Ventral Spinal Roots Research Articles

Cilostazol Ameliorates Motor Dysfunction and Schwann Cell Impairment in Streptozotocin-Induced Diabetic Rats.

This study investigated the effects of cilostazol on motor dysfunction, spinal motor neuron abnormalities, and schwannopathy in rats with diabetes. Diabetes mellitus (DM) was induced in rats via femoral intravenous streptozotocin (STZ) injection (60 mg/kg). After successful DM induction, cilostazol was administered on day 15 via oral gavage (100 mg/kg/day) for 6 weeks until sacrifice. Behavioral assays, including motor function, were performed weekly. The sciatic nerve, L5 spinal cord, and spinal ventral root were collected to evaluate the expression of the glial fibrillary acidic protein (GFAP), myelin protein zero (P0), and choline acetyltransferase (ChAT) by immunofluorescence and Western blotting. DM rats displayed decreased running speeds, running distances, and toe spread but increased foot pressure. In addition, loss of non-myelinating Schwann cells and myelin sheaths was observed in the sciatic nerve and L5 spinal ventral root. Reduced numbers of motor neurons were also found in the L5 spinal ventral horn. Cilostazol administration significantly potentiated running speed and distance; increased hind paw toe spread; and decreased foot pressure. In the sciatic nerve and L5 spinal ventral root, cilostazol treatment significantly improved non-myelinated Schwann cells and increased myelin mass. ChAT expression in motor neurons in the spinal ventral horn was improved, but not significantly. Cilostazol administration may protect sensorimotor function in diabetic rats.

Clinical Neurophysiological Methods Verify Improvement in the Motor Neural Transmission in Patients with Surgically Treated Idiopathic Scoliosis in Long-Term Follow-up

The evaluation of patients after the surgical correction of idiopathic scoliosis in a long-term follow-up with clinical neurophysiological methods has not been presented in detail. This study aimed to compare the results of neurophysiological studies in 45 girls with scoliosis of Lenke types 1–3 performed pre- (T0) and postoperatively, 1 week after surgery (T1) and 6 months after surgery (T2). The parameter values of the surface electromyography while attempting maximal contraction (mcsEMG) and the transcranial motor-evoked potentials (MEPs) recorded in the anterior tibial muscles, as well as the electroneurography (ENG) of the peripheral transmission in the peroneal nerve motor fibers, were compared. The results indicate that efferent neural conduction function both centrally and peripherally, and TA muscle function slightly improved immediately after the surgical correction of scoliosis, and further normalization appeared after six months in the long-term follow-up (at p = 0.03). The sEMG recordings indicate that half a year after surgical treatment in IS patients, the TA muscle motor unit recruitment function, as well as the muscle strength evaluated with Lovett’s scale, was comparable to the normal condition. The ENG recording results indicated a gradual reduction in the motor fiber injury symptoms, mainly of the axonal type, in the peroneal nerves. The surgeries also improved the lumbar ventral roots’ neural transmission to a normal functional status. The MEP amplitude parameter values recorded after the surgical scoliosis corrections in T1 indicated a slight improvement in the efferent transmission of neural impulses within the fibers of the spinal tracts; in the long-term T2 observation period, they reached values comparable to those recorded in healthy volunteers, bilaterally. Preoperatively (T0), the results of all the neurophysiological study parameters in the IS patients were asymmetrical at p = 0.036–0.05 and recorded as worse on the concave side, suggesting the lateralization of neurological motor deficits. One week postoperatively (T1), this asymmetry was recorded as gradually reduced, showing almost no difference between the right and left sides six months later (T2). The presented algorithm for the neurophysiological assessments performed in the pre-, intra-, and long-term postoperative periods using the mcsEMG, MEP, and ENG neurophysiological examinations, together with the clinical studies, may help in the comprehensive functional evaluation of the spinal cord tracts and ventral root neural conduction, which allows the detection of the subclinical neurological changes related to scoliosis itself and the consequences of the corrective surgery. Such an evaluation can also be significant in making final decisions regarding IS surgeries and their personalization after attempting conservative treatments with bracing and kinesiotherapy. Neurophysiological studies, as a sensitive biomarker, allowed us to predict and ascertain the final result of IS treatment in the long-term follow-up, which showed the health status of patients as being comparable to that of healthy volunteers.

