Dorsal root projections in the clawed toad (Xenopus laevis) as demonstrated by anterograde labeling with horseradish peroxidase

Horseradish peroxidase was applied to the proximal stumps of severed cervical, thoracic and lumbar dorsal roots in the clawed toad, Xenopus laevis, in order to study the course, distribution and site of termination of dorsal root fibers in the spinal cord and brain stem. The anterograde transport of horseradish peroxidase as applied in the present study proved to be a useful and reliable technique. Results show that on entering the spinal cord, dorsal root fibers segregate into a medially placed component entering the dorsal funiculus and a more laterally situated bundle in the dorsal part of the lateral funiculus. As regards its position the latter bundle presumably represents the anuran homologue of the mammalian tract of Lissauer. Moreover, a small intermediate bundle of fibers directly enters the spinal gray matter. The labeled fibers entering the dorsal funiculus and the tract of Lissauer ascend and descend in the spinal cord, displaying a longitudinal arrangement resembling that of higher vertebrates.In the spinal gray, dorsal root fibers terminate in the dorsal, central and lateral fields of Ebbesson, 25 with the last field being a major terminus for dorsal root fibers originating in the limb-innervating segments. No dorsal root fibers were found to project to the motoneuron fields. A dorsal column nucleus, which is divisible into medial and lateral compartments, is present in the obex region and extends from the level of the second spinal nerve to that of the entrance of the vagus and glossopharyngeal nerves. Dorsal root fibers from the lumbar and all thoracic segments project to the medial compartment of the dorsal column nucleus, whereas those of the cervical enlargement project to the lateral compartment.Although the anuran dorsal column nucleus appears to be less differentiated than that of higher vertebrates, its medial and lateral compartments can be considered to be the forerunners of the mammalian nucleus gracilis and nucleus cuneatus, respectively.     

猫内脏大神经一级传入纤维在脊髓灰质和薄束核中的分布

本文共用猫14只,取1～1.5mg HRP溶于7～10μl蒸馏水中,注入一侧的腹腔神经节或内脏大神经中,采用TMB成色法,观察跨神经节传递的一级内脏传人纤维在中枢神经系的分布。标记的一级内脏感觉纤维经后根进入脊髓后,绝大多数先行于背外侧束(或Lissauer束)中,少数进入后索上行。自背外侧束间断地发出内、外侧投射纤维,包绕着后角的内、外侧缘。外侧投射纤维在数量上比内侧的多,止于Ⅰ、Ⅴ、Ⅶ层和中央管周围。进入中间外侧核的纤维,再沿颅尾方向分开纵行,与交感节前细胞的纵向树突紧密平行排列。内侧投射纤维主要止于中央管周围区域。行于后索的纤维,止于闩平面以下薄束核的腹外侧部。     

Region-specific appearance of myelin constituents in the developing rat spinal cord

Summary The appearance of myelin-specific glycolipids and of myelin basic protein was studied with regard to the detailed anatomy of the rat cervical spinal cord. The expression of these constituents in particular fibre tracts and regions occurs at specific times of development between postnatal days 1 and 14. This mosaic-like appearance started in the ventral funiculus (day 1) followed by fasciculus cuneatus and ventro-lateral funiculus (day 2), and fasciculus gracilis and dorso-lateral funiculus (days 3 to 4). Cortico-spinal tract (day 11), Lissauer tract (day 14) and the commissures started to acquire myelin very late. In the grey matter, myelin constituents appeared around days 11 to 14 in a patchy pattern. These results support a concept of highly local interactions regulating oligodendrocyte differentiation. In addition, a general rostro-caudal gradient of myelin development exists in the spinal cord, which is independent of the ascending or descending nature of the fibre tracts. Appearance of myelin constitutents in the caudal spinal cord was not prevented by a neonatal transection at mid-thoracic levels.     

