Lack of permanent nigrostriatal dopamine deficit following 6-hydroxydopamine injection into the rat striatum

Summary The lesion caused by a single 6-hydroxydopamine injection into rat striatum was evaluated. In vivo positron emission tomography using a dopamine reuptake tracer revealed no consistent reduction in striatal dopamine transporter. Amphetamine rotation test was negative up to 18 weeks. A 21% reduction in striatal dopamine seen at 11 weeks was not detectable at 18 weeks. Tyrosine hydroxylase-positive neurone counts showed no decline in substantia nigra. Our results suggest that this lesion may be subject to compensation and therefore should be used with caution in studies on neuroprotective treatments of Parkinson' disease.     

Proteomic identification of biomarkers in the cerebrospinal fluid in a rat model of nigrostriatal dopaminergic degeneration

We have performed proteomic analysis in the cerebrospinal fluid in an animal model of Parkinson's disease induced by axotomy of the medial forebrain bundle. In this model, the degeneration of dopaminergic neurons was completed in 14 days, with a loss of about 50% dopaminergic neurons in the substantia nigra and a loss of more than 80% dopamine terminals in the striatum, with a similar diminution of dopamine levels in both structures. Proteins were separated by 2D electrophoresis and identified by matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF). We found significant increases of haptoglobin and transthyretin along with a decrease of Apo E concentrations in the cerebrospinal fluid of axotomized animals. Changes for haptoglobin and transthyretin were further confirmed in cerebrospinal fluid and plasma by Western blotting. These results suggest that monitoring plasma levels of these signals appears to be a promising biological marker of neuronal degeneration of the nigrostriatal dopaminergic system.     

Mechanisms of excitation and inhibition in the nigrostriatal system

The extracellular responses of neurones in the neostriatum following single pulse stimulation of the substantia nigra were investigated in urethane anaesthetized rats. Low intensity stimulation (< 10 V) evoked single large amplitude spikes while higher intensities (10–20 V) elicit a high frequency burst of small amplitude spikes or waves. When spontaneous or glutamate-induced large spikes are recorded, nigral stimulation causes their inhibition coincidentally with the development of a burst. If the burst is prevented, the inhibitory response disappears. Both the nigral evoked inhibition and burst response are unaffected by iontophoretically or systemically administered antagonists of dopamine or by chemical lesions of the dopamine-containing nigral neurones. The monosynaptic activation of large amplitude striatal neurones, which could also be identified antidromically by stimulation of the globus pallidus, was reversibly blocked by dopamine antagonists.It is concluded (a) that the burst responses are induced through the antidromic excitation of striatonigral axons within the striatum; (b) that the striatal neurones thus activated are inhibitory interneurones and (c) that the dopamine-containing neurones of the nigra make excitatory synaptic contact with a population of striatal output cells, some of which at least project to the globus pallidus.     

Benzodiazepines and gabaergic regulation of nigrostriatal neurons: Lack of tolerance

1. Decreases of 40 to 50% in striatal dopamine release by diazepam in doses above 5 mg/kg were elicited.

2. Similar actions were observed with clonazepam and nitrazepam.

3. No tolerance to these actions was evident after 3 weeks of chronic treatment.

4. These data are consistent with a potent inhibitory GABAergic regulation of nigrostriatal dopaminergic neurons.     

The effect of thrombin inhibition in a rat arterial thrombosis model.

The effect of heparin and the synthetic irreversible antithrombin D-phenylalanyl-L-prolyl-L-arginyl chloromethyl ketone (FPRCH2Cl) was studied on FeCl3-induced thrombotic occlusion of rat carotid arteries. Thrombocytopenia prevented occlusion in five of 7 rats for the 60 min observation period after FeCl3 injury demonstrating platelet dependence in this model of thrombosis. Intravenous injection of heparin (250 units/kg) followed by continuous infusion (250 units/kg/hr) failed to prevent occlusion in four of 6 rats whereas intravenous FPRCH2Cl infusion prevented occlusion at a dose of 200 nmol/kg/min during infusion in 6/6 rats. These findings indicate that thrombin plays a principle role in the platelet-dependent process of arterial thrombosis in FeCl3-damaged rat carotid arteries. Neutralization of the thrombogenic stimulus in this model by the thrombin inhibitor FPRCH2Cl suggests selective thrombin inhibition may be useful in the treatment of arterial thrombosis.     

