6-OHDA Injection Research Articles

Expression of magnesium transporter SLC41A1 in the striatum of 6-hydroxydopamine-induced parkinsonian rats

ObjectivesThe aim of this study was to investigate the expression of the mammalian Mg2+ transporter solute carrier family 41, member 1 (SLC41A1) in the striatum (STR) of a 6-hydroxydopamine (6-OHDA)-induced rat model, and its response to magnesium before the degenerative process commenced. Materials and methodsA unilateral parkinsonian rat model was induced by injection of 6-OHDA into the right medial forebrain bundle. Some rats received MgSO4 (90 mg/kg/day, intraperitoneal injection) for 7 or 14 days starting from the day following the 6-OHDA injection. The extent of dopamine depletion was determined by assessing the numbers of tyrosine hydroxylase (TH)-immunoreactive neurons in the substantia nigra pars compacta (SNc) and the apomorphine (APO)-induced rotational behavior. The mRNA and protein expression of SLC41A1 in STR were evaluated by real-time RT-PCR and western blotting respectively. ResultsAPO-induced rotations increased significantly in the 6-OHDA lesioned rats compared with the controls, with MgSO4 administration significantly improving the behavior. The numbers of TH-immunoreactive neurons in SNc were significantly lower in the lesioned side than in the unlesioned side. Administration of MgSO4 for 14 days partly ameliorated the loss of TH-positive neurons. The mRNA and protein expressions of SLC41A1 in the lesioned STR were lower in the 6-OHDA lesioned rats than in the controls at both 7 and 14 days post-lesion induction. MgSO4 supplementation partly reversed the mRNA and protein expressions of SLC41A1. ConclusionThe regulation of SLC41A1 expression is responsive to magnesium in a 6-OHDA-induced rat model, wherein 6-OHDA may alter magnesium transport in the brain.

Orexinergic neurons are involved in the chemosensory control of breathing during the dark phase in a Parkinson's disease model

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra compacta (SNpc) and the only risk factor is aging. We showed that in 6-hydroxydopamine (6-OHDA)-model of PD there is a reduction in the neuronal profile within the brainstem ventral respiratory column with a decrease in the hypercapnic ventilatory response. Here we tested the involvement of orexin cells from the lateral hypothalamus/perifornical area (LH/PeF) on breathing in a 6-OHDA PD model. In this model of PD, there is a reduction in the total number of orexinergic neurons and in the number of orexinergic neurons that project to the RTN, without changing the number of CO2-activated orexinergic neurons during the dark phase. The ventilation at rest and in response to hypercapnia (7% CO2) was assessed in animals that received 6-OHDA or vehicle injections into the striatum and saporin anti-Orexin-B or IgG saporin into the LH/PeF during the sleep and awake states. The experiments showed a reduction of respiratory frequency (fR) at rest during the light phase in PD animals only during sleep. During the dark phase, there was an impaired fR response to hypercapnia in PD animals with depletion of orexinergic neurons in awake and sleeping rats. In conclusion, the degeneration of orexinergic neurons in this model of PD can be related to impaired chemoreceptor function in the dark phase.

Dopaminergic Lesion in the Olfactory Bulb Restores Olfaction and Induces Depressive-Like Behaviors in a 6-OHDA Model of Parkinson's Disease.

Olfactory impairments and depressive behavior are commonly reported by individuals with Parkinson's disease (PD) being observed before motor symptoms. The mechanisms underlying these clinical manifestations are not fully elucidated. However, the imbalance in dopaminergic neurotransmission seems to play an important role in this context. In patients and animal models of PD, an increase in the dopaminergic interneurons of the glomerular layer in olfactory bulb (OB-gl) is observed, which may contribute to the olfactory impairment. In addition, neuronal imbalance in OB is related to depressive symptoms, as demonstrated by chemical olfactory bulbectomy. In view of that, we hypothesized that a reduction in the number or density of dopaminergic neurons present in OB could promote an olfactory improvement and, in contrast, would accentuate the depressive-like behaviors in the 6-hydroxydopamine (6-OHDA) model of PD. Therefore, we performed single or double injections of 6-OHDA within the substantia nigra pars compacta (SNpc) and/or in the OB-gl. We observed that, after 7days, the group with nigral lesion exhibited olfactory impairment, as well as the group with the lesion in the OB-gl. However, the combination of the lesions prevented the occurrence of hyposmia. In relation to depressive-like behaviors, we observed that the SNpc injury promoted depressive-like behavior, being accentuated after a double injury. Our results demonstrated the importance of the dopaminergic neurons of the OB-gl in different non-motor features of PD, since the selective reduction of these periglomerular neurons was able to induce olfactory impairment and depressive-like behaviors.