Localization of vasoactive intestinal peptide immunoreactivity in human foetus and newborn infant spinal cord

Using an indirect immunofluorescence method the distribution of vasoactive intestinal peptide (VIP) immunoreactivity was studied in human foetus and newborn infant spinal cord and dorsal root ganglia. Further, for comparison some newborn infant brains were also investigated. Vasoactive intestinal peptide-like immunoreactive fibres were exclusively found in the caudal spinal cord and corresponding dorsal root ganglia. No immunoreactive cell bodies were detected. The first appearance of VIP-like immunoreactive fibres in both spinal cord and dorsal root ganglia was suggested during the fourth month of foetal life. Most immunolabelled fibres, concentrated in the sacral segment, were distributed in the Lissauer tract, along the dorsolateral gray border, in the intermediolateral areas and near the central canal in the dorsolateral commissure. A few VIP-like immunoreactive fibres were also seen in the dorsal funiculus and occasionally in the ventral gray horn and ventral roots. Further, a large population of VIP-like immunoreactive fibres occurs longitudinally in dorsal root, in ganglia and in the spinal nerve exit zone. These findings indicate the early appearance of VIP-like immunoreactive fibres in the human foetus spinal cord and corresponding ganglia. Moreover, they emphasize that in both foetus and newborn infant spinal cord VIP-like immunoreactive fibre distribution is limited to the lumbosacral segment.     

Changes in axonal physiology and morphology after chronic compressive injury of the rat thoracic spinal cord

The spinal cord is rarely transected after spinal cord injury. Dysfunction of surviving axons, which traverse the site of spinal cord injury, appears to contribute to post-traumatic neurological deficits, although the underlying mechanisms remain unclear. The subpial rim frequently contains thinly myelinated axons which appear to conduct signals abnormally, although it is uncertain whether this truly reflects maladaptive alterations in conduction properties of injured axons during the chronic phase of spinal cord injury or whether this is merely the result of the selective survival of a subpopulation of axons. In the present study, we examined the changes in axonal conduction properties after chronic clip compression injury of the rat thoracic spinal cord, using the sucrose gap technique and quantitatively examined changes in the morphological and ultrastructural features of injured axonal fibers in order to clarify these issues. Chronically injured dorsal columns had a markedly reduced compound action potential amplitude (8.3% of control) and exhibited significantly reduced excitability. Other dysfunctional conduction properties of injured axons included a slower population conduction velocity, a longer refractory period and a greater degree of high-frequency conduction block at 200 Hz. Light microscopic and ultrastructural analysis showed numerous axons with abnormally thin myelin sheaths as well as unmyelinated axons in the injured spinal cord. The ventral column showed a reduced median axonal diameter and the lateral and dorsal columns showed increased median diameters, with evidence of abnormally large swollen axons. Plots of axonal diameter versus myelination ratio showed that post-injury, dorsal column axons of all diameters had thinner myelin sheaths. Noninjured dorsal column axons had a median myelination ratio (1.56) which was within the optimal range (1.43-1.67) for axonal conduction, whereas injured dorsal column axons had a median myelination ratio (1.33) below the optimal value. These data suggest that maladaptive alterations occur postinjury to myelin sheath thickness which reduce the efficiency of axonal signal transmission.In conclusion, chronically injured dorsal column axons show physiological evidence of dysfunction and morphological changes in axonal diameter and reduced myelination ratio. These maladaptive alterations to injured axons, including decrease in myelin thickness and the appearance of axonal swellings, contribute to the decreased excitability of chronically injured axons. These results further clarify the mechanisms underlying neurological dysfunction after chronic neurotrauma and have significant implications regarding approaches to augment neural repair and regeneration.     

