Long-term impairment of social behavior, vocalizations and motor activity induced by bilateral lesions of the fastigial nucleus in juvenile rats

LPCAT3 exacerbates early brain injury and ferroptosis after subarachnoid hemorrhage in rats

AIMS

Lysophosphatidylcholine acyltransferase 3 (LPCAT3) is known to play a pivotal role in lipid metabolism, but its role in the early brain injury (EBI) following subarachnoid hemorrhage (SAH) remains unclear. This study provides insights into LPCAT3 expression alterations and functional implications in EBI following SAH.

METHODS

SAH models of adult male Sprague-Dawley (SD) rats were established by intravascular perforation. Lentivirus vectors were administered by intracerebroventricular injection (i.c.v.) to either induce LPCAT3 overexpression or knockdown 14 days before SAH induction. Western blot, immunofluorescence, Nissl staining, MDA detection, ROS detection, iron content detection, and short-term and long-term neurobehavioral tests were performed to investigate the effects of regulated-LPCAT3 after SAH.

RESULTS

LPCAT3 levels were found to be significantly elevated in SAH. Suppression of LPCAT3 expression via shRNA improved oxidative stress, reduced brain edema, alleviated behavioral and cognitive deficits following SAH and decreased neuronal death, while upregulating LPCAT3 expression showed opposing effects.

CONCLUSION

LPCAT3 is involved in SAH-induced EBI and associated with ferroptosis. Our findings provide a referential basis for potential therapeutic interventions aimed at alleviating EBI following SAH.

Targeting DBS to the centrolateral thalamic nucleus improves movement in a lesion-based model of acquired cerebellar dystonia in mice

Dystonia is the third most common movement disorder and an incapacitating co-morbidity in a variety of neurologic conditions. Dystonia can be caused by genetic, degenerative, idiopathic, and acquired etiologies, which are hypothesized to converge on a "dystonia network" consisting of the basal ganglia, thalamus, cerebellum, and cerebral cortex. In acquired dystonia, focal lesions to subcortical areas in the network - the basal ganglia, thalamus, and cerebellum - lead to a dystonia that can be difficult to manage with canonical treatments, including deep brain stimulation (DBS). While studies in animal models have begun to parse the contribution of individual nodes in the dystonia network, how acquired injury to the cerebellar outflow tracts instigates dystonia; and how network modulation interacts with symptom latency remain as unexplored questions. Here, we present an electrolytic lesioning paradigm that bilaterally targets the cerebellar outflow tracts. We found that lesioning these tracts, at the junction of the superior cerebellar peduncles and the medial and intermediate cerebellar nuclei, resulted in acute, severe dystonia. We observed that dystonia is reduced with one hour of DBS of the centrolateral thalamic nucleus, a first order node in the network downstream of the cerebellar nuclei. In contrast, one hour of stimulation at a second order node in the short latency, disynaptic projection from the cerebellar nuclei, the striatum, did not modulate the dystonia in the short-term. Our study introduces a robust paradigm for inducing acute, severe dystonia, and demonstrates that targeted modulation based on network principles powerfully rescues motor behavior. These data inspire the identification of therapeutic targets for difficult to manage acquired dystonia.

Dopamine receptors of the rodent fastigial nucleus support skilled reaching for goal-directed action

The dopaminergic (DA) system regulates both motor function, and learning and memory. The cerebellum supports motor control and the acquisition of procedural memories, including goal-directed behavior, and is subjected to DA control. Its fastigial nucleus (FN) controls and interprets body motion through space. The expression of dopamine receptors has been reported in the deep cerebellar nuclei of mice. However, the presence of dopamine D1-like (D1R) and D2-like (D2R) receptors in the rat FN has not yet been verified. In this study, we first confirmed that DA receptors are expressed in the FN of adult rats and then targeted these receptors to explore to what extent the FN modulates goal-directed behavior. Immunohistochemical assessment revealed expression of both D1R and D2R receptors in the FN, whereby the medial lateral FN exhibited higher receptor expression compared to the other FN subfields. Bilateral treatment of the FN with a D1R antagonist, prior to a goal-directed pellet-reaching task, significantly impaired task acquisition and decreased task engagement. D2R antagonism only reduced late performance post-acquisition. Once task acquisition had occurred, D1R antagonism had no effect on successful reaching, although it significantly decreased reaching speed, task engagement, and promoted errors. Motor coordination and ambulation were, however, unaffected as neither D1R nor D2R antagonism altered rotarod latencies or distance and velocity in an open field. Taken together, these results not only reveal a novel role for the FN in goal-directed skilled reaching, but also show that D1R expressed in FN regulate this process by modulating motivation for action.