Effects of local and systemic treatment with human natural killer-1 mimetic peptide (HNK-1) after ventral root avulsion and reimplantation in mice.

Spinal ventral root injuries generate significant motoneuron degeneration, which hinders full functional recovery. The poor prognosis of functional recovery can be attributed to the use or combination of different therapeutic approaches. Several molecules have been screened as potential treatments in combination with surgical reimplantation of the avulsed roots, the gold standard approach for such injuries. Among the studied molecules, human natural killer-1 (HNK-1) stands out as it is related to the stimulation of motor axon outgrowth. Therefore, we aimed to comparatively investigate the effects of local administration of an HNK-1 mimetic peptide (mp-HNK-1) and systemic treatment with ursolic acid (UA), another HNK-1 mimetic, after ventral root avulsion and reimplantation with heterologous fibrin biopolymer (HFB). Female mice of the isogenic strain C57BL/6JUnib were divided into five experimental groups: Avulsion, Reimplantation, mp-HNK-1 (in situ), and UA (systemic treatment). Mice were evaluated 2 and 12 weeks after surgery. Functional assessment was performed every four days using the Catwalk platform. Neuronal survival was analyzed by cytochemistry, and glial reactions and synaptic coverage were evaluated by immunofluorescence. Treatment with UA elicited long-term neuroprotection, accompanied by a decrease in microglial reactions, and reactive astrogliosis. The neuroprotective effects of UA were preceded by increased glutamatergic and GABAergic inputs in the ventral spinal cord two weeks after injury. However, a single application of mp-HNK-1 had no significant effects. Functional analysis showed that UA treatment led to an improvement in motor and sensory recovery. Overall, the results indicate that UA is neuroprotective, acting on glial cells and synaptic maintenance, and the combination of these findings led to a better functional recovery.

Cannabinoid receptors involved in descending inhibition on spinal seizure-like activity in the phrenic output.

Seizure-like burst activities are induced by blockade of GABAA and/or glycine receptors in various spinal ventral roots of brainstem-spinal cord preparation from neonatal rodents. We found that this is not applicable to the phrenic nerve and that a new inhibitory descending pathway may suppress seizure-like activity in the phrenic nerve. Experiments were performed in brainstem-spinal cord preparation from newborn rats (age: 0-1 day). Left phrenic nerve and right C4 activities were recorded simultaneously. When GABAA and glycine receptors were blocked by 10 μM bicuculline and 10 μM strychnine (Bic+Str), seizure-like burst activities appeared in the fourth cervical ventral root (C4) but not the phrenic nerve. After making a transverse section at C1, the inspiratory burst activity disappeared from both C4 and the phrenic nerve, whereas seizure-like activity appeared in both nerves. We hypothesized that inhibitory descending pathways other than those via GABAA and/or glycine receptors (from the medulla to the spinal cord) work to avoid disturbance of regular respiratory-related diaphragm contraction by seizure-like activity. We found that cannabinoid receptor antagonist, AM251 was effective for the induction of seizure-like activity by Bic+Str in the phrenic nerve in brainstem-spinal cord preparation. Cannabinoid receptors may be involved in this descending inhibitory system.

Morphometric analysis of the spinal cord of the Sus scrofa (large white and landrace crossbreed).

The incidence of spinal cord (SC) injury in developed and undeveloped countries is alarming. The pig (Sus scrofa) has been recommended as a suitable research model for translational studies because of its morphophysiological similarities of organ systems with humans. There is a dearth of information on the SC anatomy of the large white and landrace crossbreed (LW-LC) pigs. We therefore aim to describe the gross morphology and morphometry of its SC. Twelve juvenile LW-LC pigs (six males and six females) were used. The skin and epaxial muscles were dissected to expose the vertebral column. The SC was carefully harvested by laminectomy, and 13 gross SC morphometric parameters were evaluated. Thirty-three spinal nerves were seen emanating from either side of the SC by means of dorsal and ventral spinal roots. The overall average of SC length and weight was 36.23 ± 1.01 cm and 16.60 ± 0.58 g, respectively. However, the mean SC length and weight were higher in females compared with males, with SC weight being statistically significant. A positive relationship between SC length and weight was significant for males (p=0.0435) but not for females (p=0.42). Likewise, the strength of the relationship between SC length and weight was significant in males (r=0.82) but not significant in females (r=0.41). Baseline data for the morphometric features of the spinal cord in the LW-LC pigs were generated, which will contribute to the knowledge of this species anatomy and useful information on regional anaesthesia that should further strengthen the drive in adopting the pig as a suitable research model for biomedical research.