Evaluation of the antiparkinsonism and neuroprotective effects of hydrogen sulfide in acute 6-hydroxydopamine-induced animal model of Parkinson’s disease: behavioral, histological and biochemical studies

Introduction: Studies have shown that hydrogen sulfide (H2S), a gaseous neurotransmitter, has neuroprotective effect. Here, we evaluated the neuroprotective activity of H2S in acute 6-hydroxydopamine (6-OHDA) animal model of Parkinson’s disease (PD).Methods: 6-OHDA was injected through stereotaxic surgery into medial forebrain bundle (MFB) of the right hemisphere to induce severe and fast degeneration in dopaminergic neurons of substantia nigra (SN). NaHS, as donor of H2S, was daily injected at doses of 3 and 5.6 mg/kg for seven days starting a few hours before the surgery. A series of behavioral tests were carried out and then, remaining tyrosine hydroxylase (TH)-positive neurons in substantia nigra pars compacta (SNc) was determined using immunohistfluresance staining. Striatal dopamine level and oxidative stress markers were also measured in the brain homogenates using immunosorbent assay kits.Results: NaHS attenuated apomorphine-induced rotational activity, decreased bias swings in elevated body swing test and increased falling time in rotarod test. Our histological and biochemical data demonstrated that NaHS treatment increases the survival of TH-positive neurons in SNc and also reduces the decreasing effect of 6-OHDA on striatal dopamine level. NaHS also reduced 6-OHDA-induced malondialdehyde overproduction but had no effect on the superoxide dismutase and glutathione peroxidase activity.Conclusion: Our results show that H2S produces significant antiparkinsonism and neuroprotective effects against 6-OHDA neurotoxicity. Since injection of 6-OHDA into MFB produces severe lesion in SN dopaminergic neurons similar to this lesion in the onset of PD in human being, our data recommend H2S as potential therapeutic target for treatment of this disease.

Glucose-Dependent Insulinotropic Polypeptide Mitigates 6-OHDA-Induced Behavioral Impairments in Parkinsonian Rats.

In the present study, the effectiveness of glucose-dependent insulinotropic polypeptide (GIP) was evaluated by behavioral tests in 6-hydroxydopamine (6-OHDA) hemi-parkinsonian (PD) rats. Pharmacokinetic measurements of GIP were carried out at the same dose studied behaviorally, as well as at a lower dose used previously. GIP was delivered by subcutaneous administration (s.c.) using implanted ALZET micro-osmotic pumps. After two days of pre-treatment, male Sprague Dawley rats received a single unilateral injection of 6-OHDA into the medial forebrain bundle (MFB). The neuroprotective effects of GIP were evaluated by apomorphine-induced contralateral rotations, as well as by locomotor and anxiety-like behaviors in open-field tests. Concentrations of human active and total GIP were measured in plasma during a five-day treatment period by ELISA and were found to be within a clinically translatable range. GIP pretreatment reduced behavioral abnormalities induced by the unilateral nigrostriatal dopamine (DA) lesion produced by 6-OHDA, and thus may be a novel target for PD therapeutic development.

Splenic 6‐hydroxydopamine Worsens Renal Inflammation and Injury in a Murine Model of Systemic Lupus Erythematosus