家兔坐骨神经初级传入纤维在脊髓内的定位投射—HRP跨越神经节追踪研究

向家兔坐骨神经的分支一胫神经、腓神经、比目鱼肌(腓肠肌)神经、腓肠皮神经分别注入HRP溶液,跨越神经节追踪了各该神经初级传入纤维在脊髓内的分布,得到了下列几点规律性认识。 1.来自皮肤的外感性传入纤维分布于后角浅层(Ⅰ—Ⅳ层),来自肌肉的Ia类粗纤维分布于后角深层及中间带外侧核区、前角。 2.外感性细纤维在后角Ⅱ、Ⅲ层有浓密的投射,各神经有特有的占位区。内脏初级传入纤维不向Ⅱ、Ⅲ层投射。 3.与痛党有关的Aδ、C纤维经Lissauer's束投射向后角Ⅰ、Ⅱ层,其它感觉的外感性纤维经后索分布于后角Ⅳ层并有一部分入Ⅲ层。 4.Ia类粗纤维经后索入灰质,首先在Ⅴ、Ⅵ层内侧部形成浓密的晶体形终末区并经Ⅵ层中央部向中间带外侧核区、前角运动核区(Ⅸ层)放散。粗纤维在后索内形成升、降支,向吻侧跨约10个节段逐节发出侧支终止在相当于Ⅴ、Ⅵ层内侧部处;向尾侧终止于骶、尾各节段的后连合核区。 5.进入脊髓的各类纤维中,止于Ⅰ、Ⅱ层的细纤维跨节段最少;止于Ⅳ层的外感性纤维向吻侧跨2—3节,向尾侧直达尾髓;Ia类粗纤维跨节段范围最大,升支可达T_9,降支直达尾髓。     

Opiate receptors in the human spinal cord: a detailed anatomical study comparing the autoradiographic localization of [3H]diprenorphine binding sites with the laminar pattern of substance P, myelin and nissl staining

The anatomical localization of opiate receptors in the human spinal cord has been examined in six cases aged 7-41 years using quantitative autoradiographic methods following the incubation of fresh, unfixed cryostat sections with [3H]diprenorphine. In order to precisely localize the distribution of receptors in the spinal cord, the laminar anatomy of the spinal grey was demonstrated at each spinal level examined using 50-microns sections stained for myelin, Nissl substance and substance P. In all cases, autoradiograms demonstrated that opiate receptors were distributed in a similar fashion in the grey matter of the cervical, thoracic, lumbar, sacral and coccygeal regions of the human spinal cord. At all 25 spinal levels examined, opiate receptors were mainly localized within the upper laminae of the dorsal horn (laminae I-III) and within the tract of Lissauer. The highest density of opiate receptors was localized within the inner segment of lamina II where the receptors formed a very dense band lying immediately dorsal to lamina III. The density of receptors in this inner region of lamina II (33 +/- 2 fmol/mg) was more than two-and-one-half times greater than that in the remaining upper laminae which showed moderate receptor densities: lamina I (12 +/- 4 fmol/mg) and outer lamina II (13 +/- 3 fmol/mg) both showed similar receptor densities which were higher than those in lamina III (10 +/- 3 fmol/mg) The tract of Lissauer (11 +/- 2 fmol/mg) also showed a moderate density of opiate receptors which was intermediate between the densities in laminae I/IIo and the density of lamina III. The density of receptors in the remaining laminae of the spinal cord varied from moderately low to virtually zero. Moderately low densities of receptors were found in laminae V, VI, VIII, IX and X with very low levels within laminae IV and VII. In particular, in lamina VII opiate receptors were unable to be detected above normal background levels in the dorsal nucleus of Clarke. These results show that, as in other mammalian species, opiate receptors in the human spinal cord are mainly concentrated in the upper laminae of the dorsal horn and in the tract of Lissauer. The possible role of these receptors in modulating spinal nociceptive information is discussed with respect to previous findings on the relationship of opiate receptors to primary afferent fibres in the spinal cord.     

