Involvement of the Dorsal Hippocampus 5-HT1A Receptors in the Regulation of Depressive-Like Behaviors in Hemiparkinsonian Rats.

BACKGROUND: Depression is one of the most common neuropsychiatric disturbances in Parkinson's disease (PD), but its pathophysiology is not definite. Lines of evidence have indicated that the hippocampus and serotonin 1A (5-HT1A) receptors are related to the regulation of depression. OBJECTIVE: The purpose of the present study was to observe the effect of 5-HT1A receptors in the dorsal hippocampus (dHIP) on PD-related depression in rats. METHODS: Unilateral 6-hydroxydopamine lesioning of the medial forebrain bundle (MFB) was used to establish the hemiparkinsonian rat model. The effects of intra-dHIP injection of the 5-HT1A receptor -agonist 8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT) or antagonist WAY-100635 on depressive-like behaviors were observed in sucrose preference and forced swim tests in control and lesioned rats. Monoamine levels including dopamine (DA), 5-HT, and noradrenaline (NA) in depression-related brain regions were determined by a neurochemical method in all groups. RESULTS: Behavioral results showed that MFB lesions induced depressive-like behaviors. Intra-dHIP injection of 8-OH-DPAT produced antidepressant effects, while WAY-100635 induced or increased the depressive-like behaviors in both control and the lesioned rats. Neurochemical results found that intra-dHIP injection of 8-OH-DPAT significantly increased DA and 5-HT levels in the medial prefrontal cortex (mPFC), lateral habenula (LHb), ventral hippocampus and amygdala in the lesioned group and decreased NA levels in the mPFC and LHb in the control group. Moreover, after injection of WAY-100635, NA levels in all these regions of the lesioned group were significantly increased. CONCLUSIONS: These findings suggest that hippocampal 5-HT1A receptors regulate depression and PD-related depression by neurochemical mechanisms.

Electroacupuncture Alleviates Motor Symptoms and Up-Regulates Vesicular Glutamatergic Transporter 1 Expression in the Subthalamic Nucleus in a Unilateral 6-Hydroxydopamine-Lesioned Hemi-Parkinsonian Rat Model.

Previous studies have shown that electroacupuncture (EA) promotes recovery of motor function in Parkinson's disease (PD). However the mechanisms are not completely understood. Clinically, the subthalamic nucleus (STN) is a critical target for deep brain stimulation treatment of PD, and vesicular glutamate transporter 1 (VGluT1) plays an important role in the modulation of glutamate in the STN derived from the cortex. In this study, a 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD was treated with 100 Hz EA for 4 weeks. Immunohistochemical analysis of tyrosine hydroxylase (TH) showed that EA treatment had no effect on TH expression in the ipsilateral striatum or substantia nigra pars compacta, though it alleviated several of the parkinsonian motor symptoms. Compared with the hemi-parkinsonian rats without EA treatment, the 100 Hz EA treatment significantly decreased apomorphine-induced rotation and increased the latency in the Rotarod test. Notably, the EA treatment reversed the 6-OHDA-induced down-regulation of VGluT1 in the STN. The results demonstrated that EA alleviated motor symptoms and up-regulated VGluT1 in the ipsilateral STN of hemi-parkinsonian rats, suggesting that up-regulation of VGluT1 in the STN may be related to the effects of EA on parkinsonian motor symptoms via restoration of function in the cortico-STN pathway.

Morphological dendritic spine changes of medium spiny neurons in the nucleus accumbens in 6-hydroxydopamine-lesioned rats treated with levodopa.

The mechanisms of dopamine dysregulation syndrome (DDS) in Parkinson's disease (PD) remain unclear, although it is known that the nucleus accumbens (NAc) plays a role in its development. Based on the hypothesis that DDS and levodopa-induced dyskinesia (LID) share a pathophysiological basis, we investigated dendritic spine morphology of medium spiny neurons (MSNs) in the NAc of a rat model of LID, because spine enlargement in MSNs of the caudate/putamen has been proposed to be a morphological hallmark of LID. Spines of NAc MSNs also became enlarged in the LID model. This result suggests that excitatory supersensitivity of MSNs in the NAc is involved in the development of DDS, similar to what occurs in the caudate/putamen in LID.