Renal inflammation is prevalent in the chronic autoimmune disease systemic lupus erythematosus (SLE) and drives the progression of kidney injury, which contributes to the morbidity and mortality. Inflammation in SLE results from a loss of self‐tolerance and the production of autoantibodies against nuclear antigens (e.g., anti‐double‐stranded (ds) DNA autoantibodies); however, other immunoregulatory mechanisms such as the cholinergic anti‐inflammatory pathway may also be dysregulated and contribute to aberrant systemic and renal inflammation in the disease. The cholinergic anti‐inflammatory pathway is a protective, neuroimmune mechanism thought to involve neurotransmission between the parasympathetic vagus and the sympathetic splenic nerves. Although a direct anatomical connection between the vagus and the splenic nerve is controversial, stimulation of these nerves results in a decrease in the production and release of pro‐inflammatory cytokines from splenic immune cells. In order to confirm the importance of the splenic nerve in this pathway, others have used 6‐hydroxydopamine (6OHDA), a neurotoxin that depletes catecholamines, to chemically denervate the spleen and thereby dampen the sympathetic component of the cholinergic anti‐inflammatory pathway. We hypothesized that splenic injection of 6OHDA would further disrupt the cholinergic anti‐inflammatory pathway in a mouse model of SLE and result in increased renal inflammation and worsened disease severity, which would highlight the importance of the splenic nerve in quelling renal inflammation. In the current study, female SLE and control mice were injected with 6OHDA (120 μg in 60 μl saline) or vehicle directly into the spleen at 33 weeks of age (n = 6/group). To confirm splenic denervation with 6OHDA, we utilized the glyoxylic acid condensation reaction on 12 μm spleen sections of representative animals and verified that catecholamine histofluorescence was diminished in 6OHDA‐treated mice (205 vs. 111 histofluorescent foci). Renal cortical TNF‐α (normalized to total protein) was increased in SLE mice compared to controls (3.1e6 ± 1.2e5 vs. 7.8e5 ± 1.6e4 intensity units; p = 0.029), and 6OHDA exacerbated this pro‐inflammatory cytokine in SLE mice (7.6e6 ± 2.4 intensity units; p = 0.048) with no effect in controls (1.8e6 ± 7.0e5 intensity units; p = 0.697). Anti‐dsDNA autoantibodies were elevated in SLE mice compared to controls (2.1e4 ± 5.7e3 vs. 1.0e4 ± 4.7e3 activity units; p = 0.013), but 6OHDA did not alter this measure of disease severity in SLE mice (1.8e4 ± 5.2e3 activity units; p = 0.692). Albumin excretion rate (AER) was elevated in SLE mice compared to controls (160.7 ± 28.0 vs. 2.7 ± 2.7 mg/dL; p < 0.001). 6OHDA accentuated the increase in AER in SLE mice (454.2 ± 150.2 mg/dL; p = 0.010) but had no effect in controls (27.5 ± 17.0 mg/dL; p = 0.754). In summary, 6OHDA aggravated renal inflammation and injury in SLE mice indicated by heightened renal cortical TNF‐α and AER. This suggests that chemical splenic denervation may disrupt endogenous, sympathetically‐mediated anti‐inflammatory mechanisms. Further studies are needed to confirm the role of the splenic nerve in regulating renal inflammation.Support or Funding InformationFunded by AHA grants 14SDG18320033 (KWM), 16PRE29910012 (GSP), and UNTHSC Intramural FundingThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A comprehensive map coupling histone modifications with gene regulation in adult dopaminergic and serotonergic neurons

The brain is composed of hundreds of different neuronal subtypes, which largely retain their identity throughout the lifespan of the organism. The mechanisms governing this stability are not fully understood, partly due to the diversity and limited size of clinically relevant neuronal populations, which constitute a technical challenge for analysis. Here, using a strategy that allows for ChIP-seq combined with RNA-seq in small neuronal populations in vivo, we present a comparative analysis of permissive and repressive histone modifications in adult midbrain dopaminergic neurons, raphe nuclei serotonergic neurons, and embryonic neural progenitors. Furthermore, we utilize the map generated by our analysis to show that the transcriptional response of midbrain dopaminergic neurons following 6-OHDA or methamphetamine injection is characterized by increased expression of genes with promoters dually marked by H3K4me3/H3K27me3. Our study provides an in vivo genome-wide analysis of permissive/repressive histone modifications coupled to gene expression in these rare neuronal subtypes.

Effects of the Serotonin 5-HT1A Receptor Biased Agonists, F13714 and F15599, on Striatal Neurotransmitter Levels Following L-DOPA Administration in Hemi-Parkinsonian Rats.

