Lesions Of Medial Forebrain Bundle Research Articles

Characterization of graded 6-Hydroxydopamine unilateral lesion in medial forebrain bundle of mice

Parkinson’s disease (PD) is the second most common age-related neurodegenerative disease, with a progressive loss of dopaminergic cells and fibers. The purpose of this study was to use different doses of 6-hydroxydopamine (6-OHDA) injection into the medial forebrain bundle (MFB) of mice to mimic the different stages of the disease and to characterize in detail their motor and non-motor behavior, as well as neuropathological features in the nigrostriatal pathway. MFB were injected with 0.5 μg, 1 μg, 2 μg of 6-OHDA using a brain stereotaxic technique. 6-OHDA induced mitochondrial damage dose-dependently, as well as substantia nigra pars compacta (SNpc) tyrosine hydroxylase-positive (TH+) cell loss and striatal TH fiber loss. Activation of astrocytes and microglia in the SNpc and striatum were consistently observed at 7 weeks, suggesting a long-term glial response in the nigrostriatal system. Even with a partial or complete denervation of the nigrostriatal pathway, 6-OHDA did not cause anxiety, although depression-like behavior appeared. Certain gait disturbances were observed in 0.5 μg 6-OHDA lesioned mice, and more extensive in 1 μg group. Despite the loss of more neurons from 2 μg 6-OHDA, there was no further impairment in behaviors compared to 1 μg 6-OHDA. Our data have implications that 1 μg 6-OHDA was necessary and sufficient to induce motor and non-motor symptoms in mice, thus a valuable mouse tool to explore disease progression and new treatment in PD.

Nigrostriatal 6-hydroxydopamine lesions increase alpha-synuclein levels and permeability in rat colon

Increasing evidence suggests that the gut–brain axis plays a crucial role in Parkinson’s disease (PD). The abnormal accumulation of aggregated alpha-synuclein (aSyn) in the brain is a key pathological feature of PD. Intracerebral 6-hydroxydopamine (6-OHDA) is a widely used dopaminergic lesion model of PD. It exerts no aSyn pathology in the brain, but changes in the gut have not been assessed. Here, 6-OHDA was administered unilaterally either to the rat medial forebrain bundle (MFB) or striatum. Increased levels of glial fibrillary acidic protein in the ileum and colon were detected at 5 weeks postlesion. 6-OHDA decreased the Zonula occludens protein 1 barrier integrity score, suggesting increased colonic permeability. The total aSyn and Ser129 phosphorylated aSyn levels were elevated in the colon after the MFB lesion. Both lesions generally increased the total aSyn, pS129 aSyn, and ionized calcium-binding adapter molecule 1 (Iba1) levels in the lesioned striatum. In conclusion, 6-OHDA-induced nigrostriatal dopaminergic damage leads to increased aSyn levels and glial cell activation particularly in the colon, suggesting that the gut–brain axis interactions in PD are bidirectional and the detrimental process may start in the brain.

Prolongation of absence seizures and changes in serotonergic and dopaminergic neurotransmission by nigrostriatal pathway degeneration in genetic absence epilepsy rats

ObjectiveBasal ganglia structures play an important role in the pathophysiology of absence epilepsy, known as remote control of absence seizures. We examined the role of the nigrostriatal dopaminergic pathway in absence epilepsy through behavioral and electroencephalography (EEG) parameters, immunohistochemical, and biochemical characteristics of dopamine and serotonin in the genetic absence epilepsy rat model. MethodsThe nigrostriatal pathway was degenerated by the injection of chemical 6-hydroxydopamine hydrobromide (6-OHDA) into the medial forebrain bundle (MFB) in Wistar and genetic absence epilepsy rats from Strasbourg (GAERS). On the 21st day after stereotaxic surgery, spike-and-wave discharges (SWDs) on EEG were recorded in GAERS groups. Thereafter, Wistar-Control, GAERS-Control, Wistar-6OHDA, GAERS-6OHDA rats were subjected to the cylinder and apomorphine-induced rotation tests. Dopaminergic or serotonergic immunoreactivity was examined in the cortex, striatum, and substantia nigra pars compacta. High-performance liquid chromatography method was used for biochemical analysis of dopamine and serotonin in the cortex and thalamus. ResultsIn behavioral analysis, the number of rotations in the GAERS-6OHDA group was significantly higher than in Wistar-6OHDA rats. The degeneration of the nigrostriatal dopaminergic pathway produced a significant increase in the cumulative duration of SWDs and the duration of each SWD in GAERS-6OHDA rats. GAERS-Control rats displayed significantly higher cortical and striatal serotonin immunoreactivity and cortical serotonin level compared to Wistar-Control animals. Moreover, cortical and striatal serotonin immunoreactivity and cortical serotonin levels increased in Wistar-6OHDA and GAERS-6OHDA groups compared to their control groups. SignificanceThe effect of 6-OHDA-induced MFB lesion on absence epilepsy was examined for the first time by comparing Wistar and GAERS rats. The nigrostriatal dopaminergic pathway as a part of the remote-control system is likely to participate in the seizure network.