Transplantation site influences the phenotypic differentiation of dopamine neurons in ventral mesencephalic grafts in Parkinsonian rats.

Foetal midbrain progenitors have been shown to survive, give rise to different classes of dopamine neurons and integrate into the host brain alleviating Parkinsonian symptoms following transplantation in patients and animal models of the disease. Dopamine neuron subpopulations in the midbrain, namely A9 and A10, can be identified anatomically based on cell morphology and ascending axonal projections. G protein-gated inwardly rectifying potassium channel Girk2 and the calcium binding protein Calbindin are the two best available histochemical markers currently used to label (with some overlap) A9- and A10-like dopamine neuron subtypes, respectively, in tyrosine hydroxylase expressing neurons both in the midbrain and grafts. Both classes of dopamine neurons survive in grafts in the striatum and extend axonal projections to their normal dorsal and ventral striatal targets depending on phenotype. Nevertheless, grafts transplanted into the dorsal striatum, which is an A9 input nucleus, are enriched for dopamine neurons that express Girk2. It remains to be elucidated whether different transplantation sites favour the differential survival and/or development of concordant dopamine neuron subtypes within the grafts. Here we used rat foetal midbrain progenitors at two developmental stages corresponding to a peak in either A9 or A10 neurogenesis and examined their commitment to respective dopaminergic phenotypes by grafting cells into different forebrain regions that contain targets of either nigral A9 dopamine innervation (dorsal striatum), ventral tegmental area A10 dopamine innervation (nucleus accumbens and prefrontal cortex), or only sparse dopamine but rich noradrenaline innervation (hippocampus). We demonstrate that young (embryonic day, E12), but not older (E14), mesencephalic tissue and the transplant environment influence survival and functional integration of specific subtypes of dopamine neurons into the host brain. We also show that irrespective of donor age A9-like, Girk2-expressing neurons are more responsive to environmental cues in adopting a dopaminergic phenotype during differentiation post-grafting. These novel findings suggest that dopamine progenitors use targets of A9/A10 innervation in the transplantation site to complete maturation and the efficacy of foetal cell replacement therapy in patients may be improved by deriving midbrain tissue at earlier developmental stages than in current practice.

Use of PEGylated Immunoliposomes to Deliver Dopamine Across the Blood-Brain Barrier in a Rat Model of Parkinson's Disease.

AIM: To treat neurodegenerative disorders such as Parkinson's disease (PD), drugs must be able to cross the blood-brain barrier (BBB). Patients with PD are deficient in dopamine (DA), a neurotransmitter that cannot pass through the BBB. Liposomes modified by adding polyethylene glycol (PEGylated liposomes (PLs)) can be conjugated with antibody to form DA-PEGylated immunoliposomes (DA-PILs), and we tested their use as carriers of DA for treating PD. METHODS: PEGylated liposomes (PLs) were prepared by evaporation method, and [(3) H]dopamine was encapsulated within the dried lipid film using a freeze/thaw cycle to form DA-PL. Thiolated OX26 MAb, an antitransferrin receptor monoclonal antibody, was then conjugated to 46-nm PEGylated liposomes. Particle size, zeta potential, and stability were assessed, and in vivo effects were determined after the intravenous injection of DA, DA-PL, and DA-PIL by examining brain tissue in normal rats and rats that underwent transection of the medial forebrain bundle to induce PD. RESULTS: The uptake of DA-PIL in the brains of this PD rat model increased about 8-fold compared with that of DA alone and about 3-fold compared with that of encapsulated DA-PEGylated liposomes (DA-PL). The volume of distribution of DA-PIL in the brain by the perfusion method was 4-fold higher than that of DA-PL, indicating that conjugation of OX26 MAb to the transferrin receptor of brain capillary endothelium mediated the effective delivery of DA to brain tissue. CONCLUSIONS: Dopamine can be effectively delivered to the brain by means of a PIL-based drug delivery system in PD rats.