Long-range projections of Adelta primary afferents in the Lissauer tract of the rat

Electrical microstimulation has been used to activate fine myelinated primary afferents running within the Lissauer tract. Stimulation of the tract at the L2/L3 border produced antidromic volleys which were recorded on the dorsal roots of more caudal spinal segments. Antidromic volleys were present in all cases for roots as far caudal as the S2 segment (L3, n=12; L4, n=6; L5, n=6; L6, n=9; S1, n=3; S2, n=6; observations in a total of 15 rats). These fibres were collaterals of primary afferents with conduction velocities in the dorsal root of up to 17.3+/-2.3 ms(-1) (mean+/-S.D., n=6; range 14-20 ms(-1)). Conduction velocities within the Lissauer tract were slower; the fastest contributing fibres had conduction velocities of 9.2+/-2.2 ms(-1) (range 6-12 ms(-1)). Lesions of the Lissauer tract caudal to the stimulation site abolished the volleys on roots lying caudal to the lesion. Most previous works have suggested that primary afferents project in the Lissauer tract for only one or two spinal segments. The present study shows that some fibres project rostrally for up to seven spinal segments (L2-S2).     

Aging process of myelinated nerve fibers in the human Lissauer tract

We calculated numbers and axonal areas of myelinated nerve fibers in the Lissauer tract of the human lumbar spinal cord (L1) from the viewpoint of the aging process. We examined 20 human spinal cords from 13 males and 7 females, age ranging from 41 to 88 years old. We found that, although the number of nerve fibers showed no significant change in relation to the age of the subject, the axonal area of myelinated nerve fiber in the Lissauer tract did decrease with age.     

顺铂联合放射治疗对大鼠脊髓损伤影响的观察

目的探讨顺铂(c isp latin,DDP)联合放射治疗对大鼠脊髓损伤的影响。方法40只W istar大鼠随机分为5组,即空白组、单纯化疗组、单纯放射组、先化后放组和先放后化组。单化组单次腹腔注射顺铂5 mg/kg。单放组和放化联合组采用瓦里安2300 C/D直线加速器6M eV电子线照射大鼠胸段脊髓,照射野为2 cm×4 cm,5Gy/次,隔日1次,总剂量为40 Gy。联合组顺铂与照射的间隔时间为3天。照射结束后5个月,行活体灌注固定,取材,光镜和电镜观察脊髓的形态学变化。结果光镜下,CT组灰质未见改变,白质内部分有髓神经纤维排列紊乱,部分髓鞘板层结构松解、扭曲。RT组灰质未见改变,白质出现部分水肿坏死,髓鞘板层模糊不清。CT+RT组脊髓灰质、白质改变明显,其中CT+放疗组的灰质内可见到明显的神经元核变成细长形,尼氏体数量减少,白质出现大片坏死。电镜下,CT组髓鞘结构出现轻度变化,表现为部分髓鞘的板层结构松解、扭曲。RT组脊髓损伤表现为板层结构水肿、粘连,模糊不清。CT+RT组的脊髓损伤程度严重,表现为正常髓鞘的板层结构完全消失,轴突及神经纤维裸露,血管增生,部分血管内皮细胞坏死。RT+CT组脊髓损伤表现为正常髓鞘的板层结构部分松解、扭曲、断裂。结论顺铂与放疗联用明显加重脊髓损伤,且放疗前加用顺铂脊髓损伤加重。     

Somatosensory evoked potentials in man: differentiation of spinal pathways responsible for conduction from the forelimb vs hindlimb

This review suggests that a previously unrecognized spinal cord pathway may be of major importance in the conduction of the somatosensory evoked potential (SEP) from the lower limb in Man. The nerve fiber type activated by a "typical" peripheral nerve stimulus used in studying the SEP will activate the posterior tibial nerve or median nerve predominantly at group I threshold. Group I fibers subserve limb proprioception. Therefore the spinal cord pathways subserving limb position sense will be the same pathways activated by a peripheral nerve stimulus used to evoke an SEP. A relatively newly recognized pathway involved with limb position sense from the lower limb is located in the dorsal portion of the lateral funiculus of the spinal cord whereas pathways subserving limb position sense in forelimb involve predominantly the dorsal column pathways. It is suggested that the dorsal columns play no major role in limb position sense from the lower limb in Man and therefore, the dorsal columns play no major role in the conduction of activity from the lower limb involved with the generation of an SEP.     

