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     

Hypothalamic effects on medullary reticular activation of deep back muscle EMG

Medullary reticular stimulation can activate deep back muscle EMG in urethane-anesthetized female rats. Midbrain central gray stimulation can facilitate brainstem reticular control over deep back muscles. Since these deep back muscles lateral longissimus (LL) and medial longissimus (ML) execute the vertebral dorsiflexion of lordosis behavior, and since the motor control hierarchy sketched above parallels lordosis behavior circuitry, we tested the hypothesis that medial hypothalamic lesions (which, in behavioral experiments, decrease lordosis) can also reduce medullary reticular activation of deep back muscle EMG. Urethane-anesthetized rats were tested systematically for amplitude of lateral longissimus (LL) and medial longissimus (ML) EMG responses to electrical stimulus trains applied to the nucleus gigantocellularis (NGC) of the medullary reticular formation, before and after electrolytic lesions of the ventromedial hypothalamus (n = 18) or control sites (n = 30). Bilateral ventromedial hypothalamic lesions were able to greatly reduce EMG responses in LL and ML, often with a time course similar to previous lordosis behavioral results. Surprisingly, lesions at the anterior ventromedial nucleus pole were particularly effective, and may reflect importance of intraventromedial local neurons. Although, on the average, various control lesions were less effective, the ventromedial hypothalamic effect was not unique. For example, it was possible to see an EMG decrease following lesions of the dorsomedial thalamus. Nevertheless, EMG loss was not well correlated with changes in the cortical EEG, and thus does not appear to be a simple consequence of changes in "arousal." In conclusion, it appears that ventromedial hypothalamic neurons can affect medullary reticular control of back muscle EMG, but must share this role with other forebrain elements.     

Vestibulospinal and reticulospinal interactions in the activation of back muscle EMG in the rat

Summary The effects of electrical stimulation of the lateral vestibular nucleus (LVN) and medullary reticular formation (RF) on electromyographic activity in axial muscles medial longissimus (ML) and lateral longissimus (LL) in the rat were studied. Long trains (150–500 ms) at 200–330 Hz and 20–100 A were sufficient to activate ML and LL at latencies of 20–100 ms from the beginning of the train. Results of stimulation at 200–330 Hz to RF or LVN showed that muscle units were activated at a fixed latency from any effective pulse in the stimulus train. Using high frequency (1 kHz) trains of 3–6 pulses to LVN, EMG activity was detected at minimum latencies of 3.5–6 ms. When conduction times from the medulla to the spinal cord, and the spinal cord to the muscle are subtracted, this latency range is consistent with monosynaptic activation. In many cases, muscle units were recruited in order of size, with both RF and LVN stimulation. Combined stimulation of LVN and RF sites in n. gigantocellularis led to EMG activity in ML and LL at currents which were insufficient to evoke activity when presented singly. When stimulation of one site (300–400 ms train) was just sufficient to evoke a response, a shorter, overlapping train (100–150 ms) to the other site led to a higher rate of muscle activity that continued through the end of the long train, even after the short train had ended. In all cases, the effect of RF facilitating LVN was similar to the effect of LVN facilitating RF. The evidence for convergence between these two systems in the medulla and the spinal cord is discussed.     

Reticulospinal neurons in the pontomedullary reticular formation of the monkey (Macaca fascicularis)

Recent neurophysiological studies indicate a role for reticulospinal neurons of the pontomedullary reticular formation (PMRF) in motor preparation and goal-directed reaching in the monkey. Although the macaque monkey is an important model for such investigations, little is known regarding the organization of the PMRF in the monkey. In the present study, we investigated the distribution of reticulospinal neurons in the macaque. Bilateral injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) were made into the cervical spinal cord. A wide band of retrogradely labeled cells was found in the gigantocellular reticular nucleus (Gi) and labeled cells continued rostrally into the caudal pontine reticular nucleus (PnC) and into the oral pontine reticular nucleus (PnO). Additional retrograde tracing studies following unilateral cervical spinal cord injections of cholera toxin subunit B revealed that there were more ipsilateral (60%) than contralateral (40%) projecting cells in Gi, while an approximately 50:50 ratio contralateral to ipsilateral split was found in PnC and more contralateral projections arose from PnO. Reticulospinal neurons in PMRF ranged widely in size from over 50 μm to under 25 μm across the major somatic axis. Labeled giant cells (soma diameters greater than 50 μm) comprised a small percentage of the neurons and were found in Gi, PnC and PnO. The present results define the origins of the reticulospinal system in the monkey and provide an important foundation for future investigations of the anatomy and physiology of this system in primates.     

