Muscle tone facilitation and inhibition after orexin-a (hypocretin-1) microinjections into the medial medulla

Orexins/hypocretins are synthesized in neurons of the perifornical, dorsomedial, lateral, and posterior hypothalamus. A loss of hypocretin neurons has been found in human narcolepsy, which is characterized by sudden loss of muscle tone, called cataplexy, and sleepiness. The normal functional role of these neurons, however, is unclear. The medioventral medullary region, including gigantocellular reticular nucleus, alpha (GiA) and ventral (GiV) parts, participates in the induction of locomotion and muscle tone facilitation in decerebrate animals and receives moderate orexinergic innervation. In the present study, we have examined the role of orexin-A (OX-A) in muscle tone control using microinjections (50 microM, 0.3 microl) into the GiA and GiV sites in decerebrate rats. OX-A microinjections into GiA sites, previously identified by electrical stimulation as facilitating hindlimb muscle tone bilaterally, produced a bilateral increase of muscle tone in the same muscles. Bilateral lidocaine microinjections (4%, 0.3 microl) into the dorsolateral mesopontine reticular formation decreased muscle rigidity and blocked muscle tone facilitation produced by OX-A microinjections into the GiA sites. The activity of cells related to muscle rigidity, located in the pedunculopontine tegmental nucleus and adjacent reticular formation, was correlated positively with the extent of hindlimb muscle tone facilitation after medullary OX-A microinjections. OX-A microinjections into GiV sites were less effective in muscle tone facilitation, although these sites produced a muscle tone increase during electrical stimulation. In contrast, OX-A microinjections into the gigantocellular nucleus (Gi) sites and dorsal paragigantocellular nucleus (DPGi) sites, previously identified by electrical stimulation as inhibitory points, produced bilateral hindlimb muscle atonia. We propose that the medioventral medullary region is one of the brain stem target for OX-A modulation of muscle tone. Facilitation of muscle tone after OX-A microinjections into this region is linked to activation of intrinsic reticular cells, causing excitation of midbrain and pontine neurons participating in muscle tone facilitation through an ascending pathway. Moreover, our results suggest that OX-A may also regulate the activity of medullary neurons participating in muscle tone suppression. Loss of OX function may, therefore, disturb both muscle tone facilitatory and inhibitory processes at the medullary level.     

The termination of spinomesencephalic fibers in cat

Summary The projections to the midbrain from the spinal cord have been investigated in the cat with the degeneration technique and by using horseradish peroxidase (HRP) as an anterograde tracer. Two types of spinal cord lesions were performed: 1) Cordotomies at cervical or thoracic levels transecting the ventral and lateral funiculi. 2) Transections of the ventral, ventrolateral, dorsolateral or dorsal funiculus, respectively, at cervical levels. In the anterograde tracing experiments HRP was injected into the spinal cord at cervical, lumbar or sacral levels.The results show large projections to the lateral and ventrolateral parts of the periaqueductal gray (PAG1), the posterior pretectal nucleus (PP) and the nucleus of Darkschewitsch (D). More moderate projections go to the medial division of the periaqueductal gray (PAGm), the cuneiform nucleus (CF), the mesencephalic reticular formation (MRF), lateral part of the deep layer of the superio colliculus (SP) and magnocellular medial geniculate nucleus (GMmc), while scattered spinal fibers are present in the dorsal part of the periaqueductal gray (PAGd), the external inferior collicular nucleus (IX), the intermediate layer of the superior colliculus (SI), the lateral part of the red nucleus (NR) and in the Edinger-Westphal portion of the oculomotor nucleus (3). In addition a few fibers are present in the interstitial nucleus of Cajal (CA) and anterior pretectal nucleus (PAc).The results indicate that at midcervical levels most of the spinomesencephalic fibers ascend in the ventral funiculus, with only a moderate fraction ascending in the ventral half of the lateral funiculus. Almost no fibers ascend in the dorso-lateral funiculus and none appear to pass in the dorsal funiculus.No distinct somatotopic pattern was found in the spinomesencephalic projections, but more fibers from cervicobrachial segments terminate in the rostral than in the caudal parts of the terminal fields in PAG, CF, SP and IX, while the lumbar fibers were more numberous in the caudal parts. PP seems to receive spinal fibers mainly from the caudal half of the cord.     

