Beneficial effects of treadmill training in a cerebral palsy-like rodent model: Walking pattern and soleus quantitative histology

Motor deficits are associated with increased glial cell activation in the hypothalamus and cerebellum of young rats subjected to cerebral palsy

Cerebral palsy (CP) is a syndrome characterized by a wide range of sensory and motor damage, associated with behavioral and cognitive deficits. The aim of the present study was to investigate the potential of a model of CP using a combination of perinatal anoxia and sensorimotor restriction of hind paws to replicate motor, behavioral and neural deficits. A total of 30 of male Wistar rats were divided into Control (C, n = 15), and CP (CP, n = 15) groups. The potential of the CP model was assessed by evaluating food intake, the behavioral satiety sequence, performance on the CatWalk and parallel bars, muscle strength, and locomotor activity. The weight of the encephalon, soleus, and extensor digitorum longus (EDL) muscles, and the activation of glial cells (microglia and astrocytes) were also measured. The CP animals showed delayed satiety, impaired locomotion on the CatWalk and open field test, reduced muscle strength, and reduced motor coordination. CP also reduced the weight of the soleus and muscles, brain weight, liver weight, and quantity of fat in various parts of the body. There was also found to be an increase in astrocyte and microglia activation in the cerebellum and hypothalamus (arcuate nucleus, ARC) of animals subjected to CP.

Early movement restriction deteriorates motor function and soleus muscle physiology

Children with low physical activity and interactions with environment experience atypical sensorimotor development and maturation leading to anatomical and functional disorganization of the sensorimotor circuitry and also to enduring altered motor function. Previous data have shown that postnatal movement restriction in rats results in locomotor disturbances, functional disorganization and hyperexcitability of the hind limb representations in the somatosensory and motor cortices, without apparent brain damage. Due to the reciprocal interplay between the nervous system and muscle, it is difficult to determine whether muscle alteration is the cause or the result of the altered sensorimotor behavior (Canu et al., 2019). In the present paper, our objectives were to evaluate the impact of early movement restriction leading to sensorimotor restriction (SMR) during development on the postural soleus muscle and on sensorimotor performance in rats, and to determine whether changes were reversed when typical activity was resumed. Rats were submitted to SMR by hind limb immobilization for 16 h / day from birth to postnatal day 28 (PND28). In situ isometric contractile properties of soleus muscle, fiber cross sectional area (CSA) and myosin heavy chain content (MHC) were studied at PND28 and PND60. In addition, the motor function was evaluated weekly from PND28 to PND60. At PND28, SMR rats presented a severe atrophy of soleus muscle, a decrease in CSA and a force loss. The muscle maturation appeared delayed, with persistence of neonatal forms of MHC. Changes in kinetic properties were moderate or absent. The Hoffmann reflex provided evidence for spinal hyperreflexia and signs of spasticity. Most changes were reversed at PND60, except muscle atrophy. Functional motor tests that require a good limb coordination, i.e. rotarod and locomotion, showed an enduring alteration related to SMR, even after one month of 'typical' activity. On the other hand, paw withdrawal test and grip test were poorly affected by SMR whereas spontaneous locomotor activity increased over time. Our results support the idea that proprioceptive feedback is at least as important as the amount of motor activity to promote a typical development of motor function. A better knowledge of the interplay between hypoactivity, muscle properties and central motor commands may offer therapeutic perspectives for children suffering from neurodevelopmental disorders.

Experimental cerebral palsy causes microstructural brain damage in areas associated to motor deficits but no spatial memory impairments in the developing rat

INTRODUCTION

Cerebral palsy (CP) is the major cause of motor and cognitive impairments during childhood. CP can result from direct or indirect structural injury to the developing brain. In this study, we aimed to describe brain damage and behavioural alterations during early adult life in a CP model using the combination of maternal inflammation, perinatal anoxia and postnatal sensorimotor restriction.

