Download the Free Unbound MEDLINE PubMed App to your smartphone or tablet.
Available for iPhone, iPad, iPod touch, and Android.
Experimental neurology [journal]
- Development and characterization of an aged onset model of Alzheimer's disease in Drosophila melanogaster. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 27.
The biggest risk factor for developing Alzheimer's disease (AD) is age. Depending on the age of onset, AD is clinically categorized into either the early-onset form (before age 60years old), or the late-onset form (after age 65years old), with the vast majority of AD diagnosed as late onset (LOAD). LOAD is a progressive neurodegenerative disorder that involves the accumulation of β-amyloid (Aβ) plaques and neurofibrillary tangles in the brains of elderly patients. Affected individuals often experience symptoms including memory loss, confusion, and behavioral changes. Though many animal models of AD exist, very few are capable of analyzing the effect of older age on AD pathology. In an attempt to better model LOAD, we developed a novel "aged AD" model using Drosophila melanogaster. In our model, we express low levels of the human AD proteins APP (Amyloid Precursor Protein) and BACE1 (β-site APP cleaving enzyme BACE) specifically in the fly's central nervous system. Advantages of our model include the onset of behavioral and neuropathological symptoms later in the fly's lifespan due to gradual accrual of Aβ within the central nervous system (CNS), making age the key factor in the behavioral and neuroanatomical phenotypes that we observe in this model.The biggest risk factor for developing Alzheimer's disease (AD) is age. However, a majority of animal models that model AD show AD pathology early, often during stages of their lifecycle where a significant amount of development is still occurring. Thus, there is a clear need to develop in vivo disease models which consider age as the main factor in developing AD-like pathology. However, to date, many of the models of AD have a difficult time incorporating older age as a significant factor in their analysis due to the methodology associated with expressing transgenic elements in animals. We describe here the creation of an animal model for AD where age is the main factor associated with development of disease phenotypes.
- The prickly, stressful business of burn pain. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 27.
- Adenosine A1 receptors stimulation reduces D1 receptor-mediated GABAergic transmission from striato-nigral terminals and attenuates L-DOPA-induced dyskinesia in dopamine-denervated mice. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 27.
γ-Aminobutyric acid A receptor (GABAAR)-mediated postsynaptic currents were recorded, in brain slices, from substantia nigra pars reticulate neurons. The selective adenosine A1 receptor (A1R) antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), increased the frequency, but not the amplitude, of spontaneous inhibitory post synaptic currents (IPSCs), in the presence of the dopamine D1 receptor agonist SKF 38393 (SKF) and phosphodiesterase 10A inhibitors (papaverine or AE90074). Under these conditions, DPCPX also increased the amplitude of evoked IPSCs (eIPSCs). The effect of DPCPX was also examined in a mouse model of Parkinson's disease (PD), generated by unilateral denervation of the dopaminergic input to the striatum. In this model, SKF alone was sufficient to increase sIPSCs frequency and eIPSCs amplitude, and these effects were not potentiated by DPCPX. To confirm a depressive effect of A1Rs on the synaptic release of GABA we used the selective A1R agonist 5'-chloro-5'-deoxy-N(6)-(±)-(endo-norborn-2-yl)adenosine (5'Cl5'd-(±)-ENBA) which has limited peripheral actions. We found that 5'Cl5'd-(±)-ENBA decreased sIPSCs frequency, without affecting their amplitude, and decreased eIPSCs amplitude. Importantly, in the PD mouse model, 5'Cl5'd-(±)-ENBA prevented the increase in sIPSC frequency and eIPSC amplitude produced by SKF. Since exaggerated DA transmission along the striato-nigral pathway is involved in the motor complications (e.g. dyskinesia) caused by prolonged and intermittent administration of L-DOPA, we examined the effect of A1R activation in mice with unilateral DA denervation. We found that 5'Cl5'd-(±)-ENBA, administered in combination with L-DOPA, reduced the development of abnormal involuntary movements. These results indicate the potential benefit of A1R agonists for the treatment of L-DOPA-induced dyskinesia and hyperkinetic disorders providing a mechanistic framework for the study of the interaction between DA and adenosine in the striatonigral system.
- Subthalamotomy-induced changes in dopamine receptors in parkinsonian monkeys. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 26.