The effects of melatonin on the striatum

Objective: Some of the neurological diseases cause morphologic changes in the striatal neurons. Medial forebrain bundle (MFB)lesion is a commonly used method to produce a Parkinsonian model rat. Melatonin is a hormone which exerts a neuroprotectiveeffect on the neurons. The aim of this study is to investigate the effect of melatonin on the dendritic morphology of striatal mediumspiny neurons (MSNs) in rats with MFB lesion.Materials and Methods: Twelve male Wistar albino rats were given saline injections into the MFB and divided into sedentary andtreatment groups. The treatment group was administered a 10 mg/kg dose of melatonin intraperitoneally for 30 days. The lesionwas confirmed histologically by Nissl staining. Golgi staining technique was applied to observe neuronal morphology. Neuronalstructures were analysed from three-dimensional images by Neurolucida (MBF Bioscience) software.Results: The MFB lesion caused a reduction in the total dendritic length and in the number of dendritic endings. The melatoninenhanced the number of dendritic endings compared to the sedentary group. The melatonin led to an increase in the total spinedensity, spine densities of thin and mushroom types.Conclusion: Melatonin improved the dendritic degeneration due to MFB lesion.

Lesions of the lateral habenula produce anxiolytic effects in a rat model of Parkinson’s disease

ABSTRACT Objective: This study was designed to investigate the effects of lateral habenula (LHb) lesion on anxiety-like behaviors in parkinsonian rats. Methods: Anxiety-like behaviors were assessed by the open field and elevated plus maze (EPM) tests in control, medial forebrain bundle (MFB)-lesioned, MFB- and LHb-lesioned and MFB-lesioned and LHb sham-lesioned rats, respectively. The levels of extracellular dopamine (DA), serotonin (5-HT) and noradrenaline (NA) in the basolateral amygdala (BLA) were measured by in vivo microdialysis and neurochemistry. Results: Compared to control rats, MFB lesions in rats decreased the percentage of time spent in the central area in the open field test and the percentages of open arm time and open arm entries in the EPM test, indicating the induction of anxiety-like behaviors, and this lesion also decreased the level of extracellular DA in the BLA. Further, rats in the MFB + LHb lesion group showed increased percentage of time spent in the central area and the percentages of open arm time and open arm entries compared to rats in the MFB lesion group, suggesting anxiolytic effects after lesioning the LHb. Neurochemical results found that lesions of the LHb increased the levels of extracellular DA and 5-HT in the BLA in the MFB and LHb lesion groups, whereas NA level was not altered. Discussion: These findings suggest that depletion of DA plays an important role in anxiety-like behaviors, and lesions of the LHb produce anxiolytic responses in MFB-lesioned rats, which are related to increased levels of extracellular DA and 5-HT in the BLA.

Doxycycline and its derivative, COL-3, decrease dyskinesia induced by l-DOPA in hemiparkinsonian rats.

