Terminations of reticulospinal fibers originating from the gigantocellular reticular formation in the mouse spinal cord

The present study investigated the projections of the gigantocellular reticular nucleus (Gi) and its neighbors—the dorsal paragigantocellular reticular nucleus (DPGi), the alpha/ventral part of the gigantocellular reticular nucleus (GiA/V), and the lateral paragigantocellular reticular nucleus (LPGi)—to the mouse spinal cord by injecting the anterograde tracer biotinylated dextran amine (BDA) into the Gi, DPGi, GiA/GiV, and LPGi. The Gi projected to the entire spinal cord bilaterally with an ipsilateral predominance. Its fibers traveled in both the ventral and lateral funiculi with a greater presence in the ventral funiculus. As the fibers descended in the spinal cord, their density in the lateral funiculus increased. The terminals were present mainly in laminae 7–10 with a dorsolateral expansion caudally. In the lumbar and sacral cord, a considerable number of terminals were also present in laminae 5 and 6. Contralateral fibers shared a similar pattern to their ipsilateral counterparts and some fibers were seen to cross the midline. Fibers arising from the DPGi were similarly distributed in the spinal cord except that there was no dorsolateral expansion in the lumbar and sacral segments and there were fewer fiber terminals. Fibers arising from GiA/V predominantly traveled in the ventral and lateral funiculi ipsilaterally. Ipsilaterally, the density of fibers in the ventral funiculus decreased along the rostrocaudal axis, whereas the density of fibers in the lateral funiculus increased. They terminate mainly in the medial ventral horn and lamina 10 with a smaller number of fibers in the dorsal horn. Fibers arising from the LPGi traveled in both the ventral and lateral funiculi and the density of these fibers in the ventral and lateral funiculi decreased dramatically in the lumbar and sacral segments. Their terminals were present in the ventral horn with a large portion of them terminating in the motor neuron columns. The present study is the first demonstration of the termination pattern of fibers arising from the Gi, DPGi, GiA/GiV, and LPGi in the mouse spinal cord. It provides an anatomical foundation for those who are conducting spinal cord injury and locomotion related research.     

The periaqueductal gray in the cat projects to lamina VIII and the medial part of lamina VII throughout the length of the spinal cord

The periaqueductal gray (PAG) plays an important role in analgesia as well as in motor activities, such as vocalization, cardiovascular changes, and movements of the neck, back, and hind limbs. Although the anatomical pathways for vocalization and cardiovascular control are rather well understood, this is not the case for the pathways controlling the neck, back, and hind limb movements. This led us to study the direct projections from the PAG to the spinal cord in the cat. In a retrograde tracing study horseradish peroxidase (HRP) was injected into different spinal levels, which resulted in large HRP-labeled neurons in the lateral and ventrolateral PAG and the adjacent mesencephalic tegmentum. Even after an injection in the S2 spinal segment a few of these large neurons were found in the PAG. Wheat germ agglutinin-conjugated HRP injections in the ventrolateral and lateral PAG resulted in anterogradely labeled fibers descending through the ventromedial, ventral, and lateral funiculi. These fibers terminated in lamina VIII and the medial part of lamina VII of the caudal cervical, thoracic, lumbar, and sacral spinal cord. Interneurons in these laminae have been demonstrated to project to axial and proximal muscle motoneurons. The strongest PAG-spinal projections were to the upper cervical cord, where the fibers terminated in the lateral parts of the intermediate zone (laminae V, VII, and the dorsal part of lamina VIII). These laminae contain the premotor interneurons of the neck muscles. This distribution pattern suggests that the PAG-spinal pathway is involved in the control of neck and back movements. Comparing the location of the PAG-spinal neurons with the results of stimulation experiments leads to the supposition that the PAG-spinal neurons play a role in the control of the axial musculature during threat display.     