Altered neuronal activity in the pedunculopontine nucleus: An electrophysiological study in a rat model of Parkinson's disease.

The pedunculopontine nucleus (PPN) is a new deep brain stimulation target for treating Parkinson's disease (PD). But the alterations of the PPN electrophysiological activities in PD are still debated. To investigate these potential alterations, extracellular single unit and local field potential (LFP) activities in the PPN were recorded in unilateral hemispheric 6-hydroxydopamine (6-OHDA) lesioned rats and in control rats, respectively. The spike activity results revealed two types of neurons (Type I and Type II) with distinct electrophysiological characteristics in the PPN. Both types of neurons had increased firing rate and changed firing pattern in lesioned rats when compared to control rats. Specifically, Type II neurons showed an increased firing rate when the rat state was switched from rest to locomotion. The LFP results demonstrated that lesioned rats had lower LFP power at 0.7-12Hz and higher power at 12-30Hz than did control animals in either resting or locomotor state. These findings provide a better understanding of the effects of 6-OHDA lesion on neuronal activities in the PPN and also provide a proof of the link between this structure and locomotion, which contributes to better understanding the mechanisms of the PPN functioning in the pathophysiology of PD.

Pathway-Specific Remodeling of Thalamostriatal Synapses in Parkinsonian Mice.

Movement suppression in Parkinson's disease (PD) is thought to arise from increased efficacy of the indirect pathway basal ganglia circuit, relative to the direct pathway. However, the underlying pathophysiological mechanisms remain elusive. To examine whether changes in the strength of synaptic inputs to these circuits contribute to this imbalance, we obtained paired whole-cell recordings from striatal direct- and indirect-pathway medium spiny neurons (dMSNs and iMSNs) and optically stimulated inputs from sensorimotor cortex or intralaminar thalamus in brain slices from control and dopamine-depleted mice. We found that dopamine depletion selectively decreased synaptic strength at thalamic inputs to dMSNs, suggesting that thalamus drives asymmetric activation of basal ganglia circuitry underlying parkinsonian motor impairments. Consistent with this hypothesis, in vivo chemogenetic and optogenetic inhibition of thalamostriatal terminals reversed motor deficits in dopamine-depleted mice. These results implicate thalamostriatal projections in the pathophysiology of PD and support interventions targeting thalamus as a potential therapeutic strategy.

Amelioration of non-motor dysfunctions after transplantation of human dopamine neurons in a model of Parkinson's disease.

BACKGROUND: Patients suffering from Parkinson's disease (PD) display cognitive and neuropsychiatric dysfunctions, especially with disease progression. Although these impairments have been reported to impact more heavily upon a patient's quality of life than any motor dysfunctions, there are currently no interventions capable of adequately targeting these non-motor deficits. OBJECTIVES: Utilizing a rodent model of PD, we investigated whether cell replacement therapy, using intrastriatal transplants of human-derived ventral mesencephalic (hVM) grafts, could alleviate cognitive and neuropsychiatric, as well as motor, dysfunctions. METHODS: Rats with unilateral 6-hydroxydopamine lesions to the medial forebrain bundle were tested on a complex operant task that dissociates motivational, visuospatial and motor impairments sensitive to the loss of dopamine. A subset of lesioned rats received intrastriatal hVM grafts of ~9 weeks gestation. Post-graft, rats underwent repeated drug-induced rotation tests and were tested on two versions of the complex operant task, before post-mortem analysis of the hVM tissue grafts. RESULTS: Post-graft behavioural testing revealed that hVM grafts improved non-motor aspects of task performance, specifically visuospatial function and motivational processing, as well as alleviating motor dysfunctions. CONCLUSIONS: We report the first evidence of human VM cell grafts alleviating both non-motor and motor dysfunctions in an animal model of PD. This intervention, therefore, is the first to improve cognitive and neuropsychiatric symptoms long-term in a model of PD.

