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The WldS gene modestly prolongs survival in the SOD1G93A fALS mouse.

The "slow Wallerian degeneration" (Wld(S)) gene is neuroprotective in numerous models of axonal degeneration. Axonal degeneration is an early feature of disease progression in the SOD1G93A mouse, a widely used model of familial amyotrophic lateral sclerosis (fALS). We crossed the Wld(S) mouse with the SOD1G93A mouse to investigate whether the Wld(S) gene could prolong survival and modify neuropathology in these mice. SOD/Wld(S) mice showed levels of motor axon loss similar to that seen in SOD1G93A mice. The presence of the Wld(S) gene, however, modestly prolonged survival and delayed denervation at the neuromuscular junction. Prolonged survival was more prominent in female mice and did not depend on whether animals were heterozygous or homozygous for the Wld(S) gene. We also report that SOD1G93A mice show significant degeneration of sensory axons during the course of disease, supporting previous data from humans demonstrating that ALS is not purely a motor disorder.

Amyotrophic Lateral Sclerosis↗

Transforming growth factor-beta 2 causes an acute improvement in the motor performance of transgenic ALS mice.

Amyotrophic lateral sclerosis (ALS) is fatal disorder, characterized by the loss of motoneurons. The therapeutic potential of transforming growth factor-beta 2 (TGF-beta2) was examined using SOD1 mice. The SOD1 mice were treated with TGF-beta2 by repeated intraperitoneal injections. The highest dose of TGF-beta2 caused a rapid and marked improvement in the motor performance of the mice. This improvement lasted for between 2 and 3 weeks after which the TGF-beta2-treated mice rapidly deteriorated. At postmortem, the motoneurons in the TGF-beta2-treated SOD1 mice exhibited a large hypertrophy of their nucleoli, nuclei, and axons. In contrast, TGF-beta2 did not reverse the mitochondrial pathology. This may explain why the beneficial effects of TGF-beta2 and other growth factor on SOD1 mice are transient: TGF-beta2 is stimulating the motoneurons metabolic rate while one of their key metabolic organelles is damaged. Consequently, TGF-beta2 may be therapeutic for the forms ALS, with minimal mitochondrial involvement.

Amyotrophic Lateral Sclerosis↗

Oral uridine pro-drug PN401 is neuroprotective in the R6/2 and N171-82Q mouse models of Huntington's disease.

Previously, uridine pro-drug 2',3',5'-tri-O-acetyluridine (PN401) was shown to be protective in the mitochondrial complex II inhibitor 3-nitropropionic acid model of Huntington's disease (HD). In this study, PN401 increased survival and improved motor function on the rotarod in both R6/2 and N171-82Q polyglutamine repeat mouse models of HD. PN401 significantly decreased neurodegeneration in both the piriform cortex and striatum although PN401 decreased huntingtin protein aggregates only in the striatum. Cortical and striatal brain-derived neurotrophic factor (BDNF) protein levels were reduced in the +/- compared to the -/- N171-82Q mice and PN401 treatment significantly increased cortical BDNF in both +/- and -/- mice, but PN401 did not affect striatal BDNF. These results suggest that PN401 may have beneficial effects in the treatment of neurodegenerative diseases such as HD.

Acetates↗

Ubiquitous expression of human SCA2 gene under the regulation of the SCA2 self promoter cause specific Purkinje cell degeneration in transgenic mice.

The objective of this work was the generation of an animal model of the SCA2 disease for future studies on the benefits of therapeutic molecules and neuropathological mechanisms that underline this human disorder. The transgenic fragment was microinjected into pronuclei of B6D2F1 X OF1 mouse hybrid strain. For Northern blots, RNAs were hybridized with a human cDNA fragment from the SCA2 gene and a mouse beta-actin cDNA fragment. Monoclonal antibody directed to the N-terminal of the ataxin 2 protein with 22Q was used for Western blot analysis. A rotating rod apparatus was utilized to measure motor coordination of mice. Immunohistochemical detection of Purkinje neurons was performed with anti-calbindin 28K as primary antibody. Ubiquitous expression of the SCA2 transgene with 75 CAG repeats regulated by the SCA2 self promoter was obtained after generation of our transgenic mice. Analysis of transgenic mice revealed significant differences of motor coordination compared with the wild type littermates. Specific degeneration of Purkinje neurons and transgene over-expression in the brain, liver and skeletal muscle, rather than in lungs and kidneys was also observed, resembling the expression pattern of the ataxin 2 in humans.