METHODS

Pregnant Wistar rats were injected intraperitoneally with 200 µg/kg LPS at embryonic days E18 and E19. Between 3 and 6 h after birth (postnatal day 0 - PND0), pups of both sexes were exposed to anoxia for 20 min. From postnatal day 2 to 21, hindlimbs of animals were immobilized for 16 h daily during their active phase. From PND40, locomotor and cognitive tests were performed using Rota-Rod, Ladder Walking and Morris water Maze. Ex-vivo MRI Diffusion Tensor Imaging (DTI) and Neurite Orientation Dispersion and Density Imaging (NODDI) were used to assess macro and microstructural damage and brain volume alterations induced by the model. Myelination and expression of neuronal, astroglial and microglial markers, as well as apoptotic cell death were evaluated by immunofluorescence.

RESULTS

CP animals showed decreased body weight, deficits in gross (rota-rod) and fine (ladder walking) motor tasks compared to Controls. No cognitive impairments were observed. Ex-vivo MRI showed decreased brain volumes and impaired microstructure in the cingulate gyrus and sensory cortex in CP brains. Histological analysis showed increased cell death, astrocytic reactivity and decreased thickness of the corpus callosum and altered myelination in CP animals. Hindlimb primary motor cortex analysis showed increased apoptosis in CP animals. Despite the increase in NeuN and GFAP, no differences between groups were observed as well as no co-localization with the apoptotic marker. However, an increase in Iba-1+ microglia with co-localization to cleaved caspase 3 was observed.

CONCLUSION

Our results suggest that experimental CP induces long-term brain microstructural alterations in myelinated structures, cell death in the hindlimb primary motor cortex and locomotor impairments. Such new evidence of brain damage could help to better understand CP pathophysiological mechanisms and guide further research for neuroprotective and neurorehabilitative strategies for CP patients.

Effects of Scalp Acupuncture on Functional Deficits Induced by Early Sensorimotor Restriction

The aim of this study was to investigate the effects of scalp acupuncture and electrostimulation, combined or not, in a disuse model consisted of early sensorimotor restriction in rats. Male Wistar pups received sensorimotor restriction from the second postnatal day (P2) until P28. Animals were divided into five different groups (n = 6): control (CT), sensorimotor restricted (SR), acupuncture (AC), electrostimulation (EL), and electroacupuncture (AC+EL). Experimental animals received sham, acupuncture, or electrical stimulation, combined or not, of two scalp regions for 7 days (P29-P35). Before treatment period (P29) and after treatment (P36), animals were evaluated with the narrow suspended bar, horizontal ladder, and stride length tests. SR animals had worse performance in the narrow suspended and horizontal ladder tasks compared with SR animals at P29 (p ≤ 0.005). Significant improvements were observed in both tasks in AC, EL, and EL+AC groups comparing P29 and P36 (p < 0.001). Also, at P35, all treated animals performed significantly better motor tasks compared with SR group (p < 0.05). There was no difference between treated groups. Finally, acupuncture and electrical stimulation, combined or not, have beneficial effect on motor performance following early developmental disuse.