Hearing loss in juvenile rats leads to excessive play fighting and hyperactivity, mild cognitive deficits and altered neuronal activity in the prefrontal cortex

Background

In children, hearing loss has been associated with hyperactivity, disturbed social interaction, and risk of cognitive disturbances. Mechanistic explanations of these relations sometimes involve language. To investigate the effect of hearing loss on behavioral deficits in the absence of language, we tested the impact of hearing loss in juvenile rats on motor, social, and cognitive behavior and on physiology of prefrontal cortex.

Methods

Hearing loss was induced in juvenile (postnatal day 14) male Sprague-Dawley rats by intracochlear injection of neomycin under general anesthesia. Sham-operated and non-operated hearing rats served as controls. One week after surgery auditory brainstem response (ABR) measurements verified hearing loss or intact hearing in sham-operated and non-operated controls. All rats were then tested for locomotor activity (open field), coordination (Rotarod), and for social interaction during development in weeks 1, 2, 4, 8, 16, and 24 after surgery. From week 8 on, rats were trained and tested for spatial learning and memory (4-arm baited 8-arm radial maze test). In a final setting, neuronal activity was recorded in the medial prefrontal cortex (mPFC).

Results

In the open field deafened rats moved faster and covered more distance than sham-operated and non-operated controls from week 8 on (both p < 0.05). Deafened rats showed significantly more play fighting during development (p < 0.05), whereas other aspects of social interaction, such as following, were not affected. Learning of the radial maze test was not impaired in deafened rats (p > 0.05), but rats used less next-arm entries than other groups indicating impaired concept learning (p < 0.05). In the mPFC neuronal firing rate was reduced and enhanced irregular firing was observed. Moreover, oscillatory activity was altered, both within the mPFC and in coherence of mPFC with the somatosensory cortex (p < 0.05).

Conclusions

Hearing loss in juvenile rats leads to hyperactive behavior and pronounced play-fighting during development, suggesting a causal relationship between hearing loss and cognitive development. Altered neuronal activities in the mPFC after hearing loss support such effects on neuronal networks outside the central auditory system. This animal model provides evidence of developmental consequences of juvenile hearing loss on prefrontal cortex in absence of language as potential confounding factor.

Behavioral analysis in laboratory rats: Challenges and usefulness of 50-kHz ultrasonic vocalizations

Many rodent species emit and detect vocalizations in the ultrasonic range. Rats use three classes of ultrasonic vocalizations depending on developmental stage, experience and the behavioral situation. Calls from one class emitted by juvenile and adult rats, the so-called 50-kHz calls, are typical for appetitive and social situations. This review provides a brief historical account on the introduction of 50-kHz calls in behavioral research followed by a survey of their scientific applications focusing on the last five years, where 50-kHz publications reached a climax. Then, specific methodological challenges will be addressed, like how to measure and report 50-kHz USV, the problem of assignment of acoustic signals to a specific sender in a social situation, and individual variability in call propensity. Finally, the intricacy of interpreting 50-kHz results will be discussed focusing on the most prevalent ones, namely as communicative signals and/or readouts of the sender's emotional status.