Mu-opioid receptor-dependent transformation of respiratory motor pattern in neonates in vitro.

Endogenous opioid peptides activating mu-opioid receptors (MORs) are part of an intricate neuromodulatory system that coordinates and optimizes respiratory motor output to maintain blood-gas homeostasis. MOR activation is typically associated with respiratory depression but also has excitatory effects on breathing and respiratory neurons. We hypothesized that low level MOR activation induces excitatory effects on the respiratory motor pattern. Thus, low concentrations of an MOR agonist drug (DAMGO, 10–200 nM) were bath-applied to neonatal rat brainstem-spinal cord preparations while recording inspiratory-related motor output on cervical spinal roots (C4-C5). Bath-applied DAMGO (50–200 nM) increased inspiratory motor burst amplitude by 40–60% during (and shortly following) drug application with decreased burst frequency and minute activity. Reciprocal changes in inspiratory burst amplitude and frequency were balanced such that 20 min after DAMGO (50–200 nM) application, minute activity was unaltered compared to pre-DAMGO levels. The DAMGO-induced inspiratory burst amplitude increase did not require crossed cervical spinal pathways, was expressed on thoracic ventral spinal roots (T4-T8) and remained unaltered by riluzole pretreatment (blocks persistent sodium currents associated with gasping). Split-bath experiments showed that the inspiratory burst amplitude increase was induced only when DAMGO was bath-applied to the brainstem and not the spinal cord. Thus, MOR activation in neonates induces a respiratory burst amplitude increase via brainstem-specific mechanisms. The burst amplitude increase counteracts the expected MOR-dependent frequency depression and may represent a new mechanism by which MOR activation influences respiratory motor output.

Preventing Axonal Sodium Overload or Mitochondrial Calcium Uptake Protects Axonal Mitochondria from Oxidative Stress-Induced Alterations.

In neuroinflammatory and neurodegenerative disorders such as multiple sclerosis, mitochondrial damage caused by oxidative stress is believed to contribute to neuroaxonal damage. Previously, we demonstrated that exposure to hydrogen peroxide (H2O2) alters mitochondrial morphology and motility in myelinated axons and that these changes initiate at the nodes of Ranvier, where numerous sodium channels are located. Therefore, we suggested that mitochondrial damage may lead to ATP deficit, thereby affecting the efficiency of the sodium-potassium ATPase and eventually leading to sodium overload in axons. The increased intra-axonal sodium may revert the axonal sodium-calcium exchangers and thus may lead to a pathological calcium overload in the axoplasm and mitochondria. Here, we used the explanted murine ventral spinal roots to investigate whether modulation of sodium or calcium influx may prevent mitochondrial alterations in myelinated axons during exogenous application of H2O2 inducing oxidative stress. For that, tetrodotoxin, an inhibitor of voltage-gated sodium ion channels, and ruthenium 360, an inhibitor of the mitochondrial calcium uniporter, were applied simultaneously with hydrogen peroxide to axons. Mitochondrial shape and motility were analyzed. We showed that inhibition of axonal sodium influx prevented oxidative stress-induced morphological changes (i.e., increase in circularity and area and decrease in length) and preserved mitochondrial membrane potential, which is crucial for ATP production. Blocking mitochondrial calcium uptake prevented decrease in mitochondrial motility and also preserved membrane potential. Our findings indicate that alterations of both mitochondrial morphology and motility in the contexts of oxidative stress can be counterbalanced by modulating intramitochondrial ion concentrations pharmacologically. Moreover, motile mitochondria show preserved membrane potentials, pointing to a close association between mitochondrial motility and functionality.