l-DOPA-induced dyskinesia is a debilitating effect of treating Parkinson's disease with this drug. New therapeutic approaches that prevent or attenuate this side effect are needed. Wistar adult male rats submitted to 6-hydroxydopamine-induced unilateral medial forebrain bundle lesion were treated with l-DOPA (p.o. 20 mg·kg-1 or s.c. 10mg·kg-1 ) once a day for 14 days. After this period, we tested if doxycycline (40 mg·kg-1 , i.p.) and COL-3 (50 and 100 nmol, i.c.v.) could reverse l-DOPA-induced dyskinesia. In an additional experiment, doxycycline was administered together with l-DOPA to verify if it would prevent l-DOPA-induced dyskinesia development. A single injection of doxycycline or COL-3 attenuated l-DOPA-induced dyskinesia. Co-treatment with doxycycline from the first day of l-DOPA suppressed the onset of dyskinesia. The improved motor response after l-DOPA was not affected by doxycycline or COL-3. Doxycycline treatment was associated with decreased immunoreactivity of FosB, COX-2, the astroglial protein GFAP and the microglial protein OX-42, which were elevated in the basal ganglia of rats exhibiting dyskinesia. Doxycycline decreased metalloproteinase-2/-9 activity, metalloproteinase-3 expression and ROS production. Metalloproteinase-2/-9 activity and production of ROS in the basal ganglia of dyskinetic rats showed a significant correlation with the intensity of dyskinesia. The present study demonstrates the anti-dyskinetic potential of doxycycline and its analogue compound COL-3 in hemiparkinsonian rats. Given the long-established and safe clinical use of doxycycline, this study suggests that these drugs might be tested to reduce or prevent l-DOPA-induced dyskinesia in Parkinson's patients.

Genetic diversity of axon degenerative mechanisms in models of Parkinson's disease

Parkinson's disease (PD) is the most common form of neurodegenerative movement disorder, associated with profound loss of dopaminergic neurons from the basal ganglia. Though loss of dopaminergic neuron cell bodies from the substantia nigra pars compacta is a well-studied feature, atrophy and loss of their axons within the nigrostriatal tract is also emerging as an early event in disease progression. Genes that drive the Wallerian degeneration, like Sterile alpha and toll/interleukin-1 receptor motif containing (Sarm1), are excellent candidates for driving this axon degeneration, given similarities in the morphology of axon degeneration after axotomy and in PD. In the present study we assessed whether Sarm1 contributes to loss of dopaminergic projections in mouse models of PD. In Sarm1 deficient mice, we observed a significant delay in the degeneration of severed dopaminergic axons distal to a 6-OHDA lesion of the medial forebrain bundle (MFB) in the nigrostriatal tract, and an accompanying rescue of morphological, biochemical and behavioural phenotypes. However, we observed no difference compared to controls when striatal terminals were lesioned with 6-OHDA to induce a dying back form of neurodegeneration. Likewise, when PD phenotypes were induced using AAV-induced alpha-synuclein overexpression, we observed similar modest loss of dopaminergic terminals in Sarm1 knockouts and controls. Our data argues that axon degeneration after MFB lesion is Sarm1-dependent, but that other models for PD do not require Sarm1, or that Sarm1 acts with other redundant genetic pathways. This work adds to a growing body of evidence indicating Sarm1 contributes to some, but not all types of neurodegeneration, and supports the notion that while axon degeneration in many context appears morphologically similar, a diversity of axon degeneration programs exist.

Activation and blockade of dorsal hippocampal serotonin4 receptors produce antidepressant effects in the hemiparkinsonian rats

Depression is a common non-motor symptom in Parkinson's disease (PD). Although serotonin4 (5-HT4) receptors and the dorsal hippocampus (dHIP) are regarded to be involved in the depression, the mechanism underlying the effects of 5-HT4 receptors in the dHIP on PD-related depression should be further investigated. In the present study, unilateral 6-hydroxydopamine lesions of the medial forebrain bundle (MFB) increased the expressions of 5-HT4 receptors and its co-localization with glutamate neurons in the CA1, CA3 and dentate gyrus. Additionally, MFB lesions induced depressive-like behaviors in the sucrose preference and forced swimming tests. The activation or blockade of dHIP 5-HT4 receptors produced antidepressant effects in the MFB lesioned rats but not in control rats. Neurochemical results showed no changes of monoamines levels in the striatum, medial prefrontal cortex (mPFC), lateral habenula (LHb), and ventral hippocampus (vHIP) in control rats after intra-dHIP injection of 5-HT4 receptors agonist BIMU8 (26 μg/rat), antagonist GR 113808 (16 μg/rat) or GR 113808/BIMU8 (26 μg/16 μg/rat). But in the lesioned rats, BIMU8, GR113808 or GR 113808/BIMU8 injection increased dopamine levels in the striatum, mPFC, LHb, and vHIP and increased 5-HT levels in the LHb. Intra-dHIP injection of GR 113808 or GR 113808/BIMU8 also increased the noradrenaline levels in the mPFC and LHb. All these results suggest that activation or blockade dHIP 5-HT4 receptors produce antidepressant effects in the hemiparkinsonian rats, which may be related to the upregulation of 5-HT4 receptors in the dHIP and the changes of monoamines in the limbic and limbic-related brain regions.