Advances in cerebellar disorders: pre-clinical models, therapeutic targets, and challenges

INTRODUCTION

Cerebellar ataxias (CAs) represent neurological disorders with multiple etiologies and a high phenotypic variability. Despite progress in the understanding of pathogenesis, few therapies are available so far. Closing the loop between preclinical studies and therapeutic trials is important, given the impact of CAs upon patients' health and the roles of the cerebellum in multiple domains. Because of a rapid advance in research on CAs, it is necessary to summarize the main findings and discuss future directions.

AREAS COVERED

We focus our discussion on preclinical models, cerebellar reserve, the therapeutic management of CAs, and suitable surrogate markers. We searched Web of Science and PubMed using keywords relevant to cerebellar diseases, therapy, and preclinical models.

EXPERT OPINION

There are many symptomatic and/or disease-modifying therapeutic approaches under investigation. For therapy development, preclinical studies, standardization of disease evaluation, safety assessment, and demonstration of clinical improvements are essential. Stage of the disease and the level of the cerebellar reserve determine the goals of the therapy. Deficits in multiple categories and heterogeneity of CAs may require disease-, stage-, and symptom-specific therapies. More research is needed to clarify how therapies targeting the cerebellum influence both basal ganglia and the cerebral cortex, poorly explored domains in CAs.

Increased cerebral cortex activation in stroke patients during electrical stimulation of cerebellar fastigial nucleus with functional near-infrared spectroscopy

Background

Electrical stimulation of the cerebellar fastigial nucleus (FNS) has been shown to protect animals against cerebral ischemic injury. However, the changes in cortical activation as a response to FNS have not been illustrated in humans.

Objective

This study aims to detect functional connectivity changes in the brain of stroke patients, and investigate the cortical activation caused by FNS through measuring the oxygenated hemoglobin concentration (HBO) in the cerebral cortex of stroke patients and healthy controls (HCs).

Methods

This study recruited 20 patients with stroke and 20 HCs with all the following factors matched: age, gender and BMI. The experiment session was made up of the pre-task baseline, FNS task period, and post-task baseline. FNS task period contains 5 blocks, each block encompassing the resting state (30 s) and the FNS state (30 s). HBO signals were acquired by functional near-infrared spectroscopy (fNIRS) from the Prefrontal Cortex (PFC), the Motor Cortex (MC) and the Occipital Cortex (OC) throughout the experiment. The Pearson correlation coefficient was used to calculate the resting-state functional connectivity strength between the two groups, and the general linear model (GLM) was used to calculate the activation of 39 fNIRS channels during FNS in stroke patients and HCs, respectively.

Results

The coupling strength of stroke patients were significantly decreased in the following regions: right MC and left MC (t = 4.65, p = 0.0007), right MC and left OC (t = 2.93, p = 0.04), left MC and left OC (t = 2.81, p = 0.04). In stroke patients, the changes in cerebral oxygenated hemoglobin (ΔHBO) among 12 channels (CH) in the bilateral PFC and bilateral MC regions were significantly increased during the FNS state (FDR corrected p < 0.05) compared with the resting state. In HCs, only 1 channel was increased (FDR corrected p < 0.05) in the left PFC during FNS.

Conclusion

By using the FNS and fNIRS techniques, the characteristics of functional connectivity were found to decrease in stroke patients. It was also noticed that FNS activates the PFC and MC regions. These findings may help to guide functional rehabilitation in stroke patients.

Fastigial nuclei surgical damage and focal midbrain disruption implicate PAG survival circuits in cerebellar mutism syndrome

BACKGROUND

Pediatric postoperative cerebellar mutism syndrome (CMS) is a rare but well-known complication of medulloblastoma (Mb) resection with devastating effects on expressive language, mobility, cognition, and emotional regulation that diminishes quality of life for many Mb survivors. The specific anatomical and neuronal basis of CMS remains obscure. We address this issue by identifying patterns of surgical damage and secondary axonal degeneration in Mb survivors with CMS.

METHODS

Children with Mb deemed high risk for CMS based on intraventricular location of the tumor had T1 images analyzed for location(s) of surgical damage using a specially developed algorithm. We used three complementary methods of spatial analysis to identify surgical damage linked to CMS diagnosis. Magnetization transfer ratio (MTR) images were analyzed for evidence of demyelination in anatomic regions downstream of the cerebellum, indicating neuronal dysfunction.