Loss of Striatonigral GABAergic Presynaptic Inhibition Enables Motor Sensitization in Parkinsonian Mice.

Degeneration of dopamine (DA) neurons in Parkinson's disease (PD) causes hypokinesia, but DA replacement therapy can elicit exaggerated voluntary and involuntary behaviors that have been attributed to enhanced DA receptor sensitivity in striatal projection neurons. Here we reveal that in hemiparkinsonian mice, striatal D1 receptor-expressing medium spiny neurons (MSNs) directly projecting to the substantia nigra reticulata (SNr) lose tonic presynaptic inhibition by GABAB receptors. The absence of presynaptic GABAB response potentiates evoked GABA release from MSN efferents to the SNr and drives motor sensitization. This alternative mechanism of sensitization suggests a synaptic target for PD pharmacotherapy.

Alterations in primary motor cortex neurotransmission and gene expression in hemi-parkinsonian rats with drug-induced dyskinesia.

Treatment of Parkinson's disease (PD) with dopamine replacement relieves symptoms of poverty of movement, but often causes drug-induced dyskinesias. Accumulating clinical and pre-clinical evidence suggests that the primary motor cortex (M1) is involved in the pathophysiology of PD and that modulating cortical activity may be a therapeutic target in PD and dyskinesia. However, surprisingly little is known about how M1 neurotransmitter tone or gene expression is altered in PD, dyskinesia or associated animal models. The present study utilized the rat unilateral 6-hydroxydopamine (6-OHDA) model of PD/dyskinesia to characterize structural and functional changes taking place in M1 monoamine innervation and gene expression. 6-OHDA caused dopamine pathology in M1, although the lesion was less severe than in the striatum. Rats with 6-OHDA lesions showed a PD motor impairment and developed dyskinesia when given L-DOPA or the D1 receptor agonist, SKF81297. M1 expression of two immediate-early genes (c-Fos and ARC) was strongly enhanced by either L-DOPA or SKF81297. At the same time, expression of genes specifically involved in glutamate and GABA signaling were either modestly affected or unchanged by lesion and/or treatment. We conclude that M1 neurotransmission and signal transduction in the rat 6-OHDA model of PD/dyskinesia mirror features of human PD, supporting the utility of the model to study M1 dysfunction in PD and the elucidation of novel pathophysiological mechanisms and therapeutic targets.

Chronic deep brain stimulation of the medial forebrain bundle reverses depressive-like behavior in a hemiparkinsonian rodent model.

Preclinical and clinical evidence suggests that depression might be associated with a dysfunction in the reward/motivation circuitry. Deep brain stimulation (DBS) of the superolateral branch of the medial forebrain bundle (MFB) has been shown in a recent clinical trial to provide a prompt and consistent improvement of depressive symptoms in treatment-resistant patients. In order to better understand the underlying mechanisms of neuromodulation in the context of depression, the effects of chronic bilateral MFB-DBS were assessed in a combined rodent model of depression and Parkinson's disease. Female Sprague-Dawley rats received unilateral 6-OHDA injection in the right MFB and were divided into three groups: CMS-STIM, CMS-noSTIM and control group. The CMS groups were submitted to chronic unpredictable mild stress (CMS) protocol for 6 weeks. MFB-DBS was applied only to the CMS-STIM group for 1 week. All groups were repeatedly probed on a series of behavioral tasks following each intervention, and to a postmortem histological analysis. CMS led to an increase in immobility in the forced swim test, to a decrease in sucrose solution consumption in the sucrose preference test, as well as to an increased production of ultrasonic vocalizations in the 22 kHz range, indicating increased negative affect. MFB-DBS reversed the anhedonic-like and despair-like behaviors. The results suggest that unilateral dopamine depletion did not preclude MFB-DBS in reversing depressive-like and anhedonic-like behavior in the rodent. Further understanding of the importance of hemispheric dominance in neuropsychiatric disorders is essential in order to optimize stimulation as a therapeutic strategy in these diseases.