Green coffee extract attenuates Parkinson's-related behaviors in animal models.

Epidemiological studies have shown an inverse association between coffee consumption and the development of Parkinson's disease (PD). The effects of the oral treatment with green (non-roasted) coffee extracts (CE, 100 or 400 mg/kg) and caffeine (31.2 mg/kg) were evaluated on catalepsy induced by haloperidol in mice, and unilateral 6-OHDA lesion of medial forebrain bundle (MFB) or striatum in rats. Also, the in vitro antioxidant activity and the monoamine levels in the striatum were investigated. CE presented a mild antioxidant activity in vitro and its administration decreased the catalepsy index. CE at the dose of 400 mg/kg induced ipsilateral rotations 14 days after lesion; however, chronic 30-day CE and caffeine treatments did not interfere with the animals' rotation after apomorphine or methamphetamine challenges in animals with MFB lesion, nor on monoamines levels. Furthermore, CE and caffeine were effective in inhibiting the asymmetry between ipsilateral and contralateral rotations induced by methamphetamine and apomorphine in animals with lesion in the striatum but did not avoid the monoamines depletion. These results indicate that CE components indirectly modulate dopaminergic transmission, suggesting a pro-dopaminergic action of CE, and further investigation must be conducted to elucidate the mechanisms of action and the possible neuroprotective role in PD.

Globus pallidus, but not entopeduncular nucleus, 6-OHDA-induced lesion attenuates L-Dopa-induced dyskinesia in the rat model of Parkinson's disease

Although extrastriatal dopaminergic (DAergic) systems are being recognized as contributors to Parkinson's disease (PD) pathophysiology, the role of extrastriatal DA depletion in L-Dopa-induced dyskinesia (LID) is still unknown. In view of the physiologic actions of DA on pallidal neuronal activity and the effects on motor behavior of local injection of DA drugs, the loss of the external (GPe, GP in rodents) and internal (GPi, entopeduncular nucleus (EP) in rodents) pallidal DAergic innervation might differentially contribute to LID. A role of pallidal serotonergic (SER) terminals in LID has been highlighted, however, the effect of DAergic innervation is unknown.We investigated the role of DAergic pallidal depletion on LID. Rats were distributed in groups which were concomitantly lesioned with 6-OHDA or vehicle (sham) in the GP, or EP, and in the medial forebrain bundle (MFB) as follows: a) MFB-sham+GP-sham, b) MFB-sham+GP-lesion, c) MFB-lesion+GP-sham, d) MFB-lesion+GP-lesion, e) MFB-sham+EP-sham, f) MFB-sham+EP-lesion, g) MFB-lesion+EP-sham, and h) MFB-lesion+EP-lesion. Four weeks later, animals were treated with L-Dopa (6 mg/kg) twice daily for 22 days.. Immunohistochemical studies were performed in order to investigate the changes in pallidal SER and serotonin transporter (SERT) levels.GP, but not EP, DAergic denervation attenuated LID in rats with a concomitant MFB lesion (p < 0.01). No differences were found in GP SERT expression between groups of animals developing or not LID.These results provide evidence of the relevance of GP DAergic innervation in LID. The conversion of levodopa to DA in GP serotonergic nerve fibers appears not to be the major mechanism underlying LID.

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-HT_1A) receptors are related to the regulation of depression. Objective:The purpose of the present study was to observe the effect of 5-HT_1A 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-HT_1A 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-HT_1A receptors regulate depression and PD-related depression by neurochemical mechanisms.

Upregulation of Cysteine Protease Cathepsin X in the 6-Hydroxydopamine Model of Parkinson's Disease.