Reticulospinal and reticuloreticular pathways for activating the lumbar back muscles in the rat

Summary These experiments tested hypotheses about the logic of reticulospinal and reticuloreticular controls over deep back muscles by examining descending efferent and contralateral projections of the sites within the medullary reticular formation (MRF) that evoke EMG responses in lumbar axial muscles upon electrical stimulation. In the first series of experiments, retrograde tracers were deposited at gigantocellular reticular nucleus (Gi) sites that excited the back muscles and in the contralateral lumbar spinal cord. The medullary reticular formation contralateral to the Gi stimulation/deposition site was examined for the presence of single- and double-labeled cells from these injections. Tracer depositions into Gi produced labeled cells in the contralateral Gi and Parvocellular reticular nucleus (PCRt) whereas the lumbar injections retrogradely labeled cells only in the ventral MRF, indicating that separate populations of medullary reticular cells project to the opposite MRF and the lumbar cord. In the second series of experiments the precise relationships between the location of neurons retrogradely labeled from lumbar spinal cord depositions of the retrograde tracer, Fluoro-Gold (FG) and effective stimulation tracks through the MRF were examined. The results indicate that the Gi sites that are most effective for activation of the back muscles are dorsal to the location of retrogradely labeled lumbar reticulospinal cells. To verify that cell bodies and not fibers of passage were stimulated, crystals of the excitatory amino acid agonist, N-methyl-d-asparate (NMDA) were deposited at effective stimulation sites in the Gi. NMDA decreased the ability of electrical stimulation to activate back muscles at 5 min postdeposition, indicating a local interaction of NMDA with cell bodies at the stimulation site. In the third series of experiments, electrical thresholds for EMG activation along a track through the MRF were compared to cells retrogradely labeled from FG deposited into the cervical spinal cord. In some experiments, Fast Blue was also deposited into the contralateral lumbar cord. Neurons at low threshold points on the electrode track were labeled following cervical depositions, indicating a direct projection to the cervical spinal cord. The lumbar depositions, again, labeled cells in MRF areas that were ventral to the locations of effective stimulation sites, primarily on the opposite side of the medulla. In addition, the lumbar depositions back-filled cells in the same cervical segments to which the Gi neurons project. These results suggest that one efferent projection from effective stimulation sites for back muscle activation is onto propriospinal neurons in the cervical cord, which in turn project to lumbar cord levels. In a final series of experiments, a stimulating electrode track through the MRF again identified low threshold and ineffective sites for activating lumbar epaxial EMG. Fluoro-Gold was deposited in the contralateral MRF (MRFc) at a low threshold stimulation site for activating back muscles on that side. Retrogradely labeled cells surrounded effective, but not ineffective, stimulation sites along the electrode track in the MRF. Thus, another projection from effective stimulation sites is to effective stimulation sites in the opposite MRF. These results suggest that neurons in Gi whose stimulation most effectively activates back muscle EMG do not project directly to the lumbar cord, but relay to cervical cord neurons, which in turn project onto lumbar neurons. The MRF commissural connections presumably amplify this descending MRF control of axial back muscles.Abbreviations ECu external cuneate - FB fast blue - FG fluorogold - Gi gigantocellular reticular nucleus - GiA gigantocellular reticular nucleus, alpha - GiV gigantocellular reticular nucleus, ventral - icp inferior cerebellar peduncle - IO inferior olive - LL lateral longissimus - ML medial longissimus - mlf medial longitudinal fasciculus - MRF medullary reticular formation - MRFc medullary reticular formation, contralateral - MVN medial vestibular nucleus - PCRt parvocellular reticular formation - PGi paragigantocellular nucleus - PrH prepositus hypoglossal nucleus - py pyramidal tract - R rhodamine microspheres - Sol nucleus of the solitary tract - Sp5 spinal trigeminal nucleus - 7 facial nucleus     