Changes of gene expression of Gal3, Hsp27, Lcn2, and Timp1 in rat substantia nigra following medial forebrain bundle transection using a candidate gene microarray.

Neuroinflammation is an early event and important contributor to the pathobiology of neurodegenerative diseases. Neuroglia, especially microglia, are a major central nervous system population that can modulate neuroinflammation. To determine potential key molecules in this process, we employed microarray analysis in the substantia nigra (SN) following medial forebrain bundle (MFB) transection and analyzed the temporal expression profiles of candidate genes implicated in neuroglial activation and functional maturation. The DNA microarray analyzed, 8913 probes. Sixty nine genes were up-regulated and 11 genes were down-regulated at least twofold compared to normal control. Of the 80 genes, 23 were related to cell metabolism, 3 related to apoptosis, 27 related to immunity. Among them, 4 genes (Galectin 3, Heat shock protein 27, Lipocalin 2, Tissue inhibitory metalloproteinase 1) seemed to be related to the neuroglial function. The candidate genes were subjected to quantitative real-time PCR, Western blotting, and immunohistochemical approaches. Expression changes similar to the microarray were evident. In a double immunofluorescence assay, Galectin 3 almost completely co-localized with OX6-positive activated microglia, and Heat shock protein 27 mainly co-localized with glial fibrillary acidic protein (GFAP) positive astrocytes. Lipocalin 2, except for a few matches of GFAP positive astrocytes, did not co-localized with any of neuroglial markers. This is the first study to evaluate gene expression changes in the SN following MFB transection, which has been used as a parkinsonian animal model. Several candidate genes with potential roles in neuroglial activation and functional maturation were identified. The molecular significance of the candidate genes in neuroglial activation and neuroinflammation remains unclear.

Continuous High-Frequency Stimulation of the Subthalamic Nucleus Improves Cell Survival and Functional Recovery Following Dopaminergic Cell Transplantation in Rodents.

Subthalamic nucleus (STN) high-frequency stimulation (HFS) is a routine treatment in Parkinson's disease (PD), with confirmed long-term benefits. An alternative, but still experimental, treatment is cell replacement and restorative therapy based on transplanted dopaminergic neurons. The current experiment evaluated the potential synergy between neuromodulation and grafting by studying the effect of continuous STN-HFS on the survival, integration, and functional efficacy of ventral mesencephalic dopaminergic precursors transplanted into a unilateral 6-hydroxydopamine medial forebrain bundle lesioned rodent PD model. One group received continuous HFS of the ipsilateral STN starting a week prior to intrastriatal dopaminergic neuron transplantation, whereas the sham-stimulated group did not receive STN-HFS but only dopaminergic grafts. A control group was neither lesioned nor transplanted. Over the following 7 weeks, the animals were probed on a series of behavioral tasks to evaluate possible graft and/or stimulation-induced functional effects. Behavioral and histological data suggest that STN-HFS significantly increased graft cell survival, graft-host integration, and functional recovery. These findings might open an unexplored road toward combining neuromodulative and neuroregenerative strategies to treat severe neurologic conditions.

Striatal tyrosine hydroxylase-positive neurons are associated with L-DOPA-induced dyskinesia in hemiparkinsonian mice.

