Quinolinic Acid Lesions Research Articles

GelMA hydrogel as a scaffold to enhance the survival and differentiation of human induced lateral ganglionic eminence precursor cells

Cell reprogramming holds enormous potential to revolutionize our understanding of neurological and neurodevelopmental disorders, as well as enhance drug discovery and regenerative medicine. We have developed a direct cell reprogramming technology that allows us to generate lineage-specific neural cells. To extend our technology, we have investigated the incorporation of directly reprogrammed human lateral ganglionic eminence precursor cells (hiLGEPs) in a 3-dimensional (3D) matrix. Hydrogels are one of the most promising bio-scaffolds for 3D cell culture, providing cells with a supportive environment to adhere, proliferate, and differentiate. In particular, gelatin methacryloyl (GelMA) hydrogels have been used for a variety of 3D biomedical applications due to their biocompatibility, enzymatic cleavage, cell adhesion and tunable physical characteristics. This study therefore investigated the effect of GelMA hydrogel encapsulation on the survival and differentiation of hiLGEPs, both in vitro and following ex vivo transplantation into a quinolinic acid (QA) lesion rat organotypic slice culture model. We demonstrate, for the first time, that the encapsulation of hiLGEPs in GelMA hydrogel significantly enhances the survival and generation of DARPP32+ striatal neurons both in vitro and following ex vivo transplant. Furthermore, GelMA-encapsulated hiLGEPs were predominantly located away from the reactive astrocyte network that forms following QA lesioning, suggesting GelMA provides a protective barrier for cells in regions of inflammatory activation. Overall, these results indicate that GelMA hydrogel has the potential to act as a 3D bio-scaffold to augment the viability and differentiation of hiLGEPs for research and translation of pharmaceutical development and regenerative medicine.

Rat cortico-striatal sagittal organotypic slice cultures as ex vivo excitotoxic striatal lesion models

Organotypic brain slice cultures are a useful tool to study neurological disease as they provide a 3-dimensional system which more closely recapitulates the in vivo cytoarchitectural complexity than standard 2-dimensional in vitro cell cultures. Building on our previously developed rat brain slice culture protocol, we have extended our findings to develop ex vivo excitotoxic lesion models by treatment of rat sagittal organotypic slices with AMPA or quinolinic acid (QA). We show that treatment of rat sagittal cortico-striatal organotypic slices with 8μM AMPA or 50μM QA causes striatal cell loss with a reduction in neuronal nuclei (NeuN)+ cells and an increase in ethidium homodimer-1 (EthD-1)+ dead cells compared to untreated slices. More specifically, following treatment with QA, we observed a reduction in medium spiny neuron DARPP32 + cells in the striatum and cortex of slices. Treatment of the slices with AMPA does not alter glial fibrillary acidic protein (GFAP) expression, while we observed an acute increase in GFAP expression 1-week post-QA exposure both in the cortex and striatum of slices. This recapitulates the excitotoxic and striatal degeneration observed in rat AMPA and QA lesion models in vivo. Our slice culture platform provides an advance over other systems with the ability to generate acute AMPA- and QA-induced striatal excitotoxicity in sagittal cortico-striatal slices which can be cultured long-term for at least 4 weeks. Our ex vivo organotypic slice culture system provides a long-term cellular platform to model neuronal excitotoxicity, with QA specifically modelling Huntington's disease. This will allow for mechanistic studies of excitotoxicity and neuroprotection, as well as the development and testing of novel therapeutic strategies with reduced cost and ease of manipulation prior to in vivo experimentation.

Neural Transplants From Human Induced Pluripotent Stem Cells Rescue the Pathology and Behavioral Defects in a Rodent Model of Huntington's Disease.

