Excitatory rubral cells encode the acquisition of novel complex motor tasks.

The red nucleus (RN) is required for limb control, specifically fine motor coordination. There is some evidence for a role of the RN in reaching and grasping, mainly from lesion studies, but results so far have been inconsistent. In addition, the role of RN neurons in such learned motor functions at the level of synaptic transmission has been largely neglected. Here, we show that Vglut2-expressing RN neurons undergo plastic events and encode the optimization of fine movements. RN light-ablation severely impairs reaching and grasping functions while sparing general locomotion. We identify a neuronal population co-expressing Vglut2, PV and C1QL2, which specifically undergoes training-dependent plasticity. Selective chemo-genetic inhibition of these neurons perturbs reaching and grasping skills. Our study highlights the role of the Vglut2-positive rubral population in complex fine motor tasks, with its related plasticity representing an important starting point for the investigation of mechanistic substrates of fine motor coordination training.

Spontaneous activity and functional connectivity in the developing cerebellorubral system.

The development of the cerebellar system depends in part on the emergence of functional connectivity in its input and output pathways. Characterization of spontaneous activity within these pathways provides insight into their functional status in early development. In the present study we recorded extracellular activity from the interpositus nucleus (IP) and its primary downstream target, the red nucleus (RN), in unanesthetized rats at postnatal days 8 (P8) and P12, a period of dramatic change in cerebellar circuitry. The two structures exhibited state-dependent activity patterns and age-related changes in rhythmicity and overall firing rate. Importantly, sensory feedback (i.e., reafference) from myoclonic twitches (spontaneous, self-generated movements that are produced exclusively during active sleep) drove neural activity in the IP and RN at both ages. Additionally, anatomic tracing confirmed the presence of cerebellorubral connections as early as P8. Finally, inactivation of the IP and adjacent nuclei using the GABAA receptor agonist muscimol caused a substantial decrease in neural activity in the contralateral RN at both ages, as well as the disappearance of rhythmicity; twitch-related activity in the RN, however, was preserved after IP inactivation, indicating that twitch-related reafference activates the two structures in parallel. Overall, the present findings point to the contributions of sleep-related spontaneous activity to the development of cerebellar networks.

Absolute number of parvicellular and magnocellular neurons in the red nucleus of the rat midbrain: a stereological study.

The absolute number of parvicellular and magnocellular neurons in the red nucleus was estimated using design-based stereological counting methods and systematic random sampling techniques. Six young adult male rats, and a complete set of serial 40-µm glycolmethacrylate sections for each rat, were used to quantify neuronal numbers. After a random start, a systematic subset (i.e. every third) of the serial sections was used to estimate the total volume of the red nucleus using Cavalieri's method. The same set of sampled sections was used to estimate the number of neurons in a known subvolume (i.e. the numerical density Nv ) by the optical disector method. Multiplication of the total volume by Nv yielded the absolute number of neurons. It was found that the right red nucleus consisted, on average, of 8400 parvicellular neurons (with a coefficient of variation of 0.16) and 7000 magnocellular neurons (0.12). These total neuronal numbers provide important data for the transfer of information through these nuclei and for species comparisons.

Interstitial branch formation within the red nucleus by deep cerebellar nuclei-derived commissural axons during target recognition.

Target recognition by developing axons is one of the fundamental steps for establishing the proper pattern of neuronal connectivity during development. However, knowledge of the mechanisms that underlie this critical event is still limited. In this study, to examine how commissural axons in vertebrates recognize their targets after crossing the midline, we analyzed in detail the behavior of postcrossing commissural axons derived from the deep cerebellar nuclei (DCN) in the developing mouse cerebellum. For this, we employed a cell-type-specific genetic labeling approach to selectively visualize DCN axons during the time when these axons project to the red nucleus (RN), one of the well-characterized targets of DCN axons. We found that, when DCN axons initially entered the RN at its caudal end, these axons continued to grow rostrally through the RN without showing noticeable morphological signs of axon branching. Interestingly, after a delay, DCN axons started forming interstitial branches from the portion of the axon shaft selectively within the RN. Because commissural axons acquire responsiveness to several guidance cues when they cross the midline, we further addressed whether midline crossing is a prerequisite for subsequent targeting by using a Robo3 knockdown strategy. We found that DCN axons were still capable of forming interstitial branches within the RN even in the absence of midline crossing. These results therefore suggest that the mechanism of RN recognition by DCN axons involves a delayed interstitial branching, and that these axons possess an intrinsic ability to respond to the target-derived cues irrespective of midline crossing.