L-3,4-Dihydroxyphenylalanine (L-DOPA) is the therapeutic gold standard in Parkinson's disease. However, long-term treatment is complicated by the induction of debilitating abnormal involuntary movements termed L-DOPA-induced dyskinesias (LIDs). Until today the underlying mechanisms of LID pathogenesis are not fully understood. The aim of this study was to reveal new factors, which may be involved in the induction of LID. We have focused on the expression of striatal tyrosine hydroxylase-positive (TH+) neurons, which are capable of producing either L-DOPA or dopamine (DA) in target areas of ventral midbrain DAergic neurons. To address this issue, a daily L-DOPA dose was administered over the course of 15 days to mice with unilateral 6-hydroxydopamine-induced lesions of the medial forebrain bundle and LIDs were evaluated. Remarkably, the number of striatal TH+ neurons strongly correlated with both induction and severity of LID as well as ΔFosB expression as an established molecular marker for LID. Furthermore, dyskinetic mice showed a marked augmentation of serotonergic fiber innervation in the striatum, enabling the decarboxylation of L-DOPA to DA. Axial, limb and orolingual dyskinesias were predominantly associated with TH+ neurons in the lateral striatum, whereas medially located TH+ neurons triggered locomotive rotations. In contrast, identified accumbal and cortical TH+ cells did not contribute to the generation of LID. Thus, striatal TH+ cells and serotonergic terminals may cooperatively synthesize DA and subsequently contribute to supraphysiological synaptic DA concentrations, an accepted cause in LID pathogenesis.

Regenerative therapy in experimental parkinsonism: mixed population of differentiated mouse embryonic stem cells, rather than magnetically sorted and enriched dopaminergic cells provide neuroprotection.

AIM: The objective of the study was to develop regenerative therapy by transplanting varied populations of dopaminergic neurons, differentiated from mouse embryonic stem cells (mES) in the striatum for correcting experimental parkinsonism in rats. METHODS: mES differentiated by default for 7 days in serum-free media (7D), or by enhanced differentiation of 7D in retinoic acid (7R), or dopaminergic neurons enriched by manual magnetic sorting from 7D (SSEA-) were characterized and transplanted in the ipsilateral striatum of 6-hydroxydopamine-induced hemiparkinsonian rats. Neurochemical, neuronal, glial and neurobehavioral recoveries were examined. RESULTS: 7R and SSEA- contained significantly reduced NANOG and high MAP2 mRNA and protein levels as revealed, respectively, by reverse transcriptase-PCR and immunocytochemistry, compared with 7D. Striatal engraftment of 7D resulted in a significantly better behavioral and neurochemical recovery, as compared to the animals that received either 7R or SSEA-. The 7R transplanted animals showed improvement neither in behavior nor in striatal dopamine level. The grafted striatum revealed increased GFAP staining intensity in 7D and SSEA-, but not in 7R cells transplanted group, suggesting a vital role played by glial cells in the recovery. Substantia nigra ipsilateral to the side of the striatum, which received transplants showed more tyrosine hydroxylase immunostained neurons, as compared to 6-hydroxydopamine-infused animals. CONCLUSION: These results demonstrate that default differentiated mixed population of cells are better than sorted, enriched dopaminergic cells, or cells containing more mature neurons for transplantation recovery in hemiparkinsonian rats.

Two-step grafting significantly enhances the survival of foetal dopaminergic transplants and induces graft-derived vascularisation in a 6-OHDA model of Parkinson's disease.