GDNF to the rescue: GDNF delivery effects on motor neurons and nerves, and muscle re-innervation after peripheral nerve injuries.

Peripheral nerve injuries commonly occur due to trauma, like a traffic accident. Peripheral nerves get severed, causing motor neuron death and potential muscle atrophy. The current golden standard to treat peripheral nerve lesions, especially lesions with large (≥ 3 cm) nerve gaps, is the use of a nerve autograft or reimplantation in cases where nerve root avulsions occur. If not tended early, degeneration of motor neurons and loss of axon regeneration can occur, leading to loss of function. Although surgical procedures exist, patients often do not fully recover, and quality of life deteriorates. Peripheral nerves have limited regeneration, and it is usually mediated by Schwann cells and neurotrophic factors, like glial cell line-derived neurotrophic factor, as seen in Wallerian degeneration. Glial cell line-derived neurotrophic factor is a neurotrophic factor known to promote motor neuron survival and neurite outgrowth. Glial cell line-derived neurotrophic factor is upregulated in different forms of nerve injuries like axotomy, sciatic nerve crush, and compression, thus creating great interest to explore this protein as a potential treatment for peripheral nerve injuries. Exogenous glial cell line-derived neurotrophic factor has shown positive effects in regeneration and functional recovery when applied in experimental models of peripheral nerve injuries. In this review, we discuss the mechanism of repair provided by Schwann cells and upregulation of glial cell line-derived neurotrophic factor, the latest findings on the effects of glial cell line-derived neurotrophic factor in different types of peripheral nerve injuries, delivery systems, and complementary treatments (electrical muscle stimulation and exercise). Understanding and overcoming the challenges of proper timing and glial cell line-derived neurotrophic factor delivery is paramount to creating novel treatments to tend to peripheral nerve injuries to improve patients’ quality of life.

Improvement of hypoventilation in Phox2b mutant mice modelling the congenital central hypoventilation syndrome by etonogestrel, a potent progestin. Perspectives for a possible potentiation by serotoninergic drugs

Congenital central hypoventilation syndrome (CCHS) is a life-threatening disorder characterized by hypoventilation during sleep and absence of the ventilatory response to CO2/H+. The disease-causing mutations are generally polyalanine repeat expansion mutations of PHOX2B. Knock-in mice bearing the 7-alanine expanded allele of PHOX2B (the most frequent mutation in patients) exhibit massive loss of retrotrapezoid nucleus neurons, lack CO2/H + chemosensitivity, and die within hours after birth. No pharmacological treatment is available. Clinical observations revealed a recovery of CO2/H+ chemosensitivity in two adult female patients with CCHS, both under desogestrel, a potent progestin used for contraceptive purpose. We previously showed that in mice, etonogestrel (ETO), the active metabolite of desogestrel, increased baseline respiratory frequency (fR) by a medullary action involving the serotoninergic (5-HT) systems. Accordingly, we hypothesized that ETO may stimulate fR on Phox2b mutant mice modelling CCHS and that 5-HT drugs would improve this respiratory effect of ETO. Experiments were made on ex vivo medullary-spinal cord preparations from conditional RTN Phox2b mutant (Egr2cre/+;Phox2b27Alaki) and OF1 WT newborn mice (P0-P2). fR was assessed by recording the 4th spinal ventral root. Effect of ETO on fR under normopH and metabolic acidosis (MA) conditions was evaluated in presence or not of 5-HT reuptake inhibitor. Without ETO, the increase in fR induced by MA observed in WT mice was absent in Egr2cre/+;Phox2b27Alaki mutant mice. ETO restored a respiratory response to MA in Egr2cre/+;Phox2b27Alaki mutant mice. In OF1 WT mice, when ETO was associated with 5-HT reuptake inhibitor, the increase in fR induced by MA was enhanced. Surprisingly, this potentiation was not retrieved in Egr2cre/+;Phox2b27Alaki mutant mice at concentrations used in OF1 WT. ETO was able to alleviate hypoventilation in Phox2b mutant mice modelling CCHS by a medullary action. Modulation of 5-HT systems may improve the respiratory effect of ETO in WT mice, but further studies are necessary to determine whether this increase of ETO effect by 5-HT extends to mutant mice.

