Physical exercise enhances adult cortical plasticity in a neonatal rat model of hypoxic-ischemic injury: Evidence from BOLD-fMRI and electrophysiological recordings

Clemastine enhances exercise-induced motor improvement in hypoxic ischemic rats

Neonatal hypoxic ischemia (HI) occurs owing to reduced cerebral oxygen levels and perfusion during the perinatal period. Brain injury after HI triggers neurological manifestations such as motor impairment, and the improvement of impaired brain function remains challenging. Recent studies suggest that cortical myelination plays a role in motor learning, but its involvement in motor improvement after HI injury is not well understood. This study aimed to investigate the impact of myelination on motor improvement following neonatal HI injury. We employed a modified Rice-Vannucci model; the right common carotid artery of postnatal day 7 (P7) Wistar rats was isolated and divided, and the rats were then exposed to hypoxic condition (90 min, 8 % O2). A total of 101 rats (66 males) were divided into four groups: trained-HI (n = 38), trained-Sham (n = 16), untrained-HI (n = 31), and untrained-Sham (n = 16). The trained groups underwent rotarod-based exercise training from P22 to P41 (3 days per week). Structural analysis using magnetic resonance imaging and immunohistochemistry (n = 6 per group) revealed increased fractional anisotropy and myelin density in the primary somatosensory cortex of the trained-HI group. We further evaluated the effect of myelination promotion on rotarod performance by administering clemastine, a myelination-promoting drug, via daily intraperitoneal injections. Clemastine did not enhance motor improvement in untrained-HI rats. However, clemastine-administered trained-HI rats (n = 7) exhibited significantly improved motor performance compared to both saline-administered trained-HI rats (n = 11) and clemastine-administered untrained-HI rats (n = 7). These findings suggest that myelination may be a key mechanism in motor improvement after HI injury and that combining exercise training with clemastine administration could be an effective therapeutic strategy for motor improvement following HI injury.

Mitochondrial Proteins Unveil the Mechanism by Which Physical Exercise Ameliorates Memory, Learning and Motor Activity in Hypoxic Ischemic Encephalopathy Rat Model

Background: Physical exercise has been shown to improve cognitive and motor functions, promoting neurogenesis and demonstrating therapeutic benefits in neurodegenerative disorders. Nonetheless, it is crucial to investigate the cellular and molecular mechanisms by which this occurs. The study aimed to investigate and evaluate the effect of swimming exercise on the changes of mitochondrial proteins in the brains of rats with hypoxic ischemic encephalopathy (HIE). Methods: the vertical pole and Morris water maze tests were used to assess the animals’ motor and cognitive functions, and western blot and immunofluorescence of brain tissue were used to assess the biomarkers of mitochondrial apoptosis and cristae stability in response to exercise training. Four groups of rats were used: (1) sham sedentary group (SHAM, NT), (2) sham exercise training group (SHAM, T) (3) hypoxic ischemic encephalopathy sedentary group (HIE, NT), and (4) hypoxic ischemic encephalopathy exercise training group (HIE, T). Results: animals with HIE showed motor and cognitive deficits, as well as increased apoptotic protein expression. Exercise, on the other hand, improved motor and cognitive functions while also suppressing the expression of apoptotic proteins. Conclusions: By stabilizing the mitochondrial cristae and suppressing the apoptotic cascade, physical exercise provided neuroprotection in hypoxic ischemia-induced brain injury.

Stem cell restores thalamocortical plasticity to rescue cognitive deficit in neonatal intraventricular hemorrhage

Severe neonatal intraventricular hemorrhage (IVH) patients incur long-term neurologic deficits such as cognitive disabilities. Recently, the intraventricular transplantation of allogeneic human umbilical cord blood-derived mesenchymal stem cells (MSCs) has drawn attention as a therapeutic potential to treat severe IVH. However, its pathological synaptic mechanism is still elusive. We here demonstrated that the integration of the somatosensory input was significantly distorted by suppressing feed-forward inhibition (FFI) at the thalamocortical (TC) inputs in the barrel cortices of neonatal rats with IVH by using BOLD-fMRI signal and brain slice patch-clamp technique. This is induced by the suppression of Hebbian plasticity via an increase in tumor necrosis factor-α expression during the critical period, which can be effectively reversed by the transplantation of MSCs. Furthermore, we showed that MSC transplantation successfully rescued IVH-induced learning deficits in the sensory-guided decision-making in correlation with TC FFI in the layer 4 barrel cortex.

Environmental Enrichment Enhances Cav 2.1 Channel-Mediated Presynaptic Plasticity in Hypoxic-Ischemic Encephalopathy

Hypoxic–ischemic encephalopathy (HIE) is a devastating neonatal brain condition caused by lack of oxygen and limited blood flow. Environmental enrichment (EE) is a classic paradigm with a complex stimulation of physical, cognitive, and social components. EE can exert neuroplasticity and neuroprotective effects in immature brains. However, the exact mechanism of EE on the chronic condition of HIE remains unclear. HIE was induced by a permanent ligation of the right carotid artery, followed by an 8% O₂ hypoxic condition for 1 h. At 6 weeks of age, HIE mice were randomly assigned to either standard cages or EE cages. In the behavioral assessments, EE mice showed significantly improved motor performances in rotarod tests, ladder walking tests, and hanging wire tests, compared with HIE control mice. EE mice also significantly enhanced cognitive performances in Y-maze tests. Particularly, EE mice showed a significant increase in Ca_v 2.1 (P/Q type) and presynaptic proteins by molecular assessments, and a significant increase of Ca_v 2.1 in histological assessments of the cerebral cortex and hippocampus. These results indicate that EE can upregulate the expression of the Ca_v 2.1 channel and presynaptic proteins related to the synaptic vesicle cycle and neurotransmitter release, which may be responsible for motor and cognitive improvements in HIE.

Functional Organization of Brain Network in Peripheral Neural Anastomosis Rats after Electroacupuncture: An ICA and Connectome Analysis

Acupuncture is a mild therapy in rehabilitation practice of peripheral nerve injury. Previous studies confirmed the deep participation of brain plasticity in the process of functional restoration. The therapeutic effect of acupuncture is also believed to be closely associated with brain plasticity, especially in the hypothalamus and limbic system. But the fuzzy neural mechanism somehow limits the application or improvement of this therapy. There is little information about the effect of acupuncture on topological properties of brain networks. Instead of functional segregation approach, we utilized graph theory method to analyze the large-scale and distributed properties of information processing. We first established rat model of sciatic nerve injury and performed rehabilitation therapy of electroacupuncture for 120 days. Meanwhile, we used independent component analysis to extract seven sub-networks from the whole brain. Then measurements of graph theory were calculated in each sub-network as well as the whole brain network. We found no significant difference of any measurement in whole brain network among intervention group, model group and normal group. But the assortativity, hierarchy, small-world properties of sub-network displayed significant differences among three groups. It induces changes of neural plasticity in several sub-networks instead of whole brain network. We attributed the changes to the enhancement of the short-term compensatory adaptation and the reduction of the long-term overacting regional information transmission. The present study may shed light on the vague distinction of large-scale property of brain networks after electroacupuncture, which leads to a better understanding of this ancient traditional Chinese therapy.