The calcium binding proteins calbindin, parvalbumin, and calretinin have specific patterns of expression in the gray matter of cat spinal cord

Calcium binding proteins (CBPs) regulate intracellular levels of calcium (Ca²⁺) ions. CBPs are particularly interesting from a morphological standpoint, because they are differentially expressed in certain sub-populations of cells in the nervous system of various species of vertebrate animals. However, knowledge on the cellular regulation governing such cell-specific CBP expression is still incomplete. In this work on the L7 segment of the cat spinal cord, we analyzed the localization and morphology of neurons expressing the CBPs calbindin-28 KD (CB), parvalbumin (PV), and calretinin (CR), and co-expressing CB and PV, CB and CR, and PV and CR. Single CBP-positive (⁺) neurons showed specific distributions: (1) CB was present in small neurons localized in laminae I, II, III and X, in small to medium size neurons in laminae III–VI, and in medium to large neurons in laminae VI–VIII; (2) PV was present in small size neurons in laminae III and IV and in medial portions of laminae V and VI, medium neurons and in lamina X at the border with lamina VII, in medium to large neurons in laminae VII and VIII; (3) CR labeling was detected in small size neurons in laminae I, II, III and VIII, in medium to large size neurons in laminae I and III–VII, and in small to medium size neurons in lamina X. Double labeled neurons were a small minority of the CBP⁺ cells. Co-expression of CB and PV was seen in 1 to 2% of the CBP⁺ cells, and they were detected in the ventral and intermediate portions of lamina VII and in lamina X. Co-localization of CB and CR was present in 0.3% of the cells and these cells were localized in lamina II. Double labeling for PV and CR occurred in 6% of the cells, and the cells were localized in ventral part of lamina VII and in lamina VIII. Overall, these results revealed distinct and reproducible patterns of localization of the neurons expressing single CBPs and co-expressing two of them. Distinct differences of CBP expression between cat and other species are discussed. Possible relations between the cat L7 neurons expressing different CBPs with the neurons previously analyzed in cat and other animals are suggested.     

Projections from the lateral vestibular nucleus to the spinal cord in the mouse

The present study investigated the projections from the lateral vestibular nucleus (LVe) to the spinal cord using retrograde and anterograde tracers. Retrogradely labeled neurons were found after fluoro-gold injections into both the cervical and lumbar cord, with a smaller number of labeled neurons seen after lumbar cord injections. Labeled neurons in the LVe were found in clusters at caudal levels of the nucleus, and a small gap separated these clusters from labeled neurons in the spinal vestibular nucleus (SpVe). In the anterograde study, BDA-labeled fiber tracts were found in both the ventral and ventrolateral funiculi on the ipsilateral side. These fibers terminated in laminae 6–9. Some fibers were continuous with boutons in contact with motor neurons in both the medial and lateral motor neuron columns. In the lumbar and sacral segments, some collaterals from the ipsilateral vestibulospinal tracts were found on the contralateral side, and these fibers mainly terminated in laminae 6–8. The present study reveals for the first time the fiber terminations of the lateral vestibular nucleus in the mouse spinal cord and therefore enhances future functional studies of the vestibulospinal system.     

Immunohistochemical study of tyrosine-hydroxylase-positive cells and fibers in the chicken spinal cord.

Tyrosine hydroxylase (TH)-positive cells and fibers were examined by immunohistochemistry in the chick spinal cord. TH-positive cells, which were located in laminae I, V and X, were most frequently found in the rostral part of the cervical spinal cord, with fewer cells being found in more caudal levels of the spinal cord. TH-positive cells located in lamina X, which were bipolar in shape, were mainly found in regions lateral as well as just ventral to the central canal. They had processes reaching to the central canal. The terminals of these cerebrospinal-fluid-contacting cells were oval in shape, and were most frequently found at the ventral wall of the central canal. There were dense clusters of TH-positive fibers in lamina X. A meshwork-like structure of TH-positive fibers was found over the lateral wall of the central canal. A high density of TH-positive fibers was also found in the medial part of laminae V-VII. In lamina IX, small numbers of TH-positive fibers were observed in the lateral motor column of the brachial spinal cord, and in the medial and lateral motor columns of the lumbosacral spinal cord. However, within the medial motor column of the brachial spinal cord TH-positive fibers were densely distributed around somal as well as dendritic profiles. Similar to our previous observations on serotoninergic fibers. TH-positive fibers were also differentially distributed in the ventral horn of the chicken spinal cord: a high density of TH-positive fibers was localized to specific regions of the spinal motor nucleus.     