Morphofunctional characteristics of skeletal muscle in rats with cerebral palsy

Knowledge of skeletal muscle adaptations is important to understand the functional deficits in cerebral palsy (CP). This study aimed to investigate the morphofunctional characteristics of skeletal muscle in a CP animal model. Initially, pregnant Wistar rats were injected intraperitoneally with saline or lipopolysaccharide over the last five days of pregnancy. The control group (n = 8) consisted of male pups born to females injected with saline. The CP group (n = 8) consisted of male pups born to females injected with lipopolysaccharide, which were submitted to perinatal anoxia [day of birth, postnatal day 0 (P0)] and sensorimotor restriction (P1-P30). The open-field test was undertaken on P29 and P45. On P48, the animals were weighed, and the plantaris muscle was collected and its weight and length were measured. Transverse sections were stained with haematoxylin-eosin, NADH-TR, Masson's trichrome and non-specific esterase reaction for analysis. and transmission electron microscopy was performed. In the CP group, reductions were observed in mobility time, number of crossings and rearing frequency, body weight, muscle weight and length, and nucleus-to-fibre and capillary-to-fibre ratios. There was a statistically significant increase in the percentage area of the muscle section occupied by collagen; reduction in the area and increase in the number of type I muscle fibres; increase in myofibrillar disorganization and Z-line disorganization and dissolution; and reduction in the area and largest and smallest diameters of neuromuscular junctions. Thus this animal model of CP produced morphofunctional alterations in skeletal muscle, that were associated with evidence of motor deficits as demonstrated by the open-field test.

Neonatal hypoxia-ischemia caused mild motor dysfunction, recovered by acrobatic training, without affecting morphological structures involved in motor control in rats

The aim of this study was to evaluated motor function and morphological aspects of the components involved in motor control (sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle) in male Wistar rats exposed to a model of neonatal hypoxic-ischemic encephalopathy (HIE) and the possible influence of different physical exercise protocols - treadmill and acrobatic. Male Wistar rats at the 7^th post-natal day (PND) were submitted to the HIE model and from the 22^nd until 60^th PND the exercise protocols (treadmill or acrobatic training) were running. After the training, the animals were evaluated in Open Field, Ladder Rung Walking and Rotarod tasks and after samples of the motor control components were collected. Our results evidenced that the acrobatic training reversed the hyperactivity and anxiety, caused locomotion improvement and decreased brain atrophy in HIE animals. We did not find morphological differences on sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle in the animals submitted to HIE model. These intriguing data support the statement of the Rice-Vannucci model does not seem to reproduce, in structures involved in control function, the damage found in humans that suffer HIE. Regarding the protocols of exercise, we proposed that the acrobatic exercise could be a good therapeutic option especially in children affected by neonatal HIE and can be responsible for good results in cognitive and motor aspects.

Early movement restriction leads to enduring disorders in muscle and locomotion

Motor control and body representation in the central nervous system (CNS) as well as musculoskeletal architecture and physiology are shaped during development by sensorimotor experience and feedback, but the emergence of locomotor disorders during maturation and their persistence over time remain a matter of debate in the absence of brain damage. By using transient immobilization of the hind limbs, we investigated the enduring impact of postnatal sensorimotor restriction (SMR) on gait and posture on treadmill, age-related changes in locomotion, musculoskeletal histopathology and Hoffmann reflex in adult rats without brain damage. SMR degrades most gait parameters and induces overextended knees and ankles, leading to digitigrade locomotion that resembles equinus. Based on variations in gait parameters, SMR appears to alter age-dependent plasticity of treadmill locomotion. SMR also leads to small but significantly decreased tibial bone length, chondromalacia, degenerative changes in the knee joint, gastrocnemius myofiber atrophy and muscle hyperreflexia, suggestive of spasticity. We showed that reduced and atypical patterns of motor outputs, and somatosensory inputs and feedback to the immature CNS, even in the absence of perinatal brain damage, play a pivotal role in the emergence of movement disorders and musculoskeletal pathologies, and in their persistence over time. Understanding how atypical sensorimotor development likely contributes to these degradations may guide effective rehabilitation treatments in children with either acquired (ie, with brain damage) or developmental (ie, without brain injury) motor disabilities.