家兔中脑网状结构内巨细胞至脊髓的投射——HRP法及WGA HRP法研究

在家兔中脑网状结构中,我们看到一些散在的巨细胞,位于红核头侧半背外方的中脑被盖内,形态和大小与延髓网状核的巨细胞相似。将HRP或WGA-HRP注入家兔颈、胸或腰段脊髓后,这些散在的巨细胞超过半数被标记。并以红核头端平面出现最多。在标记细胞附近还出现了标记终末,说明中脑网状结构与脊髓之间存在着往返联系。     

Fluorescent retrograde triple labeling of brainstem reticular neurons

The present study was aimed at the anatomical identification in the rat of neurons of the lower brainstem reticular formation which give off axonal branches ascending bilaterally to more rostral structures and descending unilaterally to the spinal cord. Three fluorescent tracers were injected in one and the same animal. Fast Blue was injected in the midbrain tegmentum, in the termination areas and fiber bundles of the ascending reticular efferents; Evans blue was injected in the midbrain tegmentum on the other side; either Nuclear Yellow or Diamidino Yellow was injected in the white and gray matter of the upper cervical cord. All three populations of single-labeled cells, as well as double labeled either from the midbrain injections or from the ipsilateral injections in the mesencephalon and spinal cord, were intermingled in the medial reticular formation. Very few cells double labeled from the contralateral mesencephalon and ipsilateral spinal cord were also seen. However, the main finding of the present study was the visualization of triple-labeled cells. The latter were mainly located ipsilaterally to the injections in the spinal cord. The present results indicate that reticular cells give off divergent multiple branches descending to the ipsilateral spinal cord and ascending bilaterally to rostral centers.     

Projections from the brain to the spinal cord in the mouse

The cells that project from the brain to the spinal cord have previously been mapped in a wide range of mammalian species, but have not been comprehensively studied in the mouse. We have mapped these cells in the mouse using retrograde tracing after large unilateral Fluoro-Gold (FG) and horseradish peroxidase (HRP) injections in the C1 and C2 spinal cord segments. We have identified over 30 cell groups that project to the spinal cord, and have confirmed that the pattern of major projections from the cortex, diencephalon, midbrain, and hindbrain in the mouse is typically mammalian, and very similar to that found in the rat. However, we report two novel findings: we found labeled neurons in the precuneiform area (an area which has been associated with the midbrain locomotor center in other species), and the epirubrospinal nucleus. We also found labeled cells in the medial division of central nucleus of the amygdala in a small number of cases. Our findings should be of value to researchers engaged in evaluating the impact of spinal cord injury and other spinal cord pathologies on the centers which give rise to descending pathways.     

豚鼠脑桥被盖部位HRP逆行标记的传入联系

本研究应用HRP微电泳技术,将HRP注射至豚鼠脑桥的腹侧被盖和背侧被盖,追踪其逆行传入投射。将HRP注射至脑桥腹侧被盖后,中脑上丘腹侧的中脑水管周围灰质和网状结构交界处(MSR),具有较密集的标记神经元。此外,在下丘腹侧的楔状核(MLR)、三叉神经脊束核、延髓网状巨细胞核、前庭内和外侧核、蓝斑及其腹侧的网状结构部分以及脊髓颈膨大灰质,也观察到了标记细胞。将HRP注射至脑桥背侧被盖后,脑桥尾侧网状核和延髓巨细胞网状核的标记神经元较多,前庭内、外侧核和外侧楔束核也见到标记细胞,中脑部位仅在红核及其附近见到少量标记细胞。蓝斑及其腹侧的网状结构部分和脊髓灰质未见标记细胞。     