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by loss of midbrain dopaminergic neurons in the substantia nigra pars compacta (SNc). In vitro, a contribution to neuroinflammation and neurotoxicity has been shown for the lysosomal protease cathepsin X; however, its expression and its role in PD remain unknown. Therefore, the current study was designed to address the regional, cellular, and subcellular localization and activity of cathepsin X in hemi-parkinsonian rats with 6-hydroxydopamine (6-OHDA)-induced excitotoxicity in the unilateral medial forebrain bundle (MFB) lesion. We report for the first time that cathepsin X expression and activity are rapidly increased in the ipsilateral SNc after injection of 6-OHDA into the MFB reaching a maximum after 12 h but seem to stay strongly upregulated after 4 weeks after injection. At early time points of 6-OHDA injection into the MFB, the increased cathepsin X is localized in the lysosomes in the neuronal, predominantly tyrosine hydroxylase-positive dopaminergic cells. After 12 h of 6-OHDA induced lesion, only a few activated microglial cells are positive for cathepsin X whereas, in 4 weeks post-lesion accompanied with complete loss of dopaminergic neurons, there is persistent cathepsin X upregulation restricted to activated glia cells. Taken together, our results demonstrate that cathepsin X upregulation in the lesioned dopaminergic system may play a role as a pathogenic factor in PD. Moreover, inhibition of cathepsin X expression or activity may be useful in protecting the nigrostriatal dopaminergic projection in the PD.

Involvement of prelimbic 5-HT7 receptors in the regulation of anxiety-like behaviors in hemiparkinsonian rats

ABSTRACTObjective: At present, little is known about the role of serotonin7 (5-HT7) receptor in anxiety, particularly in Parkinson’s disease-related anxiety. Here, we tested whether 5-HT7 receptors in the prelimbic (PrL) cortex are involved in the regulation of anxiety-like behaviors in sham-operated rats and rats with unilateral 6-hydroxydopamine lesions of the medial forebrain bundle (MFB).Methods: The open field and elevated plus maze (EPM) tests were performed to study the influence of MFB lesion and intra-PrL injection of 5-HT7 agonist AS19 (0.5, 1 or 2 μg/rat) and antagonist SB269970 (1.5, 3 or 6 μg/rat) on anxiety-like behaviors. Additionally, changes in monoamine levels in limbic and limbic-related brain regions were observed after intra-PrL injection of AS19 (2 μg/rat) and SB269970 (6 μg/rat).Results: The MFB lesion induced anxiety-like behaviors compared to sham-operated rats. Intra-PrL injection of AS19 showed anxiolytic effects by the open field and EPM tests in two groups of rats, and administration of SB269970 showed anxiogenic responses. However, the doses producing these effects in the lesioned rats were higher than those in sham-operated rats. Neurochemical results showed that intra-PrL injection of AS19 increased dopamine, 5-HT and noradrenaline (NA) levels in the medial prefrontal cortex, ventral hippocampus and amygdala in two groups of rats, whereas SB269970 decreased 5-HT and NA levels in these brain regions.Discussion: 5-HT7 receptors in the PrL are involved in the regulation of anxiety-like behaviors, which is attributable to changes in dopamine, 5-HT and NA levels in the limbic and limbic-related brain regions after activation and blockade of 5-HT7 receptors.Abbreviations: 6-OHDA: 6-hydroxydopamine; DMSO: dimethyl sulfoxide; DA: dopamine; EPM: elevated plus maze; MFB: medial forebrain bundlem; PFC: medial prefrontal cortex; NA: noradrenaline; PD: Pakinson's disease; PrL: prelimbic; 5-HT: serotonin; vHip: ventral hippocampus

Limitations of the rat medial forebrain lesion model to study prefrontal cortex mediated cognitive tasks in Parkinson’s disease

Parkinson’s Disease (PD) is a progressive movement disorder characterized by the loss of dopaminergic neurons in the midbrain. Besides motor impairment, PD patients exhibit non-motor symptoms that negatively impact their quality of life and often manifest prior to motor deficits. One such symptom is mild cognitive impairment (PD-MCI), which is comprised of deficits in executive function such as working memory, attention, cognitive flexibility, and spatial memory. The 6-hydroxydopamine (6-OHDA) induced unilateral medial forebrain bundle (MFB) lesion animal model successfully recapitulates PD motor impairment but is also used to assess non-motor deficits. The present study utilizes a unilateral 6-OHDA induced MFB lesion rodent model to investigate prefrontal cortex (PFC)-mediated cognitive processes that are impaired in PD patients. In a test of attentional set shifting, PD rodents demonstrated deficits in simple discrimination, but not in rule reversal or extradimensional shifts. PD rodents also exhibited deficits in a temporal order memory task but had no deficits in novel/spatial object recognition or object-in-place tasks. These results reveal limitations of the 6-OHDA induced unilateral MFB lesion model to completely recapitulate PD-MCI symptoms suggesting a need for better lesion models to study PD-MCI.