亮氨酸脑啡肽样和P物质样免疫反应物在大鼠延髓迷走神经背核簇和网状结构内的分布

用PAP法研究亮氨酸脑啡肽样(L—ENK—LI)和P物质样(SP—LI)免疫反应物在大鼠延髓迷走神经背核簇和网状结构内的分布。证明在孤束核、迷走神经背核、外侧网状核外侧部及其外侧的区域内有大量的L-ENK样终末和纤维,在背侧和腹侧网状核之间的移行区内有中等量的分布,其余区内为少量。L-ENK样胞体在孤束核、咀侧腹外侧网状核、巨细胞网状核的腹侧部和α部、外侧旁巨细胞核以及中缝大核内均有许多分布,在迷走神经背核的尾侧部、背侧和腹侧网状核之间的移行区有中等量,其余区内为少量。SP样反应物的分布与L-ENK样物类似,但其终末和纤维的数量较L-ENK者略少,阳性胞体的数量除了在中缝核及外侧旁巨细胞核内侧端中的量较L-ENK样胞体多以外,在其余区内均较少。     

大鼠前庭核向脑干呕吐区的间接投射

前庭信息调节内脏活动的神经通路是产生运动病的结构基础,但至今尚未明了。本研究旨在探讨接受初级前庭传入信息的前庭核到脑干呕吐中枢的神经通路。向大鼠前庭内侧核和前庭下核内注入顺行追踪剂生物素化葡聚糖胺(BDA),向脑干呕吐区注入逆行追踪剂荧光金(FG),用荧光组织化学方法显示BDA顺行标记纤维和终末,在荧光显微镜下观察BDA顺行标记纤维和终末与荧光金逆行标记细胞的重叠区域。结果发现在延髓背侧巨细胞旁核(DPGi)、巨细胞网状核(Gi)和小细胞网状核(PCRt)有顺行标记纤维与逆行标记细胞的重叠。表明前庭核可能经DPGi、Gi和PCRt向呕吐区有间接投射,此结果为进一步揭示前庭信号引发恶心、呕吐的神经机制提供了形态学依据。     

Arrangement of neurons in the medullary reticular formation and raphe nuclei projecting to thoracic, lumbar and sacral segments of the spinal cord in the cat

Summary The distribution of neurons in the medullary reticular formation and raphe nuclei projecting to thoracic, lumbar and sacral spinal segments was studied, using the technique of retrograde transport of horseradish peroxidase (HRP), alone or in combination with nuclear yellow (NY). Retrogradely labeled cells were observed in the lateral tegmental field (FTL), paramedian reticular nucleus, magnocellular reticular nucleus (Mc), in the gigantocellular nucleus (Gc), lateral reticular nucleus (LR), lateral paragigantocellular nucleus (PGL), rostral ventrolateral medullary reticular formation (RVR), as well as in the medullary raphe nuclei following the injection of the tracer substance(s) into various levels of the spinal cord. The FTL, the ventral portion of the paramedian reticular nucleus (PRv), Mc, LR, PGL and the raphe nuclei were found to project to thoracic, lumbar and sacral spinal segments. This projection was bilateral; the contralaterally projecting fibers crossed the midline at or near their termination site. The dorsal portion of the paramedian reticular nucleus (PRd), Gc and the RVR projected mainly to thoracic segments. This projection was unilateral. Experiments in which the HRP-injection was combined with lesion of the spinal cord showed that some descending raphe-spinal axons coursed presumably alongside the central canal. Experiments with two tracer substances suggested that some reticulo and raphe-spinal neurons had axon collaterals terminating both in thoracic and sacral spinal segments.Abbreviations CC Central Canal - FTL Lateral Tegmental Field - Gc Gigantocellular Nucleus - IO Inferior Olive - LR Lateral Reticular Nucleus - Mc Magnocellular Reticular Nucleus - Nc Cunetae Nucleus - Ng Gracile Nucleus - P Pyramidal Tract - PGL Lateral Paragigantocellular Nucleus - PRd Paramedian Reticular Nucleus,dorsal portion - PRv Paramedian Reticular Nucleus, ventral portion - RB Restiform Body - Ro Nucleus Raphe Obscurus - Rm Nucleus Raphe Magnus - Rpa Nucleus Raphe Pallidus - RVR Rostral Ventrolateral Medullary Reticular Formation - TSp5 Tractus Spinalis Nervi Trigemini - V4 Fourth Ventricle - 12N Hypoglossal Nerve - A B C D E and F correspond to levels Fr 16.0 Fr 14.7 Fr 12.7 Fr 11.6 Fr 10.0 and Fr 9.2 posterior to the frontal zero     