NAIP protects the nigrostriatal dopamine pathway in an intrastriatal 6-OHDA rat model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder of the basal ganglia, associated with the inappropriate death of dopaminergic neurons of the substantia nigra pars compacta (SNc). Here, we show that adenovirally mediated expression of neuronal apoptosis inhibitor protein (NAIP) ameliorates the loss of nigrostriatal function following intrastriatal 6-OHDA administration by attenuating the death of dopamine neurons and dopaminergic fibres in the striatum. In addition, we also addressed the role of the cysteine protease caspase-3 activity in this adult 6-OHDA model, because a role for caspases has been implicated in the loss of dopamine neurons in PD, and because NAIP is also a reputed inhibitor of caspase-3. Although caspase-3-like proteolysis was induced in the SNc dopamine neurons of juvenile rats lesioned with 6-OHDA and in adult rats following axotomy of the medial forebrain bundle, caspase-3 is not induced in the dopamine neurons of adult 6-OHDA-lesioned animals. Taken together, these results suggest that therapeutic strategies based on NAIP may have potential value for the treatment of PD.     

Differential expression of Fos and Zif268 in the nigrostriatal system after methamphetamine administration in a rat model of Parkinson's disease

The goal of this study was to examine the topological specificity of methamphetamine-induced activation of the immediate-early gene proteins, Fos and Zif268, in the nigrostriatal system in a unilateral 6-hydroxydopamine (6-OHDA) rat model of Parkinson's disease with or without intrastriatal grafts of fetal ventral mesencephalon. Methamphetamine (3 mg/kg, i.p.) induced Fos-like immunoreactivity (FLI) dominantly in the striatum and the globus pallidus (GP) on the intact side as well as in the substantia nigra pars reticulata (SNr) on the lesioned side in the 6-OHDA rats. Lower levels of methamphetamine-induced FLI in the striatum and GP on the lesioned side were restored by intrastriatal grafts which could completely suppress the methamphetamine-induced rotation. In the striatum, a similar tendency could be observed between Fos and Zif268 immunoreactivity following methamphetamine. However, sparse immunoreactivity of Zif268 could be detected in the GP and SNr on both sides in the 6-OHDA rats. Intrastriatal grafts had little influence on Zif268 expression in these two regions. The differential expression of Fos and Zif268 was observed among the three regions of the nigrostriatal system following methamphetamine in the 6-OHDA rats. This may suggest that Fos and Zif268 therefore possess gene-specific and region-specific functions in the basal ganglia nuclei.     

Dopamine receptor changes following destruction of the nigrostriatal pathway: Lack of a relationship to rotational behavior

Phenomena consistent with postsynaptic supersensitivity developed in the rat neostriatum following the destruction of dopaminergic afferent neurons. A gradual in-increase in the densoty of binding sites for [³H]spiperone occurred over a 2–3 week period. This increase was apparent only after the almost complete loss of dopamine-containing nerve terminals as measured by the depletion of endogenous dopamine. The properties of the receptor labeled by [³H]spiperone were not altered by denervation. Elimination of dopamine-containing nerve endings in the neostriatum was accompanied by the gradual development of an increase in dopamine-sensitive adenylate cyclase activity in homogenates of the caudate ipsilateral to the lesion as compared to the contralateral side. The administration of apomorphine led to pronounced circling behavior. This effect occurred rapidly and was maximal within 3 days following destruction of dopaminergic neurons. The increase in the density of dopamine receptors and in a receptor-mediated function may partially account for the development of enhanced electrophysiological responses to dopamine agonists in the neostriatum. However, the results do not explain the drug-induced rotational behavior which develops after destruction of the dopamine-containing nigrostriatal pathway. This behavioral phenomenon clearly preceded the appearance of receptor alterations in the corpus striatum.     

Generalized brain and skin proteasome inhibition in Huntington's disease

Mutated intracellular huntingtin is widely expressed in tissues of Huntington's disease (HD) patients. Intraneuronal nuclear protein aggregates of mutant huntingtin are present in HD brains, suggesting a dysfunction of the ubiquitin proteasome system (UPS). Because many cells and tissues can cope with the abnormal gene effects while others dysfunction and die, we determined gene-induced effects and considered the hypothesis that the gene causes multiple intracellular problems, but severe pathology is seen only in selected brain regions. In this study, we found inhibition of UPS function in both early (0-1, with no or little neuronal loss) and late (3-4, with more severe neuronal loss) stage HD patients' cerebellum, cortex, substantia nigra and caudate-putamen brain regions. Late HD stage increases in ubiquitin levels were unique to caudate-putamen. HD patients' skin fibroblasts also had UPS inhibition similar to brain despite increases in proteasome beta-subunit expression. Gene delivery and expression of proteasome activator PA28 increased UPS function in normal but not HD fibroblasts. These generalized UPS problems are associated with severe neuronal pathology only when coupled with decreases in brain-derived neurotrophic factor levels, mitochondrial complex II/III activity, and increases of ubiquitin levels particularly as seen in the caudate-putamen of HD patients.     