The Effects of Two Different Exercise Programs on the Ultrastructural Features of the Sciatic Nerve and Soleus Muscle After Sciatic Crush

Peripheral nerve injuries constitute a significant medical problem and the recovery is critically dependent on post-injury treatment. In this study, following sciatic nerve crush, we investigated the effects of a 4-week endurance training program (ET) and balance and coordination training program (BCT) on the ultrastructural features of the sciatic nerve and soleus muscle. The animals were randomly divided into Sham, non-trained (NT), ET, and BCT groups each of which included three animals. Ultra-thin cross and longitudinal sections (70-85 nm) were digitized and analyzed comparatively. The electron micrographic analysis of the sciatic nerve showed similar organelles features in the injury groups (myelin debris and swelling mitochondria). Nonetheless, the ET group presented better ultrastructural features as demonstrated by the greater predominance of rounded fibers and more defined organization in the myelinated axon bundles. In the soleus muscle's analyses, the injured groups demonstrated similar organelles' features (nucleus contained highly heterochromatic nuclei and smaller mitochondria). However, ET and BCT groups showed apparently enlarged myofibril cross-sectional areas and less collagen around muscle fibers, although, the ET group displayed reduced intermyofibrillar spaces and more closely aligned myofilaments when compared with the BCT group. Based on electron micrographic analysis, our findings suggest the presence of ultrastructural differences between the Sham, NT, and the trained groups. Therefore, exercise type seems to be responsible for producing some different positive features in the trained groups, while ET seems to have a more pronounced influence on the ultrastructural features of the sciatic nerve and the soleus muscle after a crush injury. Anat Rec, 300:1654-1661, 2017. © 2017 Wiley Periodicals, Inc.

Long-term exercise training as a modulator of mammary cancer vascularization

BACKGROUND

Breast cancer remains a leading cause of death by cancer worldwide. It is commonly accepted that angiogenesis and the expression of angiogenic factors such as vascular endothelial growth factor-A (VEGF-A) is associated with the increased risk of metastasis and poor patient outcome.

OBJECTIVE

This work aimed to evaluate the effects of long-term exercise training on the growth and vascularization of mammary tumors in a rat model.

MATERIALS AND METHODS

Fifty female Sprague-Dawley rats were divided into four groups: two N-methyl-N-nitrosourea (MNU)-exposed groups (exercised and sedentary) and two control groups (exercised and sedentary). MNU was administered once, intraperitoneally at 7 weeks-old. Animals were then exercised on a treadmill for 35 weeks. Mammary tumors were evaluated using thermography, ultrasonography [Power Doppler (PDI), B Flow and contrast-enhanced ultrasound (CEUS)], and immunohistochemistry (VEGF-A).

RESULTS

Both, MNU sedentary and exercised groups showed 100% of tumor incidence, but exercised animals showed less tumors with an increased latency period. Exercise training also enhanced VEGF-A immunoexpression and vascularization (microvessel density, MVD) (p<0.05), and reduced histological aggressiveness. Ultrasound and thermal imaging analysis confirmed the enhanced vascularization of tumors on exercised animals.

CONCLUSION

Long-term exercise training increased VEGF-A expression, leading to enhanced tumor vascularization and reduced tumor burden, multiplicity and histological aggressiveness.

Balance and coordination training, but not endurance training, enhances synaptophysin and neurotrophin-3 immunoreactivity in the lumbar spinal cord after sciatic nerve crush

INTRODUCTION

Numerous rehabilitation treatments have been shown to be useful for peripheral and central restoration after (PNI).

METHODS

After sciatic nerve crush, we investigated 4 weeks of endurance training (ET) and balance and coordination training (BCT) with sciatic function index, hind-paw stride length, and spinal cord dorsal horn synaptophysin and neurotrophin-3 immunoreactivity.

RESULTS

Our results demonstrated no significant differences between the non-trained (NT), ET, and BCT groups in sciatic functional index, and in stride-length analysis, but the ET showed higher values compared with the NT group. Synaptophysin immunoreactivity was higher in the BCT group compared with the NT group, and neurotrophin-3 immunoreactivity in the BCT group was greater compared with the other groups.

CONCLUSION

BCT can positively affect spinal cord plasticity after a (PNI), and these modifications are important in the rehabilitation process.