大鼠运动核内5-羟色胺1A、2A、5A受体的定位分布

为了阐明５ 羟色胺在中枢神经系统内与运动神经元结合的精确部位,本研究用免疫细胞化学技术分别观察了大鼠躯体运动核和内脏运动核内５ 羟色胺１Ａ、２Ａ、５Ａ 受体的定位分布。在躯体运动核内观察到：（１）５ 羟色胺１Ａ 受体样阳性神经元和纤维主要分布于动眼神经核、滑车神经核、三叉神经运动核、面神经核、舌下神经核和脊髓前角;（２）５ 羟色胺２Ａ 受体样阳性神经元主要见于动眼神经核、三叉神经运动核、面神经核、舌下神经核和脊髓前角,但阳性纤维和终末却密集地分布于三叉神经运动核、面神经核、舌下神经核和脊髓前角等处,除此之外动眼神经核、滑车神经核、展神经核和疑核内也能见到中等密度的阳性纤维和终末,纤维和终末的分布范围和染色浓度、密度都较神经元为明显;（３）少量淡染的５ 羟色胺５Ａ 受体样阳性神经元和稀疏的阳性纤维及终末主要见于三叉神经运动核、面神经核、舌下神经核和脊髓前角。在内脏运动核内观察的结果是：（１）动眼神经副交感核（Ｅ Ｗ 核）、上涎核、迷走神经背核、骶髓副交感核和胸髓侧角内仅有少量５ 羟色胺１Ａ 受体样阳性神经元、纤维和终末分布;（２）５ 羟色胺２Ａ 受体样阳性神经元和较密集的阳性纤维和终末见于Ｅ Ｗ 核、迷走神经背核、骶?     

Reticulospinal and vestibulospinal pathways in the snake Python regius

In the present HRP study extensive reticulospinal projections and more modestly developed vestibulospinal pathways have been demonstrated in the snake Python regius. The funicular trajectories of the main reticulospinal pathways have been shown: via the lateral funiculus pass spinal projections of the nucleus reticularis superior pars lateralis, the nucleus reticularis inferior and nucleus raphes inferior; via the ventral funiculus fibers arising in the nucleus reticularis superior and nucleus reticularis medius. Spinal projections of the locus coeruleus and subcoeruleus area reach their targets via both the lateral and ventral funiculi. Two vestibulospinal pathways have been demonstrated: an ipsilateral tractus vestibulospinalis lateralis arising in the ventrolateral vestibular nucleus, and a contralateral tractus vestibulospinalis medialis from the descending and ventromedial vestibular nuclei. After HRP gel implants into the vestibular nuclear complex direct vestibulocollic projections to motoneurons in the rostral spinal cord were observed. Spinal projections from the ventral part of the nucleus reticularis inferior and the descending and ventromedial vestibular nuclei are mainly aimed at the thin "neck area" (approximately the first 50 spinal segments). This area is extensively used in such acts as orientation and prey-catching, requiring a rather delicate brain stem control.     

Afferent and efferent connections of the ventrolateral tegmental area in the rat

 The present study examined the organization of afferent and efferent connections of the rat ventrolateral tegmental area (VLTg) by employing the retrograde and anterograde axonal transport of Fluorogold and Phaseolus vulgaris-leucoagglutinin, respectively. Our interest was focused on whether the anatomical connections of the VLTg would provide evidence as to the involvement of this reticular area in audiomotor behavior. Our retrograde experiments revealed that minor inputs to the VLTg arise in various telencephalic structures, including the cerebral cortex. Stronger projections originate in the lateral preoptic area, the zona incerta, the nucleus of the posterior commissure and some other thalamic areas, the lateral substantia nigra, the deep layers of the superior colliculus, the dorsal and lateral central gray, the deep mesencephalic nucleus, the paralemniscal zone, the intercollicular nucleus, the external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleus, the deep cerebellar nuclei, the gigantocellular and lateral paragigantocellular reticular nuclei, the prepositus hypoglossal nucleus, the spinal trigeminal nuclei, and the intermediate layers of the spinal cord. Most importantly, we disclosed strong auditory afferents arising in the dorsal and ventral cochlear nuclei and in the cochlear root nucleus. The efferent projections of the VLTg were found to be less widespread. Telencephalic structures do not receive any input from the VLTg. Moderate projections were seen to diencephalic reticular areas, the zona incerta, the nucleus of the posterior commissure, and to various other thalamic areas. The major VLTg projections terminate in the deep layers of the superior colliculus, the deep mesencephalic nucleus, the intercollicular nucleus and external cortex of the inferior colliculus, the oral and caudal pontine reticular nucleus, the gigantocellular and lateral paragigantocellular reticular nuclei, and in the medial column of the facial nucleus. From our data, we conclude that the VLTg might play a role in sensorimotor behavior. Accepted: 3 April 1997     