Cholecystokinin-8-like-immunoreactive fibers in rat lumbosacral autonomic regions are sexually dimorphic and altered by a reduction of androgen receptors

Cholecystokinin-8-like-immunoreactive (CCK-8-LI) fibers in laminae VII and X of the rat lumbosacral spinal cord demarcate the position of preganglionic autonomic neurons. This investigation reveals that adult male Sprague-Dawley, or King-Holtzman/Sprague-Dawley rats contain more CCK-8-LI fibers in lumbosacral laminae VII and X than adult females. Furthermore, testicular feminization mutation male rats (which lack 85-90% of their functional androgen receptors) contain fewer CCK-8-LI fibers than normal male or female rats, with the amount of CCK-8-LI being reduced to a greater extent in the sympathetic vs. the parasympathetic regions of the lumbosacral spinal cord. Thus, CCK-8-LI in testicular feminization mutation male rats has a distinctly female-like pattern. These results suggest that testosterone is a regulatory factor for CCK-8-LI fibers found in laminae VII and X of the lumbosacral spinal cord. Sexual dimorphism in lumbosacral CCK-8-LI fibers may contribute to modulating the final common pathway which differentially regulates the reproductive organs and stereotypic reproductive behavior, and may be involved with the sex differences described for pain.     

Anatomical evidence for red nucleus projections to motoneuronal cell groups in the spinal cord of the monkey

In 4 rhesus monkeys wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injections were made in the mesencephalic tegmentum. In 3 cases with injections involving the red nucleus (RN), rubrospinal fibers descended mainly contralaterally to terminate in laminae V, VI and dorsal VII of the spinal cord and in the lateral motoneuronal cell groups at the level of the cervical and lumbosacral enlargements. In all 4 cases the area of the interstitial nucleus of Cajal (INC) was injected, which resulted in labeled interstitiospinal fibers in the medial part of the ipsilateral ventral funiculus of the spinal cord. The results indicate that there is no major qualitative difference between the mesencephalic (RN and INC) and motor cortical projections to the spinal cord.     

Benzodiazepine receptors in the human spinal cord: a detailed anatomical and pharmacological study

The anatomical distribution and pharmacological characteristics of benzodiazepine receptors in the human spinal cord were examined in four cases aged 20-41 years using in vitro autoradiography and biochemical assays of [3H]flunitrazepam binding. In all cases, the autoradiograms demonstrated that benzodiazepine receptors were distributed in a consistently similar fashion in the gray matter of the cervical, thoracic, lumbar and sacral regions of the human spinal cord. At all levels, the highest densities of benzodiazepine receptors were found to be localized within lamina II of the dorsal horn as defined on cytoarchitectonic, myeloarchitectonic and substance P immunocytochemical criteria. Within this lamina the receptors were concentrated mainly in its deeper, inner portion which lies immediately adjacent to lamina III, with some overlap dorsally into the outer segment of lamina II and ventrally into the adjacent region of lamina III. The lowest density of receptors was found in regions of laminae I, IV, VII and X; in particular, in lamina VII the lowest concentration of receptors was found in the dorsal nucleus of Clarke and the sacral parasympathetic nucleus. The remaining laminae of the spinal gray (laminae, V, VI, VIII and IX) showed a moderate density of receptors. Biochemical assays of membranes prepared from the lumbosacral cord indicated that these [3H]flunitrazepam binding sites have high affinity and have the pharmacological characteristics of the "central" Type II benzodiazepine receptor. These results show a high concentration of Type II benzodiazepine receptors in the substantia gelatinosa of the human spinal cord and suggest a possible role for these receptors in spinal sensory functions.     

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。     

Descending serotonergic fibers in the dorsolateral and ventral funiculi of cat spinal cord

Although there is much evidence for the presence of serotonergic fibers in the spinal gray matter, there is little evidence for the location of descending serotonergic fiber tracts in the spinal white matter. Using a highly sensitive immunocytochemical technique, we localized serotonin-immunoreactive axons throughout the white and gray matter of the spinal cord. Prominent concentrations of serotonergic axons were found in the dorsolateral and ventral funiculi. It is likely that these two descending fiber tracts contribute serotonergic input to the dorsal and ventral horns, respectively.     

Immunocytochemistry of B-50 (GAP-43) in the spinal cord and in dorsal root ganglia of the adult cat