Analysis of Variance↗

Nicotine prevents HIVgp120-caused electrophysiological and motor disturbances in rats.

Human immunodeficiency virus (HIV)-associated dementia (HAD) is a frequent complication in HIV+ subjects. Several electrophysiological markers and motor control are altered in HIV+ subjects, including event-related potentials (N2-P3 changes). These are electrophysiological indicators of cognitive processing. The mechanisms by which HIV induces neurophysiological abnormality is still under research. However, several neurotransmitters have been implicated. For example, glutamate and the vasoactive intestinal neuropeptide (VIP). In this study, we support further this notion indicating that HIVgp120, a glycoprotein derived from HIV, is involved in the pathogenesis of neuropsychiatric abnormalities. We also have observations suggesting that one HIVgp120 mechanism of action is to interfere with cholinergic neurotransmission. Our results indicate that event-related potentials (ERP) were affected by HIVgp120, in particular N2 and P3. In addition, motor coordination was severely affected. Both parameters were maintained near normality when rats were simultaneously treated with nicotine. These results support further an HIVgp120-caused alteration of cholinergic neurotransmission that might be part of the etiology of neuropsychiatric disturbances.

Animals↗

Therapeutic effects of clenbuterol in a murine model of amyotrophic lateral sclerosis.

We investigated the effects of clenbuterol, a beta2-adrenoceptor agonist with known anabolic and neuroprotective properties, on G93A-SOD1 mice, a transgenic murine model of familial amyotrophic lateral sclerosis (ALS). Relative to saline-treated vehicle controls (0.2 ml/kg/day; i.p.), early pathologic G93A-SOD1 mice treated with clenbuterol (1.5 mg/kg/day; i.p.) demonstrated a delayed onset of hindlimb signs as measured by rotarod performance, slowed disease progression, as well as trends toward mitigated losses of lumbar motoneurons and body weight. Responses in female G93A-SOD1 mice were favorable to those of males, suggesting synergistic effects between clenbuterol and sex-specific factors. Overall, our data suggest that clenbuterol offers therapeutic effects on ALS-related neuromuscular degeneration.

Adrenergic beta-Agonists↗

Intravenous administration of human neural stem cells induces functional recovery in Huntington's disease rat model.

An animal model induced by striatal quinolinic acid (QA) injection shows ongoing striatal degeneration mimicking Huntington's disease. To study the migratory ability and the neuroprotective effect of human neural stem cells (NSCs) in this model, we transplanted NSCs (5 x 10(6)) or saline intravenously at 7 days after unilateral QA injection. NSCs-group exhibited the reduced apomorphine-induced rotation and the reduced striatal atrophy compared to the control. PCR analysis for the human-specific ERV-3 gene supported an evidence of the engraftment of human NSCs in the rat brain. X-gal+ cells were found in and around the damaged striatum and migrated NSCs differentiated into neurons and glias. This result indicates that intravenously injected human NSCs can migrate into the striatal lesion, decrease the following striatal atrophy, and induce long-term functional improvement in a glutamate toxicity-induced striatal degeneration model.

Animals↗

Combined treatment of vascular endothelial growth factor and human neural stem cells in experimental focal cerebral ischemia.