Course of spinocerebellar axons in the ventral and lateral funiculi of the spinal cord with projections to the posterior cerebellar termination area: an experimental anatomical study in the cat,using a retrograde tracing technique

The course of retrogradely labeled spinocerebellar fibers in the ventral and lateral funiculi of the spinal cord was studied following injections of wheat germ agglutinin-conjugated horseradish peroxidase into the posterior spinocerebellar termination area in the cat. Fibers labeled from unilateral injections into the paramedian lobule were found on the same side in the dorsal part of the lateral funiculus (DLF), corresponding to the dorsal spinocerebellar tract (DSCT), but contralaterally in the ventral part of the lateral funiculus (VLF) and in the ventral funiculus (VF), corresponding to the ventral spinocerebellar tract (VSCT). Following injections into the posterior vermis, labeled fibers were less numerous. Most of them were found in the DSCT and only very few in the VSCT. Previously identified cells of origin of these spinocerebellar tracts were labeled in these experiments and counted. They correlated well with the extents and the locations of the injections that had been made into the two termination sites. These results represent novel detailed information on the location of axons projecting to the two main posterior spinocerebellar termination sites in the spinal white matter in the cat.     

Distribution of catecholamines in the brain stem and spinal cord of the lizard Varanus exanthematicus: an immunohistochemical study based on the use of antibodies to tyrosine hydroxylase

Antibodies to tyrosine hydroxylase were used to study the distribution of nerve cells, fibers and terminals, containing catecholamines, in the lizard Varanus exanthematicus, by means of the indirect immunofluorescence technique. Tyrosine hydroxylase-containing cell bodies occurred in the hypothalamus, the ventral and dorsal tegmentum mesencephali, the substantia nigra, the isthmic reticular formation, in and ventrolaterally to the locus coeruleus, in the nucleus tractus solitarii and in a lateral part of the nucleus reticularis inferior. In addition tyrosine hydroxylase-containing cell bodies were found throughout the spinal cord, ventral to the central canal. Tyrosine hydroxylase-immunoreactive terminal areas in the brain stem were seen in the nucleus interstitialis of the fasciculus longitudinalis medialis, the nucleus raphes superior, the locus coeruleus, several parts of the reticular formation and the nucleus descendens nervi trigemini. Ascending catecholaminergic pathways could be traced from the ventral mesencephalic tegmentum as well as from the dorsal isthmic tegmentum rostralwards, through the lateral hypothalamus. These pathways correspond to the mesostriatal and isthmocortical projections respectively, as described in mammals. Furthermore, ascending catecholaminergic fibers could be traced from the catecholaminergic cell groups in the medulla oblongata to the isthmus, where they intermingle with the locus coeruleus neurons. These pathways correspond to the medullohypothalamic projection and to the dorsal periventricular system in mammals. Descending catecholaminergic fibers to the spinal cord pass via the dorsomedial part of the lateral funiculus, and mainly terminate in the dorsal horn. The results obtained in the present study have been placed in a comparative perspective, which illustrates the constancy of catecholaminergic innervation throughout phylogeny.     

Distribution of some peptides (substance P, [Leu]enkephalin, [Met]enkephalin) in the brain stem and spinal cord of a lizard, Varanus exanthematicus