Cerebellar Premotor Output Neurons Collateralize to Innervate the Cerebellar Cortex.

Motor commands computed by the cerebellum are hypothesized to use corollary discharge, or copies of outgoing commands, to accelerate motor corrections. Identifying sources of corollary discharge, therefore, is critical for testing this hypothesis. Here we verified that the pathway from the cerebellar nuclei to the cerebellar cortex in mice includes collaterals of cerebellar premotor output neurons, mapped this collateral pathway, and identified its postsynaptic targets. Following bidirectional tracer injections into a distal target of the cerebellar nuclei, the ventrolateral thalamus, we observed retrogradely labeled somata in the cerebellar nuclei and mossy fiber terminals in the cerebellar granule layer, consistent with collateral branching. Corroborating these observations, bidirectional tracer injections into the cerebellar cortex retrogradely labeled somata in the cerebellar nuclei and boutons in the ventrolateral thalamus. To test whether nuclear output neurons projecting to the red nucleus also collateralize to the cerebellar cortex, we used a Cre-dependent viral approach, avoiding potential confounds of direct red nucleus-to-cerebellum projections. Injections of a Cre-dependent GFP-expressing virus into Ntsr1-Cre mice, which express Cre selectively in the cerebellar nuclei, retrogradely labeled somata in the interposed nucleus, and putative collateral branches terminating as mossy fibers in the cerebellar cortex. Postsynaptic targets of all labeled mossy fiber terminals were identified using immunohistochemical Golgi cell markers and electron microscopic profiles of granule cells, indicating that the collaterals of nuclear output neurons contact both Golgi and granule cells. These results clarify the organization of a subset of nucleocortical projections that constitute an experimentally accessible corollary discharge pathway within the cerebellum.

Glutamate neurons in the substantia nigra compacta and retrorubral field.

Dopaminergic neurons of the substantia nigra compacta (SNC), ventral tegmental area (VTA) and retrorubral field (RRF) play a role in reward, motivation, learning, memory, and movement. These neurons are intermingled with GABAergic neurons. Recent evidence shows that the VTA contains glutamatergic neurons expressing vesicular glutamate transporter type 2 (VGluT2); some of them co-express tyrosine hydroxylase (TH). Here, we used a combination of radioactive in situ hybridisation and immunohistochemistry to explore whether any of the vesicular glutamate transporters [vesicular glutamate transporter type 1 (VGluT1), VGluT2, or vesicular glutamate transporter type 3 (VGluT3)] were encoded by neurons in the SNC or RRF. We found expression of VGluT2 mRNA, but not of VGluT1 or VGluT3, in the SNC and RRF. These VGluT2 neurons rarely showed TH immunoreactivity. Within the SNC, the VGluT2 neurons were infrequently found at the rostral level, but were often seen at the medial and caudal levels intercalated in the mediolateral portion of the dorsal tier, at a ratio of one VGluT2 neuron per 4.4 TH neurons. At this level, VGluT2 neurons were also found in the adjacent substantia nigra reticulata and substantia nigra pars lateralis. Within the RRF, the VGluT2 neurons showed an increasing rostrocaudal gradient of distribution. The RRF proportion of VGluT2 neurons in relation to TH neurons was constant throughout the rostrocaudal levels, showing an average ratio of one VGluT2 neuron per 1.7 TH neurons. In summary, we provide evidence indicating that the SNC and RRF, which are traditionally considered to be dopaminergic areas, have neurons with the ability to participate in glutamate signaling.

Mesencephalic neuronal populations: new insights on the ventral differentiation programs.

The midbrain is a complex structure where different functions are located. This formation is mainly involved in the visual and auditory information process (tectum) and visual movements and motor coordination (tegmentum). Here we display a complete description of midbrain anatomy based on the prosomeric model and of the developmental events that take place to generate this structure. We also summarize the new data about the differentiation and specification of the basal populations of the midbrain. The neural tube suffers the influence of several secondary organizers. These signaling centers confer exact positional information to the neuroblasts. In the midbrain these centers are the Isthmic organizer for the antero-posterior axis and the floor and roof plates for the dorso-ventral axis. This segment of the brain contains, in the dorsal part, structures such as the collicula (superior and inferior), tectal grey and the preisthmic segment, and in the basal plate, neuronal populations such as the oculomotor complex, the dopaminergic substantia nigra and the ventral tegmental area, the reticular formation and the periacueductal grey. Knowledge of the genetic cascades involved in the differentiation programs of the diverse populations will be extremely important to understand not only how the midbrain develops, but how degenerative pathologies, such as Parkinson's disease, occurs. These cascades are triggered by signaling molecules such as Shh, Fgf8 or Wnt1 and are integrated by receptor complexes and transcription factors. These are directly responsible for the induction or repression of the differentiation programs that will produce a specific neuronal phenotype.

