Current research in neurobiology最新文献

Primary neuronal cultures have proven to be a powerful tool for studying mechanisms in neuroscience. It is technically challenging and expensive to reproduce high quality viable neuronal cultures. Laboratories that are not experienced or equipped to prepare primary neuron cultures may have difficulty producing consistent cultures for experiments. It has previously been shown that live rat embryonic hippocampal cultures can be shipped from laboratories that produce them. Here, we show that variations to this procedure allow for shipping postnatal mouse cultures of hippocampal and cortical primary neurons using standard commercial couriers. We also show that after shipping, primary neurons are viable, express synaptic markers, and demonstrate physiological activity, making them relevant models over immortalized cell lines. Among the many applications of this technique would be the preparation of cultured neurons from transgenic mouse lines in one laboratory and sharing them with distant collaborators, reducing variability.

Background

Somatosensory deficits are frequently seen in acute stroke patients and may recover over time and affect functional outcome. However, the underlying mechanism of function recovery remains poorly understood. In the present study, progressive function alteration of the secondary somatosensory cortex (S2) and its relationship with regional perfusion and neurological outcome were examined using a monkey model of stroke.

Methods and materials

Rhesus monkeys (n = 4) were induced with permanent middle cerebral artery occlusion (pMCAo). Resting-state functional MRI, dynamic susceptibility contrast perfusion MRI, diffusion-weighted, T₁ and T₂ weighted images were collected before surgery and at 4–6, 48, and 96 h post stroke on a 3T scanner. Progressive changes of relative functional connectivity (FC), cerebral blood flow (CBF), and CBF/Tmax (Time to Maximum) of affected S2 regions were evaluated. Neurological deficits were assessed using the Spetzler approach.

Results

Ischemic lesion was evidently seen in the MCA territory including S2 in each monkey. Relative FC of injured S2 regions decreased substantially following stroke. Spetzler scores dropped substantially at 24 h post stroke but slightly recovered from Day 2 to Day 4. Relative FC progressively increased from 6 to 48 and 96 h post stroke and correlated significantly with relative CBFand CBF/Tmax changes.

Conclusion

The present study revealed the progressive alteration of function connectivity in S2 during acute stroke. The preliminary results suggested the function recovery might start couple days post occlusion and collateral circulation might play a key role in the recovery of somatosensory function after stroke insult. The relative function connectivity in S2 may provide additional information for prediction of functional outcome in stroke patients.

Charcot-Marie-Tooth disease type 1A (CMT1A) is the most prevalent hereditary demyelinating neuropathy. This autosomal, dominantly inherited disease is caused by a duplication on chromosome 17p which includes the peripheral myelin protein 22 (PMP22) gene. There is clinical evidence that the disability in CMT1A is to a large extend due to axonal damage rather than demyelination. Over-expression of PMP22 is recently thought to impede cholesterol trafficking causing a total shutdown of local cholesterol and lipid synthesis in the Schwann cells, thus disturbing their ability to remyelinate. But there is a large variety in disease burden between CMT1A patients with the same genetic defect, indicating the presence of modifying factors that affect disease severity. One of these potential factors is the immune system. Several reports have described patients with co-occurrence of CMT1A with chronic inflammatory demyelinating disease or Guillain-Barré syndrome. We have previously shown in multiple animal models that the innate immune system and specifically the terminal complement system is a driver of inflammatory demyelination. To test the contribution of the terminal complement system to neuroinflammation and disease progression in CMT1A, we inhibited systemic complement C6 in two transgenic mouse models for CMT1A, the C3-PMP22 and C3-PMP22 c-JunP0Cre models. Both models over-express human PMP22, and one (C3-PMP22 c-JunP0Cre) also has a Schwann cell-specific knockout of c-Jun, a crucial regulator of myelination controlling autophagy. We found that systemic inhibition of C6 using antisense oligonucleotides affects the neuroinflammation, Rho GTPase and ERK/MAPK signalling pathways in the CMT1A mouse models. The cholesterol synthesis pathway remained unaffected. Analysis of motor function during treatment with C6 antisense oligonucleotides did not reveal any significant improvement in the CMT1A mouse models. This study shows that the contribution of the terminal complement system to progressive loss of motor function in the CMT1A mouse models tested is limited.