Huntington’s disease (HD) is a devastating, autosomal-dominant inheritance disorder with the progressive loss of medium spiny neurons (MSNs) and corticostriatal connections in the brain. Cell replacement therapy has been proposed as a potential therapeutic strategy to treat HD. Among various types of stem cells, human-induced pluripotent stem cells (iPSCs) have received special attention to develop disease modeling and cell therapy for HD. In the present study, the therapeutic effects of neural precursor cells (NPCs) derived from a human iPSC line (1231A3-NPCs) were investigated in the quinolinic acid (QA)-lesioned rat model of HD. 1231A3-NPCs were transplanted into the ipsilateral striatum 1 week after QA lesioning, and the transplanted animals showed significant behavioral improvements for up to 12 weeks based on the staircase, rotarod, stepping, apomorphine-induced rotation, and cylinder tests. Transplanted 1231A3-NPCs also partially replaced the lost neurons, enhanced endogenous neurogenesis, reduced inflammatory responses, and reconstituted the damaged neuronal connections. Taken together, these results strongly indicate that NPCs derived from iPSCs can potentially be useful to treat HD in the future.

Longitudinal Magnetic Resonance Spectroscopy andDiffusion Tensor Imaging in Sheep (Ovis aries) With Quinolinic Acid Lesions of the Striatum: Time-Dependent Recovery of N-Acetylaspartate and Fractional Anisotropy.

We created an excitotoxic striatal lesion model of Huntington disease (HD) in sheep, using the N-methyl-d-aspartate receptor agonist, quinolinic acid (QA). Sixteen sheep received a bolus infusion of QA (75 µL, 180 mM) or saline, first into the left and then (4 weeks later) into the right striatum. Magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) of the striata were performed. Metabolite concentrations and fractional anisotropy (FA) were measured at baseline, acutely (1 week after each surgery) and chronically (5 weeks or greater after the surgeries). There was a significant decrease in the neuronal marker N-acetylaspartate (NAA) and in FA in acutely lesioned striata of the QA-lesioned sheep, followed by a recovery of NAA and FA in the chronically lesioned striata. NAA level changes indicate acute death and/or impairment of neurons immediately after surgery, with recovery of reversibly impaired neurons over time. The change in FA values of the QA-lesioned striata is consistent with acute structural disruption, followed by re-organization and glial cell infiltration with time. Our study demonstrates that MRS and DTI changes in QA-sheep are consistent with HD-like pathology shown in other model species and that the MR investigations can be performed in sheep using a clinically relevant human 3T MRI scanner.

Intracerebral Transplantation of BDNF-overexpressing Human Neural Stem Cells (HB1.F3.BDNF) Promotes Migration, Differentiation and Functional Recovery in a Rodent Model of Huntington's Disease.

Huntington’s disease (HD) is a dominantly inherited neurodegenerative disorder caused by abnormally expanded CAG repeats in the huntingtin gene. The huntingtin gene mutation leads to the progressive degeneration of striatal GABAergic medium spiny neurons (MSN) and reduces the level of brain-derived neurotrophic factor (BDNF) in HD patient’s brain. BDNF is an essential neurotrophic factor for the cortico-striatal synaptic activity and the survival of GABAergic neurons. In this study, we transplanted BDNF-overexpressing human neural stem cells (HB1.F3.BDNF) into the contra-lateral side of unilateral quinolinic acid (QA)-lesioned striatum of HD rat model. The results of in vivo transplantation were monitored using various behavioral tests, 4.7 T animal magnetic resonance imaging (MRI) and immunohistochemical staining. We observed that the QA-lesioned rats receiving HB1.F3.BDNF cells exhibited significant behavioral improvements in the stepping, rotarod and apomorphine-induced rotation tests. Interestingly, contralaterally transplanted cells were migrated to the QA-lesioned striatum and the size of lateral ventricle was reduced. Histological analyses further revealed that the transplanted cells, which had migrated to the QA lesion site, were differentiated into the cells of GABAergic, MSN-type neurons expressing DARPP-32, and neural networks were established between the transplanted cells and the host brain, as revealed by retrograde tracing. Finally, there was a significant reduction of inflammatory response in HB1.F3.BDNF-transplanted HD animal model, compared with vehicle-transplanted group. Taken together, these results suggest that HB1.F3.BDNF can be an effective therapeutic strategy to treat HD patients in the future.