Acupuncture prevents 6-hydroxydopamine-induced neuronal death in the nigrostriatal dopaminergic system in the rat Parkinson's disease model

Parkinson's disease (PD) is a chronic neurodegenerative disorder, and it has been suggested that treatments promoting survival and functional recovery of affected dopaminergic neurons could have a significant and long-term therapeutic value. In the present study, we investigated the neuroprotective effects of acupuncture on the nigrostriatal system in rat unilaterally lesioned with 6-hydroxydopamine (6-OHDA, 4 microg/microl, intrastriatal injection) using tyrosine hydroxylase (TH) and receptor for brain-derived neurotrophic factor, trkB, immunohistochemistries. Two weeks after the lesions were made, rats presented with asymmetry in rotational behavior (118.3 +/- 17.5 turns/h) following injection with apomorphine, a dopamine receptor agonist (0.5 mg/kg, sc). In contrast, acupunctural treatment at acupoints GB34 and LI3 was shown to significantly reduce this motor deficit (14.6 +/- 13.4 turns/h). Analysis via TH immunohistochemistry revealed a substantial loss of cell bodies in the substantia nigra (SN) (45.7% loss) and their terminals in the dorsolateral striatum ipsilateral to the 6-OHDA-induced lesion. However, acupunctural treatment resulted in the enhanced survival of dopaminergic neurons in the SN (21.4% loss) and their terminals in the dorsolateral striatum. Acupuncture also increased the expression of trkB significantly (35.6% increase) in the ipsilateral SN. In conclusion, we observed that only acupuncturing without the use of any drug has the neuroprotective effects against neuronal death in the rat PD model and these protective properties of acupuncture could be mediated by trkB.     

阿扑吗啡对6-羟基多巴损伤的黑质纹状体大鼠的保护

摘要：目的本研究旨在评定6-羟基多巴损伤纹状体后黑质和腹侧被盖区的变化,并探讨阿扑吗啡在该模型中可能存在的神经保护作用。方法 6-羟基多巴损伤纹状体模型：在造模前15分钟,连续22天皮下注射阿扑吗啡10mg／kg．d。在第5周时,观察大鼠行为学（安啡他明诱导的旋转数目）、组织化学（TH／Nissl染色后黑质和腹侧被盖区的多巴胺细胞）、神经化学（高压液相法测定纹状体的多巴胺含量）改变。结果阿扑吗啡不仅消弱安啡他明诱导的旋转数日,而且,显著减少黑质的损伤（与对照组相比,多巴胺细胞达到69％,细胞形态恢复正常）和腹侧被盖区的损伤（多巴胺细胞增加了60％,细胞形态恢复正常）;并且,阿扑吗啡显著消弱6-羟基多巴损伤纹状体的多巴胺含量,使DOPAC／DA率恢复正常。结论在6-羟基多巴损伤纹状体模型中,阿扑吗啡不仅有神经保护作用,而且有神经营养作用。但神经营养作用局限于腹侧被盖区,并随着用药时间延长而增加。     

阿扑吗啡对6-羟基多巴损伤的黑质纹状体大鼠的保护(英文)

目的本研究旨在评定6-羟基多巴损伤纹状体后黑质和腹侧被盖区的变化,并探讨阿扑吗啡在该模型中可能存在的神经保护作用。方法6-羟基多巴损伤纹状体模型:在造模前15分钟,连续22天皮下注射阿扑吗啡10 mg/kg·d。在第5 周时,观察大鼠行为学(安啡他明诱导的旋转数目)、组织化学(TH/Nissl 染色后黑质和腹侧被盖区的多巴胺细胞)、神经化学(高压液相法测定纹状体的多巴胺含量)改变。结果阿扑吗啡不仅消弱安啡他明诱导的旋转数目,而且,显著减少黑质的损伤(与对照组相比,多巴胺细胞达到69%,细胞形态恢复正常)和腹侧被盖区的损伤(多巴胺细胞增加了60%,细胞形态恢复正常); 并且,阿扑吗啡显著消弱6-羟基多巴损伤纹状体的多巴胺含量,使DOPAC/DA率恢复正常。结论在6-羟基多巴损伤纹状体模型中,阿扑吗啡不仅有神经保护作用,而且有神经营养作用。但神经营养作用局限于腹侧被盖区,并随着用药时间延长而增加。     