Various aspects of cortical face processing have been studied by assessing event related potentials (ERP). It has been described in the literature that mismatch negativity (MMN), a well-studied ERP, is not only modulated by sensory features but also emotional valence. However, the exact impact of emotion on the temporo-spatial profile of visual MMN during face processing remains inconsistent. By employing a sequential oddball paradigm using both neutral and emotional deviants, we were able to differentiate two distinct vMMN subcomponents. While an early subcomponent at 150–250 ms is elicited by emotional salient facial stimuli, the later subcomponent at 250–400 ms seems to reflect the detection of regularity violations in facial recognition per se, unaffected by emotional salience. Our results suggest that emotional valence is encoded in vMMN signal strength at an early stage of facial processing. Furthermore, we assume that of facial processing consists of temporo-spatially distinct, partially overlapping levels concerning different facial aspects.

Modern neuroscience approaches including optogenetics, calcium imaging, and other genetic manipulations have facilitated our ability to dissect specific circuits in rodent models to study their role in neurological disease. These approaches regularly use viral vectors to deliver genetic cargo (e.g., opsins) to specific tissues and genetically-engineered rodents to achieve cell-type specificity. However, the translatability of these rodent models, cross-species validation of identified targets, and translational efficacy of potential therapeutics in larger animal models like nonhuman primates remains difficult due to the lack of efficient primate viral vectors. A refined understanding of the nonhuman primate nervous system promises to deliver insights that can guide the development of treatments for neurological and neurodegenerative diseases. Here, we outline recent advances in the development of adeno-associated viral vectors for optimized use in nonhuman primates. These tools promise to help open new avenues for study in translational neuroscience and further our understanding of the primate brain.

We recently generated a nonhuman primate (NHP) model of the neurodegenerative disorder Huntington's disease (HD) using adeno-associated viral vectors to express a fragment of mutant HTT protein (mHTT) throughout the cortico-basal ganglia circuit. Previous work by our group established that mHTT-treated NHPs exhibit progressive motor and cognitive phenotypes which are accompanied by mild volumetric reductions of cortical-basal ganglia structures and reduced fractional anisotropy (FA) in the white matter fiber pathways interconnecting these regions, mirroring findings observed in early-stage HD patients. Given the mild structural atrophy observed in cortical and sub-cortical gray matter regions characterized in this model using tensor-based morphometry, the current study sought to query potential microstructural alterations in the same gray matter regions using diffusion tensor imaging (DTI), to define early biomarkers of neurodegenerative processes in this model. Here, we report that mHTT-treated NHPs exhibit significant microstructural changes in several cortical and subcortical brain regions that comprise the cortico-basal ganglia circuit; with increased FA in the putamen and globus pallidus and decreased FA in the caudate nucleus and several cortical regions. DTI measures also correlated with motor and cognitive deficits such that animals with increased basal ganglia FA, and decreased cortical FA, had more severe motor and cognitive impairment. These data highlight the functional implications of microstructural changes in the cortico-basal ganglia circuit in early-stage HD.

The Animal Research Declaration is committed to establishing cohesive and rigorous ethical standards to safeguard the welfare of nonhuman primates (NHPs) engaged in neuroscience research (Petkov et al., 2022 this issue). As part of this mission, there is an expanding dialogue amongst neuroscientists, philosophers, and policymakers, that is centred on diverse aspects of animal welfare and scientific practice. This paper emphasises the necessity of integrating the assessment of animal sentience into the declaration. Animal sentience, in this context, refers to the recognized capacity that animals have for various kinds of subjective experience, with an associated positive or negative valence (Browning and Birch, 2022). Accordingly, NHP neuroscience researchers should work toward instituting a standardised approach for evaluating what can be termed "individual sentience profiles," representing the unique manner in which an individual NHP experiences specific events or environments. The adoption of this novel parameter would serve a triad of indispensable purposes: enhancing NHP welfare throughout research involvement, elevating the quality of life for NHPs in captivity, and refining the calibre of research outcomes.