L-dopa response pattern in a rat model of mild striatonigral degeneration.

BackgroundUnresponsiveness to dopaminergic therapies is a key feature in the diagnosis of multiple system atrophy (MSA) and a major unmet need in the treatment of MSA patients caused by combined striatonigral degeneration (SND). Transgenic, alpha-synuclein animal models do not recapitulate this lack of levodopa responsiveness. In order to preclinically study interventions including striatal cell grafts, models that feature SND are required. Most of the previous studies focused on extensive nigral and striatal lesions corresponding to advanced MSA-P/SND. The aim of the current study was to replicate mild stage MSA-P/SND with L-dopa failure.Methods and resultsTwo different striatal quinolinic acid (QA) lesions following a striatal 6-OHDA lesion replicating mild and severe MSA-P/SND, respectively, were investigated and compared to 6-OHDA lesioned animals. After the initial 6-OHDA lesion there was a significant improvement of motor performance after dopaminergic stimulation in the cylinder and stepping test (p<0.001). Response to L-dopa treatment declined in both MSA-P/SND groups reflecting striatal damage of lateral motor areas in contrast to the 6-OHDA only lesioned animals (p<0.01). The remaining striatal volume correlated strongly with contralateral apomorphine induced rotation behaviour and contralateral paw use during L-dopa treatment in cylinder and stepping test (p<0.001).ConclusionOur novel L-dopa response data suggest that L-dopa failure can be induced by restricted lateral striatal lesions combined with dopaminergic denervation. We propose that this sequential striatal double-lesion model replicates a mild stage of MSA-P/SND and is suitable to address neuro-regenerative therapies aimed at restoring dopaminergic responsiveness.

Neurological Examination of Sheep (Ovis aries) with Unilateral and Bilateral Quinolinic Acid Lesions of the Striatum Assessed by Magnetic Resonance Imaging

Neurological Examination of Sheep (Ovis aries) with Unilateral and Bilateral Quinolinic Acid Lesions of the Striatum Assessed by Magnetic Resonance Imaging

The Effect of Tissue Preparation and Donor Age on Striatal Graft Morphology in the Mouse

Huntington's disease (HD) is a progressive neurodegenerative disease in which striatal medium spiny neurons (MSNs) are lost. Neuronal replacement therapies aim to replace MSNs through striatal transplantation of donor MSN progenitors, which successfully improve HD-like deficits in rat HD models and have provided functional improvement in patients. Transplants in mouse models of HD are more variable and have lower cell survival than equivalent rat grafts, yet mice constitute the majority of transgenic HD models. Improving the quality and consistency of mouse transplants would open up access to this wider range of rodent models and facilitate research to increase understanding of graft mechanisms, which is essential to progress transplantation as a therapy for HD. Here we determined how donor age, cell preparation, and donor/host strain choice influenced the quality of primary embryonic grafts in quinolinic acid lesion mouse models of HD. Both a within-strain (W-S) and a between-strain (B-S) donor/host paradigm were used to compare transplants of donor tissues derived from mice at embryonic day E12 and E14 prepared either as dissociated suspensions or as minimally manipulated tissue pieces (TP). Good graft survival was observed, although graft volume and cellular composition were highly variable. The effect of cell preparation on grafts differed significantly depending on donor age, with E14 cell suspensions yielding larger grafts compared to TP. Conversely, TP were more effective when derived from E12 donor tissue. A W-S model produced larger grafts with greater MSN content, and while high levels of activated microglia were observed across all groups, a greater number was found in B-S transplants. In summary, we show that the effect of tissue preparation on graft morphology is contingent on the age of donor tissue used. The presence of microglial activation in all groups highlights the host immune response as an important consideration in mouse transplantation.