Peak-dose dyskinesia is associated with the dramatic increase in striatal dopamine levels that follows L-DOPA administration. The 'false neurotransmitter' hypothesis postulates that the latter is likely due to an aberrant processing of L-DOPA by serotonergic neurons. In keeping with this hypothesis, two highly selective 'biased agonists' of 5-HT1A receptors-namely F13714 and F15599 (NLX-101)-were recently shown to exhibit exceptionally potent anti-dyskinetic activity without impairing L-DOPA therapeutic properties despite their differential targeting of 5-HT1A receptor sub-populations. In this study, we investigated whether these two compounds dampened peak L-DOPA-induced dopamine microdialysate levels in the striatum of hemi-parkinsonian rats. Acute administration of either F13714 (0.04 and 0.16mg/kg i.p.) or F15599 (0.16 and 0.64mg/kg, i.p.) blunted L-DOPA (2mg/kg)-induced increases in dopamine microdialysate levels in the denervated striatum (following unilateral injection of 6-OHDA into the medial forebrain bundle). No significant changes were observed on the intact side of the brain. Concurrently, both drugs profoundly reduced striatal serotonin levels on both sides of the brain. In addition, F13714 and F15599, in the presence of L-DOPA, produced a dose-dependent increase in glutamate levels, but this effect was restricted to later time points. These finding support the interpretation that F13714 and F15599 mediate their anti-dyskinetic effects by blunting of the peak in dopamine levels via activation of somatodendritic serotonin 5-HT1A receptors and the consequent inhibition of serotonergic neurons. This study adds to the growing body of evidence supporting the development of a potent 5-HT1A receptor agonist for treatment of peak-dose dyskinesia.

P.2.005 - Knock-down of G protein-coupled receptor 88 in the striatum reduces psychiatric symptoms in a rat non-motor model of Parkinson’s disease

Although Parkinson's disease (PD) is commonly defined as a progressive motor disorder, it entails many psychiatric non-motor symptoms (NMS) such as depression and cognitive alterations that are irresponsive to L-DOPA treatment and are thus in need of new and more specific targets for their treatment. This underpins interest in Gpr88, a brain-specific orphan G-protein coupled receptor whose expression in the striatal medium spiny neurons is modulated by L-DOPA as well as 6-hydroxydopamine (6OHDA) lesions [1]. Knock-down (KD) of Gpr88 in the ventral striatum (STR) normalizes motor and cognitive alterations in a rat model of psychosis [2], so in this study, we evaluated the impact of Gpr88-KD on depressed mood, sensorimotor gating and social recognition in a model of psychiatric NMS of PD. Partial lesions reproducing several psychiatric symptoms of PD were induced by bilateral stereotaxic injections of 6OHDA (12µg/hemisphere), or control saline, in the dorsolateral STR of rats. Then, Gpr88 was knocked-down using a lentiviral vector co-expressing the emerald Green Fluorescent Protein (emGFP) marker and either a specific (miR-Gpr88) or control (miR-neg) microRNA. These vectors were bilaterally injected into either the ventral (v), dorsomedial (dm), or dorsolateral (dl) STR (2 or 6µl/hemisphere, in the ventral or dorsal regions respectively). The rats were then tested for: depression with the forced swim test (FST); sensorimotor filtering with the Prepulse Inhibition test (PPI, prepulses ranging from 70-80dB and pulse = 110dB); and social recognition with the social novelty discrimination (SND) test, which measures discrimination of a novel from a familiar juvenile rat (score ≥ 3 in controls). The efficacy of the 6-OHDA lesion was quantified by the loss of Tyrosine Hydroxylase (TH) immunofluorescence, and the lentiviral transduction extent and location was validated by emGFP detection. Statistical analyses were performed using one-way ANOVA followed by Bonferroni corrections. Results are expressed as means ± SEM. The 6-OHDA lesion was limited to the dlSTR where it induced a significant loss of TH immunoreactivity (-57.10% ± 4.23, p Taken together, these results indicate that striatal Gpr88 KD moderates striatal dopamine depletion related alterations in mood, sensory motor gating and social discrimination in a model of NMS of PD. This study thus highlights the relevance of GPR88 as a potential target for the control of the psychiatric symptoms of PD, and possibly of other neuropsychiatric diseases.

Analysis of respiratory movements in a mouse model of late Parkinson’s disease submitted to stress

Parkinson’s disease (PD) is known to cause tremor and rigidity, but other symptoms such as respiratory and autonomic dysfunctions are a major cause of disability and mortality in patients. In this study, we examined respiratory movements by using cineradiography on a murine model of late/advanced PD. Under surgical anesthesia, C57BL/6J mice received an injection of either 6-OHDA or vehicle solution to the right striatum. Two weeks after surgery, the animals had their respiratory movements recorded by video X-ray without any restraint. During recordings the animals were submitted to a mild acute-stress challenge. Behavioral tests were performed to assess the severity of the 6-OHDA lesion. As a result, behavioral tests confirmed severe motor impairments in 6-OHDA mice as compared to controls. 6-OHDA mice showed a predominantly thoracic respiratory pattern with reduced diaphragmatic excursion, and reduced respiratory frequency after stress. These results suggest that advanced nigrostrial degeneration may cause respiratory alterations with the features of obstructive-type respiratory disorders.