The red nucleus and the rubrospinal projection in the mouse.

We studied the organization and spinal projection of the mouse red nucleus with a range of techniques (Nissl stain, immunofluorescence, retrograde tracer injections into the spinal cord, anterograde tracer injections into the red nucleus, and in situ hybridization) and counted the number of neurons in the red nucleus (3,200.9 ± 230.8). We found that the rubrospinal neurons were mainly located in the parvicellular region of the red nucleus, more lateral in the rostral part and more medial in the caudal part. Labeled neurons were least common in the rostral and caudal most parts of the red nucleus. Neurons projecting to the cervical cord were predominantly dorsomedially placed and neurons projecting to the lumbar cord were predominantly ventrolaterally placed. Immunofluorescence staining with SMI-32 antibody showed that ~60% of SMI-32-positive neurons were cervical cord-projecting neurons and 24% were lumbar cord-projecting neurons. SMI-32-positive neurons were mainly located in the caudomedial part of the red nucleus. A study of vGluT2 expression showed that the number and location of glutamatergic neurons matched with those of the rubrospinal neurons. In the anterograde tracing experiments, rubrospinal fibers travelled in the dorsal portion of the lateral funiculus, between the lateral spinal nucleus and the calretinin-positive fibers of the lateral funiculus. Rubrospinal fibers terminated in contralateral laminae 5, 6, and the dorsal part of lamina 7 at all spinal cord levels. A few fibers could be seen next to the neurons in the dorsolateral part of lamina 9 at levels of C8-T1 (hand motor neurons) and L5-L6 (foot motor neurons), which is consistent with a view that rubrospinal fibers may play a role in distal limb movement in rodents.

Temporal-spatial changes in Sonic Hedgehog expression and signaling reveal different potentials of ventral mesencephalic progenitors to populate distinct ventral midbrain nuclei.

BACKGROUND: The ventral midbrain contains a diverse array of neurons, including dopaminergic neurons of the ventral tegmental area (VTA) and substantia nigra (SN) and neurons of the red nucleus (RN). Dopaminergic and RN neurons have been shown to arise from ventral mesencephalic precursors that express Sonic Hedgehog (Shh). However, Shh expression, which is initially confined to the mesencephalic ventral midline, expands laterally and is then downregulated in the ventral midline. In contrast, expression of the Hedgehog target gene Gli1 initiates in the ventral midline prior to Shh expression, but after the onset of Shh expression it is expressed in precursors lateral to Shh-positive cells. Given these dynamic gene expression patterns, Shh and Gli1 expression could delineate different progenitor populations at distinct embryonic time points. RESULTS: We employed genetic inducible fate mapping (GIFM) to investigate whether precursors that express Shh (Shh-GIFM) or transduce Shh signaling (Gli1-GIFM) at different time points give rise to different ventral midbrain cell types. We find that precursors restricted to the ventral midline are labeled at embryonic day (E)7.5 with Gli1-GIFM, and with Shh-GIFM at E8.5. These precursors give rise to all subtypes of midbrain dopaminergic neurons and the anterior RN. A broader domain of progenitors that includes the ventral midline is marked with Gli1-GIFM at E8.5 and with Shh-GIFM at E9.5; these fate-mapped cells also contribute to all midbrain dopaminergic subtypes and to the entire RN. In contrast, a lateral progenitor domain that is labeled with Gli1-GIFM at E9.5 and with Shh-GIFM at E11.5 has a markedly reduced potential to give rise to the RN and to SN dopaminergic neurons, and preferentially gives rise to the ventral-medial VTA. In addition, cells derived from Shh- and Gli1-expressing progenitors located outside of the ventral midline give rise to astrocytes. CONCLUSIONS: We define a ventral midbrain precursor map based on the timing of Gli1 and Shh expression, and suggest that the diversity of midbrain dopaminergic neurons is at least partially determined during their precursor stage when their medial-lateral position, differential gene expression and the time when they leave the ventricular zone influence their fate decisions.

Neuroprotective and growth-promoting effects of bone marrow stromal cells after cervical spinal cord injury in adult rats.