Balance and coordination training and endurance training after nerve injury

INTRODUCTION

Different rehabilitation treatments have proven useful in accelerating regeneration.

METHODS

After sciatic nerve crush in rats, we tested balance and coordination training (BCT) and endurance training (ET) through sensorimotor tests and analyzed nerve and muscle morphology.

RESULTS

After BCT and ET, rats performed better in sensorimotor tests than did non-trained animals. However, only BCT maintained sensorimotor function during training. Furthermore, BCT and ET produced significantly larger muscle area than in non-trained animals.

CONCLUSIONS

These findings indicate that BCT and ET, when initiated in the early phase after sciatic nerve injury, improve morphological properties of the soleus muscle and sciatic nerve, but only the task-oriented BCT maintained sensorimotor function. The success of rehabilitative strategies appears to be highly task-specific, and strategies that stimulate sensory pathways are the most effective in improving balance and/or coordination parameters.

Molecular mechanisms of treadmill therapy on neuromuscular atrophy induced via botulinum toxin A

Botulinum toxin A (BoNT-A) is a bacterial zinc-dependent endopeptidase that acts specifically on neuromuscular junctions. BoNT-A blocks the release of acetylcholine, thereby decreasing the ability of a spastic muscle to generate forceful contraction, which results in a temporal local weakness and the atrophy of targeted muscles. BoNT-A-induced temporal muscle weakness has been used to manage skeletal muscle spasticity, such as poststroke spasticity, cerebral palsy, and cervical dystonia. However, the combined effect of treadmill exercise and BoNT-A treatment is not well understood. We previously demonstrated that for rats, following BoNT-A injection in the gastrocnemius muscle, treadmill running improved the recovery of the sciatic functional index (SFI), muscle contraction strength, and compound muscle action potential (CMAP) amplitude and area. Treadmill training had no influence on gastrocnemius mass that received BoNT-A injection, but it improved the maximal contraction force of the gastrocnemius, and upregulation of GAP-43, IGF-1, Myo-D, Myf-5, myogenin, and acetylcholine receptor (AChR) subunits α and β was found following treadmill training. Taken together, these results suggest that the upregulation of genes associated with neurite and AChR regeneration following treadmill training may contribute to enhanced gastrocnemius strength recovery following BoNT-A injection.

Treadmill running upregulates the expression of acetylcholine receptor in rat gastrocnemius following botulinum toxin A injection

Treadmill running is a commonly used training method for patients with spasticity to improve functional performance. Botulinum toxin has been widely used therapeutically to reduce contraction force of spastic muscle. However, the effects of treadmill running in neuromuscular junction expression and motor unit physiology on muscle following botulinum toxin injection are not well established. To assess the effects of treadmill running on neuromuscular recovery of gastrocnemius following botulinum toxin A (BoNT-A) injection, we observed changes in gene expression. We hypothesized that the expression of acetylcholine receptor (AChR), myogenesis, and nerve plasticity could be enhanced. Twenty-four Sprague-Dawley rats received botulinum toxin injection in right gastrocnemius and were then randomly assigned into untrained control and treadmill running groups. The rats assigned to the treadmill running group were trained on a treadmill 3 times/week with a running speed of 15 m/min for 8 weeks. The duration of training was 20 min per session. Muscle strength and gene expression of AChR subunit (α, β, δ, γ, and ε), MyoD, Myf-5, MRF4, myogenin, p21, IGF-1, GAP43, were analyzed. Treadmill running had no influence on gastrocnemius mass, but improved the maximal contraction force of the gastrocnemius in the treadmill running group (p < 0.05). Upregulation of GAP-43, IGF-1, Myo-D, Myf-5, myogenin, and AChR subunits α and β were found following treadmill running. The expression of genes associated with neurite and AChR regeneration following treadmill exercise was upregulated, which may have contributed to enhanced recovery of gastrocnemius strength.