Pirouetting pigs: A large non-primate animal model based on unilateral 6-hydroxydopamine lesioning of the nigrostriatal pathway

IntroductionThe rotating 6-hydroxydopamine (6-OHDA) rat model has long been important when developing new treatment strategies for Parkinson’s disease (PD). Similar non-human primate models have been developed for translational research purposes as large animal models are required by regulatory bodies as an intermediate “phase 0” trial step. However, experimental research in non-human primates encounters several economical and regulatory issues, which may be avoided by the alternative use of pigs as a large animal model for experimental brain research. ObjectiveThe primary aim of this study was to examine if unilateral injections of 6-OHDA into the Göttingen minipig nigrostriatal pathway would lead to dopaminergic imbalance and rotational behavior similar to the 6-OHDA unilateral symptomatic model of PD created in other species. The secondary aim was to attempt to verify the rotational behavior as a parkinsonian symptom using subthalamic deep brain stimulation (STN-DBS) to minimize the elicited rotational pattern. Materials and methodsUsing an MRI-based stereotactic procedure, ten female Göttingen minipigs were injected unilaterally with 6-OHDA in the nigrostriatal pathway. Postoperatively, an MRI was performed, and the animals were injected with amphetamine and apomorphine and observed for rotational behavior. After a survival period of three months the brains were removed and immunohistochemically stained for tyrosine hydroxylase (TH). One week before sacrifice two animals had DBS electrodes unilaterally implanted in the subthalamic nucleus and various stimulation protocols were conducted during amphetamine challenge. ResultsAs expected most animals rotated towards the side of the lesion when given amphetamine (3.5–4.0 mg/kg), whereas the predicted opposite response to apomorphine were much harder to reproduce. T1- and T2-weighted postoperative MRI could demonstrate the size and the location of the 6-OHDA injection. Postmortem TH-staining of the final two animals receiving a medial and a lateral injection of 25 μL of 6-OHDA (8 μg/μL, injection rate 5 μL/min) into the diencephalic nigrostriatal pathway showed a prominent unilateral decrease in TH-staining of the substantia nigra pars compacta, the ventral tegmental area and the nigrostriatal pathway on the lesioned side. These two animals displayed spontaneous rotational behavior toward the lesioned side for the first 2–3 days postoperatively, and this behavior could later on be reelicited by amphetamine and attenuated by ipsilateral STN-DBS. ConclusionFemale Göttingen minipigs are susceptible to unilateral dopaminergic degeneration when properly injected unilaterally with sufficient amounts of 6-OHDA in the nigrostriatal pathway. The location of the 6-OHDA injections and thus the accuracy of the employed stereotaxy can be verified in vivo using MRI postoperatively. The injected minipigs display unilateral parkinsonism with a well-defined rotational response to amphetamine that may be ameliated by STN-DBS performed on the lesioned side. The response to apomorphine was, however, not consistent, illustrating that further work on this promising non-primate large animal model is needed, before it is fully similar to the established 6-OHDA models in other species.

Dopamine, Noradrenaline and Serotonin Receptor Densities in the Striatum of Hemiparkinsonian Rats following Botulinum Neurotoxin-A Injection