BACKGROUND AIMS: Bone marrow stromal cells (BMSC) have been shown to provide neuroprotection after transplantation into the injured central nervous system. The present study investigated whether adult rat BMSC differentiated along a Schwann cell lineage could increase production of trophic factors and support neuronal survival and axonal regeneration after transplantation into the injured spinal cord. METHODS: After cervical C4 hemi-section, 5-bromo-2-deoxyuridine (BrdU)/green fluorescent protein (GFP)-labeled BMSC were injected into the lateral funiculus at 1 mm rostral and caudal to the lesion site. Spinal cords were analyzed 2-13 weeks after transplantation. RESULTS AND CONCLUSIONS: Treatment of native BMSC with Schwann cell-differentiating factors significantly increased production of brain-derived neurotrophic factor in vitro. Transplanted undifferentiated and differentiated BMSC remained at the injection sites, and in the trauma zone were often associated with neurofilament-positive fibers and increased levels of vascular endothelial growth factor. BMSC promoted extensive in-growth of serotonin-positive raphaespinal axons and calcitonin gene-related peptide (CGRP)-positive dorsal root sensory axons into the trauma zone, and significantly attenuated astroglial and microglial cell reactions, but induced aberrant sprouting of CGRP-immunoreactive axons in Rexed's lamina III. Differentiated BMSC provided neuroprotection for axotomized rubrospinal neurons and increased the density of rubrospinal axons in the dorsolateral funiculus rostral to the injury site. The present results suggest that BMSC induced along the Schwann cell lineage increase expression of trophic factors and have neuroprotective and growth-promoting effects after spinal cord injury.

Activity of red nucleus neurons in the cat during postural corrections.

The dorsal-side-up body posture in standing quadrupeds is maintained by the postural system, which includes spinal and supraspinal mechanisms driven by somatosensory inputs from the limbs. A number of descending tracts can transmit supraspinal commands for postural corrections. The first aim of this study was to understand whether the rubrospinal tract participates in their transmission. We recorded activity of red nucleus neurons (RNNs) in the cat maintaining balance on the periodically tilting platform. Most neurons were identified as rubrospinal ones. It was found that many RNNs were profoundly modulated by tilts, suggesting that they transmit postural commands. The second aim of this study was to examine the contribution of sensory inputs from individual limbs to posture-related RNN modulation. Each RNN was recorded during standing on all four limbs, as well as when two or three limbs were lifted from the platform and could not signal platform displacements. By comparing RNN responses in different tests, we found that the amplitude and phase of responses in the majority of RNNs were determined primarily by sensory input from the corresponding (fore or hind) contralateral limb, whereas inputs from other limbs made a much smaller contribution to RNN modulation. These findings suggest that the rubrospinal system is primarily involved in the intralimb postural coordination, i.e., in the feedback control of the corresponding limb and, to a lesser extent, in the interlimb coordination. This study provides a new insight into the formation of supraspinal motor commands for postural corrections.

Nkx6-1 controls the identity and fate of red nucleus and oculomotor neurons in the mouse midbrain.

Little is known about the cues controlling the generation of motoneuron populations in the mammalian ventral midbrain. We show that Otx2 provides the crucial anterior-posterior positional information for the generation of red nucleus neurons in the murine midbrain. Moreover, the homeodomain transcription factor Nkx6-1 controls the proper development of the red nucleus and of the oculomotor and trochlear nucleus neurons. Nkx6-1 is expressed in ventral midbrain progenitors and acts as a fate determinant of the Brn3a(+) (also known as Pou4f1) red nucleus neurons. These progenitors are partially dorsalized in the absence of Nkx6-1, and a fraction of their postmitotic offspring adopts an alternative cell fate, as revealed by the activation of Dbx1 and Otx2 in these cells. Nkx6-1 is also expressed in postmitotic Isl1(+) oculomotor and trochlear neurons. Similar to hindbrain visceral (branchio-) motoneurons, Nkx6-1 controls the proper migration and axon outgrowth of these neurons by regulating the expression of at least three axon guidance/neuronal migration molecules. Based on these findings, we provide additional evidence that the developmental mechanism of the oculomotor and trochlear neurons exhibits more similarity with that of special visceral motoneurons than with that controlling the generation of somatic motoneurons located in the murine caudal hindbrain and spinal cord.

Shh dependent and independent maintenance of basal midbrain.