The distribution of substance P-like and [Leu]- and [Met]enkephalin-immunoreactive cell bodies, fibers and terminal structures in the brain stem and spinal cord of a lizard, Varanus exanthematicus, was studied with the indirect immunofluorescence technique, using antibodies to these peptides. Substance P-like immunoreactive cell bodies were found in the hypothalamus, in a periventricular cell group in the rostral mesencephalon, in the interpeduncular nucleus, in and ventral to the descending nucleus of the trigeminal nerve, in and directly ventral to the nucleus of the solitary tract, scattered in the brain stem reticular formation and in the trigeminal and spinal ganglia. A rather widespread distribution of substance P-like immunoreactivity was found in the brain stem and spinal cord, mainly concentrated in striatotegmental projections related to visceral and/or taste information (nucleus of the solitary tract, parabrachial region), in the descending nucleus of the trigeminal nerve and in the dorsal horn of the spinal cord (areas I and II). In the spinal cord also around the central canal (area X and adjacent parts of area V-VI) a distinct substance P innervation was found. The ventral horn receives only a very sparse substance P innervation. The distribution of [Leu]- and [Met]enkephalin in the brain stem and spinal cord of Varanus exanthematicus is less impressive than that of substance P. Enkephalinergic cell bodies were found particularly in the caudal hypothalamus. Small populations of enkephalinergic cell bodies were found in the vestibular nuclear complex, in the nucleus of the solitary tract, in and around the descending nucleus of the trigeminal nerve and throughout the rhombencephalic reticular formation. Enkephalins are likely to be present in efferent projections of the striatum, in projections related to taste and/or visceral information (nucleus of the solitary tract, parabrachial region) and in descending pathways to the spinal cord. Enkephalinergic fibers are present in the lateral funiculus and enkephalin-immunoreactive cell bodies are found in the reticular formation, particularly the inferior reticular nucleus which is known to project to the spinal cord. In the spinal cord enkephalinergic terminal structures were found especially in the superficial layer of the dorsal horn (areas I and II) and around the central canal. The ventral horn including the motoneuron area receives only a relatively sparse enkephalinergic innervation.     

Divergence of lamina VII and VIII neurones of S1 and S2 segments of the cat's spinal cord to the cerebellum and the reticular formation.

Cerebellar and reticular projections of neurones located in sacral segments of the spinal cord were electrophysiologically investigated in alpha-chloralose anaesthetized cats. Antidromic action potentials were recorded following stimulation of the contralateral restiform body (coRB), contralateral gigantocellular nucleus (coGRN) as well as ipsi- and contralateral lateral funiculus of the 13th thoracic segment (iTh13 and coTh13). Eighty-seven neurones were found in the medial lamina VII and lamina VIII of the gray matter of S1 and S2 segments. Their axons ascended in lateral funiculi on the contralateral side and in 46 cases also on the ipsilateral side of the spinal cord. A projection to coRB was found in 20 neurones, to coGRN in 10 and dual projections to both coRB and coGRN in 20 neurones. Axons of the remaining 37 cells were found to ascend to the level of Th13 only. Conduction velocities of neurones investigated were comprised in the range 35-83 m/s and no significant differences were found between particular groups. However, an evident decrease in conduction was observed in most neurones when comparing proximal to distal parts of their axons, suggesting the possibility of more extensive divergence than indicated in this study. The pattern of projections revealed that the information from the periphery is conveyed in parallel to various supraspinal and possibly also spinal centres.     

大鼠脊髓P物质受体定位分布的免疫细胞化学研究

用免疫细胞化学技术对大鼠脊髓和脊神经节内Ｐ物质受体的定位分布进行了系统的研究。结果证明，Ｐ物质受体阳性胞体和树突主要密集地分布于脊髓全长的Ⅰ层，此外，还发现Ⅱ层的外侧部出现少量阳性胞体和树突，来自Ⅲ层的阳性树突穿过Ⅱ层后进入Ⅰ层；Ⅲ～Ⅳ和Ⅹ层也可见中等密度的阳性胞体和树突；Ⅵ层和Ⅶ层仅见少量阳性胞体和树突，但胸髓中间带外侧核、骶髓副交感运动核、骶髓后连合核内可见大量浓染的阳性胞体和树突；Ⅷ、Ⅸ层、Ｏｎｕｆ氏核、外侧颈核和外侧脊索核也有阳性胞体和树突．灰质内的阳性胞体的树突还伸向前索和外侧索，有时可达脊髓的边缘．此外，脊神经节内也可见少量散在且均匀分布的小型阳性胞体．     

Raphe magnus-induced descending inhibition of spinal nociceptive neurons is mediated through contralateral spinal pathways in the cat

In anesthetized cats, extracellular recordings were made from lumbar spinal dorsal horn neurons, driven by noxious radiant skin heating. Heat-evoked responses were inhibited during electrical stimulation in the medullary nucleus raphe magnus (NRM). To identify the spinal pathways mediating this descending inhibition, reversible blocks in the spinal cord white matter were produced by microinjection of the local anesthetic lidocaine. Descending inhibition from the NRM was significantly reduced during blocks in the dorsal and medial, but not ventral parts of the contralateral lateral funiculus (LF). Blocks at any site in the ipsilateral LF failed to affect NRM-induced descending inhibition. These results indicate that NRM-induced inhibition of nociceptive dorsal horn neurons is conveyed primarily in fibers descending in the contralateral spinal white matter.     