Parkinson’s disease (PD) is characterized by a degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) that causes a dopamine (DA) deficit in the caudate-putamen (CPu) accompanied by compensatory changes in other neurotransmitter systems. These changes result in severe motor and non-motor symptoms. To disclose the role of various receptor binding sites for DA, noradrenaline, and serotonin in the hemiparkinsonian (hemi-PD) rat model induced by unilateral 6-hydroxydopamine (6-OHDA) injection, the densities of D1, D2/D3, α1, α2, and 5HT2A receptors were longitudinally visualized and measured in the CPu of hemi-PD rats by quantitative in vitro receptor autoradiography. We found a moderate increase in D1 receptor density 3 weeks post lesion that decreased during longer survival times, a significant increase of D2/D3 receptor density, and 50% reduction in 5HT2A receptor density. α1 receptor density remained unaltered in hemi-PD and α2 receptors demonstrated a slight right-left difference increasing with post lesion survival.In a second step, the possible role of receptors on the known reduction of apomorphine-induced rotations in hemi-PD rats by intrastriatally injected Botulinum neurotoxin-A (BoNT-A) was analyzed by measuring the receptor densities after BoNT-A injection. The application of this neurotoxin reduced D2/D3 receptor density, whereas the other receptors mainly remained unaltered.Our results provide novel data for an understanding of the postlesional plasticity of dopaminergic, noradrenergic and serotonergic receptors in the hemi-PD rat model. The results further suggest a therapeutic effect of BoNT-A on the impaired motor behavior of hemi-PD rats by reducing the interhemispheric imbalance in D2/D3 receptor density.

Protective and therapeutic activity of honokiol in reversing motor deficits and neuronal degeneration in the mouse model of Parkinson's disease.

Parkinson's disease (PD) is a progressive and profound movement disorder resulting from neurodegeneration in the nigrostriatal dopaminergic system, but current treatment neither cures nor stops PD from advancing. Based on the ability to suppress oxidative stress, excitotoxicity, and neuroinflammation, the potential of honokiol as a novel neuroprotective agent for PD treatment was determined. The hemi-parkinsonian model was used to investigate the protective and therapeutic effects of honokiol on motor dysfunctions and dopaminergic neurodegeneration in mice, with a single unilateral striatal injection of 6-hydroxydopamine (6-OHDA). One day after 6-OHDA-induced lesion, the mice exhibited spontaneous ipsilateral turning, motor imbalance, and incoordination which were mild with a single administration of honokiol prior to 6-OHDA injection. Thereafter, honokiol was continually applied daily for 14 days, which ameliorated apomorphine-induced contralateral rotation and reduced the loss of tyrosine hydroxylase-immunoreactive (TH-ir) fibers in the lesioned striatum. In addition, honokiol posttreatment, beginning on day 8 after 6-OHDA lesion, for 14 days efficiently rescued motor deficits and recovered the TH-ir neuronal loss in both the lesioned striatum and the ipsilateral substantia nigra. The 6-OHDA-induced increases in nigrostriatal expression of inducible nitric oxide synthase (iNOS) and decreases in that of nNOS were also reversed by honokiol posttreatment. These findings revealed that honokiol has both protective and therapeutic effects on motor impairments and dopaminergic progressive damage, at least in part through modulation of NOS signaling, in 6-OHDA-lesioned mice. Honokiol may represent a potential therapeutic candidate for the management of motor symptoms and neurodegeneration in PD.

Apelin-13 ameliorates cognitive impairments in 6-hydroxydopamine-induced substantia nigra lesion in rats

Although Parkinson's disease (PD) is well known with its motor deficits, the patients often suffer from cognitive dysfunction. Apelin, as the endogenous ligand of the APJ receptor, is found in several brain regions such as substantia nigra and mesolimbic pathway. However, the role of apelin in cognition and cognitive disorders has not been fully clarified. In this study the effects of apelin-13 were investigated on cognitive disorders in rat Parkinsonism experimental model. 6-hydroxydopamine (6-OHDA) was administrated into the substantia nigra. Apelin-13 (1, 2 and 3μg/rat) was administered into the substantia nigra one week after the 6-OHDA injection. Morris water maze (MWM), object location and novel object recognition tests were performed one month after the apelin injection. 6-OHDA-treated animals showed a significant impairment in cognitive functions which was revealed by the increased in the escape latency and traveled distance in MWM test and decreased in the exploration index in novel object recognition and object location tasks. Apelin-13 (3μg/rat) significantly attenuates the mentioned cognitive impairments in 6-OHDA-treated animals.In conclusion, the data support the pro-cognitive property of apelin-13 in 6-OHDA-induced cognitive deficit and provided a new pharmacological aspect of the neuropeptide apelin.