Herophilus, Erasistratus, Aretaeus, and Galen: ancient roots of the Bell-Magendie Law.

Since the early 19th century, significant controversy has persisted over the competing claims of two men, Charles Bell and François Magendie, to a pivotal discovery: that the dorsal spinal roots subserve sensation, whereas the ventral spinal roots subserve motion. However, the foundations of neuroanatomy on which Bell and Magendie built their research was formed two millennia in advance. Exploration of the work of four ancient scholars--Herophilus, Erasistratus, Aretaeus, and Galen--reveals a remarkable early appreciation of the separate neural pathways (if not the correct physiology) responsible for sensory and motor control.

Caffeine Abolishes TrkB Receptor‐Dependent Respiratory‐Related Spinal Motor Facilitation in Isolated Neonatal Rat Brainstem‐Spinal Cords In Vitro

Caffeine is the main treatment for apnea of prematurity because it stimulates breathing, reduces duration of respiratory support, and increases infant survival. Caffeine has multiple neuronal effects, but it is a well‐established adenosine A2a receptor (A2aR) antagonist. In adult rats, A2aR blockade increases the magnitude of intermittent hypoxia‐induced, TrkB receptor‐dependent, long‐term facilitation of phrenic motor output. In neonates, it is not known whether caffeine blocks A2aRs and enhances TrkB receptor‐induced facilitation of respiratory motor output. To test this question, neonatal (P0‐P3) rat brainstem‐spinal cords were isolated and respiratory‐related motor output recorded from C4‐C5 ventral spinal roots. Bath‐applied dihydroxyflavone (DHF, TrkB receptor agonist, 5–10 μM, 9‐min, n=22) increased respiratory motor burst amplitude by 13 ± 3% relative to baseline at 75 min following drug application, whereas vehicle dimethylsulfoxide‐treated time controls decreased burst amplitude by 11 ± 4% relative to baseline (n=15; p<0.001). A background caffeine application (50–250 μM; 15 min) that overlapped a DHF application (5–10 μM, 9 min) abolished DHF‐induced spinal motor facilitation (burst amplitude was decreased by 7 ± 4% relative to baseline at 75 min). The lack of DHF‐induced spinal motor facilitation with caffeine pretreatment could be due to decreased endogenous signaling in neonatal rat A2aRs (i.e., little or no crosstalk inhibition), or other caffeine effects, such as phosphodiesterase inhibition. If TrkB‐dependent spinal motor facilitation is beneficial in neonates, then caffeine administration may compromise one compensatory mechanism during apnea of prematurity.Support or Funding InformationSupported by: NS085226 (JJW), HL105511 (TLB)

Bladder reinnervation by somatic nerve transfer to pelvic nerve vesical branches does not reinnervate the urethra.

AimsWe sought to determine whether somatic lumbar nerve transfer to the pelvic nerve's anterior vesical branch after sacral decentralization for detrusor muscle reinnervation also leads to aberrant innervation of the bladder outlet.MethodsTwenty‐six female mongrel hound dogs underwent transection of sacral dorsal and ventral spinal roots (ie, sacral decentralization). Immediately afterward, 12 received genitofemoral nerve transfer and 9 received femoral nerve branch transfer. Five were left sacrally decentralized. Controls included 3 sham‐operated and 6 unoperated. Eight months postsurgery, the bladder and urethra were injected with retrograde tracing dyes cystoscopically. After 3 weeks, detrusor and urethral pressures were assayed electrophysiologically immediately before euthanasia and characterization of neural reinnervation.ResultsElectrical stimulation of spinal cords or roots did not lead to increased urethral sphincter pressure in nerve transfer animals, compared with decentralized animals, confirming a lack of functional reinnervation of the bladder outlet. In contrast, mean detrusor pressure increased after lumbar cord/root stimulation. In sham/unoperated animals, urethral and bladder dye injections resulted in labeled neurons in sacral level neural structures (dorsal root ganglia [DRG], sympathetic trunk ganglia [STG], and spinal cord ventral horns); labeling absent in decentralized animals. Urethral dye injections did not result in labeling in lumbar or sacral level neural structures in either nerve transfer group while bladder dye injections lead to increased labeled neurons in lumbar level DRG, STG, and ventral horns, compared to sacrally decentralized animals.ConclusionPelvic nerve transfer for bladder reinnervation does not impact urethral sphincter innervation.