大鼠三叉神经脊束核尾侧亚核和脊髓向丘脑和臂旁核的强啡肽能和一氧化氮能投射

本文用荧光金逆行追踪与免疫荧光组化染色相结合的方法，对大鼠三叉神经脊束核尾侧亚核和颈髓背角浅层向丘脑腹基底复合体和臂旁核的强啡肽能和NO能投射进行了研究．强啡肽原前体样阳性胞体主要位于尾侧亚核和颈髓背角的Ⅰ层和Ⅱ层外侧部；NOS样阳性胞体主要位于尾侧亚核和颈够背角Ⅱ层，Ⅰ层较少。将荧光金注入丘脑腹基底复合体后，荧光金逆标神经元主要见于对侧尾侧亚核、颈髓背角的Ⅰ层和外侧网状核，Ⅱ层偶见；将荧光金注入臂旁核后，逆标神经元主要见于同侧尾侧亚核和颈髓背角的Ⅰ、Ⅱ层，少量位于外侧网状核。尾侧亚核向丘脑瓜基底复合体投射神经元的16．6％，向臂旁核投射神经元的24．8％呈强啡肽原前体样阳性；颈髓背角浅层向丘脑腹基底复合体投射神经元的19．2％，向臂旁核投射神经元的272％呈强啡肽原前体样阳性。向丘脑腹基底复合体和臂旁核投射的强啡肽原前体／荧光金双标神经元分别占尾侧亚核浅层内强啡肽原前体样阳性神经元总数的7％和18％，分别占颈髓背角浅层内强啡肽原前体样阳性神经元总数的8．1％和21．9％。这些双标神经元多呈大梭形及中等大圆形和梨形。由昆侧亚核向丘脑腹基底复合体投射神经元的5．1％呈NOS阳性，向臂旁核投射神经元的11．8％呈NOS阳性。由颈髓背角浅层向丘脑版?     

大鼠三叉神经脊束核尾侧亚核和脊髓向丘脑和臂旁核的谷氨酸能投射

本研究用荧光金逆行追踪与免疫荧光组比技术相结合的方法,对大鼠三叉神经脊束核尾侧亚核和脊髓向丘脑和臂旁核的谷氨酸能投射进行了观察。磷酸激活的谷氨酸胺酶（PAG）是谷氨酸能神经元的特异性标识物。PAG样阳性胞体主要位于三叉神经脊束核尾侧亚核和颈髓背角的Ⅰ层,少量PAG样阳性胞体也见于它们的Ⅱ层外侧部及外侧网状核。将荧光金注入丘脑腹基底复合体后．荧光金逆标神经元主要见于对侧三叉神经脊束核尾侧亚核和颈髓背角的Ⅰ层及外侧网状核;将荧光金注入臂旁核后,荧光金逆标神经元也主要见于对侧三叉神经脊束核尾侧亚核和颈髓背角的Ⅰ层及外侧网状核。三叉神经脊束核尾侧亚核向丘脑腹基底复合体投射神经元的12．4％,向臂旁核投射神经元的13．2％呈PAG样阳性;颈髓背角浅层向丘脑瓜基底复合体投射神经元的12．7％,向臂旁核投射神经元的14．3％呈PAG样阳性。向丘脑腹基底复合体和臂旁核投射的PAG／荧光金双标神经元分别占三叉神经脊束核尾侧亚核浅层内PAG样阳性神经元总数的13％和24．6％,向丘脑腹基底复合体和臂旁核投射的PAG／荧光金双标神经元分别占颈髓背角浅层内PAG样阳性神经元总数的11．6％和30．1％。外侧网状核内的部分PAG样阳性神经元也向丘脑腹基底复合体或臂旁核投射。Ⅰ层内的双?     

Inhibition of primate spinothalamic tract neurons by stimulation in periaqueductal gray or adjacent midbrain reticular formation