The Effect of Pro-Neurogenic Gene Expression on Adult Subventricular Zone Precursor Cell Recruitment and Fate Determination After Excitotoxic Brain Injury

Despite the presence of on-going neurogenesis in the adult mammalian brain, neurons are generally not replaced after injury. Using a rodent model of excitotoxic cell loss and retroviral (RV) lineage tracing, we previously demonstrated transient recruitment of precursor cells from the subventricular zone (SVZ) into the lesioned striatum. In the current study we determined that these cells included migratory neuroblasts and oligodendrocyte precursor cells (OPC), with the predominant response from glial cells. We attempted to override this glial response by ectopic expression of the pro-neurogenic genes Pax6 or Dlx2 in the adult rat SVZ following quinolinic acid lesioning. RV-Dlx2 over-expression stimulated repair at a previously non-neurogenic time point by enhancing neuroblast recruitment and the percentage of cells that retained a neuronal fate within the lesioned area, compared to RV-GFP controls. RV-Pax6 expression was unsuccessful at inhibiting glial fate and intriguingly, increased OPC cell numbers with no change in neuronal recruitment. These findings suggest that gene choice is important when attempting to augment endogenous repair as the lesioned environment can overcome pro-neurogenic gene expression. Dlx2 over-expression however was able to partially overcome an anti-neuronal environment and therefore is a promising candidate for further study of striatal regeneration.

18F]DPA-714 PET imaging of translocator protein TSPO (18 kDa) in the normal and excitotoxically-lesioned nonhuman primate brain

We aimed to characterize pharmacologically the TSPO- radioligand [(18)F]DPA-714 in the brain of healthy cynomolgus monkeys and evaluate the cellular origin of its binding in a model of neurodegeneration induced by intrastriatal injection of quinolinic acid (QA). [(18)F]DPA-714 PET images were acquired before and at 2, 7, 14, 21, 49, 70, 91days after putaminal lesioning. Blocking and displacement studies were carried out (PK11195). Different modelling approaches estimated rate constants and V T (total distribution volume) which was used to measure longitudinal changes in the lesioned putamen. Sections for immunohistochemical labelling were prepared at the same time-points to evaluate correlations between in vivo [(18)F]DPA-714 binding and microglial/astrocytic activation. [(18)F]DPA-714 showed a widespread distribution with a higher signal in the thalamus and occipital cortex and lower binding in the cerebellum. TSPO was expressed throughout the whole brain and about 73% of [(18)F]DPA-714 binding was specific for TSPO in vivo. The one-tissue compartment model (1-TCM) provided good and reproducible estimates of V T and rate constants, and V T values from the 1-TCM and the Logan approach were highly correlated (r (2) = 0.85). QA lesioning induced an increase in V T, which was +17%, +54%, +157% and +39% higher than baseline on days 7, 14, 21 and 91 after QA injection, respectively. Immunohistochemistry revealed an early microglial and a delayed astrocytic activation after QA injection. [(18)F]DPA-714 binding matched TSPO immunopositive areas and showed a stronger colocalization with CD68 microglia than with GFAP-activated astrocytes. [(18)F]DPA-714 binds to TSPO with high specificity in the primate brain under normal conditions and in the QA model. This tracer provides a sensitive tool for assessing neuroinflammation in the human brain.