Nuclear Factor-kappaB Gates Nav1.7 Channels in DRG Neurons via Protein-Protein Interaction.

SummaryIt is well known that nuclear factor-kappaB (NF-κB) regulates neuronal structures and functions by nuclear transcription. Here, we showed that phospho-p65 (p-p65), an active form of NF-κB subunit, reversibly interacted with Nav1.7 channels in the membrane of dorsal root ganglion (DRG) neurons of rats. The interaction increased Nav1.7 currents by slowing inactivation of Nav1.7 channels and facilitating their recovery from inactivation, which may increase the resting state of the channels ready for activation. In cultured DRG neurons TNF-α upregulated the membrane p-p65 and enhanced Nav1.7 currents within 5 min but did not affect nuclear NF-κB within 40 min. This non-transcriptional effect on Nav1.7 may underlie a rapid regulation of the sensibility of the somatosensory system. Both NF-κB and Nav1.7 channels are critically implicated in many physiological functions and diseases. Our finding may shed new light on the investigation into the underlying mechanisms.

Timed GDNF gene therapy using an immune-evasive gene switch promotes long distance axon regeneration.

Neurosurgical repair in patients with proximal nerve lesions results in unsatisfactory recovery of function. Gene therapy for neurotrophic factors is a powerful strategy to promote axon regeneration. Glial cell line-derived neurotrophic factor (GDNF) gene therapy promotes motor neuron survival and axon outgrowth; however, uncontrolled delivery of GDNF results in axon entrapment. We report that time-restricted GDNF expression (1 month) using an immune-evasive doxycycline-inducible gene switch attenuated local axon entrapment in avulsed reimplanted ventral spinal roots, was sufficient to promote long-term motor neuron survival (24 weeks) and facilitated the recovery of compound muscle action potentials by 8 weeks. These improvements were associated with an increase in long-distance regeneration of motor axons. In contrast, persistent GDNF expression impaired axon regeneration by inducing axon entrapment. These findings demonstrate that timed expression can resolve the deleterious effect of uncontrolled growth factor delivery and shows that inducible growth factor gene therapy can be employed to enhance the efficacy of axon regeneration after neurosurgical repair of a proximal nerve lesion in rats. This preclinical study is an important step in the ongoing development of a neurotrophic factor gene therapy for patients with severe proximal nerve lesions.

Alterations in the spinal cord and ventral root after cerebral infarction in non-human primates.

Cerebral infarction does not only cause focal injury in the ischemic site, but also secondary non-ischemic damage at the remote areas of nervous system associated with the primary focus. This study investigated the changes in the spinal cord and ventral root after middle cerebral artery occlusion (MCAO) in cynomolgus monkeys (Macaca fascicularis). Adult male cynonolgus monkeys (4-5 years, 5.5-7.5 kg) were subjected to MCAO (n = 6) or sham surgery (n = 4). After 12 weeks, spinal cords and the ventral roots were harvested. Morphometric alterations in the spinal cord were detected at C5 and L5 levels via immunofluorescence. The profiles of C5 and L5 ventral roots were displayed by toluidine blue staining and transmission electron microscopic examination. Significant axonal loss in the contralateral corticospinal tract and abnormally enlarged axons in the ipsilateral were observed in monkeys with MCAO. The number of neurons in the contralateral ventral horn got declined while that in the ipsilateral was almost unaffected after MCAO compared with sham controls. Glial activation post-MCAO was observed in the bilateral corticospinal tract and the ventral horn. Aberrant nerve fibers appeared frequently in the contralateral ventral roots of MCAO monkey but rarely in the ipsilateral. These results indicate that focal cerebral infarction leads to pathological alterations in the spinal cord and ventral roots in non-human primates.