Recent studies have indicated the beneficial effects of vascular endothelial growth factor (VEGF), and transplanted neural stem cells (NSCs) in cerebral ischemia. We investigated the effects of the combined administration of NSCs and VEGF on focal cerebral ischemia in adult rats. Four groups (n = 12, respectively)--group 1 (ischemia-only), group 2 (ischemia + VEGF), group 3 (ischemia + NSCs) and group 4 (ischemia + NSCs + VEGF)--were compared. Human NSCs (HB1.F3), labeled with Lac Z+ or PKH26, were given intravenously 24h after surgery (5 x 10(6) cells). At 48 h after surgery, recombinant human VEGF (50 microg/kg) was infused intravenously (1 microg/(kg min)). Behavioral tests using the modified limb placing and rotarod tests were performed every week following ischemia. Immunohistochemistry for endothelial barrier antigen (EBA), VEGF and Nissl staining were performed at day 35 after ischemia. Group 4 showed better behavioral recovery at 7, 14 and 28 days than group 3 (p = 0.020, 0.005 and 0.043, respectively). These functional recoveries were correlated with enhanced EBA immunoreactivities at day 35 after ischemia, especially in the ipsilesional striatum. Group 4 showed lesser degree of brain atrophy in cortex and striatum, when compared with other groups. The distribution of VEGF was not co-localized with NSCs. Our results suggest that VEGF may act synergistically on NSC-transplanted, ischemic brain via a pro-angiogenic effect.

Animals↗

Effects of age and dopamine D2L receptor-deficiency on motor and learning functions.

Decreases in the activity or density of dopamine D2 receptor (D2R) have been associated with age-related changes and neurodegenerative diseases such as Parkinson's disease. There are two isoforms of the D2R, termed the D2 long receptor (D2LR) and D2 short receptor (D2SR). To study the function of these two isoforms and their role in aging, we generated mice selectively lacking D2LR (D2L-/-). Here, we showed that middle-aged (12 months) to aged wild-type (WT) mice (22-24 months) displayed significantly lower levels of motor and learning functions than young WT mice (3 months). Interestingly, young D2L-/- mice (which still express D2SR) showed behavioral deficits similar to aged WT mice. It is possible that deletion of the D2LR might facilitate the aging process in mice. Our results also suggest that a deterioration of the D2LR (but not D2SR) system during aging may account, at least in part, for the motor and learning deficits exhibited in aged WT mice. We also showed that the critical age at which significant reduction in behavior occurred varied among different behaviors. Defining the age-related critical periods and understanding the role of the two D2R isoforms in aging may facilitate the development of new strategies for delaying or ameliorating age-related motor and learning impairments.

Age Factors↗

Molecular mechanism of the neurotrophic effect of GDNF on DA neurons: role of protein kinase CK2.

Glial cell line-derived neurotrophic factor (GDNF) is suggested as a specific neurotrophic factor for midbrain dopamine (DA) neurons, but the molecular mechanism underlying the neuroprotective action of GDNF is not well known. In the present study, we have shown that GDNF increased protein kinase CK2 activity in rat substantia nigra (SN) in a dose-dependent and time-dependent manner. This effect is prevented by prior treatment of the receptor Ret blocker K-252b. Immunostaining results also revealed that CK2 is expressed in TH-positive neurons in mesencephalon culture. Transfection of the wildtype CK2alpha DNA increased, whereas transfection of the catalytically inactive CK2alphaA156 mutant DNA decreased CK2 activity in the SN. CK2alphaA156 mutant DNA also antagonized the enhancing effect of GDNF on CK2 activity. It also antagonized the enhancing effects of GDNF on tyrosine hydroxylase (TH) protein level in the SN, DA turnover in the striatum and rotarod performance in rats. Further, CK2alpha wildtype DNA increased, whereas CK2alphaA156 mutant DNA decreased TH activity in the SN without altering the TH protein level. On the other hand, the DA neuron toxin 1-methyl-4-phenylpyridinium iodide (MPP+) markedly decreased the number of TH-positive neurons and TH protein level in the SN, decreased DA level in the striatum and impaired rotarod performance in rats. Over-expression of the CK2alpha wildtype DNA partially, but significantly, prevented the deteriorating effect of MPP+ on these measures. Prior administration of MPP+ also antagonized the enhancing effect of GDNF on CK2 activity. These results together suggest that the CK2 signaling pathway contributes to the neuroprotective action of GDNF on DA neurons.