Sonic hedgehog (Shh) is well known as the molecule responsible for the induction and maintenance of ventral neural tube structures. Recent data have shown that ventral neuronal populations react differentially to the amount of this morphogen not only in the spinal cord, but also in more rostral parts of the brain, like the midbrain. A dorsal expansion in the Shh expression domain modifies the differentiation program in this territory. The lack of Shh produces alterations in the development of this area as well. Here, for the first time, we analyze in detail the development of the different mesencephalic basal nuclei in the absence of Shh. We report that the oculomotor complex is lost, the dopaminergic populations are strongly affected but the red nucleus is maintained. These results point out that not all the midbrain neuronal populations are dependent on Shh for their maintenance, as previously thought. Based on our results and recently published data, we suggest the existence of a specific genetic pathway for the specification of the mesencephalic red nucleus. Foxa2 could be the candidate gene that might control this genetic pathway.

Functional connectivity of the human red nucleus in the brain resting state at 3T.

BACKGROUND AND PURPOSE: Previous structural data obtained with diffusion tensor imaging axonal tracking have demonstrated possible in vivo connections between the human red nucleus (RN) and the sensorimotor and associative cortical areas. However, tractographic reconstructions can include false trajectories because of, for instance, the low spatial resolution of diffusion images or the inability to precisely detect fiber crossings. The rubral network was therefore reassessed by functional connectivity during the brain resting state. Because the RN is located very close to the substantia nigra (SN), the nigral network was also studied to ensure that these 2 circuits were correctly dissociated. MATERIALS AND METHODS: Data from 14 right-handed healthy volunteers were acquired at rest and analyzed by region-of-interest (ROI)-based functional connectivity. The blood oxygen level-dependent (BOLD) signal intensity fluctuations of separate ROIs located in the RN and SN were successively used to identify significant temporal correlations with BOLD signal intensity fluctuations of other brain regions. RESULTS: Low-frequency BOLD signal intensity of the RN correlated with signal intensity fluctuations in the cerebellum; mesencephalon; SN; hypothalamus; pallidum; thalamus; insula; claustrum; posterior hippocampus; precuneus; and occipital, prefrontal, and fronto-opercular cortices. Despite some cortical and subcortical overlaps with nigral connectivity, this rubral network was clearly distinct from the nigral network, which showed a strong correlation with the striatum; cerebellar vermis; and more widespread frontal, prefrontal, and orbitofrontal cortical areas. CONCLUSIONS: During the brain resting state, the human RN participates in cognitive circuits related to salience and executive control, and that may partly represent a subclass of its structural connectivity as revealed by tractography.

The role of different glutamate receptors in the mediation of glutamate-evoked excitation of red nucleus neurons after simulated microgravity in rat.

The present study investigates changes in red nucleus (RN) neuronal activity and the role of glutamate receptors (GluRs) after simulated microgravity (tail-suspension) in the rat using single-unit recording and microinjection. The results showed that tail-suspension for 3, 7, and 14 days could induce a significant decrease in spontaneous firing rate of RN neurons in a time-dependent manner. Unilateral microinjection of glutamate into the RN significantly increased the firing rate of RN neurons, but the increased firing rate was significantly reduced following tail-suspension time. Microinjection of the NMDA receptor antagonist MK-801 or the non-NMDA receptor antagonist DNQX into the RN blocked this excitatory effect induced by glutamate. However, microinjection of the metabotropic glutamate receptor (mGluR) antagonist (+/-)-MCPG into the RN had no effect. These results suggest that simulated microgravity can reduce excitability of RN neurons following a functional impairment of glutamate receptors. NMDA and non-NMDA receptors, but not mGluRs, are involved in the mediation of glutamate-evoked excitation of RN neurons. The decrease in excitability of RN neurons may be involved in simulated microgravity-induced muscle atrophy.

Ipsilateral actions from the feline red nucleus on hindlimb motoneurones.

The main aim of the study was to investigate whether neurones in the ipsilateral red nucleus (NR) affect hindlimb motoneurones. Intracellular records from motoneurones revealed that both EPSPs and IPSPs were evoked in them via ipsilaterally located premotor interneurones by stimulation of the ipsilateral NR in deeply anaesthetized cats in which only ipsilaterally descending tract fibres were left intact. When only contralaterally descending tract fibres were left intact, EPSPs mediated by excitatory commissural interneurones were evoked by NR stimuli alone while IPSPs mediated by inhibitory commissural interneurones required joint stimulation of the ipsilateral NR and of the medial longitudinal fascicle (MLF, i.e. reticulospinal tract fibres). Control experiments led to the conclusion that if any inadvertently coactivated axons of neurones from the contralateral NR contributed to these PSPs, their effect was minor. Another aim of the study was to investigate whether ipsilateral actions of NR neurones, pyramidal tract (PT) neurones and reticulospinal tract neurones descending in the MLF on hindlimb motoneurones are evoked via common spinal relay neurones. Mutual facilitation of these synaptic actions as well as of synaptic actions from the contralateral NR and contralateral PT neurones showed that they are to a great extent mediated via the same spinal neurones. A more effective activation of these neurones by not only ipsilateral corticospinal and reticulospinal but also rubrospinal tract neurones may thus contribute to the recovery of motor functions after injuries of the contralateral corticospinal tract neurones. No evidence was found for mediation of early PT actions via NR neurones.