Recordings were made from spinothalamic tract (STT) cells in the lumbosacral enlargement of anesthetized monkeys. The cells were identified by antidromic activation from the contralateral ventral posterior lateral nucleus of the thalamus. Electrical stimulation at sites within the periaqueductal gray, the adjacent midbrain reticular formation, or the deep layers of the tectum were found to inhibit the activity of STT cells. In general, midbrain stimulation inhibited the background discharges and the responses of wide dynamic range cells evoked by innocuous and noxious cutaneous stimulation (29 of 37 cases). However, for six cells, midbrain stimulation preferentially inhibited the responses to noxious stimulation. The evoked responses of all 10 high-threshold cells were inhibited. In only two cases was midbrain stimulation ineffective, and no excitatory effects were observed. The mean latency to onset of inhibition resulting from midbrain stimulation was 24.9 +/- 7.2 ms (n = 35). The amount of inhibition produced by midbrain stimulation was graded with stimulus intensity. For example, trains of stimuli (333 Hz) at 50 microA produced a mean inhibition to 81.7 +/- 16.6% of control, while 200 microA resulted in a mean inhibition to 36.3 +/- 21.7%. Not only was the inhibition increased by the use of stronger current intensities, but the duration of inhibition was prolonged. Midbrain stimulation inhibited the responses of STT cells to volleys in both the A-fibers and the C-fibers of the sural nerve. However, there was a selective action in that the responses to C-fiber volleys were more strongly inhibited than were the responses to A-fiber volleys. Lesions placed in the white matter of the upper cervical spinal cord reduced the inhibition produced by stimulation in either the midbrain or the nucleus raphe magnus. The extent to which the inhibition was reduced was proportional to the extent of the cord lesions. However, even when there was an interruption of the entire lateral funiculus on the side of an STT cell and of the dorsal quadrant of the contralateral side, there was still substantial inhibition following stimulation in either brain stem site. It is concluded that while part of the inhibition is mediated by pathways descending in the dorsal lateral funiculus (DLF), at least some depends on pathways coursing through the ventral spinal cord. Inhibition of STT cells may contribute to the neuronal mechanism of the analgesia that results from stimulation in the periaqueductal gray matter in awake, behaving animals.     

The Mesencephalic Reticular Formation as a Conduit for Primate Collicular Gaze Control: Tectal Inputs to Neurons Targeting the Spinal Cord and Medulla

The superior colliculus (SC), which directs orienting movements of both the eyes and head, is reciprocally connected to the mesencephalic reticular formation (MRF), suggesting the latter is involved in gaze control. The MRF has been provisionally subdivided to include a rostral portion, which subserves vertical gaze, and a caudal portion, which subserves horizontal gaze. Both regions contain cells projecting downstream that may provide a conduit for tectal signals targeting the gaze control centers which direct head movements. We determined the distribution of cells targeting the cervical spinal cord and rostral medullary reticular formation (MdRF), and investigated whether these MRF neurons receive input from the SC by the use of dual tracer techniques in Macaca fascicularis monkeys. Either biotinylated dextran amine or Phaseolus vulgaris leucoagglutinin was injected into the SC. Wheat germ agglutinin conjugated horseradish peroxidase was placed into the ipsilateral cervical spinal cord or medial MdRF to retrogradely label MRF neurons. A small number of medially located cells in the rostral and caudal MRF were labeled following spinal cord injections, and greater numbers were labeled in the same region following MdRF injections. In both cases, anterogradely labeled tectoreticular terminals were observed in close association with retrogradely labeled neurons. These close associations between tectoreticular terminals and neurons with descending projections suggest the presence of a trans‐MRF pathway that provides a conduit for tectal control over head orienting movements. The medial location of these reticulospinal and reticuloreticular neurons suggests this MRF region may be specialized for head movement control. Anat Rec, 292:1162–1181, 2009. © 2009 Wiley‐Liss, Inc.     

Distribution of corticospinal neurons with collaterals to the lower brain stem reticular formation in monkey (Macaca fascicularis)