Effects of treadmill running on rat gastrocnemius function following botulinum toxin A injection

Exercise can improve and maintain neural or muscular function, but the effects of exercise in physiological adaptation to paralysis caused by botulinum toxin A has not been well studied. Twenty-four rats were randomly assigned into control and treadmill groups. The rats assigned to the treadmill group were trained on a treadmill three times per week with the running speed set at 15 m/min. The duration of training was 20 min/session. Muscle strength, nerve conduction study and sciatic functional index (SFI) were used for functional analysis. Treadmill training improved the SFI at 2, 3, and 4 weeks (p = 0.01, 0.004, and 0.01, respectively). The maximal contraction force of the gastrocnemius muscle in the treadmill group was greater than in the control group (p < 0.05). The percentage of activated fibers was higher in the treadmill botox group than the percentage for the control botox group, which was demonstrated by differences in amplitude and area of compound muscle action potential (CMAP) under the curve between the groups (p < 0.05). After BoNT-A injection, treadmill improved the physiological properties of muscle contraction strength, CMAP amplitude, and the recovery of SFI.

Treadmill training induces plasticity in spinal motoneurons and sciatic nerve after sensorimotor restriction during early postnatal period: new insights into the clinical approach for children with cerebral palsy

The aim of the present study was to investigate whether locomotor stimulation training could have beneficial effects on the morphometric alterations of spinal cord and sciatic nerve consequent to sensorimotor restriction (SR). Male Wistar rats were exposed to SR from postnatal day 2 (P2) to P28. Control and experimental rats underwent locomotor stimulation training in a treadmill for three weeks (from P31 to P52). The cross-sectional area (CSA) of spinal motoneurons innervating hind limb muscles was determined. Both fiber and axonal CSA of myelinated fibers were also assessed. The growth-related increase in CSA of motoneurons in the SR group was less than controls. After SR, the mean motoneuron soma size was reduced with an increase in the proportion of motoneurons with a soma size of between 0 and 800 μm(2). The changes in soma size of motoneurons were accompanied by a reduction in the mean fiber and axon CSA of sciatic nerve. The soma size of motoneurons was reestablished at the end of the training period reaching controls level. Our results suggest that SR during early postnatal life retards the growth-related increase in the cell body size of motoneurons in spinal cord and the development of sciatic nerve. Additionally, three weeks of locomotor stimulation using a treadmill seems to have a beneficial effect on motoneurons' soma size.

Balance and coordination training after sciatic nerve injury

INTRODUCTION

Numerous therapeutic interventions have been tested to enhance functional recovery after peripheral nerve injuries.

METHODS

After sciatic nerve crush in rats we tested balance and coordination and motor control training in sensorimotor tests and analyzed nerve and muscle histology.

RESULTS

The balance and coordination training group and the sham group had better results than the sedentary and motor control groups in sensorimotor tests. The sham and balance and coordination groups had a significantly larger muscle area than the other groups, and the balance and coordination group showed significantly better values than the sedentary and motor control groups for average myelin sheath thickness and g-ratio of the distal portion of the nerve.

CONCLUSIONS

The findings indicate that balance and coordination training improves sciatic nerve regeneration, suggesting that it is possible to revert and/or prevent soleus muscle atrophy and improve performance on sensorimotor tests.

Botulinum toxin assessment, intervention and follow-up for paediatric upper limb hypertonicity: international consensus statement

The primary objective of this paper was to evaluate the published evidence of efficacy and safety of botulinum neurotoxin (BoNT) injections in paediatric upper limb hypertonia (PULH). Secondary objectives included the provision of clinical context, based on evidence and expert opinion, in the areas of assessment, child and muscle selection, dosing, and adjunctive treatment. A multidisciplinary panel of authors systematically reviewed, abstracted, and classified relevant literature. Recommendations were based on the American Academy of Neurology (AAN) evidence classification. Following a literature search, 186 potential articles were screened for inclusion, and 15 of these met the criteria and were reviewed. Grade A evidence was found to support the use of BoNT to reach individualized therapeutic goals for PULH. There is grade B evidence (probably effective) for tone reduction following BoNT injections and grade U evidence (inconclusive) for improvement in upper limb (UL) activity and function. BoNT injections were generally found to be safe and well tolerated with the most common side effect identified as a transient decrease in grip strength.