Demyelination and remyelination in the dorsal funiculus of the rat spinal cord after heat injury

Summary Part of the dorsal funiculus of the adult male rat (Wistar) spinal cord was treated for l h at the thoracolumbar level by running hot water, at approximately 48–50 ° C, through a polyethylene tube 2 mm in diameter in contact with the dura. Animals were fixed 1 day to 4 weeks later and the spinal cords were examined by light and electron microscopy. The affected area in the dorsal funiculus was approximately 1 mm long and less than 1 mm wide at the dorsal surface, and varied from 0.4 to 0.7 mm in depth.Within 3 days after treatment, almost all the myelin sheaths in the affected area were degraded, leaving the axons denuded, and at the same time astrocyte endfeet at the glial limiting membrane were swollen and partly destroyed. Almost all the denuded axons remained intact, exhibiting no noticeable morphological changes. There was evidence of a moderate vasogenic oedema, but minimal signs of haemorrhage in the lesion. Seven days after treatment, many immature Schwann cells but no oligodendrocytes were found between the denuded axons. By 2 weeks many of the denuded axons were remyelinated, and by 4 weeks almost all of those axons located near the pial and perivascular surfaces had been remyelinated by Schwann cells, while most of those located in the deep and marginal zones bordering the adjoining intact areas were remyelinated by oligodendrocytes. Longitudinal sections revealed that at nodes of Ranvier PNS-type myelin sheaths were apposed by either intact or newly formed CNS-type myelin sheaths. A typical glial limiting membrane was not reformed beneath the pial surface, but an inconspicuous one was found between the PNS- and CNS-type fibre areas.     

Reimplantation of avulsed lumbosacral ventral roots in the rat ameliorates injury-induced degeneration of primary afferent axon collaterals in the spinal dorsal columns

Injuries to the cauda equina/conus medullaris portion of the spinal cord can result in motor, sensory, and autonomic dysfunction, and neuropathic pain. In rats, unilateral avulsion of the motor efferents from the lumbosacral spinal cord results in at-level allodynia, along with a corresponding glial and inflammatory response in the dorsal horn of the spinal cord segments immediately rostral to the lesion. Here, we investigated the fate of intramedullary primary sensory projections following a motor efferent lesion. The lumbosacral (L6 and S1) ventral roots were unilaterally avulsed from the rat spinal cord (VRA; n=9). A second experimental group had the avulsed roots acutely reimplanted into the lateral funiculus (Imp; n=5), as this neural repair strategy is neuroprotective, and promotes the functional reinnervation of peripheral targets. A laminectomy-only group served as controls (Lam; n=7). At 8 weeks post-lesion, immunohistochemical examination showed a 42% reduction (P<0.001) in the number of RT97-positive axons in the ascending tracts of the dorsal funiculus of the L4-5 spinal segment in VRA rats. Evidence for degenerating myelin was also present. Reimplantation of the avulsed roots ameliorated axon and myelin degeneration. Axons in the descending dorsal corticospinal tract were unaffected in all groups, suggesting a specificity of this lesion for spinal primary sensory afferents. These results show for the first time that a lesion restricted to motor roots can induce the degeneration of intramedullary sensory afferents. Importantly, reimplantation of the lesioned motor roots ameliorated sensory axon degeneration. These data further support the therapeutic potential for reimplantation of avulsed ventral roots following trauma to the cauda equina/conus medullaris.     

Neurotoxic effects of zoniporide: a selective inhibitor of the NA+/H+ exchanger isoform 1

Zoniporide, an inhibitor of the Na+-H+ exchanger-1, was administered by continuous intravenous infusion to rats and dogs for up to 1 month. In 1-month studies, histological and functional changes were observed in select portions of the peripheral nervous system; however, these findings were not detected in 2-week studies at similar or higher doses. In the 1-month rat study, there was dose-dependent, minimal, focal, or multifocal nerve fiber (axonal) degeneration in the spinal cord and/or sciatic nerve. In a follow-up rat study, findings included slowing of caudal nerve conduction velocity and axonal degeneration in the spinal cord (dorsal funiculus), dorsal roots, dorsal root ganglia (DRG), radial, sciatic, and tibial nerves. In the 1-month dog study, there was impairment of the patellar reflex and associated postural reaction changes, minimal to marked proximal nerve fiber degeneration in the DRG, and minimal nerve fiber degeneration in the dorsal roots and funiculi of the spinal cord. Minimal nerve fiber degeneration of equivocal significance was noted in various peripheral nerves. Taken together, these findings were consistent with a specific effect on peripheral sensory nerve fibers. These studies demonstrated that zoniporide produces clinical, electrophysiologic, and microscopic evidence of peripheral sensory axonopathy and establishes the importance of careful preclinical evaluation of neurological function.     