Pain is a common symptom associated with disorders involving the orofacial structures. Most acute orofacial painful conditions are easily recognized, but the pharmacological treatment may be limited by the adverse events of current available drugs and/or patients’ characteristics. In addition, chronic orofacial pain conditions represent clinical challenges both, in terms of diagnostic and treatment. There is growing evidence that specialized pro-resolution lipid mediators (SPMs) present potent analgesic effects, in addition to their well characterized role in the resolution of inflammation. Maresins (MaR-1 and MaR-2) were the last described members of this family, and MaR-2 analgesic action has not yet been reported. Herein the effect of MaR-2 in different orofacial pain models was investigated. MaR-2 (1 or 10 ng) was always delivered via medullary subarachnoid injection, which corresponds to the intrathecal treatment. A single injection of MaR-2 caused a significant reduction of phases I and II of the orofacial formalin test in rats. Repeated injections of MaR-2 prevented the development of facial heat and mechanical hyperalgesia in a model of post-operative pain in rats. In a model of trigeminal neuropathic pain (CCI-ION), repeated MaR-2 injections reversed facial heat and mechanical hyperalgesia in rats and mice. CCI-ION increased c-Fos positive neurons and CGRP⁺ activated (nuclear pNFkB) neurons in the trigeminal ganglion (TG), which were restored to sham levels by MaR-2 repeated treatment. In conclusion, MaR-2 showed potent and long-lasting analgesic effects in inflammatory and neuropathic pain of orofacial origin and the inhibition of CGRP-positive neurons in the TG may account for MaR-2 action.

The mechanism that reweights oculomotor vectors based on visual features is unclear. However, the latency of oculomotor visual activations gives insight into their antecedent featural processing. We compared the oculomotor processing time course of grayscale, task-irrelevant static and motion distractors during target selection by continuously measuring a battery of human saccadic behavioral metrics as a function of time after distractor onset. The motion direction was towards or away from the target and the motion speed was fast or slow. We compared static and motion distractors and observed that both distractors elicited curved saccades and shifted endpoints at short latencies (∼25 ms). After 50 ms, saccade trajectory biasing elicited by motion distractors lagged static distractor trajectory biasing by 10 ms. There were no such latency differences between distractor motion directions or motion speeds. This pattern suggests that additional processing of motion stimuli occurred prior to the propagation of visual information into the oculomotor system. We examined the interaction of distractor processing time (DPT) with two additional factors: saccadic reaction time (SRT) and saccadic amplitude. Shorter SRTs were associated with shorter DPT latencies of biased saccade trajectories. Both SRT and saccadic amplitude were associated with the magnitude of saccade trajectory biases.

Three decades following the introduction of the first Rb knockout (KO) mouse model, the role of this critical protein in regulating brain development during embryogenesis and beyond remains a major scientific interest. Rb is a tumor suppressor gene known as the master regulator of the G1/S checkpoint and control of cell cycle progression in stem and progenitor cells, but also their differentiated progeny. Here, we review the recent literature about the various Rb conditional Knockout (cKO) and inducible Knockout (iKO) models studied thus far, highlighting how findings should always be interpreted in light of the model and context under inquiry especially when studying the role of Rb in neuronal survival. There is indeed evidence of age-specific, cell type-specific and region-specific effects following Rb KO in the embryonic and the adult mouse brain. In terms of modeling neurodegenerative processes in human diseases, we discuss cell cycle re-entry (CCE) as a candidate mechanism underlying the increased vulnerability of Rb-deficient neurons to cell death. Notably, mouse models may limit the extent to which CCE due to Rb inactivation can mimic the pathological course of these disorders, such as Alzheimer's disease. These remarks ought to be considered in future research when studying the consequences of Rb inactivation on neuronal generation and survival in rodents and their corresponding clinical significance in humans.