Ascending and descending projections to medullary reticular formation sites which activate deep lumbar hack muscles in the rat

Summary The purpose of this study was to determine ascending and descending afferents to a medullary reticular formation (MRF) site that, when electrically stimulated, evoked EMG activity in lumbar deep back muscles. In anesthetized female rats, the MRF was explored with electrical stimulation, using currents less than 50 A, while EMG activity was recorded from the ipsilateral lateral longissimus (LL) and medial longissimus (ML). MRF sites that evoked muscle activity were located in the gigantocellular nucleus (Gi). At the effective stimulation site, the retrograde fluorescent tracer, Fluoro-Gold (FG), was deposited via a cannula attached to the stimulating electrode. In matched-pair control experiments, FG was deposited at MRF sites that were ineffective in producing EMG activity in LL and ML, for comparison of afferent projections to effective versus ineffective sites. Labeled cells rostral to FG deposition at effective MRF sites were located in the preoptic area, hypothalamus, limbic forebrain and midbrain, with particularly high numbers in the ipsilateral midbrain central gray, tegmentum, paraventricular nucleus and amygdala. At medullary levels, there was a heavy projection from the contralateral Gi. FG labeled cells were also located in the contralateral parvocellular reticular nucleus, and lateral, medial and spinal vestibular nuclei. Labeled cells with ascending projections were observed in greatest number in the rostral cervical spinal cord, with fewer cells at mid cervical levels and even fewer in the lumbar spinal cord. These labeled cells were located primarily in lamina V, VII, VIII and X. Locations of labeled cells following FG deposition at ineffective MRF sites were similar. However, there was a striking difference in the number of cells retrogradely labeled from the effective MRF sites compared to ineffective MRF sites. Significantly greater numbers of labeled cells were observed in the contralateral MRF, the midbrain, and the cervical spinal cord from the FG deposition at effective stimulation sites. These results suggest that one characteristic of MRF sites that activate epaxial muscles is a larger amount of afferent input, from the midbrain central gray and from contralateral Gi, compared to ineffective MRF sites. Ascending and descending inputs converge at the effective MRF sites, and the larger number of descending projections suggests a more powerful contribution of these afferents to deep lumbar back muscle activation.Abbreviations Amyg amygdala - Aq Aqueduct - C Cervical spinal cord - CC Central canal - ECu External cuneate - F Fornix - FG Fluoro-Gold - Gi Gigantocellular reticular nucleus - GiA Gigantocellular reticular nucleus, alpha - GiV Gigantocellular reticular nucleus, ventral - icp inferior cerebellar peduncle - IO Inferior olive - L Lumbar spinal cord - LL Lateral longissimus - LVN Lateral vestibular nucleus - MCG Midbrain central gray - ML Medial longissimus - ml medial lemniscus - MRF Medullary reticular formation - MVN Medial vestibular nucleus - OT Optic tract - PCRt Parvocellular reticular nucleus - Pn Pontine nuclei - PnO Pontine reticular nucleus, oral - PPT Pedunculopontine tegmental nucleus - PVN Paraventricular nucleus - py pyramidal tract - Sol nucleus of the solitary tract - Sp5 Spinal trigeminal nucleus - VMN Ventromedial nucleus - 3v third ventricle - 7 Facial nucleus - 12 hypoglossal nucleus     

Tachykinin immunoreactivity in terminals of trigeminal afferent fibers in adult and fetal monkey thalamus