Summary An earlier retrograde double-labeling study in cat showed that up to 30% of the corticospinal neurons in the medial and anterior parts of the precruciate motor area represent branching neurons which project to both the spinal cord and the reticular formation of the lower brain stem. These neurons were found to be concentrated in the rostral portion of the motor cortex, from where axial and proximal limb movements can be elicited. In the present study the findings in the macaque monkey are reported. The fluorescent retrograde tracer DY was injected unilaterally in the spinal cord at C2 and the fluorescent tracer FB was injected ipsilaterally in the medial tegmentum of the medulla oblongata. In the contralateral hemisphere large numbers of single DY-labeled corticospinal neurons and single FBlabeled corticobulbar neurons were present. A substantial number of DY-FB double-labeled corticospinal neurons were also found, which must represent branching neurons projecting to both the spinal cord and the bulbar reticular formation. These neurons were present in: 1. The anterior portion of the cingulate corticospinal area in the lower bank of the cingulate sulcus; 2. The supplementary motor area (SMA); 3. The rostral part of precentral corticospinal area; 4. The upper portion of the precentral face representation area; 5. The caudal bank of the inferior limb of the arcuate sulcus; 6. The posterior part of the insula. In these areas 10% to 30% of the labeled neurons were double-labeled. The functional implications of the presence of branching corticospinal neurons in these areas is discussed.Abbreviations A nucleus ambiguus - AS arcuate sulcus - C cuneate nucleus - Cing. S. cingulate sulcus - corp. call. corpus callosum - CS central sulcus - Cx external cuneate nucleus - DCN dorsal column nuclei - dl dorsolateral intermediate zone - IO inferior olive - IP intraparietal sulcus - Lat. Fis. lateral fissure - LR lateral reticular nucleus - LS lunate sulcus - ML medial lemniscus - MLF medial longitudinal fascicle - mn motoneuronal pool - MRF medial reticular formation - Occ. occipital pole - P pyramid - PG pontine grey - PS principle sulcus - RB restiforme body - RF reticular formation - S solitary nucleus - SPV spinal trigeminal complex - STS superior temporal sulcus - Sup. Col. superior colliculus - TB trapezoid body - VC vestibular complex - vm ventromedial intermediate zone - III nucleus oculomotorius - VI nucleus abducens - VII nucleus, n. facialis - X motor nucleus n. vagus - XII nucleus hypoglossus Supported in part by grant 13-46-96 of FUNGO/ZWO (Dutch organisation for fundamental research in medicine)     

Effects of midbrain and medullary stimulation on spinomesencephalic tract cells in the cat

1. The effects of electrical stimulation at different rostrocaudal levels of the midbrain, and at sites in the rostral medulla ipsilateral and contralateral to spinal recording sites, were evaluated against the responses of 46 cells belonging to the cat spinomesencephalic tract (SMT). 2. Inhibitory and/or excitatory effects of brain stem stimulation were observed on SMT cells that responded best (26 cells) or exclusively (12 cells) to noxious mechanical or thermal stimuli, as well as on 7 cells responding only to tap and/or stimulation of deep tissues. Recording sites for 32 cells were located in laminae V-VIII (27 cells) and laminae I-III (5 cells). 3. Midbrain stimulation sites were located in the superior colliculus, central gray (CG), red nucleus, and the midbrain reticular formation. Both inhibitory-only and excitatory-only effects were observed, although the most common effect of midbrain stimulation was excitation followed by inhibition (mixed effects). The effects of stimulation at different midbrain levels were determined for each cell. Stimulation in the caudal, middle, or rostral midbrain was often found to exert different effects on the same SMT cell. 4. Stimulation in the rostral medulla at sites located in nucleus raphe magnus (NRM), nucleus reticularis gigantocellularis, and nucleus reticularis magnocellularis produced the same complement of effects observed with midbrain stimulation. Excitation followed by inhibition was the most common effect observed. 5. Stimulus intensities required to produce excitatory or inhibitory effects from midbrain were 114 +/- 85 (SD) microA and 210 +/- 91 microA, respectively. Stimulus currents required to produce excitatory or inhibitory effects from medullary stimulation sites were 124 +/- 56 microA and 70 +/- 60 microA, respectively. The mean currents required to produce mixed effects were 221 +/- 120 microA (midbrain) and 127 +/- 71 microA (medulla). Increasing the stimulus intensity used to evaluate brain stem effects increased the magnitude and duration of effects for 33 cells. Mixed effects were observed on 11 cells at stimulus intensities greater than those required to produce inhibitory-only effects. 6. Significant differences were found between the latencies of excitation and inhibition produced from different brain stem levels. These differences suggest that midbrain and medullary stimulation activate descending pathways with a wide range of conduction velocities and/or supraspinal and spinal connectivities. 7. The spinal trajectory of pathways contributing to the varied effects of brain stem stimulation as well as the complex receptive fields (RFs) of SMT cells were evaluated by the placement of lesions in the cervical spinal cord.(ABSTRACT TRUNCATED AT 400 WORDS)     

The afferent connections of the inferior olivary complex in rats: A study using the retrograde transport of horseradish peroxidase