Treadmill step training-induced adaptive muscular plasticity in a chronic paraplegia model

The purpose of this study was to provide evidence that treadmill step training is capable of attenuating muscle atrophy and may regulate brain derived neurotrophic factor (BDNF) in soleus muscle after complete spinal cord transection (SCT) at T8-T9 in rats. Five days after SCT, spinal animals started a 9-week step-training program on a treadmill with partial body weight support and manual step help. The muscular trophism was studied by analyzing muscle weight and myofiber cross-sectional area of the soleus, while Western blot analysis was used to detect BDNF expression in the same muscle. Step training, initiated immediately after SCT in rats, may partially impede/revert muscular atrophy in chronic paralyzed soleus muscle. Moreover, treadmill step training promoted upregulation of the BDNF in soleus muscle, which was positively correlated with muscle weight and myofiber cross-sectional size. These findings have important implications for the comprehension of the neurobiological substrate that promotes exercise-induced effects on paralyzed skeletal muscle and suggests treadmill training is a viable therapeutic approach in spinal cord injuries.

Challenges Facing Quantification of Rat Locomotion along Beams of Varying Widths

Optoelectronic motion capture systems have been widely used to investigate temporal gait parameters in humans and animals in order to understand function and behavioural attributes of different pathologies, e.g. Parkinson's disease (PD). The aim of the present paper was to investigate the practicality of utilising this system to investigate the effects of a unilateral 6-hydroxydopamine (6-OHDA) lesion on rat locomotion while walking on beams of varying widths (graduated, narrow, and wide). Temporal gait parameters of ten male Lister Hooded rats (five controls and five hemiparkinsonian) were observed using passive markers placed in locations that were representative of their four limbs and their body axis. The results demonstrate that marker-based motion capture can provide an effective and simple approach to quantifying temporal gait parameters for rat models of PD. They also reveal how the width of the path affects the locomotion in both experimental cohorts. Such measurements can be compared with human motion analysis to explore correlations between the animal model and human behaviour, which is an important step for translational medicine.

Different effects of anoxia and hind-limb immobilization on sensorimotor development and cell numbers in the somatosensory cortex in rats

Cerebral palsy (CP) is a group of movement and posture disorders attributed to insults in the developing brain. In rats, CP-like motor deficits can be induced by early hind-limb sensorimotor restriction (SR; from postnatal days P2 to P28), associated or otherwise with perinatal anoxia (PA; on P0 and P1). In this study, we address the question of whether PA, early SR or a combination of both produces alterations to sensorimotor development. Developmental milestones (surface righting, cliff aversion, stability on an inclined surface, proprioceptive placing, auditory startle, eye opening) were assessed daily from P3 to P14. Motor skills (horizontal ladder and beam walking) were evaluated weekly (from P31 to P52). In addition, on P52, the thickness of the somatosensory (S1) and cerebellar cortices, and corpus callosum were measured, and the neuronal and glial cell numbers in S1 were counted. SR (with or without PA) significantly delayed the stability on an inclined surface and hastened the appearance of the placing reflex and impaired motor skills. No significant differences were found in the thickness measurements between the groups. Quantitative histology of S1 showed that PA, either alone or associated with SR, increased the number of glial cells, while SR alone reduced neuronal cell numbers. Finally, the combination of PA and SR increased the size of neuronal somata. We conclude that SR impairs the achievement of developmental milestones and motor skills. Moreover, both SR and PA induce histological alterations in the S1 cortex, which may contribute to sensorimotor deficits.