Summary The distribution of the neural-specific growth associated protein B-50 (GAP-43), which persists in the mature spinal cord and dorsal root ganglia, has been studied by light and electron microscopic immunohistochemistry in the cat. Throughout the spinal cord, B-50 immunoreactivity was seen confined to the neuropil, whereas neuronal cell bodies were unreactive. The most conspicuous immunostaining was observed in the dorsal horn, where it gradually decreased from superficial laminae (I–II) toward more ventral laminae (III–V), and in the central portion of the intermediate gray (mainly lamina X). In these regions, the labelling was localized within unmyelinated, small diameter nerve fibres and axon terminals. In the rest of the intermediate zone (laminae VI–VIII), B-50 immunoreactivity was virtually absent. The intermediolateral nucleus in the thoracic and cranial lumbar cord showed a circumscribed intense B-50 immunoreactivity brought about by the labelling of many axon terminals on preganglionic sympathetic neurons. In motor nuclei of the ventral horn (lamina IX), low levels of B-50 immunoreactivity were present in a few axon terminals on dendritic and somal profiles of motoneurons. In dorsal root ganglia, B-50 immunoreactivity was mainly localized in the cell bodies of small and medium-sized sensory neurons. The selective distribution of persisting B-50 immunoreactivity in the mature cat throughout sensory, motor, and autonomie areas of the spinal cord and in dorsal root ganglia suggests that B-50-positive systems retain in adult life the capacity for structural and functional plasticity.     

Localization of spinal neurons activated during locomotion using the c-fos immunohistochemical method

The c-fos immunohistochemical method of activity-dependent labeling was used to localize locomotor-activated neurons in the adult cat spinal cord. In decerebrate cats, treadmill locomotion was evoked by electrical stimulation of the mesencephalic locomotor region (MLR). Spontaneous or MLR-evoked fictive locomotion was produced in decerebrate animals paralyzed with a neuromuscular blocking agent. After bouts of locomotion during a 7- to 9-h time period, the animals were perfused and the L3-S1 spinal cord segments removed for immunohistochemistry. Control animals were subjected to the same surgical procedures but no locomotor task. Labeled cells were concentrated in Rexed's laminae III and IV of the dorsal horn and laminae VII, VIII, and X of the intermediate zone/ventral horn after treadmill locomotion. Cells in laminae VII, VIII, and X were labeled after fictive locomotion, but labeling in the dorsal horn was much reduced. In control animals, c-fos labeling was a small fraction of that observed in the locomotor animals. The results suggest that labeled cells in laminae VII, VIII, and X are premotor interneurons involved in the production of locomotion, whereas the laminae III and IV cells are those activated during locomotion due to afferent feedback from the moving limb. c-fos-labeled cells were most numerous in the L5-L7 segments, consistent with the distribution of locomotor activated neurons detected through the use of MLR-evoked field potentials.     

Spinoreticular neurons in the second sacral segment of the feline spinal cord.

In continuation of previous electrophysiological studies on the location of ascending tract neurones within the second sacral segment of the feline spinal cord, the spinoreticular projections of these neurones have been investigated. Following electrical stimulation of the axonal terminals of 37 spinoreticular neurons via a tungsten electrode placed stereotactically in the contralateral nucleus reticularis gigantocellularis, antidromic potentials from their cell bodies were recorded with glass microelectrodes both extra- and intracellularly. The axons of these neurones were additionally excited from the dorsolateral funiculi of the contralateral (n = 37) and ipsilateral (n = 30) side at the lowermost thoracic spinal level. The latencies of antidromic excitation from the brainstem to the second sacral segment ranged from 3.2 to 11.8 ms (mean, 5.9 ms), whereas the corresponding axonal conduction velocities were between 27.1 and 100 m/s. The neurones examined in this study were found to be situated in the medial lamina VII of Rexed and the area adjacent to the central canal (n = 13), the medial lamina VIII (n = 12), medial laminae V and VI (n = 10) and in laminae II and III (n = 2). Three medium-sized (40-60 microm) of triangular- or oval-shaped neurones were visualized in medial laminae VII and VIII following the intracellular labelling with horseradish peroxidase.     

Routes of entry into the cerebellum of spinocerebellar axons from the lower part of the spinal cord