Retrograde transport of horseradish peroxidase (HRP) was used to define the origin of afferents to the inferior olivary complex (IOC) in rats. Using both ventral and dorsal surgical approaches to the brainstem, HRP was injected into the IOC through a micropipette affixed to the tip of a 1-μl Hamilton syringe. After a 2-day postoperative survival, animals were sacrificed by transcardiac perfusion with a 1% paraformaldehyde-1.25% gluteraldehyde solution, and brains were processed according to the DeOlmos protocol (1977), using o-dianisidine as the chromogen. Labeled cells were found at many levels of the nervous system extending from lumbar spinal cord to cerebral cortex. This wide-ranging input from numerous regions clearly underscores the complexity of the IOC and its apparent involvement in several functions. Within the spinal cord, labeled neurons were identified from cervical to lumbar but not at sacral levels. These neurons were found contralaterally in the neck region of the dorsal horn and in the medial portions of the intermediate gray. In the caudal brainstem, reactive cells in the dorsal column nuclei, the spinal trigeminal nucleus, and the subnucleus y of the vestibular complex were observed primarily contralateral to the injection sites. Labeling within the gigantocellular, magnocellular, ventral, and lateral reticular nuclei and the nucleus prepositus hypoglossi was primarily ipsilateral. Reactive neurons in the medial and inferior vestibular nuclei were predominantly ipsilateral or contralateral to HRP injections into the caudal or rostral IOC, respectively. The dentate and interposed nuclei of the cerebellum contained small, lightly labeled neurons primarily contralateral to the injection site, while the fastigial nuclei contained a few relatively large, heavily labeled cells bilateral to caudal olivary injections. Ipsilaterally labeled mesencephalic regions included the periaqueductal gray, interstitial nucleus of Cajal, rostromedial red nucleus, ventral tegmental area, medial terminal nucleus of the accessory optic tract, nucleus of the optic tract, and the lateral deep mesencephalic nucleus. The caudal part of the pretectum and small cells of the stratum profundum of the superior colliculus were labeled predominantly contralateral to the injection. In the caudal diencephalon labeled neurons were most numerous within the nucleus of Darkschewitsch and the subparafascicular nucleus, primarily ipsilateral to olivary injections. Scattered reactive neurons were also found within the ipsilateral zone incerta. With the exception of the zona incerta, all labeled mesencephalic and diencephalic nuclei had some bilateral representation of labeled cells. No labeled neurons were identified within the basal ganglia, while numerous reactive cells were found bilaterally within layer V of the frontal and parietal cerebral cortex.     

大鼠脑干5-羟色胺能和儿茶酚胺能神经元向孤束核的投射——荧光金标记结合免疫荧光技术研究

应用荧光金逆行追踪和免疫荧光技术相结合的方法,对投射至大鼠孤束核的５－羟色胺能和儿茶酚胺能神经纤维的脑干来源进行了研究。结果证明,将荧光金注入一侧孤束核的中尾段,逆标神经元分布于脑干下行抑制系统的大部分核团。结合５－羟色胺和酪氨酸羟化酶免疫荧光组织化学技术研究发现：荧光金／５－ＨＴ 双重反应阳性神经元分布于中脑导水管周围灰质的腹外侧区、中缝背核、脑桥被盖网状核、脑桥尾侧网状核、中缝桥核、中缝正中核、中缝大核、巨细胞网状核α部、中缝隐核和中缝苍白核等核团,其中中央灰质腹外侧区、中缝大核、巨细胞网状核α部、中缝隐核、中缝苍白核等处的荧光金／５－ＨＴ 双重反应阳性神经元数量占脑干向孤束核投射的５－ＨＴ 阳性神经元总数的近７０％ （６９．９１％ ）;荧光金／酪氨酸羟化酶双重反应阳性神经元主要分布于脑干中脑中央灰质腹外侧区、Ａ７、蓝斑及蓝斑下核（Ａ６）、Ａ５、巨细胞网状核α部和Ａ１ 等核团,其中中央灰质腹外侧区、Ａ５、巨细胞网状核α部和Ａ１ 内的荧光金／酪氨酸羟化酶神经元数量占脑干向孤束核投射的酪氨酸羟化酶阳性神经元总数的８８．１７％ 。本研究提示,大鼠脑干下行抑制系统形成了至ＮＴＳ中尾段的以中脑中央灰质腹外侧区及中缝大核、?     

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     

Spinal distribution and collateral projections of rat spinomesencephalic tract cells.