Salidroside Protection Against Oxidative Stress Injury Through the Wnt/β-Catenin Signaling Pathway in Rats with Parkinson’s Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease, and recent studies suggested that oxidative stress (OS) contributes to the cascade that leads to dopamine cell degeneration in PD. In this study, we hypothesized that salidroside (SDS) offers protection against OS injury in 6-hydroxydopamine (6-OHDA) unilaterally lesioned rats as well as the underlying mechanism. SDS and LiCl (activators of the Wnt/β-catenin signaling pathway) administration alone and in combination with 6-OHDA injection in rats was performed 3 days before modeling for 17 consecutive days to verify the regulatory mechanism by which SDS affects the Wnt/β-catenin signaling pathway as well as to evaluate the protective effect of SDS on PD in relation to OS in vivo. In addition, pheochromocytoma 12 (PC12) cells were incubated with 10 µmol/L SDS or LiCl alone or with both in combination for 1 h followed by a 24-h incubation with 100 µmol/L 6-OHDA to obtain in vitro data. In vivo the administration of LiCl was found to ameliorate behavioral deficits and dopaminergic neuron loss; increase superoxide dismutase (SOA) activity, glutathione peroxidase (GSH-Px) levels, and glycogen synthase kinase 3β phosphorylation (GSK-3β-Ser9); reduce malondialdehyde (MDA) accumulation in the striatum and the GSK-3β mRNA level; as well as elevate β-catenin and cyclinD1 mRNA and protein levels in 6-OHDA-injected rats. This SDS treatment regimen was found to strengthen the beneficial effect of LiCl on 6-OHDA-injected rats. In vitro LiCl treatment decreased the toxicity of 6-OHDA on PC12 cells and prevented apoptosis. Additionally, LiCl treatment increased SOA activity, GSH-Px levels, and GSK-3β-Ser9 phosphorylation; decreased MDA accumulation in the striatum and GSK-3β mRNA levels; as well as increased β-catenin and cyclinD1 mRNA and protein levels in 6-OHDA-treated PC12 cells. Additionally, SDS treatment increased the protective effect of LiCl on 6-OHDA-treated PC12 cells. Evidence from experimental models suggested that SDS may confer neuroprotection against the neurotoxicity of 6-OHDA in response to OS injury and showed that these beneficial effects may be related to regulation of the Wnt/β-catenin signaling pathway. Therefore, SDS might be a potential therapeutic agent for treating PD.

Time-course behavioral features are correlated with Parkinson's disease‑associated pathology in a 6-hydroxydopamine hemiparkinsonian rat model.

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. For decades, the unilateral 6-hydroxydopamine (6-OHDA) rat model has been employed to investigate the pathogenesis and therapy of PD. However, the behavior and associated pathological features of the model long term have not previously been described dynamically. In the present study, the unilateral model was established by 6-OHDA injection in the striatum. The PD rat model was determined 2 weeks following surgery, according to the apomorphine (APO)-induced rotations, cylinder, rotarod and open field tests. TH-positive neurons and fibers in the substantia nigra pars compacta (SNpc) and striatum, respectively, and glial activation in the SNpc, determined by glial fibrillary acidic protein (GFAP) expression for astrocytes and CD11b (Mac1) expression for microglia, were detected by immunohistological staining. Correlation analysis was performed to understand the association between PD-associated behavior and pathology. The behavioral impairment progressively deteriorated during the process of experiment. In addition, the decrease in TH-positive neurons was associated with an increase in GFAP- and Mac1-positive cells in the SNpc. Linear regression analysis indicated the association between behavioral and pathological changes. The results of the present study indicate that the APO-induced rotation, cylinder and rotarod tests are all sensitive and reliable strategies to predict the loss of TH+ neurons. These results provide a potential intervention time-point and a comprehensive evaluation index system for assessment of PD therapeutic strategies using the hemiparkinsonian rat.

Raphe Pallidus is Not Important to Central Chemoreception in a Rat Model of Parkinson’s Disease

Central chemoreceptors are primarily sensitive to changes in CO2/H+, and such changes lead to intense breathing activity. Medullary raphe and retrotrapezoid nucleus (RTN) neurons are candidates for central chemoreceptors because they are unusually pH sensitive. The pathophysiology of Parkinson’s disease (PD) is related to the reduction of neurons in the substantia nigra pars compacta (SNpc) that express dopamine, although other neurons can also be degenerated in this pathology. In rodent models of PD, we showed an impairment of the hypercapnia ventilatory response due to a reduction in the number of RTN chemosensitive neurons. Here, we aimed to investigate if serotonine-expressing neurons in the Raphe pallidus/parapyramidal region (RPa/PPy) are also involved in the modulation of breathing during central chemoreception activation in a PD animal model. PD was induced in male Wistar rats with bilateral injection of 6-OHDA (6-hydroxydopamine; 24 µg/µl) into the striatum, which leads to a reduction in the catecholaminergic neurons of the SNpc by 89%. In PD animals, we noticed a reduction in the number of RPa neurons that project to the RTN, without a change in the number of hypercapnia-activated (7% CO2) raphe neurons. The PD animals that received injection of the toxin saporin anti-SERT into the RPA/PPy region did not show a further reduction of respiratory frequency (fR) or ventilation (VE) at rest or during hypercapnia challenge. These experiments demonstrate that serotonergic neurons of RPa/PPy are not involved in the breathing responses induced by central chemoreceptor activation in a PD animal model.