Animals↗

Intracellular Abeta and cognitive deficits precede beta-amyloid deposition in transgenic arcAbeta mice.

The brain pathology of Alzheimer's disease is characterized by abnormally aggregated Abeta in extracellular beta-amyloid plaques and along blood vessel walls, but the relation to intracellular Abeta remains unclear. To address the role of intracellular Abeta deposition in vivo, we expressed human APP with the combined Swedish and Arctic mutations in mice (arcAbeta mice). Intracellular punctate deposits of Abeta occurred concomitantly with robust cognitive impairments at the age of 6 months before the onset of beta-amyloid plaque formation and cerebral beta-amyloid angiopathy. beta-Amyloid plaques from arcAbeta mice had distinct dense-core morphologies with blood vessels appearing as seeding origins, suggesting reduced clearance of Abeta across blood vessels in arcAbeta mice. The co-incidence of intracellular Abeta deposits with behavioral deficits support an early role of intracellular Abeta in the pathophysiological cascade leading to beta-amyloid formation and functional impairment.

Age Factors↗

The kv4.2 potassium channel subunit is required for pain plasticity.

A-type potassium currents are important determinants of neuronal excitability. In spinal cord dorsal horn neurons, A-type currents are modulated by extracellular signal-regulated kinases (ERKs), which mediate central sensitization during inflammatory pain. Here, we report that Kv4.2 mediates the majority of A-type current in dorsal horn neurons and is a critical site for modulation of neuronal excitability and nociceptive behaviors. Genetic elimination of Kv4.2 reduces A-type currents and increases excitability of dorsal horn neurons, resulting in enhanced sensitivity to tactile and thermal stimuli. Furthermore, ERK-mediated modulation of excitability in dorsal horn neurons and ERK-dependent forms of pain hypersensitivity are absent in Kv4.2(-/-) mice compared to wild-type littermates. Finally, mutational analysis of Kv4.2 indicates that S616 is the functionally relevant ERK phosphorylation site for modulation of Kv4.2-mediated currents in neurons. These results show that Kv4.2 is a downstream target of ERK in spinal cord and plays a crucial role in pain plasticity.

Action Potentials↗

Treatment with valproate after status epilepticus: effect on neuronal damage, epileptogenesis, and behavioral alterations in rats.

Epileptogenesis, i.e. the process leading to epilepsy with spontaneous recurrent seizures, can be initiated by a number of brain damaging insults, including traumatic brain injury, status epilepticus (SE), and stroke. Such acquired epilepsy is often associated with memory impairment and behavioral problems. There has been a growing interest in the use of antiepileptic drugs (AEDs) for neuroprotection and prevention or modification of epileptogenesis induced by such brain insults. One promising candidate in this respect is valproic acid (VPA), a widely used AED that has been reported to exert neuroprotective activity in a number of in vitro and in vivo models. The present study investigated whether VPA reduces brain damage and improves functional outcome in a rat model of post-SE epilepsy. A self-sustaining SE was induced by prolonged electrical stimulation of the basal amygdala via a depth electrode. SE was terminated after 4 h by diazepam, immediately followed by onset of treatment with VPA. VPA was injected i.p. at a bolus dose of 400 mg/kg, followed by three times daily administration of 200 mg/kg for 4 weeks. A control group received vehicle instead of VPA after SE. Spontaneous seizures were recorded in all rats of both groups following termination of treatment, without significant inter-group difference in seizure frequency or severity. However, treatment with VPA after SE prevented the hyperexcitability and locomotor hyperactivity observed in vehicle-treated epileptic rats. Furthermore, VPA completely counteracted the neuronal damage in the hippocampal formation, including the dentate hilus. The data demonstrate that, although VPA does not prevent the occurrence of spontaneous seizures after SE, it exerts powerful neuroprotective effects and prevents part of the behavioral alterations, demonstrating that administration of VPA immediately after SE exerts a favorable effect on long-term functional outcome.