Gait Analysis for Early Detection of Motor Symptoms in the 6-OHDA Rat Model of Parkinson's Disease.

Computer-supported gait analysis has proven to be effective for the comprehensive assessment of gait changes in rodent models of neurodegenerative and neurological disorders. However, full characterization of individual gait parameters is required for specific neurological or neurodegenerative disorders such as Parkinson's disease (PD). Gait disturbances in particular present as the most constraining set of symptoms in PD, finally depriving patients from most activities of normal daily living. In this study, we have characterized the gait pattern abnormalities observed in two rat models of PD: the medial forebrain bundle (MFB) 6-OHDA lesion model and the striatal 6-OHDA lesion model. Our data indicates significant changes in 21 different gait parameters in the MFB lesion cohort. We observed a steady decline in the overall walking speed and cadence, as well as significant alterations in the gait parameters stride length, initial dual stance, paw print position, step cycle, swing phase of the step cycle, stand index, phase dispersion, print length, and print area in at least one of the paws. These alterations correlated with the extent of tyrosine hydroxylase (TH) neuronal loss observed in this group. These alterations were detected as early as 1 week post lesion. In contrast, limited gait dysfunction was detected in the striatal lesion cohort related to the low level of TH neuronal loss detected in this group. In this study we have demonstrated that gait analysis is a reliable method for the detection of motor deficiencies in a MFB 6-OHDA lesion model of PD and may prove a clinically relevant, low impact method of testing functional impairment as early as 1 week post lesion.

Lesions of the lateral habenula improve working memory performance in hemiparkinsonian rats.

The lateral habenula (LHb) is an important structure involved in various brain functions, because it controls the activity of dopaminergic and serotonergic systems in the midbrain. The impairment of working memory commonly occurs in Parkinson's disease; however, it is not clear whether the LHb involves in the regulation of working memory in rats with unilateral 6-hydroxydopamine lesions of the medial forebrain bundle (MFB). In this study, we found that the MFB lesions in rats decreased choice accuracy as measured by the T-maze rewarded alternation test compared to control rats, indicating the induction of working memory impairment, and decreased dopamine (DA) levels in the medial prefrontal cortex (mPFC), hippocampus and amygdala. Further, rats in the MFB and LHb lesion group showed increased choice accuracy compared to rats in the MFB lesion group, indicating the enhancement of working memory after lesioning the LHb. Neurochemical results found that lesions of the LHb increased DA levels in the mPFC, hippocampus and amygdala in the MFB and LHb lesion group, as well as serotonin (5-HT) level in the mPFC. These findings suggest that DA depletion plays a key role in working memory impairment, and lesions of the LHb improve working memory in the MFB-lesioned rats, which involves in increases in the levels of DA and 5-HT in the mPFC, hippocampus and amygdala. Additionally, the present results may have implications for improving our understanding of the neuropathology and/or treatment of PD.

Phrenic and hypoglossal nerve activity during respiratory response to hypoxia in 6-OHDA unilateral model of Parkinson's disease

AimsParkinson's disease (PD) patients apart from motor dysfunctions exhibit respiratory disturbances. Their mechanism is still unknown and requires investigation. Our research was designed to examine the activity of phrenic (PHR) and hypoglossal (HG) nerves activity during a hypoxic respiratory response in the 6-hydroxydopamine (6-OHDA) model of PD. Main methodsMale adult Wistar rats were injected unilaterally with 6-OHDA (20μg) or the vehicle into the right medial forebrain bundle (MFB). Two weeks after the surgery the activity of the phrenic and hypoglossal nerve was registered in anesthetized, vagotomized, paralyzed, and mechanically ventilated rats under normoxic and hypoxic conditions. Lesion effectiveness was confirmed by the cylinder test, performed before the MFB injection and 14days after, before the respiratory experiment. Key findings6-OHDA lesioned animals showed a significant increase in normoxic inspiratory time. Expiratory time and total time of the respiratory cycle were prolonged in PD rats after hypoxia. The amplitude of the PHR activity and its minute activity were increased in comparison to the sham group at recovery time and during 30s of hypoxia. The amplitude of the HG activity was increased in response to hypoxia in 6-OHDA lesioned animals. The degeneration of dopaminergic neurons decreased the pre-inspiratory/inspiratory ratio of the hypoglossal burst amplitude during and after hypoxia. SignificanceUnilateral MFB lesion changed the activity of the phrenic and hypoglossal nerves. The altered pre-inspiratory hypoglossal nerve activity indicates modifications to the central mechanisms controlling the activity of the HG nerve and may explain respiratory disorders seen in PD, i.e. apnea.