复方丹参注射液对大鼠急性脊髓损伤后神经再生的影响

目的　探讨丹参对急性脊髓损伤的影响及作用机制。方法给实验性脊髓损伤大鼠腹腔注射复方丹参注射液 ,观测脊髓组织学及超微结构变化。结果用药后大鼠脊髓内髓鞘断裂减轻 ,吞噬细胞清除组织降解物 ,神经元变性恢复。结论　丹参对大鼠急性脊髓损伤后神经修复及再生有促进作用     

Dorsal column nuclei afferents in the lateral funiculus of the cat: Distribution pattern and absence of sprouting after chronic deafferentation

Summary In adult cats the successive degeneration technique has been used to demonstrate the existence and distribution pattern of lateral funicular fibers to the dorsal column nuclei (DCN) originating from the brachial and thoracic cord. In a first operation, interruption of the dorsal columns at appropriate cervical levels and of the lateral funiculus at low thoractic levels was performed. Thirteen months later, a lesion was made in the lateral funiculus at upper brachial or uppermost thoracic levels. Fiber degeneration in the DCN consequent to this second operation is not contaminated by damage to dorsal roots or by interruption of lateral funicular afferents from lumbo-sacro-coccygeal segments. All animals were sacrified 7 days after the second operation. Serial sections through the medulla oblongata, impregnated with the Fink-Heimer technique, show that fibers ascending from brachial levels in the dorsal part of the lateral funiculus reach the cuneate nucleus either by a dorsomedial route through the tegmentum or by ascending in the restiform body. Degenerated fibers distribute selectively to the rostral part, and to a lesser extent to the base, of the cuneate nucleus. Only very few fibers ascending from thoracic levels in the lateral funiculus distribute to the DCN.Abbreviation List CUN cuneate nucleus - DV dorsal motor nucleus of vagus nerve - EC external cuneate nucleus - GR gracile nucleus - HYP hypoglossal nucleus - int nucleus intercalatus - PH nucleus praepositus hypoglossi - PM paramedian nucleus - SOL solitary nucleus and tract - VEST vestibular complex - X nucleus X of Brodal and Pompeiano (1957) - Z nucleus Z of Brodal and Pompeiano (1957) - V spin spinal trigeminal nucleus     

Serotonin is found in myelinated axons of the dorsolateral funiculus in monkeys.

Physiological measurements suggest that the inhibition of primate spinothalamic tract cells by serotonin is mediated by myelinated axons. Previous morphologic studies emphasize that most serotonin-containing axons in the spinal cord are unmyelinated. Accordingly, the possibility that some serotonin-containing axons in the primate dorsolateral funiculus of the spinal cord are myelinated was investigated. Macaque monkeys were given L-tryptophan and the monoamine oxidase inhibitor, nialamide, intraperitoneally 1 h prior to sacrifice to increase axonal stores of serotonin. The animals were perfused (0.05 or 0.5% glutaraldehyde, 4% paraformaldehyde), and transverse sections of the thoracic cord were reacted with antibody against serotonin and then prepared for electron microscopy. Many of the immunostained axons in the dorsolateral funiculus included fine, myelinated fibers with diameters of 0.7-2.2 microns. Unmyelinated serotonin-containing axons were also observed. The observation of myelinated serotonin-containing axons in the white matter of the monkey dorsolateral funiculus contradicts the view that the descending serotoninergic projection consists entirely of unmyelinated fibers, particularly since the conduction velocity of the fine fibers would be too slow to account for the earliest latency of descending inhibition following stimulation in the brainstem. The presence of myelinated serotoninergic axons presumably accounts for the latencies reported for the inhibition of primate spinothalamic cells following stimulation of the periaqueductal gray, an inhibition that can be blocked with serotonin antagonists and that is associated with the release of serotonin in the dorsal horn.     