HIF-1alpha inhibition ameliorates neonatal brain injury in a rat pup hypoxic-ischemic model

In this study, we tested if caspase-3 inhibition decreased ischemia-induced Aβ elevation by reducing β-secretase (BACE1) activity. Changes in caspase-3, Aβ and BACE1 levels were detected in rat striatum on different days after middle cerebral artery occlusion using immunostaining. We found that the positive labeled cells of activated caspase-3, Aβ, and BACE1 were significantly and time-dependently increased in the ipsilateral striatum. The results of Western blotting and RT-PCR showed that caspase-3 inhibitor Z-DEVD-FMK reduced BACE1 mRNA and protein levels, and inhibited its protease activity, thereby decreasing the amount of APP C99 and Aβ in ischemic brains. Moreover, Z-DEVD-FMK reduced BACE1 and GFAP double-labeled cells, but not GFAP protein levels or GFAP-labeled cells, in the ipsilateral striatum. Thus, we demonstrated that caspase-3 inhibition attenuated ischemia-induced Aβ formation by reducing BACE1 production and activity. This finding provides a therapeutic strategy for preventing Aβ accumulation and reducing the risk of neurodegeneration after stroke.     

Lack of feedback inhibition on rat basolateral amygdala following stress or withdrawal from sedative-hypnotic drugs

Previous research has demonstrated that suppression of inhibition in projection neurons of the basolateral complex of the amygdala (BLA) represents an essential mechanism underlying the emergence of negative emotional responses, including exaggerated fear and anxiety. The present work evaluates inhibitory postsynaptic potentials (IPSPs) in pyramidal projection neurons of the BLA in rats subjected to either diazepam or ethanol withdrawal or uncontrollable stress. These are experimental paradigms conducive to a negative emotional state. In slices containing the BLA, IPSPs were studied using whole-cell patch clamp. In control animals, a small IPSP was evoked by sub-threshold stimulation of the external capsule. When an action potential (AP) was evoked by supra-threshold stimuli, IPSPs were considerably larger; these IPSPs were sensitive to blockade of GABA(A) receptors by picrotoxin. However, IPSPs were clearly reduced in diazepam- or ethanol-withdrawn and in stressed rats. Firing of an AP by a depolarizing pulse applied through the patch pipette consistently evoked an inhibitory postsynaptic current (IPSC) in the pyramidal neurons of control animals from all three experimental models; these IPSCs were mediated by GABA(A) receptor activation and were blocked after suppression of glutamatergic transmission. In contrast, no IPSCs were observed in slices from diazepam- or ethanol-withdrawn or stressed animals, although the depolarizing pulse regularly evoked an AP in pyramidal neurons. It is concluded that, in withdrawn or stressed rats, GABAergic disinhibition occurs due to attenuation or suppression of feedback inhibition.     

Paroxetine engenders analgesic effects through inhibition of p38 phosphorylation in a rat migraine model

In this study,a model of migraine was established by electrical stimulation of the superior sagittal sinus in rats.These rats were then treated orally with paroxetine at doses of 2.5,5,or 10 mg/kg per day for 14 days.Following treatment,mechanical withdrawal thresholds were significantly higher,extracellular concentrations of 5-hydroxytryptamine in the periaqueductal grey matter and nucleus reticularis gigantocellularis were higher,and the expression of phosphorylated p38 in the trigeminal nucleus caudalis was lower.Our experimental findings suggest that paroxetine has analgesic effects in a rat migraine model,which are mediated by inhibition of p38 phosphorylation.     

Comparison of the capability of GDNF, BDNF, or both, to protect nigrostriatal neurons in a rat model of Parkinson's disease

Both glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) can protect nigrostriatal dopaminergic neurons from neurotoxins in rodent and monkey models of Parkinson's disease (PD). These two neurotrophic factors are usually tested individually. This study was designed to compare GDNF, BDNF, or both, for their capabilities to correct behavioral deficits and protect nigrostriatal dopaminergic neurons in a rat model of PD. Gene transfer used a helper virus-free Herpes Simplex Virus (HSV-1) vector system and a modified neurofilament heavy gene promoter that supports long-term expression in forebrain neurons. Rats received unilateral intrastriatal injections of HSV-1 vectors that express either GDNF or BDNF, or both vectors, followed by intrastriatal injections of 6-hydroxydopamine (6-OHDA). Recombinant GDNF or BDNF was detected in striatal neurons in rats sacrificed at 7 months after gene transfer. Of note, GDNF was significantly more effective than BDNF for both correcting behavioral deficits and protecting nigrostriatal dopaminergic neurons. Expression of both neurotrophic factors was no more effective than expression of only GDNF. These results suggest that GDNF is more effective than BDNF for correcting the rat model of PD, and that there are no detectable benefits from expressing both of these neurotrophic factors.     