Polylysine-modified polyethylenimine (PEI-PLL) mediated VEGF gene delivery protects dopaminergic neurons in cell culture and in rat models of Parkinson's Disease (PD).

In this report, we exploited the potential of PEI-PLL to deliver VEGF gene for the potential therapeutic treatment of PD by using both cell culture and animal models of PD. To the best of our knowledge, this is the first report describing the use of novel polymeric gene carriers for the delivery of VEGF gene to DA neurons with improved transfection efficiency. Finally, the study will lead to a significant advancement in the field of non-viral PD gene therapy treatment.

Morphological Changes in a Severe Model of Parkinson's Disease and Its Suitability to Test the Therapeutic Effects of Microencapsulated Neurotrophic Factors.

The unilateral 6-hydroxydopamine (6-OHDA) lesion of medial forebrain bundle (MFB) in rats affords us to study the advanced stages of Parkinson's disease (PD). Numerous evidences suggest synergic effects when various neurotrophic factors are administered in experimental models of PD. The aim of the present work was to assess the morphological changes along the rostro-caudal axis of caudo-putamen complex and substantia nigra (SN) in the referred model in order to test the suitability of a severe model to evaluate new neurorestorative therapies. Administration of 6-OHDA into MFB in addition to a remarkable depletion of dopamine in the nigrostriatal system induced an increase of glial fibrillary acidic protein (GFAP)-positive cells in SN and an intense immunoreactivity for OX-42, vascular endothelial growth factor (VEGF), and Lycopersycum esculentum agglutinin (LEA) in striatum and SN. Tyrosine hydroxylase (TH) immunostaining revealed a significant decrease of the TH-immunopositive striatal volume in 6-OHDA group from rostral to caudal one. The loss of TH-immunoreactive (TH-ir) neurons and axodendritic network (ADN) was higher in caudal sections. Morphological recovery after the implantation of microspheres loaded with VEGF and glial cell line-derived neurotrophic factor (GDNF) in parkinsonized rats was related to the preservation of the TH-ir cell number and ADN in the caudal region of the SN. In addition, these findings support the neurorestorative role of VEGF+GDNF in the dopaminergic system and the synergistic effect between both factors. On the other hand, a topological distribution of the dopaminergic system was noticeable in the severe model, showing a selective vulnerability to 6-OHDA and recovering after treatment.

Altered melatonin MT1 receptor expression in the ventral midbrain following 6-hydroxydopamine lesions in the rat medial forebrain bundle

The indoleamine hormone melatonin protects dopamine neurons in the rat nigrostriatal pathway following 6-hydroxydopamine lesioning, and an increase in striatal melatonin levels has been detected in this model of Parkinson's disease. Melatonin induces the expression of tyrosine hydroxylase, the rate-limiting enzyme for dopamine synthesis, in the ventral midbrain, where G protein-coupled melatonin receptors are present. Based on the interaction between the melatonergic and dopaminergic systems, we hypothesized that 6-hydroxydopamine-induced degeneration of dopamine neurons would affect the expression of melatonin receptors in the nigrostriatal pathway. Following unilateral injection of 6-hydroxydopamine into the rat striatum or medial forebrain bundle, there was a significant increase in apomorphine-induced contralateral rotations in lesioned animals as compared to sham controls. A loss of tyrosine hydroxylase immunoreactivity and/or immunofluorescence in the striatum and substantia nigra was seen in animals lesioned in either the striatum or medial forebrain bundle, indicating degeneration of dopamine neurons. There were no significant differences in melatonin MT1 receptor protein expression in the striatum or substantia nigra, between intrastriatally lesioned animals and sham controls. In contrast, lesions in the medial forebrain bundle caused a significant increase in MT1 receptor mRNA expression (p<0.03) on the lesioned side of the ventral midbrain, as compared with the contralateral side. Given the presence of MT1 receptors on neurons in the ventral midbrain, these results suggest that a compensatory increase in MT1 transcription occurs to maintain expression of this receptor and neuroprotective melatonergic signaling in the injured brain.