Deep cerebellar stimulation enhances cognitive recovery after prefrontal traumatic brain injury in rodent

Carry-Over Effect of Deep Cerebellar Stimulation-Mediated Motor Recovery in a Rodent Model of Traumatic Brain Injury

BACKGROUND

We previously demonstrated that deep brain stimulation (DBS) of lateral cerebellar nucleus (LCN) can enhance motor recovery and functional reorganization of perilesional cortex in rodent models of stroke or TBI.

OBJECTIVE

Considering the treatment-related neuroplasticity observed at the perilesional cortex, we hypothesize that chronic LCN DBS-enhanced motor recovery observed will carry-over even after DBS has been deactivated.

METHODS

Here, we directly tested the enduring effects of LCN DBS in male Long Evans rats that underwent controlled cortical impact (CCI) injury targeting sensorimotor cortex opposite their dominant forepaw followed by unilateral implantation of a macroelectrode into the LCN opposite the lesion. Animals were randomized to DBS or sham treatment for 4 weeks during which the motor performance were characterize by behavioral metrics. After 4 weeks, stimulation was turned off, with assessments continuing for an additional 2 weeks. Afterward, all animals were euthanized, and tissue was harvested for further analyses.

RESULTS

Treated animals showed significantly greater motor improvement across all behavioral metrics relative to untreated animals during the 4-week treatment, with functional gains persisting across 2-week post-treatment. This motor recovery was associated with the increase in CaMKIIα and BDNF positive cell density across perilesional cortex in treated animals.

CONCLUSIONS

LCN DBS enhanced post-TBI motor recovery, the effect of which was persisted up to 2 weeks beyond stimulation offset. Such evidence should be considered in relation to future translational efforts as, unlike typical DBS applications, treatment may only need to be provided until such time as a new function plateau is achieved.

Deep brain stimulation mitigates memory deficits in a rodent model of traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a major life-threatening event. In addition to neurological deficits, it can lead to long-term impairments in attention and memory. Deep brain stimulation (DBS) is an established therapy for movement disorders that has been recently investigated for memory improvement in various disorders. In models of TBI, stimulation delivered to different brain targets has been administered to rodents long after the injury with the objective of treating motor deficits, coordination and memory impairment.

OBJECTIVE

To test the hypothesis that DBS administered soon after TBI may prevent the development of memory deficits and exert neuroprotective effects.

METHODS

Male rats were implanted with DBS electrodes in the anterior nucleus of the thalamus (ANT) one week prior to lateral fluid percussion injury (FPI). Immediately after TBI, animals received active or sham stimulation for 6 h. Four days later, they were assessed in a novel object/novel location recognition test (NOR/NLR) and a Barnes maze paradigm. After the experiments, hippocampal cells were counted. Separate groups of animals were sacrificed at different timepoints after TBI to measure cytokines and brain derived neurotrophic factor (BDNF). In a second set of experiments, TBI-exposed animals receiving active or sham stimulation were injected with the tropomyosin receptor kinase B (TrkB) antagonist ANA-12, followed by behavioural testing.

RESULTS

Rats exposed to TBI given DBS had an improvement in several variables of the Barnes maze, but no significant improvements in NOR/NLR compared to Sham DBS TBI animals or non-implanted controls. Animals receiving stimulation had a significant increase in BDNF levels, as well as in hippocampal cell counts in the hilus, CA3 and CA1 regions. DBS failed to normalize the increased levels of TNFα and the proinflammatory cytokine IL1β in the perilesional cortex and the hippocampus of the TBI-exposed animals. Pharmacological experiments revealed that ANA-12 administered alongside DBS did not counter the memory improvement observed in ANT stimulated animals.

CONCLUSIONS

DBS delivered immediately after TBI mitigated memory deficits, increased the expression of BDNF and the number of hippocampal cells in rats. Mechanisms for these effects were not related to an anti-inflammatory effect or mediated via TrkB receptors.

Non-pharmacological interventions for traumatic brain injury

Heterogeneity and variability of symptoms due to the type, site, age, sex, and severity of injury make each case of traumatic brain injury (TBI) unique. Considering this, a universal treatment strategy may not be fruitful in managing outcomes after TBI. Most of the pharmacological therapies for TBI aim at modifying a particular pathway or molecular process in the sequelae of secondary injury rather than a holistic approach. On the other hand, non-pharmacological interventions such as hypothermia, hyperbaric oxygen, preconditioning with dietary adaptations, exercise, environmental enrichment, deep brain stimulation, decompressive craniectomy, probiotic use, gene therapy, music therapy, and stem cell therapy can promote healing by modulating multiple neuroprotective mechanisms. In this review, we discussed the major non-pharmacological interventions that are being tested in animal models of TBI as well as in clinical trials. We evaluated the functional outcomes of various interventions with an emphasis on the links between molecular mechanisms and outcomes after TBI.