Following transplantation of foetal primary dopamine (DA)-rich tissue for neurorestaurative treatment of Parkinson's disease (PD), only 5-10% of the functionally relevant DAergic cells survive both in experimental models and in clinical studies. The current work tested how a two-step grafting protocol could have a positive impact on graft survival. DAergic tissue is divided in two portions and grafted in two separate sessions into the same target area within a defined time interval. We hypothesized that the first graft creates a "DAergic" microenvironment or "nest" similar to the perinatal substantia nigra that stimulates and protects the second graft. 6-OHDA-lesioned rats were sequentially transplanted with wild-type (GFP-, first graft) and transgenic (GFP+, second graft) DAergic cells in time interims of 2, 5 or 9days. Each group was further divided into two sub-groups receiving either 200k (low cell number groups: 2dL, 5dL, 9dL) or 400k cells (high cell number groups: 2dH, 5dH, 9dH) as first graft. During the second transplantation, all groups received the same amount of 200k GFP+ cells. Controls received either low or high cell numbers in one single session (standard protocol). Drug-induced rotations, at 2 and 6weeks after grafting, showed significant improvement compared to the baseline lesion levels without significant differences between the groups. Rats were sacrificed 8weeks after transplantation for post-mortem histological assessment. Both two-step groups with the time interval of 2days (2dL and 2dH) showed a significantly higher survival of DAergic cells compared to their respective standard control group (2dL, +137%; 2dH, +47%). Interposing longer intervals of 5 or 9days resulted in the loss of statistical significance, neutralising the beneficial two-step grafting effect. Furthermore, the transplants in the 2dL and 2dH groups had higher graft volume and DA-fibre-density values compared to all other two-step groups. They also showed intense growth of GFP+ vessels - completely absent in control grafts - in regions where the two grafts overlap, indicating second-graft derived angiogenesis. In summary, the study shows that two-step grafting with a 2days time interval significantly increases DAergic cell survival compared to the standard protocol. Furthermore, our results demonstrate, for the first time, a donor-derived neoangiogenesis, leading to a new understanding of graft survival and development in the field of cell-replacement therapies for neurodegenerative diseases.

The NK1 receptor antagonist N-acetyl-L-tryptophan reduces dyskinesia in a hemi-parkinsonian rodent model.

BACKGROUND: Dyskinesia or abnormal involuntary movements (AIMs) are a disabling effect of chronic L-DOPA administration and consequent pulsatile stimulation of dopamine receptors. This abnormal activation causes maladaptive changes including upregulation of FosB expression in dynorphin containing striatal cells. Substance P (SP) is co-localized within dynorphin positive cells and is increased within the substantia nigra by L-DOPA (L-3,4-dihydroxyphenylalanine) treatment. Accordingly, we determined if treatment with a SP NK1 receptor antagonist reduced the onset of L-DOPA induced dyskinesia (LID) in the hemi-parkinsonian rodent model. METHODS: Adult male Sprague-Dawley rats underwent unilateral 6-OHDA (6-hydroxydopamine-hydrobromide) lesions of the medial forebrain bundle. At day 21, daily administration commenced of either L-DOPA (6 mg/kg plus 15 mg/kg of benseraside), L-DOPA with the NK1 antagonist N-acetyl-L-tryptophan (NAT) or equal volume of saline. Animals were tested with the rodent AIM scale assessing axial, contralateral forelimb and orolingual AIMs. Assessment of L-DOPA induced turning was undertaken, and motor function determined using the accelerating rotarod and adjusting step test. Dopaminergic neuronal counts and immunoreactivity for SP and FosB were undertaken. RESULTS: All animals treated with L-DOPA alone developed dyskinesia, whereas combined administration of NAT with L-DOPA significantly reduced onset of AIMs and prevented mild to moderate dyskinesia. In non-dyskinetic NAT treated animals, similar numbers of FosB+ striatal cells were recorded as in saline treated animals. Importantly NAT treatment did not interfere with the anti-parkinsonian effect of L-DOPA. CONCLUSION: Daily administration of a SP NK1 receptor antagonist may represent a novel treatment regime that reduces the onset of LID whilst conserving motor function.

The effects of unilateral 6-OHDA lesion in medial forebrain bundle on the motor, cognitive dysfunctions and vulnerability of different striatal interneuron types in rats.