Subthalamotomy allows a reduction of doses of L-DOPA in dyskinetic patients while its antiparkinsonian benefits are preserved. However, the mechanisms of the potentiation of this response to medication remain to be elucidated. Hence, dopamine D1 and D2 receptors as well as the dopamine transporter were investigated using receptor binding autoradiography. D1 receptor, D2 receptor, preproenkephalin and preprodynorphin mRNAs levels were measured by in situ hybridization. Four dyskinetic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) parkinsonian monkeys that underwent unilateral subthalamotomy were compared to four controls, four saline-treated and four L-DOPA-treated MPTP monkeys. Dopamine, its metabolites and its transporter were extensively and similarly decreased in all parkinsonian monkeys. D1 receptor specific binding was decreased in the striatum of all MPTP monkeys. The L-DOPA-induced decrease in D1 receptor specific binding was reversed in the striatum ipsilateral to subthalamotomy. D1 receptor mRNA levels followed a similar pattern. D2 receptor specific binding and mRNA levels remained unchanged in all groups. Striatal preproenkephalin mRNA levels were overall increased in MPTP monkeys; the STN-lesioned parkinsonian group had significantly lower values than the saline-treated and L-DOPA-treated parkinsonian monkeys in the dorsolateral putamen. Striatal preprodynorphin mRNA levels remained unchanged in MPTP monkeys compared to controls whereas it increased in all monkeys treated with L-DOPA compared to controls; subthalamotomy induced a decrease in the dorsolateral putamen ipsilateral to surgery. The improved motor response to L-DOPA after subthalamotomy in the parkinsonian monkeys investigated may be associated with an increased synthesis and expression of D1 receptors ipsilateral to STN lesion of the direct pathway.
- Angiotensin type 1 receptor blockage reduces L-dopa-induced dyskinesia in the 6-OHDA model of Parkinson's disease. Involvement of Vascular Endothelial Growth Factor and interleukin-1β [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 23.
Non-neuronal factors such angiogenesis and neuroinflammation may play a role in L-dopa induced dyskinesias (LID). Vascular endothelial growth factor (VEGF) and proinflammatory cytokines such as interleukin-1β (IL-1β) have been found to be involved in LID. The renin-angiotensin system (RAS) is involved in the inflammatory response and VEGF synthesis via type 1 (AT1) receptors. However, it is not known whether the RAS plays a role in LID and whether AT1 antagonists could constitute a useful therapy against LID. In this study, we investigated whether manipulation of brain RAS is effective in preventing LID. Blocking AT1 receptors with candesartan significantly reduces LID in the 6-OHDA rat model. Chronic dopaminergic denervation induces an increase in striatal levels of VEGF and IL-1β. Dyskinetic animals showed significantly higher levels of VEGF and IL-1β in the lateral striatum and the substantia nigra, as revealed by western blot and real time-PCR analysis. Interestingly, animals treated with both candesartan and L-dopa displayed significantly lower levels of VEGF, IL-1β and dyskinesia than those treated with L-dopa alone. The stimulatory effect of angiotensin II (AII) on VEGF expression was confirmed by addition of AII to primary mesencephalic cultures and intraventricular administration of AII in rats. The results of the present study reveal for first time that blockage of AT-1 receptors reduces LID. A candesartan-induced decrease in VEGF and IL-1β may be responsible for the beneficial effects, suggesting the brain RAS as a new target for LID treatment in PD patients.
- Special Issue on amyotrophic lateral sclerosis. [EDITORIAL]
- Exp Neurol 2014 Aug 23.
- Matrix metalloproteinase-2 is downregulated in sciatic nerve by streptozotocin induced diabetes and/or treatment with minocycline: Implications for nerve regeneration. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 23.
Minocycline is an inhibitor of matrix metalloproteinases (MMPs) and has been shown to have analgesic effects. Whilst increased expression of MMPs is associated with neuropathic pain, MMPs also play crucial roles in Wallerian degeneration and nerve regeneration. In this study we examined the expression of MMP-2, MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1/-2 in the sciatic nerve of control and streptozotocin-induced diabetic rats treated with either vehicle or minocycline by quantitative PCR and gelatin zymography. We assessed the effects of minocycline on nerve conduction velocity and intraepidermal nerve fibre (IENF) deficits in diabetic neuropathy and investigated the effects of minocycline or MMP-2 on neurite outgrowth from primary cultures of dissociated adult rat sensory neurons. We show that MMP-2 is expressed constitutively in the sciatic nerve in vivo and treatment with minocycline or diabetes leads to downregulation of MMP-2 expression and activity. The functional consequence of this is IENF deficits in minocycline-treated nondiabetic rats and an unsupportive microenvironment for regeneration in diabetes. Minocycline reduces levels of MMP-2 mRNA and nerve growth factor-induced neurite outgrowth. Furthermore, in vivo minocycline treatment reduces preconditioning-induced in vitro neurite outgrowth following a sciatic nerve crush. In contrast, the addition of active MMP-2 facilitates neurite outgrowth in the absence of neurotrophic support and pre-treatment of diabetic sciatic nerve substrata with active MMP-2 promotes a permissive environment for neurite outgrowth. In conclusion we suggest that MMP-2 downregulation may contribute to the regenerative deficits in diabetes. Minocycline treatment also downregulates MMP-2 activity and is associated with inhibitory effects on sensory neurons. Thus, caution should be exhibited with its use as the balance between beneficial and detrimental outcomes may be critical in assessing the benefits of using minocycline to treat diabetic neuropathy.