Loss of neuronal projections in the dystrophin-deficient mdx mouse is not progressive.

Lack of dystrophin is known to reduce several cerebral fiber systems. To investigate if the loss of fibers is progressive, we analyzed projections of the trigeminal sensory system to the red nucleus in 3, 6, and 12 month old dystrophin-deficient mdx mice. The retrograde tracer fluorogold was injected in the magnocellular part of the red nucleus, and the number of labeled neurons in the oral part of the spinal trigeminal nucleus (Sp5O) was counted. We found that the number of labeled Sp5O neurons was reduced by 50% in mdx mice compared to age-matched control mice. The number of labeled Sp5O neurons did not change significantly between 3 and 12 months neither in mdx nor in control mice. In addition, the number of labeled neurons in the interstitial system of the trigeminal nerve was reduced by 43% in mdx mice. We conclude that fiber loss did not continue beyond the age of 3 months. Our data suggest that lack of full-length dystrophin impairs neuronal migration or axonal outgrowth, or increases neuronal death during fetal or early life.

Projections from the anterior interposed nucleus to the red nucleus diminish with age in the mouse.

To analyse the effect of ageing on the projection of the anterior interposed nucleus to the red nucleus, we injected the retrograde tracer fluorogold in the red nucleus of 3-, 6- and 12-month-old mice. The number of labelled neurones in the anterior interposed nucleus fell by 9% between 3 and 6 months and by another 9% between 6 and 12 months (all P < 0.001). This suggests that loss of neurones from the cerebellar nuclei starts well before old age.

BYHWD rescues axotomized neurons and promotes functional recovery after spinal cord injury in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Buyang Huanwu Decoction (BYHWD), a Chinese prescription that has been used for hundreds of years to treat paralysis, has gained attention recently due to its significant neuroprotective properties. AIM OF THE STUDY: This study was to investigate whether BYHWD treatment protected axotomized rubrospinal neurons (RN) following spinal cord injury (SCI) in rats. MATERIALS AND METHODS: Adult rats received a right lateral funiculus transection at the level between C3 and C4, and were either treated with BYHWD or with distilled water (DW) via gastrogavage. Effects on RN viability and atrophy were determined by Nissl staining, axon regeneration was examined by biotinylated dextran amine (BDA) tracing techniques and functional recovery was studied by a test of forelimb usage during spontaneous vertical exploration. RESULTS: RN cell number and mean somal size were 20% and 29% higher, respectively, in BYHWD-treated rats relative to DW-treated rats. There were a small number of BDA-labeled axons in the caudal of injury site in BYHWD-treated rats, whereas no caudal axonal regeneration was detected in DW-treated rats. BYHWD-treated rats used the injured forelimb more often than rats treated with DW. CONCLUSIONS: These results indicate that administration of BYHWD following SCI protects injured neurons, promotes regeneration, and enhances functional recovery.

The interstitial system of the trigeminal spinal tract projects to the red nucleus in mice.

We studied projections from the interstitial system of the spinal trigeminal tract (InSy-S5T) to the red nucleus of the mouse with retrograde tracers (fluorogold and latex microbeads impregnated with rhodamine and fluorescein). Injections in the magnocellular part of the red nucleus caused labeling of cells in the rostral, intermediate, and caudal paratrigeminal nucleus (Pa5), dorsal paramarginal nucleus (PaMD), insular trigemeo-lateral cuneate nucleus (I5CuL), and the trigeminal extension of the parvocellular reticular formation (5RPC). All projections were bilateral, but contralateral projections were stronger. The number of retrogradely labeled cells in the InSy-S5T in 3-, 6-, and 12-month-old mice was similar. Injections restricted to the parvocellular red nucleus did not label the nuclei of the InSy-S5T. This projection from the InSy-S5T to the red nucleus may mediate modulation of the facial muscles by pain and other sensory information.