Animals↗

Comparative effects of acute or chronic administration of levodopa to 6-hydroxydopamine-lesioned rats on the expression of glutamic acid decarboxylase in the neostriatum and GABAA receptors subunits in the substantia nigra, pars reticulata.

Current evidence suggests that behavioral sensitization to the chronic administration of levodopa (L-DOPA) to dopamine-depleted animals involves a plasticity of GABA-mediated signaling in output regions of the basal ganglia. The purpose of this study was to compare in adult rats with a unilateral 6-hydroxydopamine (6-OHDA) lesion the effects of an acute or chronic (for 3 or 7 days) injection of L-DOPA on mRNA levels encoding for glutamic acid decarboxylase (GAD65 and GAD67) in the striatum and GABA(A) receptor alpha1, beta2 and gamma2 subunits in the substantia nigra, pars reticulata (SNr), by in situ hybridization histochemistry. In addition, immunostaining levels for the alpha1 subunit were examined in the SNr. In agreement with previous studies, we found that L-DOPA administration increased GAD mRNA levels in the striatum of 6-OHDA-lesioned rats. However, the magnitude of this effect increased with the number of injections of L-DOPA. On the other hand, we found that 6-OHDA lesions resulted in increases in alpha1, beta2 and gamma2 mRNA levels in the ipsilateral SNr, which were normalized or decreased compared with the contralateral side by the acute or chronic administration of L-DOPA. In addition, alpha1 immunostaining in the SNr was significantly decreased in rats injected for 7 days but not for 3 days or acutely with L-DOPA. Our results demonstrate that a chronic administration of L-DOPA results in a progressive increase in GAD and decrease in GABA(A) receptor expression in the striatum and SNr, respectively. They provide further evidence that behavioral sensitization and dyskinesia induced by a chronic administration of L-DOPA in an experimental model of Parkinson's disease is paralleled by a plasticity of GABA-mediated signaling in the SNr.

Adrenergic Agents↗

Vitamin A deficiency induces motor impairments and striatal cholinergic dysfunction in rats.

Vitamin A and its derivatives, retinoids, are involved in the regulation of gene expression by binding two nuclear receptor families, retinoic acid receptors and retinoid X receptors. Retinoid receptors are highly expressed in the striatum, revealing an involvement of this system in the control of movement as demonstrated by previous observations in knockout mice. To further assess the role of retinoids in adult striatal function, the present study investigated the effect of vitamin A deprivation on rat motor activity and coordination, the rate of synthesis and release of dopamine, the functioning of D1 and D2 receptors and their expression in the striatum. Moreover, the content of acetylcholine in the striatum was measured. Results show that 24 weeks of postnatal vitamin A deprivation induced severe locomotor deficits and impaired motor coordination. Vitamin A deprivation rats showed a significant hyperactivity following D1 receptor stimulation by R(+)-6-chloro-7,8-dihydroxy-1-phenyil-2,3,4,5-tetrahydro-1H-3-benzazepine or amphetamine and reduced catalepsy in response to haloperidol treatment. This different response to the above drugs is not due to a change in striatal DA release or synthesis between vitamin A deprivation and control animals. In situ hybridization experiments showed identical level of expression for the D1 and D2 receptor transcripts. On the other hand, the striatal tissue content of acetylcholine was reduced significantly by about 30% starting from the initial manifestation of motor deficits. We suggest that the locomotor impairment could be imputable to the dysfunction in striatal cholinergic interneurons. Our results stress the basic role of vitamin A in the maintenance of basal ganglia motor function in the adult rat brain.

Acetylcholine↗

Continuous exposure to glial cell line-derived neurotrophic factor to mature dopaminergic transplants impairs the graft's ability to improve spontaneous motor behavior in parkinsonian rats.