The distribution of cells belonging to the rat spinomesencephalic tract was studied by means of the retrograde transport of fluorescent dyes. Bilateral midbrain injections of cytoplasmic and nuclear tracers were made in order to evaluate the location of ipsilateral, contralateral, or bilaterally projecting cells. Spinal neurons with ascending projections to midbrain and descending propriospinal projections were identified by midbrain and spinal injections of different cytoplasmic labels. The locations of spinomesencephalic tract cells included seven regions of the spinal gray matter: marginal zone, lateral neck of the dorsal horn, nucleus proprius, the region around the central canal, the lateral cervical and spinal nuclei and the ventral horn. Cells projecting to the ipsilateral or contralateral midbrain had similar distributions and were frequently found in clusters with overlapping dendritic fields. Approximately 75% of spinomesencephalic cells projected to the contralateral midbrain. The largest contribution to the spinomesencephalic tract cell population was found in cervical cord segments 1-4. Cells with bilateral projections accounted for nearly 2% of all labeled cells, whereas 5% had both ascending and descending projections. Spinomesencephalic cells were found to have varying dendritic fields and morphology, e.g. fusiform, pyramidal, round/oval, and multipolar. The results of the present study lend further support to the view that the spinomesencephalic tract is a multi-component pathway with varied origins and projection targets.     

大鼠脑干至脊髓5-羟色胺投射纤维的起源——免疫细胞化学和酶组织化学双重标记法

本文应用 HRP 逆行追踪与免疫细胞化学相结合的双重标记技术,研究了大鼠脑干至脊髓5-羟色胺(5-HT)投射纤维的起源,并对中缝核群和网状结构内5-HT 阳性细胞、HRP 标记细胞和5-HT-HRP 双重标记细胞进行了数量分析。结果表明,1.在延髓、脑桥尾侧部,5-HT-HRP双重标记细胞约占5-HT 阳性细胞的55%;占 HRP 标记细胞的45%。中脑仅有极少数5-HT-HRP双重标记细胞。2.脑干至脊髓5-HT 下行投射,主要起源于中缝苍白核、中缝隐核、中缝大核和延髓浅表弓状纤维区,所含双重标记细胞约占双重标记细胞总数的68%。3.浅表弓状纤维区、舌下神经根间核、中缝苍白核和中缝隐核主要为5-HT 下行投射;中缝大核及周围网状结构主要为非5-HT 下行投射。     

Afferent organization of the lateral reticular nucleus in the rat: An anterograde tracing study

Summary The organization of the afferent projections to the lateral reticular nucleus of the rat was investigated following placement of horseradish peroxidase-conjugated wheatgerm agglutinin into the red nucleus, fastigial nucleus, various levels of the spinal cord or the sensorimotor area of the cerebral cortex. The pattern of distribution of anterogradely labelled profiles visualized with tetramethylbenzidine revealed that the caudal three-fourths of the lateral reticular nucleus received a large, topographically organized projection from the entire length of the contralateral spinal cord. The lateral part of the rostral half of the lateral reticular nucleus received a small projection from the contralateral red nucleus, the dorsal part of the middle third of the nucleus received a diffuse projection from the contralateral fastigial nucleus, and the extreme rostromedial part of the nucleus received a sparse projection from the contralateral cerebral cortex. The dorsal part of the middle third of the lateral reticular nucleus also received a small projection from the ipsilateral cervical spinal cord. The distribution of afferent fibres from different levels of the spinal cord, red nucleus, and fastigial nucleus overlapped substantially in the middle third of the lateral reticular nucleus, whereas the cerebral cortical receiving area was separate. These data suggest that the middle third of the lateral reticular nucleus integrates spinal and supraspinal impulses to the cerebellum, while the rostral part of the nucleus is involved in a separate cerebral cortico-cerebellar pathway.Abbreviations DSC dorsal spinocerebellar - ECN external cuneatus nucleus - F fastigial nucleus - FRA flexor reflex afferents - HRP horseradish peroxidase - IO inferior olivary nucleus - IP interpositus nucleus - LRN lateral reticular nucleus - MCP magnocellular portion - M-LRN magnocellular LRN - NA nucleus ambiguus - NSTT nucleus of the spinal tract of the trigeminal nerve - PCP parvicellular portion - R red nucleus - STP subtrigeminal portion - STT spinal tract of the trigeminal nerve - TMB tetramethylbenzidine - VSC ventral spinocerebellar - WGA wheatgerm agglutinin - b-VFRT bilateral ventral flexor reflex tract - c-VFRT contralateral ventral flexor reflex tract - i-FT ipsilateral forelimb tract