RESULTS

Spatial analyses highlighted damage to the fastigial nuclei and their associated cerebellar cortices as the strongest predictors of CMS. CMS-related MTR decrease was greatest in the ventral periaqueductal gray (PAG) area and highly consistent in the left red nucleus.

CONCLUSION

Our evidence points to disruption of output from the fastigial nuclei as a likely causal trigger for CMS. We propose that core CMS symptoms result from a disruption in the triggering of survival behaviors regulated by the PAG, including the gating of vocalization and volitional movement. The fastigial nuclei provide the densest output to the PAG from the cerebellum, thus sparing these structures may provide a greater likelihood of CMS prevention.

Cerebellar Mutism Syndrome in Pediatric Neuro-oncology: A Multidisciplinary Perspective and Call for Research Priorities

Cerebellar mutism syndrome (CMS), also known as posterior fossa syndrome, occurs in a subset of children after posterior fossa tumor resection, most commonly medulloblastoma. Patients with this syndrome exhibit often transient, although protracted, symptoms of language impairment, emotional lability, cerebellar, and brainstem dysfunction. However, many patients experience persistent neurological deficits and lasting neurocognitive impairment. Historically, research and clinical care were hindered by inconsistent nomenclature, poorly defined diagnostic criteria, and uncertainty surrounding risk factors and etiology. Proposed diagnostic criteria include two major symptoms, language impairment and emotional lability, as proposed by the international Board of the Posterior Fossa Society in their consensus statement as well as other experts in this field. Risk factors most commonly associated with development of CMS include midline tumor location, diagnosis of medulloblastoma and specific tumor subtype, younger age at diagnosis, and preoperative language impairment. A proposed etiology of CMS includes disruption of the cerebellar outflow tracts, the cerebellar nuclei, and their efferent projections through the superior cerebellar peduncle. Treatment for CMS remains supportive. Herein, we present a comprehensive overview of CMS etiology, diagnosis, risk factors, clinical presentation, and clinical management. In addition, we identify essential multidisciplinary research priorities to advance diagnostics, prevention, and intervention efforts for patients with, or at risk for, development of CMS.

PTEN and AKT/GSK-3β/CRMP-2 signaling pathway are involved in neuronal apoptosis and axonal injury in early brain injury after SAH in rats

In early brain injury (EBI) after subarachnoid hemorrhage (SAH), white matter (WM) axonal injury plays a key role in the prognosis of the disease. The purpose of this study was to investigate the effects of phosphatase and tensin homolog deleted on chromosome ten (PTEN) on axonal injury and neuronal apoptosis post-SAH in rats and to find its underlying mechanism. Adeno-associated virus was injected into the lateral ventricle to suppress or promote PTEN. Neural function post-SAH in animals was determined by the modified Garcia score, beam balance, and Rotarod test, and the blood–brain barrier disruption was assessed by the brain water content. Axonal injury post-SAH was observed by TEM and determined by IF, and neuron apoptosis was measured by TUNEL staining. The mechanism was analyzed by Western blot to detect p-PTEN/PTEN, p-AKT/AKT, p-GSK-3β/GSK-3β, p-CRMP-2/CRMP-2, axonal injury marker β-APP and pro- and anti-apoptosis proteins, including Bax and Bcl-2, expression. We found 1. After knocking down PTEN, neuronal apoptosis and axonal injury were alleviated, and nerve function and blood–brain barrier were protected; accordingly, after overexpression of PTEN, neuronal apoptosis and axon damage were aggravated, and nerve function damage and blood–brain barrier damage were increased. 2. PTEN and AKT/GSK-3β/CRMP-2 pathway were jointly involved in regulating neuronal apoptosis and WM axon injury after SAH. According to our research, PTEN was a negative factor of EBI, and together with the AKT/GSK-3β/CRMP-2 signaling pathway aggravates neuronal apoptosis and WM axon damage after SAH. Inhibition of PTEN expression may become a new target for SAH treatment.