Summary Among the newly discovered spinocerebellar cell groups, those at lumbar and more caudal levels of the cat's spinal cord were studied with regard to which of the two cerebellar peduncles, the restiform body or the superior cerebellar peduncle, is used by their axons. Bilateral injections with horseradish peroxidase were made into either of the anterior lobe or the posterior cerebellar termination area for spinocerebellar fibers, following unilateral transections of either the superior cerebellar peduncle or the restiform body, combined with low contralateral transections of the lateral and ventral funiculi. Following transection of the superior cerebellar peduncle, labeled neurons were found ipsilateral to the transection in the column of Clarke and in laminae IV–VI at L 3–L 7. Contralaterally, labeled neurons were found in the ventromedial nucleus and lamina VIII of the ventral horn in the sacro-coccygeal segments and in the medial part of lamina VII at L 6 and more caudal levels. All these neurons were regarded as sending their axons through the restiform body. Following transection of the restiform body, labeled neurons were found in the following areas contralateral to the transection: the dorsolateral nucleus of the L 3–L 6 segments, the lateral part of lamina VII at L 3–L 5/6, the medial part of lamina VII in L 6 and more caudal segments, and the ventrolateral nucleus of L 4–L 5. Ipsilaterally, labeled neurons were found in lamina VIII at L 4–L 6. All these neurons were regarded as sending their axons through the superior cerebellar peduncle. In addition to new information about the peduncular routes of spinocerebellar neurons, the study has given confirming evidence as to the crossing conditions for different spinocerebellar cell groups. The findings should be useful in future studies on the organization of the spinocerebellar systems.Abbreviations BC brachium conjunctivum - BP brachium pontis - C cuneate nucleus - CC column of Clarke - DL dorsolateral nucleus - DSCT dorsal spinocerebellar tract - G gracile nucleus - lam lamina - lat lateral - LRN lateral reticular nucleus - LVN lateral vestibular nucleus - med medial - N.d. nucleus dentatus - N.f. nucleus fastigii - N.i. nucleus interpositus - p pyramidal tract - p. ant. pars anterior (of the paramedian lobule) - p. copul. pars copularis (of the paramedian lobule) - pfl. d dorsal paraflocculus - pmd paramedian lobule - p. post. pars posterior (of the paramedian lobule) - RB restiform body - SCP superior cerebellar peduncle - SVN spinal vestibular nucleus - VL ventrolateral nucleus - VM ventromedial nucleus - VSCT ventral spinocerebellar tract - I-X (on cerebellar diagrams) cerebellar lobules according to Larsell (1953) - IV–IX (on spinal cord diagrams), laminae according to Rexed (1954) - V (on brainstem diagrams) trigeminal nucleus - VI (on brainstem diagram) abducens nucleus - XII (on brainstem diagrams) hypoglossal nucleus On leave from Capital Institute of Medicine, Beijing, The People's Republic of China     

Catecholaminergic and dopamine-containing neurons in the spinal cord of pigeons: an immunohistochemical study

Within the different species belonging to the vertebrate radiation, catecholaminergic elements of the spinal cord present a partly conservative, partly variable pattern. Unfortunately, the overall picture is far from clear since the situation for birds is largely obscure. Therefore, we examined the distribution of dopamine (DA)- and tyrosine hydroxylase (TH)-positive cells and fibers in the spinal cord of the adult pigeon by immunohistochemistry. TH-immunoreactive cells were located within two restricted areas. One group of cells with multipolar shape was located in laminae VI and VII, close to the white-gray border. These cells were more frequently found at rostral and caudal levels while being scarce at cervical-thoracic levels. The second group of cells was located in lamina VIII surrounding the central canal. These cells were bipolar in shape and were found ventrally and laterally to the central canal, with most of them contacting the lumen of the canal through a separate process. The TH-immunoreactive fibers were distributed in both the gray and the white matter. In the gray matter, they were mainly distributed around the central canal (lamina VIII), in the ventral horn close to the border of laminae VII-IX and in the lateral part of the dorsal horn in laminae II-VI. In the white matter the fibers were present in the lateral columns running longitudinal to the main axis. DA-immunoreactive cells were also located within two restricted areas, closely matching the distribution of TH-immunopositive ones. Additionally, the DA-immunoreactive cells had the same shape as the TH-immunoreactive cells, as bipolar neurons contacted the central canal and multipolar ones were located in the laminae VI and VII. Also the distribution of DA- and TH-immunoreactive fibers roughly matched. Both, DA-immunoreactive cells and fibers were scarcer than TH-immunoreactive ones. This finding suggests that the catecholaminergic system in the spinal cord consists of DA-immunoreactive cells as well as other catecholaminergic cells.     

Distribution of the sacral neurones of origin of the ascending spinal tracts with axons passing through the lateral funiculi of the lowermost thoracic segments: an experimental HRP study in the cat.