Novel method for restoration of anorectal function following spinal cord injury via nerve transfer in rats

ObjectivesNerve transfer has been developed to restore partial function after serious nerve injuries, for example, restoring bladder control after spinal cord injury (SCI). Our aim here was to establish a preclinical proof-of-concept model using nerve transfer for restoring anorectal function after SCI.SettingWe used laminectomy to model SCI, and bilateral spinal ventral and dorsal nerve root anastomosis to re-establish connectivity to the anorectal musculature.MethodsMultidisciplinary methods were used to assess the anatomical and functional integrity of the alternative spinal-to-anorectal nerve circuit. Adult rats were used to establish the model. Bilateral anterior and posterior L5 nerve roots were surgically matched with anterior and posterior of S1 nerve roots by microscopic anastomosis to establish an artificial rectal reflex arc with complete sensory and motor pathways. Twelve weeks later, we used retrograde nerve tracing and neurohistomorphological analysis to assess anatomical integrity of the new artificial rectal reflex arc. Anorectal manometry was used to assess the function of the new nerve circuit.ResultsRetrograde tracing with recombinant attenuated pseudo rabies virus indicated that the new neural pathway was successfully established to the anorectal musculature after experimental SCI. Toluidine blue-stained sections of the anastomosis site revealed normal-appearing nerve fiber morphology and regeneration, and transmission electron microscopy revealed myelinated axons. Anorectal manometry revealed significant anorectal functional recovery.ConclusionThese results suggest that our model is a feasible first step in developing an alternative reflex pathway after laminectomy at L4 to S2 and shows promise for effective restoration of anorectal function.

Swimming rhythm generation in the caudal hindbrain of the lamprey.

The spinal cord has been well established as the site of generation of the locomotor rhythm in vertebrates, but studies have suggested that the caudal hindbrain in larval fish and amphibians can also generate locomotor rhythms. Here, we investigated whether the caudal hindbrain of the adult lamprey ( Petromyzon marinus and Ichthyomyzon unicuspis) has the ability to generate the swimming rhythm. The hindbrain-spinal cord transition zone of the lamprey contains a bilateral column of somatic motoneurons that project via the spino-occipital (S-O) nerves to several muscles of the head. In the brainstem-spinal cord-muscle preparation, these muscles were found to burst and contract rhythmically with a left-right alternation when swimming activity was evoked with a brief electrical stimulation of the spinal cord. In the absence of muscles, the isolated brainstem-spinal cord preparation also produced alternating left-right bursts in S-O nerves (i.e., fictive swimming), and the S-O nerve bursts preceded the bursts occurring in the first ipsilateral spinal ventral root. After physical isolation of the S-O region using transverse cuts of the nervous system, the S-O nerves still exhibited rhythmic bursting with left-right alternation when glutamate was added to the bathing solution. We conclude that the S-O region of the lamprey contains a swimming rhythm generator that produces the leading motor nerve bursts of each swimming cycle, which then propagate down the spinal cord to produce forward swimming. The S-O region of the hindbrain-spinal cord transition zone may play a role in regulating speed, turning, and head orientation during swimming in lamprey. NEW & NOTEWORTHY Although it has been well established that locomotor rhythm generation occurs in the spinal cord of vertebrates, it was unknown whether the hindbrain of the adult vertebrate nervous system can also generate the locomotor rhythm. Here, we show that the isolated hindbrain-spinal cord transition zone of adult lamprey can generate the swimming rhythm. In addition, the swimming bursts of the hindbrain lead the bursts occurring in the first segment of the spinal cord.

Exaggerated Cardiovascular Response to Muscle Mechanoreflex Activation in Type 2 Diabetic Rats