Functional recovery following intrastriatal transplantation of fetal dopaminergic neurons in animal models of Parkinson's disease is, at least in part, dependent on the number of surviving dopaminergic neurons and the degree of graft-derived dopaminergic reinnervation of the host striatum. In the present study, we analyzed whether continuous exposure of glial cell line-derived neurotrophic factor (GDNF) to mature dopaminergic grafts could further boost the functional outcome of widespread intrastriatal dopaminergic grafts. Rats with dopamine-denervating lesions received multiple intrastriatal transplants of fetal dopaminergic cells and graft-induced behavioral effects were analyzed in drug-induced and spontaneous motor behaviors. At three months after grafting, animals received intrastriatal injections of recombinant lentiviral vectors encoding for either human GDNF or the green fluorescent protein. Continuous exposure of GDNF to the grafts did not boost the functional recovery beyond what was observed in the control animals. Rather, in some of the spontaneous motor behaviors, animals in the GDNF-group showed deterioration as compared with control animals, and this negative effect of GDNF was associated with a down-regulation of the tyrosine hydroxylase enzyme. Based on these and our earlier results, we propose that intrastriatal administration of GDNF at the time of or shortly after grafting is highly effective in initially promoting the cell survival and fiber outgrowth from the grafts. However, once the grafts are mature, GDNF's ability to boost dopaminergic neurotransmission follows the same dynamics as for the native nigral dopaminergic neurons, which appears to be dependent on the concentration of GDNF. Since rather low doses of glial cell line-derived neurotrophic factor at nanogram levels appear to saturate these effects, it may be critical to adjust GDNF levels using tightly regulated gene expression systems.

Analysis of Variance↗

Short and long-term motor skill learning in an accelerated rotarod training paradigm.

Rodent models of motor skill learning include skilled forelimb reaching and acrobatic locomotor paradigms. This study characterizes motor skill learning in the accelerated rotarod task. Thirty Long-Evans rats (300-400 g) were trained on an accelerated rotarod (1cm/s(2)) over eight consecutive sessions (=days, 20 trials each). Improvement in rotarod velocities mastered before falling off the rod was observed within and between sessions (plateau after five sessions). Intrasession improvement was incompletely retained at the beginning of the next day's session. Over several training sessions, intrasession improvement diminished, suggesting a ceiling effect. After 1 week of pause, the rotarod skill was retained. Locomotor exercise in a running wheel for 30 min before the first rotarod session did not affect intrasession improvement. Running-wheel exposure for 6 days did not diminish the rate of rotarod skill learning (steepness of the learning curve) but improved overall performance (upward shift of curve). Video analysis of gait on the rotarod showed that rats developed a motor strategy by modifying their gait patterns during training. The data demonstrate that rotarod improvement is not the result of enhanced general locomotor ability or fitness, which are trained in the running wheel, but requires a change in the motor strategy to master the task. Accelerated rotarod training can be regarded a valid paradigm for motor skill learning over short (intrasession, minutes) and long time frames (intersession, days).

Analysis of Variance↗

Nociceptor-specific gene deletion using heterozygous NaV1.8-Cre recombinase mice.

NaV1.8 is a voltage-gated sodium channel expressed only in a subset of sensory neurons of which more than 85% are nociceptors. In order to delete genes in nociceptive neurons, we generated heterozygous transgenic mice expressing Cre recombinase under the control of the NaV1.8 promoter. Functional Cre recombinase expression replicated precisely the expression pattern of NaV1.8. Cre expression began at embryonic day 14 in small diameter neurons in dorsal root, trigeminal and nodose ganglia, but was absent in non-neuronal or CNS tissues into adulthood. Sodium channel subtypes were normal in isolated DRG neurons. Pain behaviour in response to mechanical or thermal stimuli, and in acute, inflammatory and neuropathic pain was also normal. These data demonstrate that the heterozygous NaV1.8-Cre mouse line is a useful tool to analyse the effects of deleting floxed genes on pain behaviour.

Animals↗