Myelin basic protein immunohistochemistry: a study of the early stages of myelination in the brainstem of the rat.

An immunohistochemical study of MBP distribution in the brainstem of neonate till 16 d old rats based on the peroxidase-antiperoxidase method is described. Axons already invested with immunoreactive sheaths were found in neonate rats in the ventral funiculus of the cervical spinal cord and in the medial longitudinal fascicle of the medulla oblongata. Fibres commencing with myelination showed a closely spaced array of varicosities in longitudinal sections which diminished gradually. A caudo-rostral decrease in density of myelinated fibres in the brainstem was found in the medial and dorsal longitudinal fascicles. In contrast to other pathways, myelination in the fibres of the corticospinal tract in the brainstem occurred in a strictly synchronized pattern. The same temporal pattern of myelination was also observed in the cervical corticospinal tract, except that a few myelinated fibres had been visible much earlier within the area of the tract. At the exit of cranial nerves, the transitorial zone from central to peripheral myelin was outlined by a decrease in immunostaining.     

Termination patterns of calcitonin gene-related peptide-immunoreactive nerve fibers in the dorsal horn of the human spinal cord

Summary CGRP-immunoreactive varicose nerve fibers displayed three kinds of termination patterns in the cervical, thoracic and lumbar segments of the human spinal cord. Bundles of immunoreactive fibers formed a loose network in lamina I. A homogenous band of immunoreactive fibers filled lamina II. Multiple bundles of CGRP-positive fibers coursed through the superficial laminae towards deep portions of the grey matter. In the lumbar segments, in contrast to the cervical and thoracic segments, the bundles could be followed deep into the dorsal funiculus. Bundles of varicose immunoreactive fibers were seen to twine around the dendrites of neurons located in lamina I, in the dorsal funiculus of the lumbar segments and deep in the dorsal horn (laminae III–V). The corresponding types of large and medium-sized neurons were found in silver impregnated adjacent spinal cord sections. It is suggested that neurons in the above locations preferentially receive multiple contacts from CGRP-containing nerve fibers along their extensive dendritic arborizations (CGRP-target neurons).     

Microsurgical Anatomy of Lumbosacral Nerve Rootlets for Highly Selective Rhizotomy in Chronic Spinal Cord Injury

It is known that selective sacral roots rhizotomy is effective for relieving the neurogenic bladder associated with spinal cord injury. The goal of this study is to review the surgical anatomy of the lumbosacral nerve rootlets and to provide some morphological bases for highly selective sacral roots rhizotomy. Spinal cord dissections were performed on five cadavers under surgical microscope. At each spinal cord segment, we recorded the number, diameter and length of the rootlets, subbundles and bundles from the L1 to S2 spinal segments, and the length of the dorsal/ventral root entry zone. Peripheral nervous system myelin was examined by immunohistochemistry. We found: (1) the ventral or the dorsal root of the lumbosacral segment of the spinal cord was divided into one to three nerve bundles and each bundle was subdivided into one to three subbundles. Each subbundle further gave out two to three rootlets connected with the spinal cord; (2) there were no significant differences in the number of rootlets within the L1 to S2 segments, but the size of rootlets and the length of nerve roots varied (P < 0.05); and (3) the more myelinated fibers a rootlet contained, the larger transection area it had. The area of peripheral nervous system myelin positive cells and the total area of rootlets were correlated (P < 0.001). Thus, during highly selective sacral roots rhizotomy, the ventral and dorsal roots can be divided into several bundles of rootlets, and we could initially distinct the rootlets by their diameters. Anat Rec, 2010. © 2010 Wiley‐Liss, Inc.