Improvement of mitochondrial NAD+/FAD+-linked state-3 respiration by caffeine attenuates quinolinic acid induced motor impairment in rats: Implications in Huntington's disease

BackgroundChronic quinolinic acid (QA) lesions in rats closely resemble Huntington's disease like conditions. Oxidative stress and mitochondrial dysfunction have long been implicated in the neurotoxic effects of QA acting through N-methyl-d-aspartate (NMDA) receptors. Reports suggest that inhibition of adenosine A2A receptor function elicits neuroprotective effect in QA induced neurotoxicity in rats. Caffeine, a preferential A2A receptor antagonist imitates antioxidant like actions and exerts neuroprotective effects in various neurodegenerative conditions. Thus, the present study was designed to evaluate the neuroprotective effects of caffeine against QA induced neurotoxicity in rats. MethodsIn the present study, QA (200nmol/2μl saline) has been administered bilaterally to the striatum of rats followed by chronic caffeine (10, 20 and 40mg/kg) administration for 21 days. Motor performance of the animals was evaluated in weekly intervals and subsequently after 21 days, the animals were sacrificed and measurement of mitochondrial complexes activity, respiration rate and endogenous antioxidant levels were carried out in the striatal region. ResultsSingle intrastriatal QA administration resulted in drastic reduction in body weight, marked motor impairment (decreased total locomotor activity in actophotometer and impaired grip strength in rotarod), increased oxidative stress, impaired mitochondrial complexes activities and decreased state 3 respiration (NAD+/FAD+-linked) in rats. However, chronic treatment of caffeine for 21 days significantly attenuated the QA induced behavioural, biochemical and mitochondrial alterations displaying neuroprotective efficacy. ConclusionThe study highlights the possible involvement of A2A receptor antagonism in the neuroprotective effect of caffeine against QA induced mitochondrial dysfunction and oxidative stress in rats.

Excitotoxic brain injury in adult zebrafish stimulates neurogenesis and long-distance neuronal integration.

Zebrafish maintain a greater capacity than mammals for central nervous system repair after injury. Understanding differences in regenerative responses between different vertebrate species may shed light on mechanisms to improve repair in humans. Quinolinic acid is an excitotoxin that has been used to induce brain injury in rodents for modeling Huntington's disease and stroke. When injected into the adult rodent striatum, this toxin stimulates subventricular zone neurogenesis and neuroblast migration to injury. However, most new neurons fail to survive and lesion repair is minimal. We used quinolinic acid to lesion the adult zebrafish telencephalon to study reparative processes. We also used conditional transgenic lineage mapping of adult radial glial stem cells to explore survival and integration of neurons generated after injury. Telencephalic lesioning with quinolinic acid, and to a lesser extent vehicle injection, produced cell death, microglial infiltration, increased cell proliferation, and enhanced neurogenesis in the injured hemisphere. Lesion repair was more complete with quinolinic acid injection than after vehicle injection. Fate mapping of her4-expressing radial glia showed injury-induced expansion of radial glial stem cells that gave rise to neurons which migrated to injury, survived at least 8 weeks and formed long-distance projections that crossed the anterior commissure and synapsed in the contralateral hemisphere. These findings suggest that quinolinic acid lesioning of the zebrafish brain stimulates adult neural stem cells to produce robust regeneration with long-distance integration of new neurons. This model should prove useful for elucidating reparative mechanisms that can be applied to restorative therapies for mammalian brain injury.

JAK2 inhibition is neuroprotective and reduces astrogliosis after quinolinic acid striatal lesion in adult mice

Quinolinic acid (QA) striatal lesion in rodents induces neuronal death, astrogliosis and migration of neuroblasts from subventricular zone to damaged striatum. These phenomena occur in some human neurodegenerative illnesses, but the underlying mechanisms are unknown. We investigated the effect of AG490, a Janus-kinase 2 (JAK2) inhibitor, on astrogliosis, neuronal loss and neurogenesis in the striatum of adult mice after unilateral infusion of QA (30nmol). Animals were given subcutaneous injections of AG490 (10mg/kg) or vehicle immediately after lesion and then once daily for six days. Brain sections were used for neuronal stereological quantification, immunohistochemical and Western Blotting analyses for GFAP and doublecortin, markers of astrocytes and neuroblasts, respectively. The total area of doublecortin-positive cells (ADPC) and the number of neurons (NN) in the lesioned (L) and contralateral (CL) sides were evaluated. Neurogenesis index (NI=ADPC(L)/ADPC(CL)) and neuronal ratio (NR=NN(L)/NN(CL)) were calculated. After QA administration, blotting for GFAP showed an ipsilateral decrease of 19% in AG490- vs vehicle-treated animals. NR was 25% higher in mice given AG490 vs controls given vehicle. NI showed a decrease of 21% in AG490- vs vehicle-treated mice. Our results indicate that JAK2 inhibition reduces QA lesion and suggest that astrogliosis may impair neuronal survival in this model.