- The mixed blessing of treating symptoms in acute vestibular failure - Evidence from a 4-aminopyridine experiment. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 22.
Early symptomatic treatment of acute unilateral vestibulopathy is thought to impede the course of ensuing central vestibular compensation (VC). Despite the great clinical importance of this hypothesis there is no experimental evidence of its validity. The present study addressed this question by investigating the direct effect of 4-aminopyridine (4-AP) on ocular motor and postural symptoms in acute unilateral vestibulopathy as well as its long-term consequences for VC in a rat model of chemical unilateral labyrinthectomy (UL). After UL, one group of Sprague-Dawley rats was treated with 4-AP p.o. (1mg/kg/day), another with 0.9% NaCl solution p.o. for 3days. Behavioural testing for symptoms of vestibular tone imbalance was done 1day before and 1, 2, 3, 5, 7, 9, 15, 21, and 30days after UL. In addition, sequential whole-brain [(18)F]-FDG-μPET was performed before and 1, 3, 7, 15, and 30days after UL to examine and visualize 4-AP-induced modulation of VC. Administration of 4-AP on days 1-3 significantly improved postural imbalance 2h after administration compared to that in controls. This effect was only transient. Remarkably, the 4-AP group had a prolonged and impaired course of postural compensation compared to that of controls. The μPET revealed a significant increase of regional cerebral glucose metabolism (rCGM) in the vestibulocerebellum 2h after administration of 4-AP. However, the 4-AP group exhibited a persistent asymmetry of rCGM after day 3 in the vestibular nuclei and posterolateral thalami. In conclusion, this study confirms the hypothesis that early pharmacological abatement of vestibular symptoms impedes VC.
- Commentary on Myers et al.: Growing role of the innate immunity receptor CD36 in central nervous system diseases. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 22.
Activation of innate immunity by sterile inflammation has emerged as a key event in selected CNS diseases, with a defining impact on all stages of the pathological process. Due to its multiple functions and assembly with other pattern recognition receptors, the innate immunity receptor CD36 has been implicated in a wide variety of brain pathologies, ranging from acute brain injury to neurodegeneration. However, the role of CD36 is complex involving both tissue destruction, related mainly to oxidative stress and inflammation, and beneficial reparative effects due to the involvement of CD36 in tissue repair and reorganization. A recent paper of Meyer at al. provided novel evidence for a role of CD36 also in spinal cord trauma, a condition in which the effect of CD36 was found to be univocally deleterious. This commentary will provide a brief overview of the pathobiology of CD36 and its expanding role in diseases of the brain and spinal cord.
- Agrin requires specific proteins to selectively activate γ-aminobutyric acid neurons for pain suppression. [JOURNAL ARTICLE]
- Exp Neurol 2014 Aug 21.
Agrin, a heparan sulfate proteoglycan functioning as a neuro-muscular junction inducer, has been shown to inhibit neuropathic pain in sciatic nerve injury rat models, via phosphorylation of N-Methyl-d-aspartate receptor NR1 subunits in gamma-aminobutyric acid neurons. However, its effects on spinal cord injury-induced neuropathic pain, a debilitating syndrome frequently encountered after various spine traumas, are unknown. In the present investigation, we studied the 50kDa agrin isoform effects in a quisqualic acid dorsal horn injection rat model mimicking spinal cord injury-induced neuropathic pain. Our results indicate that 50kDa agrin decreased only in the dorsal horn of neuropathic animals and increased 50kDa agrin expression in the dorsal horn, via intra-spinal injection of adeno-associated virus serum type two, suppressed spinal cord injury-induced neuropathic pain. Also, the reason why 50kDa agrin only activates the N-Methyl-d-aspartate receptor NR1 subunits in the GABA neurons, but not in sensory neurons, is unknown. Using immunoprecipitation and Western-blot analysis, two dimensional gel separation, and mass spectrometry, we identified several specific proteins in the reaction protein complex, such as neurofilament 200 and mitofusin 2, that are required for the activation of the NR1 subunits of gamma-aminobutyric acid inhibitory neurons by 50kDa agrin. These findings indicate that 50kDa agrin is a promising agent for neuropathic pain treatment.