The locations of 249 cell bodies of the ascending tract neurones in the grey matter of S1-S3 segments of the spinal cord were reconstructed by histochemical staining, after their axons (or axonal collaterals) at the level of the Thl3 segment were injected with horseradish peroxidase (HRP). In three cats in which the injections of HRP were restricted to the lateral part of the lateral funiculi (llf), about 84% of 159 retrogradely labelled cells were found on the contralateral side, while about 16% were located ipsilaterally. They were the most numerous in S2, S3 and S1 segments, respectively, and the neurones were distributed mainly in the lateral laminae I-VII, medial laminae V, VI and lamina VIII. In three other animals in which the injections of the marker were limited to the dorsal part of the lateral funiculi (dlf), 84 of the 90 ascending tract neurones were found to be distributed in the S2 and S3 segments both ipsi- (lateral laminae III-V) and contralaterally, (lateral laminae IV and V as well as the medial laminae VII and VIII) in similar numbers. The remaining six of the 90 cells with only contralateral projections at the dorsolateral funiculus at Thl3 were scattered within the S1 segment. These data are consistent with the results of studies on sacral spinocerebellar, spinothalamic and spinoreticular projections, as well as the localization of sacral spinocervical and priopriospinal neurones. They may also imply the importance of the bilateral fiber course of the neurones of origin of ascending tracts in the S2 and S3 segments within the dorsolateral funiculus.     

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     

Spinal projections from the presumptive midbrain locomotor region in the mouse

The mesencephalic locomotor region (MLR) plays an important role in the control of locomotion, but there is ongoing debate about the anatomy of its connections with the spinal cord. In this study, we have examined the spinal projections of the mouse precuneiform nucleus (PrCnF), which lies within the boundaries of the presumptive MLR. We used both retrograde and anterograde labeling techniques. Small clusters of labeled neurons were seen in the medial portion of the PrCnF following fluoro-gold injections in the upper cervical spinal cord. Fewer labeled neurons were seen in the PrCnF after upper thoracic injections. Following the injection of anterograde tracer (biotinylated dextran amine) into the PrCnF, labeled fibers were clearly observed in the spinal cord. These fibers traveled in the ventral and lateral funiculi, and terminated mainly in the medial portions of laminae 7, 8, and 9, as well as area 10, with an ipsilateral predominance. Our observations indicate that projections from the PrCnF to the spinal cord may provide an anatomical substrate for the role of the MLR in locomotion.     

Projections from the paralemniscal nucleus to the spinal cord in the mouse

The present study investigated the projection from the paralemniscal nucleus (PL) to the spinal cord in the mouse by injecting the retrograde tracer fluoro-gold to different levels of the spinal cord and injecting the anterograde tracer biotinylated dextran amine into PL. We found that PL projects to the entire spinal cord with obvious contralateral predominance—420 neurons projected to the contralateral cervical cord and 270 to the contralateral lumbar cord. Fibers from PL descended in the dorsolateral funiculus on the contralateral side and terminated in laminae 5, 6, 7, and to a lesser extent in the dorsal and ventral horns. A smaller number of fibers also descended in the ventral funiculus on the ipsilateral side and terminated in laminae 7, 8 and, to a lesser extent in lamina 9. The present study is the first demonstration of the PL fiber termination in the spinal cord in mammals. The PL projection to the spinal cord may be involved in vocalization and locomotion.     

Ascending propriospinal afferents to area X (substantia grisea centralis) of the spinal cord in the rat

Area X (the tenth area) of the spinal cord is a region surrounding the central canal and extending throughout the spinal cord length. Using anterograde and retrograde labeling techniques, ascending propriospinal projections to area X were examined in the rat. For anterograde tracing of axons, biotinylated dextran was injected into middle-thoracic, lumbar, or sacral-caudal segments. Unilateral injections resulted in bilateral labeling of terminals in area X of all segments rostral to the injections. The distribution of labeled terminals was conspicuous in regions dorsal and lateral to the central canal. The labeled axons were derived from the ventrolateral and the lateral cord. They coursed through lamina VII, giving off terminal axons. While giving off terminal axons in area X, they coursed further rostrally or caudally along the central canal or crossed over the central canal to terminate in the contralateral area X. Possible cells of origin of these ascending afferents were examined after injections of wheat germ agglutinin-horseradish peroxidase into regions surrounding the central canal (area X) at the cervical or thoracic level. Retrogradely labeled neurons were consistently seen in area X, and laminae VII and VIII of the thoracic and lumbar segments. The present study shows that ascending propriospinal axons project to area X of all spinal levels rostral to the cells of origin and suggests that some of these afferents may originate from neurons in area X and laminae VII and VIII. Based on previous data, it is surmised that area X functions, through these intricate interconnections, as a site for integration or modulation of somatic or nociceptive and visceroceptive sensation. Received: 3 July 1997 / Accepted: 8 October 1997