18F]desmethoxyfallypride as a novel PET radiotracer for quantitative in vivo dopamine D2/D3 receptor imaging in rat models of neurodegenerative diseases

[(18)F]desmethoxyfallypride ([(18)F]DMFP) is a promising tracer for longitudinal assessment of striatal dopamine D2/D3-receptor (D2R) availability by positron emission tomography (PET) in small animal models. We explored the feasibility of [(18)F]DMFP-PET to image D2R availability in rat models of Huntington's (HD) and Parkinson's disease (PD). Animals received either unilateral intrastriatal quinolinic acid lesions or medial forebrain bundle injections of 6-OHDA to produce the loss of striatal projection neurones or deplete the striatal dopamine, corresponding to established animal models for HD and PD, respectively. Three weeks after lesioning, PET scans were acquired on a microPET Focus 120 system following the tail vein injection of [(18)F]DMFP. [(18)F]DMFP-PET clearly visualized lesion induced decreases and increases of D2R availability. In vivo estimates of D2R binding and changes thereof gained by pharmacokinetic analyses correlated significantly with D2R density and its change provided by in vitro [(3)H]raclopride-autoradiography. In conclusion, [(18)F]DMFP-PET is a suitable method for in vivo D2R-assessment in preclinical research, e.g for monitoring cell-based therapies.

Behavioral and histological analysis of a partial double‐lesion model of parkinson‐variant multiple system atrophy

Multiple system atrophy (MSA) is a neurodegenerative disease with progressive autonomic failure, cerebellar ataxia (MSA-C), and parkinsonism (MSA-P) resulting from neuronal loss in multiple brain areas associated with oligodendroglial cytoplasmic α-synuclein inclusion bodies. No effective treatments exists, and MSA-P patients often fail to respond to L-DOPA because of the loss of striatal dopaminergic receptors. Rendering MSA-P patients sensitive to L-DOPA administration following striatal tissue transplantation has been proposed as a possible novel therapeutic strategy to improve the clinical condition. Here we describes simple, skilled, and sensorimotor behavior deficits in a unilateral partial double-lesion (DL) rat model of MSA-P. The sequential striatal double-lesion model mimicks early MSA-P pathology by combining partial 6-hydroxydopamine (6-OHDA) followed by striatal quinolinic acid (QA) lesion. Animals were tested on spontaneous, learned, or drug-induced behavioral tasks on multiple occasions pre- and postsurgery. The data show robust, lateralized deficits, and the partial 6-OHDA and the double-lesioned animals were most impaired. Importantly, this study identified a behavioral deficit profile unique to the double-lesion animals and distinctive from the single 6-OHDA- or the QA-lesioned animals. Histology confirmed an approximately 40% dopamine loss in the striatum in the 6-OHDA and double-lesion animals as well as a similar loss of striatal projection neurons in the QA and double-lesion animals. In summary, we have established the behavioral deficit profile of a partial double-lesion rat model mimicking the early stage of MSA-P.