Epigenetic Regulation of Neural Transmission after Cerebellar Fastigial Nucleus Lesions in Juvenile Rats

Structural and functional abnormalities in the cerebellar midline region, including the fastigial nucleus, have been reported in neuropsychiatric disorders, also comprising the cerebellar cognitive affecting syndrome. In rats, early fastigial lesions reduce social interaction during development and lead to cognitive and emotional deficits in adults, accompanied by compromised neuronal network activity. Since epigenetic mechanisms are implicated in the etiology of neuropsychiatric disorders, we investigated whether fastigial nucleus lesions in juvenile rats would impact epigenetic regulation of neural transmission. The fastigial nucleus was lesioned bilaterally in 23-day-old male rats. Sham-lesion and naïve rats served as controls. DNA methylation was investigated for target genes of the GABAergic, dopaminergic, glutamatergic and oxytocinergic systems in brain regions with anatomic connections to the fastigial nucleus, i.e., medial prefrontal cortex, nucleus accumbens, striatum, thalamus, and sensorimotor cortex. Protein expression was examined for the respective target genes in case of altered DNA methylation between lesion and control groups. Lesioning of the fastigial nucleus led to significant differences in the epigenetic regulation of glutamate decarboxylase 1 and the oxytocin receptor in the nucleus accumbens and the prefrontal cortex. No differences were found for the other target genes and brain regions. Our findings indicate that epigenetic dysregulation after lesioning of the fastigial nucleus may influence long-term recovery and the emergence of behavioral changes. Together with previous behavioral and electrophysiological investigations of this rat model, these observations can play a role in the cerebellar cognitive affective syndrome and other neuropsychiatric disorders.

A Paravermal Trans-Cerebellar Approach to the Posterior Fossa Tumor Causes Hypertrophic Olivary Degeneration by Dentate Nucleus Injury

Simple Summary

Posterior fossa tumor surgery is challenging due to the proximity and exposure of cerebellar structures. A favorable operative approach is unknown. Following lesions to the dentato–rubro–olivary-pathway, a neurodegenerative disease called hypertrophic olivary degeneration (HOD) can occur. This study for the first time demonstrates that paravermal trans-cerebellar approaches are associated with a significantly higher likelihood of HOD on MRI when compared to other approaches. This finding can well be attributed to dentate nucleus (DN) injury. Furthermore, cerebellar mutism syndrome (CMS) was discussed in the literature to be correlated with HOD due to a functional overlap of pathways involved. We found no such correlation in this study, but HOD was shown to be a reliable indicator for surgical disruption of efferent cerebellar pathways involving the DN. Henceforth, neurosurgeons should consider more midline or lateral approaches in posterior fossa surgery to spare the DN whenever feasible, and focus on cerebellar functional anatomy in their preoperative planning.

Abstract

Background: In brain tumor surgery, injury to cerebellar connectivity pathways can induce a neurodegenerative disease called hypertrophic olivary degeneration (HOD), along with a disabling clinical syndrome. In children, cerebellar mutism syndrome (CMS) is another consequence of damage to cerebello–thalamo–cortical networks. The goal of this study was to compare paravermal trans-cerebellar to other more midline or lateral operative approaches in their risk of causing HOD on MR-imaging and CMS. Methods: We scanned our neurosurgical database for patients with surgical removal of pilocytic astrocytoma, ependymoma and medulloblastoma in the posterior fossa. Fifty patients with a mean age of 22.7 (±16.9) years were identified and analyzed. Results: HOD occurred in n = 10/50 (20%) patients within four months (median), always associated with contralateral dentate nucleus (DN)-lesions (p < 0.001). Patients with paravermal trans-cerebellar approach significantly more often developed HOD (7/11; 63.6%) when compared to other approaches (3/39; 7.7%; p < 0.001). Injury to the DN occurred more frequently after a paravermal approach (8/11 vs. 13/39 patients; p < 0.05). CMS was described for n = 12/50 patients (24%). Data indicated no correlation of radiological HOD and CMS development. Conclusions: A paravermal trans-cerebellar approach more likely causes HOD due to DN-injury when compared to more midline or lateral approaches. HOD is a radiological indicator for surgical disruption of cerebellar pathways involving the DN. Neurosurgeons should consider trajectories and approaches in the planning of posterior fossa surgery that spare the DN, whenever feasible.