Summary Immunocytochemistry of fetal and adult monkey thalamus reveals a dense concentration of tachykinin immunoreactive fibers and terminals in the dorsolateral part of the VPM nucleus in which the contralateral side of the head, face and mouth is represented. The immunoreactive fibers enter the VPM nucleus from the thalamic fasciculus and electron microscopy reveals that they form large terminals resembling those of lemniscal axons and terminating in VPM on dendrites of relay neurons and on presynaptic dendrites of interneurons. Double labeling strategies involving immunostaining for tachykinins after retrograde labeling of brainstem neurons projecting to the VPM failed to reveal the origin of the fibers. The brainstem trigeminal nuclei, however, are regarded as the most likely sources of the VPM-projecting, tachykinin positive fibers.Abbreviations AB ambiguus nucleus - AN abducens nucleus - C cuneate nucleus - CD dorsal cochlear nucleus - CL central lateral nucleus - CM centre médian nucleus - D dendrite - DR dorsal raphe - DV dorsal vagal nucleus - EC external cuneate nucleus - FM medial longitudinal fasciculus - FN facial nucleus - G gracile nucleus - Gc gigantocellular reticular formation - HN hypoglossal nucleus - ICP inferior cerebellar peduncle - IO inferior olivary complex - LC locus coeruleus - LL lateral lemniscus - LM medial lemniscus - M5 motor trigeminal nucleus - NS solitary nucleus - OS superior olivary complex - P dendritic protrusion - Pb parabrachial nucleus - Pc parvocellular reticular formation - PLa anterior pulvinar nucleus - Pp prepositus hypoglossi nucleus - Ps presynaptic region - Py pyramidal tract - P5 principal sensory trigeminal nucleus - R reticular nucleus - RF reticular formation - RL lateral reticular nucleus - S5 spinal trigeminal nucleus - T terminal - T5 spinal trigeminal tract - VL lateral vestibular nucleus - VM medial vestibular nucleus - VMb basal ventral medial nucleus - VPI ventral posterior inferior nucleus - VPL ventral posterior lateral nucleus - VPM ventral posterior medial nucleus - VR ventral raphe - VS superior vestibular nucleus - VSp spinal vestibular nucleus - ZI zona incerta - 5 trigeminal nerve - 6 abducens nerve - 7 facial nerve     

The spinal route of sympatho-inhibitory pathways descending from the medulla oblongata

1. The effect of making discrete lesions in the cervical spinal cord on the brainstem elicited inhibition of a spinal somato-sympathetic reflex response has been studied in anaesthetized cats. 2. Electrical stimulation within three areas of the medulla caused an inhibition of the spinal component of the reflex response elicited in thoracic white rami communicantes by stimulation of intercostal nerves. The three medullary areas studied were the ventrolateral medulla and the caudal rephe nucleus, from where bulbospinal monoamine neurones originate, and the ventromedial reticular formation. 3. The inhibitory effects of stimulation in the ventrolateral medulla and raphe nucleus were abolished by the destruction of parts of the ipsilateral dorsolateral funiculus of the cervical spinal cord, whereas the inhibition produced by ventromedial reticular formation stimulation was abolished by lesions which included part of the ventral quadrant of the cord. 4. The time course of the inhibitory effects of electrical stimulation of descending sympatho-inhibitory tracts in the cervical spinal cord was studied in unanaesthetized decerebrate cats spinalized at C1. Inhibition obtained from the dorsolateral funiculus characteristically had a longer time to onset than inhibition obtained from the ventrolateral and ventral funiculi.     

P物质阳性神经纤维对球海绵体肌和坐骨海绵体肌运动神经元的支配——HRP逆行示踪与免疫细胞化学研究

本研究应用 HRP逆行示踪与免疫细胞化学相结合的双重反应技术观察了 P物质纤维与前角躯体运动神经元的关系。用 WGA-HRP经大鼠球海绵体肌和坐骨海绵体肌注射后 ,逆行示踪标记的运动神经元分布于 L5 和 L6脊髓前角的背内侧核和背外侧核内侧部。 SP能纤维广泛分布于脊髓灰质 ,其中以后角最为密集。光镜下可见在前角的背内侧核和背外侧核内 ,SP阳性纤维呈点状和带有钮扣状膨大的纤维分布于逆行标记的运动神经元周围。电镜下可见 SP阳性纤维终末含有少量的大型囊泡和多量的清亮小泡。常见 SP阳性纤维末梢与 HRP逆行标记的运动神经元有紧密联系 ,并证明二者形成突触结构。本研究首次证实脑下行 P物质阳性纤维对调控球海绵体肌和坐骨海绵体肌运动神经元有直接支配关系 ,提示 P物质能纤维参与阴茎勃起和射精过程     

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.