Mesenchymal stem cells induced to secrete neurotrophic factors attenuate quinolinic acid toxicity: A potential therapy for Huntington's disease

Huntington's disease (HD) is a hereditary, progressive and ultimately fatal neurodegenerative disorder. Excitotoxicity and reduced availability of neurotrophic factors (NTFs) likely play roles in HD pathogenesis. Recently we developed a protocol that induces adult human bone marrow derived mesenchymal stem cells (MSCs) into becoming NTF secreting cells (NTF+ cells). Striatal transplantation of such cells represents a promising autologous therapeutic approach whereby NTFs are delivered to damaged areas. Here, the efficacy of NTF+ cells was evaluated using the quinolinic acid (QA) rat model for excitotoxicity. We show that NTF+ cells transplanted into rat brains after QA injection survive transplantation (19% after 6weeks), maintain their NTF secreting phenotype and significantly reduce striatal volume changes associated with QA lesions. Moreover, QA-injected rats treated with NTF+ cells exhibit improved behavior; namely, perform 80% fewer apomorphine induced rotations than PBS-treated QA-injected rats. Importantly, we found that MSCs derived from HD patients can be induced to become NTF+ cells and exert efficacious effects similarly to NTF+ cells derived from healthy donors. To our knowledge, this is the first study to take adult bone marrow derived mesenchymal stem cells from patients with an inherited disease, transplant them into an animal model and evidence therapeutic benefit. Using MRI we demonstrate in vivo that PBS-treated QA-injected striatae exhibit increasing T2 values over time in lesioned regions, whereas T2 values decrease in equivalent regions of QA-injected rats treated with NTF+ cells. We conclude that NTF cellular treatment could serve as a novel therapy for managing HD.

Decreasing Levels of the cdk5 Activators, p25 and p35, Reduces Excitotoxicity in Striatal Neurons

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by an expanded CAG trinucleotide repeat sequence in the huntingtin gene. The resulting poly-glutamine expansion in the huntingtin protein imparts a novel toxic gain of function causing selective loss of medium spiny neurons (MSNs) in the striatum. Although the exact mechanism of cell death is unclear, recent evidence suggests involvement of NMDA-receptor mediated excitotoxicity and aberrant cyclin dependent kinase 5 (cdk5) activity in striatal cells undergoing neurodegeneration. In this study we directly tested the effect of reduced levels of p25 and p35, two proteins required for cdk5 activation, on striatal neurodegeneration using mice with targeted deletion of p35. Quinolinic acid (QA) injected into the striatum of mice causes NMDA-receptor mediated cell death, and these QA-induced striatal lesions were examined in p35 hemizygous null (p35+/-) and wildtype (WT) mice. Striatal QA lesion volumes were 30% smaller in p35+/- mice than in WT mice. Furthermore, primary neuronal cultures of MSNs from P0 p35+/- pups displayed 33% less apoptotic neurons following NMDA treatment than those from WT pups. Examination of YAC128 mouse model of HD showed elevated p25 levels in striatum following intrastriatal QA injection. Our findings provide direct evidence for p25 and p35 involvement in excitotoxic neurodegeneration of MSNs and suggest a role for the cdk5 pathway in HD striatal neurodegeneration.

Evaluation of a multiple system atrophy model in rats using multitracer microPET

A double toxin-double lesion strategy is appropriate for mimicking of striatonigral degeneration. Because knowledge of human pathology is limited, animal models must be well characterized prior to testing of therapeutic approaches to treat multiple system atrophy. In double-toxin animal models, however, reduced contralateral rotation after apomorphine injection is restored within a few weeks via an unknown mechanism; the animals thus revert to PD status. We assessed this phenomenon using multitracer microPET and tissue staining. Five adult male Wistar rats received injections of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle (MFB), followed 3 weeks later by injections of quinolinic acid (QA) into the ipsilateral striatum. Apomorphine-induced rotation tests were performed 1 week after each injection, and 6 and 10 weeks after QA injection. Rotarod tests were performed weekly after 6-OHDA injection. MSA-p status was characterized by microPET 5 and 10 weeks after QA injection using the tracers 2-deoxy-2-[(18)F]-fluoro-D-glucose ([(18)F]-FDG) and [(18)F]-N-(3-fluoropropyl)-2-carbomethoxy-3-(4-iodophenyl)nortropane ([(18)F]-FP-CIT). Histological changes were evaluated by tyrosine hydroxylase (TH) and cresyl violet staining. The numbers of apomorphine-induced rotations increased contralaterally after 6-OHDA lesions were created, but decreased significantly after QA administration (p = 0.007). Five weeks after QA injection, however, contralateral rotation again increased and persisted for 1 month. Rotarod rotation differed significantly between the intact and PD states (p < 0.05), but not between the PD and MSA-p states. MicroPET revealed glucose hypometabolism and dopamine transporter (DAT) impairment on the lesioned side of the striatum 1 and 2 months after QA lesion surgery. Loss of nigral cells was confirmed by TH immunostaining, and striatal atrophy was observed upon cresyl violet staining. Pathological changes consistent with MSA-p can be generated by the double toxin-double lesion method and persist during follow-up. Behavioral tests, such as drug-induced rotation and rotarod tests, are not appropriate for long-term follow-up in the MSA-p model, suggesting the need for development of more appropriate behavioral tests.

