.0/100 microm, which is far lower than our previous estimate of 18.8/100 microm from substance P-containing fibres in these laminae. These results indicate that although the dendrites of large neurons in laminae III and IV which possess the neurokinin-1 receptor pass through regions of the dorsal horn in which many types of primary afferent terminate, their synaptic input from primary afferents is organized in a highly selective manner.     

The central projections of visceral primary afferent neurons of the inferior mesenteric plexus and hypogastric nerve and the location of the related sensory and preganglionic sympathetic cell bodies in the rat

Summary The central projections of visceral primary afferents of the inferior mesenteric plexus and hypogastric nerve of the rat were investigated using the transganglionic transport of horseradish peroxidase (HRP). In addition, the location of the corresponding spinal ganglion cells as well as the preganglionic sympathetic neurons is demonstrated.Labelled afferent axons were found in dorsal roots, dorsal root entry zone (preferentially in its lateral part), in all parts of the tract of Lissauer, and in the dorsolateral funiculus. Preterminal axons and/or terminals were distributed mainly to laminae I, IIa and the nucleus of the dorsolateral funiculus. Fewer afferents reached laminae IIb, III–V and X. Afferent projections are densest at L1 and 2 and the caudal T13, but extend up to T10 rostrally, and at least down to L4 caudally. A few visceral afferents ascend to the nucleus gracilis.The great majority of sensory and preganglionic sympathetic cell bodies is located at levels L1 and 2 bilaterally. A few cells are found in decreasing numbers rostrally up to T11.Preganglionic sympathetic neurons (PSN) are located in nucleus intermediolateralis (IML), n. intercalatus (IC) and n. commissuralis dorsalis (DCN). Axons of DCN and IC neurons run laterally, joining those of IML neurons on their way to the ventral roots. Dendrites of IML neurons ramify in all directions but preferentially to the dorsal horn and dorsolateral funiculus. Dendrites of IC and DCN neurons are distributed mainly mediolaterally, the latter also ventrally around the canalis centralis.