Exaggerated astrocyte reactivity after nigrostriatal deafferentation in the aged rat

Although clinical experience suggests that brain injury in the aged is associated with a poor prognosis, little research has examined this phenomenon at a cellular or molecular level. Unilateral 6-hydroxydopamine lesions of the nigrostriatal system were produced in 6-, 15- or 24-month-old rats. In the deafferented neostriatum, the time-dependent induction of glial fibrillary acidic protein (GFAP) was larger and persisted longer in the aged rats. The response of middle-aged rats was intermediate. In contrast, no induction of S-100 or glutamine synthetase was observed in any age group. In a second series of rats with stab wounds in the neostriatum, there were substantially larger GFAP inductions than after deafferentation, but fewer effects of age. However, in both lesion paradigms, GFAP staining increased in the contralateral striatum of old rats, but not in young rats. These data support and extend our earlier work describing larger GFAP RNA inductions after fornix transections in aged mouse hippocampus. The consistency of this exaggerated glial reactivity in the aged brain after modest injury suggests the following: 1) aged astrocytes are more sensitive to gliotrophic factors released by terminal degeneration, 2) larger quantities of such factors are produced after injury, 3) clearance of these factors is delayed in old rodents, and/or 4) aged astrocytes are less able to terminate GFAP inductions after activation. Given the potential role of inflammatory reactions as pathogenic mechanisms in Alzheimer's dementia, these data suggest that age-related glial hypersensitivity may independently increase the risk for some degenerative diseases. J. Comp. Neurol. 388:106–119, 1997. © 1997 Wiley-Liss, Inc.     

Dopamine receptor sensitivity following nigrostriatal lesion in the aged rat

This investigation sought to determine whether the ability to regulate dopamine receptor sensitivity following removal of dopaminergic innervation is altered during aging. Aged (24–26 months old) Fischer 344 rats compared with young (6 months old) rats had lower levels of dopamine and dopamine receptor binding ([³H]ADTN), but no change of dopamine-stimulated adenylate cyclase activity. Unilateral lesion of the nigrostriatal pathway produced equivalent dopaminergic denervation in rats of both age groups. The denervated striata of young rats had greatly enhanced dopaminergic sensitivity as evidenced by apomorphine induced rotational behavior and increased dopamine stimulated adenylate cyclase activity and [³H]ADTN binding. Old rats responded similarly with a very high degree of increased dopaminergic sensitivity in both the behavioral and biochemical parameters, demonstrating that the ability to regulate dopamine receptors remains basically intact. However, deficits of supersensitivity occured in apomorphine induced rotational behavior and [³H]ADTN binding and there was a large deficit in the guanine nucleotide sensitive subcomponent of [³H]ADTN binding. Supersensitivity of dopamine stimulated adenylate cyclase was not altered. The diminished ability to develop supersensitivity to [³H]ADTN binding could contribute to decreased [³H]ADTN binding in unlesioned rats.     

Lack of inhibition in Parkinson's disease: evidence from a lexical decision task

Persons affected by Parkinson's disease (PD) often show an increased semantic priming effect from target words in lexical decision tasks (hyper-priming) as compared to age-matched controls. In this study, a lexical decision task was used to investigate both semantic priming (Experiment 1) and repetition priming (Experiment 2) from distractor words in PD patients and age-matched controls. With this negative priming procedure, target words in successive trials are never related, and therefore participants always have to switch between unrelated target words. Instead, it is the distractor prime word that is either related or unrelated to the subsequent target, giving the measure of priming. Results showed that PD patients demonstrated a robust effect of positive semantic priming from distractor words. Participants from the control group did not show any semantic priming effect (positive or negative) from distractors. Similarly, PD patients showed positive repetition priming from distractor words, but the control group showed significant repetition negative priming. These results support the view that the hyper-priming effect typically shown by persons with Parkinson's disease is the result of impaired inhibitory processes required to control word activation during reading.