Quinolinic acid lesions of the pedunculopontine nucleus impair sleep architecture, but not locomotion, exploration, emotionality or working memory in the rat

Anatomical and functional studies have shown that the NADPH-diaphorase-positive cholinergic neurons of the pedunculopontine nucleus (PPN) send projections to several areas in the brain. The purpose of this work was to investigate whether bilateral lesions with quinolinic acid, a neurotoxin with greater selectivity for NADPH-diaphorase-positive neurons, aimed at the compact portion of the PPN would affect the performance of adaptive behaviors, such as sleep, locomotion, and spontaneous alternation. Lesioned animals were divided in a low lesion group (LL, <50% neuron loss) and a high lesion group (HL, ≥50% neuron loss). The LL animals did not show any significant changes in sleep patterns, as compared to controls. In contrast, the HL group showed a significant increase in the number of REM sleep periods, and a reduction of REM sleep average duration, but did not differ in the total time spent in REM sleep. HL animals also showed an increase in the number of SWS periods, though wakefulness parameters did not show significant alterations. The duration and number of both REM and SWS sleep episodes were significantly correlated with the number of NADPH-diaphorase-positive neurons in the PPN. The short-term habituation pattern of locomotion, the vertical exploratory activity, as well as the thigmotaxis (an index of emotionality), displayed by LL and HL rats in a novel environment were similar to those of control animals. Likewise, there were no significant differences in spontaneous alternation among the groups. Our results indicate that quinolinic acid lesions of NADPH-diaphorase-positive cholinergic neurons localized in the posterior region of the PPN disrupt normal sleep structure, while motor activity and spontaneous alternation remain unaffected.

Protective effect of Ketamine on the quinolinic acid-induced lesion in a rat model of Huntington's disease

Objective As a non-competitive NMDA receptor antagonist, Ketamine is a commonly used anaesthetic agent. Quinolinic acid (QA) is a glutamate analogue that exerts its excitotoxic effect also via the NMDAR. We tested the QA lesion effect under the conditions of various dosage of Ketamine, to explore the protective effect of Ketamine on the QA-induced striatal lesion. Methods Thirty SD females were unilaterally lesioned using QA: two group were anaesthetised with different dose of ketamine and the other with isoflurane. The surgical coordinates and the dosage of QA were identical. Two weeks post-lesion, the animals were tested on stepping test, and staircase test, followed by perfusion, immunohistochemical and volumetric analysis. Results The isoflurane group, compared with the ketamine groups, showed larger striatal lesions and significant differences in other behavioral measurements reflecting the extent of the lesion (P<0.05). Beside, there were statistically differences between these two ketamine groups in aspect of lesion volume and behavioral performances. Conclusion The use of ketamine anaesthesia in the excitotoxic model can effectively alleviate the development of the lesion and it works in a dose-dependent way. Key words: Ketamine; Isoflurane; Excitotoxicity; Striatum; Protective effect