In this study, the motor deficit, cognition impairment and the vulnerability of different striatal interneurons to the 6-hydroxydopamine (6-OHDA)-induced excitotoxicity in unilateral medial forebrain bundle (MFB) lesion rats were analyzed by employing behavioral test, immunohistochemistry and Western blot methods. The apomorphine-induced rotation after MFB lesion was used as a valid criterion of motor deficit. The 6-OHDA damaged rats had limb rigidity with longer hang time compared to the controls in the grip strength test. Cognitive and mnemonic deficits of rats with unilateral MFB lesion were observed by the water maze task. The MFB lesion resulted in a significant loss of tyrosine hydroxylase (TH)+ cells in the contralateral striatum or substantia nigra. After dopaminergic depletion, the numbers of calretinin (Cr)+ and choline acetyltransferase (ChAT)+ interneurons were notably reduced while these of neuropeptide Y (NPY)+ were markedly increased in the striatum. No noticeable change in the number of parvalbumin (Parv)+ interneurons was found in 6-OHDA rats. In addition, the fiber densities for each individual interneuron were increased after 6-OHDA treatment, especially for the fiber densities of Parv+ and Cr+ interneurons. The Western blot analysis further confirmed the results described above. In conclusion, the MFB lesion model is suitable to mimic Parkinson's disease (PD), and our results are helpful for further understanding the underlying mechanism and the specific functions of various striatal interneurons in the pathological process of PD.

Relation between microPET imaging and rotational behavior in a parkinsonian rat model induced by medial forebrain bundle axotomy.

The purpose of the current study was to examine the relation between apomorphine (APO) induced rotational behavior and the pre- and post-synaptic dopaminergic function in a parkinsonian rat model induced by medial forebrain bundle (MFB) axotomy. The brains of these rats were unilaterally lesioned by mechanical transection of the nigrostriatal dopamine pathway at the MFB. Behavioral studies were carried out by APO challenge prior to and 1, 3, and 5 weeks after MFB axotomy. MicroPET scans with [(11)C]CFT and [(11)C]raclopride were performed 2 days after the behavioral test. The two PET scans were separated by an interval of 24-48 h. Immunohistochemistry was conducted 4 days after the last PET scan. Our data showed that [(11)C]CFT binding decreased progressively 1, 3, and 5 weeks postlesion, and there was a significant nonlinear correlation between [(11)C]CFT uptake ratio (right/left) and APO induced rotations. In contrast, [(11)C]raclopride binding only increased significantly 3 weeks postlesion, and there was a positive linear correlation between [(11)C]raclopride uptake ratio (right/left) and APO induced rotations. Postmortem immunohistochemical studies confirmed the loss of both striatal dopamine fibers and nigral neurons on the lesioned side. These findings not only demonstrate the relation between APO induced rotational behavior and the pre- and post-synaptic dopamine function but also indicate the utility and validity of in vivo PET imaging in understanding disease mechanisms and progression, which should in turn lead to development of new therapies.

Down-regulation of microglial activity attenuates axotomized nigral dopaminergic neuronal cell loss.

BACKGROUND: There is growing evidence that inflammatory processes of activated microglia could play an important role in the progression of nerve cell damage in neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease which harbor features of chronic microglial activation, though the precise mechanism is unknown. In this study, we presented in vivo and ex vivo experimental evidences indicating that activated microglia could exacerbate the survival of axotomized dopaminergic neurons and that appropriate inactivation of microglia could be neuroprotective. RESULTS: The transection of medial forebrain bundle (MFB) of a rat induced loss of dopaminergic neurons in a time-dependent manner and accompanied with microglial activation. Along with microglial activation, production of reactive oxygen species (ROS) was upregulated and TH/OX6/hydroethidine triple-immunofluorescence showed that the microglia mainly produced ROS. When the activated microglial cells that were isolated from the substantia nigra of the MFB axotomized animal, were transplanted into the substantia nigra of which MFB had been transected at 7 days ago, the survival rate of axotomized dopaminergic neurons was significantly reduced as compared with sham control. Meanwhile, when the microglial activation was attenuated by administration of tuftsin fragment 1-3 (microglia inhibitory factor) into the lateral ventricle using mini-osmotic pump, the survival rate of axotomized dopaminergic neurons was increased. CONCLUSION: The present study suggests that activated microglia could actively produce and secrete unfavorable toxic substances, such as ROS, which could accelerate dopaminergic neuronal cell loss. So, well-controlled blockade of microglial activation might be neuroprotective in some neuropathological conditions.