Monitoring of Heart Rate and Activity Using Telemetry Allows Grading of Experimental Procedures Used in Neuroscientific Rat Models

In animal experimentation, welfare and severity assessments of all procedures applied to animals are necessary to meet legal and ethical requirements, as well as public interests. So far, the methods suggested for this purpose are time consuming and personnel intensive. Also, evidence-based biostatistical methods for this purpose are still rare. We here tested whether the classification of heart rate (HR) and activity (Act) data monitored by telemetry in the home cage by unsupervised k-means-based class-labeling and subsequent Support Vector Machine (SVM) analysis allows severity assessment and grading of experimental procedures of different domains, including surgery, injection, behavioral testing, and routine handling for maintenance. Telemetric devices were subcutaneously implanted in young adult male Crl:CD(SD) and BDIX/UImHanZtm rats. After recovery, rats were randomly subjected to different experimental procedures, i.e., handling and cage change as routine maintenance, Rat Grimace Scale, burrowing, and social interaction for welfare assessment, as well as repeated subcutaneous injections. Thereafter, rats were either intracranially implanted with electrodes or injected with tumor cells. Directly after each procedure, HR and Act were monitored by telemetry in the home cage for 4 h. Application of k-means and SVM algorithms on the obtained data sets from baseline (as no stress), cage change (exploratory Act), and intracranial surgery (as burden) measurements computed three classes described as low HR/low Act, high HR/high Act, and high HR/low Act, respectively. Validation of the SVM model by entering data from all procedures confirmed the allocation to the high HR/low Act class (burden) after surgery, which lasted longer after subcutaneous transmitter implantation than after intracranial surgery. The majority of data points from repeated injections, behavioral testing, and maintenance handling were allocated to the low HR/low Act and high HR/high Act classes. Overall, the SVM model based on HR and Act data monitored in home cage after procedures may be useful for the classification and grading of experimental procedures of different domains.

Lesion of the Fastigial Nucleus in Juvenile Rats Deteriorates Rat Behavior in Adulthood, Accompanied by Altered Neuronal Activity in the Medial Prefrontal Cortex

The cerebellar cognitive affective syndrome may result from various cerebellar injuries. Although it is not exactly known which anatomical structures are involved, the fastigial nucleus has been thought to play a pivotal role according to recent studies. Here we investigate whether bilateral fastigial nucleus lesions in juvenile rats affect cognitive-associative and limbic related functions in adulthood. Furthermore, potential effects on the neuronal activity in the medial prefrontal cortex (mPFC) and local field coherence with the sensorimotor cortex (SMCtx) were evaluated. The fastigial nucleus was lesioned bilaterally by thermocoagulation via stereotaxically inserted electrodes in 23-day old male Sprague Dawley rats. Naïve and sham-lesioned rats (electrodes inserted above the nucleus and no electrical current applied) served as controls. As adults, all groups were tested for cognitive-associative function, social behavior, and anxiety. Thereafter, electrophysiological recordings were obtained under urethane anesthesia. Finally, lesions and recording sites were histologically verified. Spatial learning in a radial maze test and learning in an operant learning paradigm was disturbed in rats with fastigial lesions. Furthermore, in the elevated plus maze anxiety was enhanced, whereas social behavior was not affected. Electrophysiological recordings showed enhanced local field coherence between mPFC and SMCtx across all frequency bands. Impaired cognitive and affective functions together with enhanced coherence between mPFC and SMCtx after bilateral fastigial nucleus lesions indicate that the fastigial nucleus contribute to the development of the cerebellar cognitive affective syndrome and associated motor behavior.