Transcriptome analysis reveals the neuroprotective effect of Dlg4 against fastigial nucleus stimulation-induced ischemia/reperfusion injury in rats

BACKGROUND

Previous studies have demonstrated that electrical stimulation of the cerebellar fastigial nucleus (FNS) can considerably decrease infarction volume and improve neurofunction restoration following cerebral ischemia. Nevertheless, the molecular mechanism of the neuroprotective effect of FNS is still vague.

METHODS

In this study, we developed a rat model of ischemia/reperfusion that included 1 h FNS followed by reperfusion for 3, 6, 12, 24, and 72 h. The expression profile of molecular alterations in brain tissues was obtained by transcriptome sequencing at five different time points. The function and pathway of miRNA expression pattern and core genes were annotated by Allen Brain Atlas, STRING database and Cytoscape software, so as to explore the mechanism of FNS-mediated neuroprotection.

RESULTS

The results indicated that FNS is associated with the neurotransmitter cycle pathway. FNS may regulate the release of monoamine neurotransmitters in synaptic vesicles by targeting the corresponding miRNAs through core Dlg4 gene, stimulate the Alternative polyadenylation (APA) incident's anti -apoptosis effect on the brain, and stimulate the interaction activation of neurons in cerebellum, cortex/thalamus and other brain regions, regulate neurovascular coupling, and reduce cerebral damage.

CONCLUSION

FNS may activate neuronal and neurovascular coupling by regulating the release of neurotransmitters in synaptic vesicles through the methylation of core Dlg4 gene and the corresponding transcription factors and protein kinases, inducing the anti-apoptotic mechanism of APA events. The findings from our investigation offer a new perspective on the way brain tissue responds to FNS-driven neuroprotection.

Electrical stimulation methods and protocols for the treatment of traumatic brain injury: a critical review of preclinical research

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of disabilities resulting from cognitive and neurological deficits, as well as psychological disorders. Only recently, preclinical research on electrical stimulation methods as a potential treatment of TBI sequelae has gained more traction. However, the underlying mechanisms of the anticipated improvements induced by these methods are still not fully understood. It remains unclear in which stage after TBI they are best applied to optimize the therapeutic outcome, preferably with persisting effects. Studies with animal models address these questions and investigate beneficial long- and short-term changes mediated by these novel modalities.

METHODS

In this review, we present the state-of-the-art in preclinical research on electrical stimulation methods used to treat TBI sequelae. We analyze publications on the most commonly used electrical stimulation methods, namely transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), deep brain stimulation (DBS) and vagus nerve stimulation (VNS), that aim to treat disabilities caused by TBI. We discuss applied stimulation parameters, such as the amplitude, frequency, and length of stimulation, as well as stimulation time frames, specifically the onset of stimulation, how often stimulation sessions were repeated and the total length of the treatment. These parameters are then analyzed in the context of injury severity, the disability under investigation and the stimulated location, and the resulting therapeutic effects are compared. We provide a comprehensive and critical review and discuss directions for future research. RESULTS AND CONCLUSION: We find that the parameters used in studies on each of these stimulation methods vary widely, making it difficult to draw direct comparisons between stimulation protocols and therapeutic outcome. Persisting beneficial effects and adverse consequences of electrical simulation are rarely investigated, leaving many questions about their suitability for clinical applications. Nevertheless, we conclude that the stimulation methods discussed here show promising results that could be further supported by additional research in this field.

Neuromodulation Therapies in Pre-Clinical Models of Traumatic Brain Injury: Systematic Review and Translational Applications

Traumatic brain injury (TBI) has been associated with several lasting impairments that affect quality of life. Pre-clinical models of TBI have been studied to further our understanding of the underlying short-term and long-term symptomatology. Neuromodulation techniques have become of great interest in recent years as potential rehabilitative therapies after injury because of their capacity to alter neuronal activity and neural circuits in targeted brain regions. This systematic review aims to provide an overlook of the behavioral and neurochemical effects of transcranial direct current stimulation (tDCS), transcranial magnetic stimulation (TMS), deep brain stimulation (DBS), and vagus nerve stimulation (VNS) in pre-clinical TBI models. After screening 629 abstracts, 30 articles were pooled for review. These studies showed that tDCS, TMS, DBS, or VNS delivered to rodents restored TBI-induced deficits in coordination, balance, locomotor activity and improved cognitive impairments in memory, learning, and impulsivity. Potential mechanisms for these effects included neuroprotection, a decrease in apoptosis, neuroplasticity, and the restoration of neural circuit abnormalities. The translational value, potential applicability, and the interpretation of these findings in light of outcome data from clinical trials in patients with TBI are discussed.