Evidence suggests that the cardiovascular response to physical activity is excessively heightened in patients with type 2 diabetes mellitus (T2DM). However, the mechanisms underlying this exaggerated circulatory responsiveness remain to be fully elucidated. The exercise pressor reflex (EPR) is a primary contributor to autonomic cardiovascular regulation during physical exercise. Mechanically (mechanoreflex) and metabolically (metaboreflex) sensitive components mediate EPR function. We have shown previously that the metaboreflex is overactive in T2DM whereas the function of the mechanoreflex remains undetermined in this disease. PURPOSE: To assess mechanoreflex activity in T2DM rats. It was hypothesized that the heightened cardiovascular response to exercise in T2DM is induced, in part, by functional alterations in the muscle mechanoreflex. METHODS: T2DM was induced in Sprague-Dawley rats by a combination of both a low-dose streptozotocin injection (30-35 mg/kg, ip) and a 14-16 wk high-fat diet. In control rats (normal diet; no steptozotocin; n=34) and T2DM (n=10) rats, the EPR was activated by electrically-inducing hindlimb muscle contraction via stimulation of spinal ventral roots. The mechanically-sensitive component of the EPR was selectively activated by passively stretching hindlimb muscle. RESULTS: Compared to control animals, sympathetic and pressor responses to EPR activation were significantly greater in T2DM rats (RSNA: Δ=122±20 vs. 61±8 %, P<0.05; MAP: Δ=49±5 vs. 20±2 mmHg, P<0.05). Passive stretch likewise evoked greater increases in RSNA (Δ=81±16 vs. 31±5 %, P<0.05) and MAP (Δ=38±7 vs. 13±2 mmHg, P<0.05) in T2DM rats compared to healthy controls. CONCLUSIONS: These data demonstrate the skeletal muscle mechanoreflex is overactive in T2DM. This is an important finding as it suggests that both the metaboreflex (as previously reported) and mechanoreflex contribute significantly to the generation of EPR overactivity in T2DM possibly accounting for the abnormally large cardiovascular response to exercise in this disease. Supported by the Lawson & Rogers Lacy Research Fund in Cardiovascular Disease

Expression patterns of Slit and Robo family members in adult mouse spinal cord and peripheral nervous system.

The secreted glycoproteins, Slit1-3, are classic axon guidance molecules that act as repulsive cues through their well characterised receptors Robo1-2 to allow precise axon pathfinding and neuronal migration. The expression patterns of Slit1-3 and Robo1-2 have been most characterized in the rodent developing nervous system and the adult brain, but little is known about their expression patterns in the adult rodent peripheral nervous system. Here, we report a detailed expression analysis of Slit1-3 and Robo1-2 in the adult mouse sciatic nerve as well as their expression in the nerve cell bodies within the ventral spinal cord (motor neurons) and dorsal root ganglion (sensory neurons). Our results show that, in the adult mouse peripheral nervous system, Slit1-3 and Robo1-2 are expressed in the cell bodies and axons of both motor and sensory neurons. While Slit1 and Robo2 are only expressed in peripheral axons and their cell bodies, Slit2, Slit3 and Robo1 are also expressed in satellite cells of the dorsal root ganglion, Schwann cells and fibroblasts of peripheral nerves. In addition to these expression patterns, we also demonstrate the expression of Robo1 in blood vessels of the peripheral nerves. Our work gives important new data on the expression patterns of Slit and Robo family members within the peripheral nervous system that may relate both to nerve homeostasis and the reaction of the peripheral nerves to injury.

Constriction of the buccal branch of the facial nerve produces unilateral craniofacial allodynia

Despite pain being a sensory experience, studies of spinal cord ventral root damage have demonstrated that motor neuron injury can induce neuropathic pain. Whether injury of cranial motor nerves can also produce nociceptive hypersensitivity has not been addressed. Herein, we demonstrate that chronic constriction injury (CCI) of the buccal branch of the facial nerve results in long-lasting, unilateral allodynia in the rat. An anterograde and retrograde tracer (3000MW tetramethylrhodamine-conjugated dextran) was not transported to the trigeminal ganglion when applied to the injury site, but was transported to the facial nucleus, indicating that this nerve branch is not composed of trigeminal sensory neurons. Finally, intracisterna magna injection of interleukin-1 (IL-1) receptor antagonist reversed allodynia, implicating the pro-inflammatory cytokine IL-1 in the maintenance of neuropathic pain induced by facial nerve CCI. These data extend the prior evidence that selective injury to motor axons can enhance pain to supraspinal circuits by demonstrating that injury of a facial nerve with predominantly motor axons is sufficient for neuropathic pain, and that the resultant pain has a neuroimmune component.