Protective role of chrysin on 6-hydroxydopamine-induced neurodegeneration a mouse model of Parkinson's disease: Involvement of neuroinflammation and neurotrophins

Chrysin is a natural flavonoid which is found in bee propolis, honey and various plants, and neuroprotective effect of chrysin in mice was previously demonstrated by our group. Neuroinflammation, neurotrophic factors and neuronal recovery factors associated with the neuroprotective effect of this flavonoid require further investigations. Thus, now we investigated the possible involvement of inflammatory cytokines, neurotrophic factors and neuronal recovery in the effect of chrysin in 6-hydroxidopamine (6-OHDA), a well-established model of Parkinson's disease, in striatum of mice. The 6-OHDA microinjection induced behavioral alterations on the rotarod test and apomorphine-induced circling behavior in mice. 6-OHDA administration elevated levels of tumour necrosis factor-α, interferon-gamma, interleukin-1β, interleukin-2, interleukin-6 and nuclear factor-kappa B and decreased the interleukin-10 levels, total reactive antioxidant potential and total antioxidant reactivity in striatum, as well as, modified the calcium-binding protein B (S100B), brain-derived neurotrophic factor, nerve growth factor and glial cell line-derived neurotrophic factor levels. The intrastriatal injection of 6-OHDA also induced an decrease of dopamine, 3,4-dihydroxyphenylacetic acid, homovanylic acid levels and tyrosine hydroxylase content. Oral treatment with chrysin (10 mg/kg, 28 days), culminated with the prevention of these alterations occasioned by 6-OHDA. These results corroborated with the neuroprotective effect of chrysin in the treatment of Parkinson's disease and, indicated the mechanism involved throught the inflammatory cytokines, neurotrophic factors and recovery of dopaminergic neurons in striatum.

Impaired chemosensory control of breathing after depletion of bulbospinal catecholaminergic neurons in rats.

Bulbospinal catecholaminergic neurons located in the rostral aspect of the ventrolateral medulla (C1 neurons) or within the ventrolateral pons (A5 neurons) are involved in the regulation of blood pressure and sympathetic outflow. A stimulus that commonly activates the C1 or A5 neurons is hypoxia, which is also involved in breathing activation. Although pharmacological and optogenetic evidence suggests that catecholaminergic neurons also regulate breathing, a specific contribution of the bulbospinal neurons to respiratory control has not been demonstrated. Therefore, in the present study, we evaluated whether the loss of bulbospinal catecholaminergic C1 and A5 cells affects cardiorespiratory control during resting, hypoxic (8% O2), and hypercapnic (7% CO2) conditions in unanesthetized rats. Thoracic spinal cord (T4-T8) injections of the immunotoxin anti-dopamine β-hydroxylase-saporin (anti-DβH-SAP-2.4ng/100nl) and the retrograde tracer Fluor-Gold or ventrolateral pontine injections of 6-OHDA were performed in adult male Wistar rats (250-280g, N=7-9/group). Anti-DβH-SAP or 6-OHDA eliminated most bulbospinal C1 and A5 neurons or A5 neurons, respectively. Serotonergic neurons and astrocytes were spared. Depletion of the bulbospinal catecholaminergic cells did not change cardiorespiratory variables under resting condition, but it did affect the response to hypoxia and hypercapnia. Specifically, the increase in the ventilation, the number of sighs, and the tachycardia were reduced, but the MAP increased during hypoxia in anti-DβH-SAP-treated rats. Our data reveal that the bulbospinal catecholaminergic neurons (A5 and C1) facilitate the ventilatory reflex to hypoxia and hypercapnia.

Intrastriatal Chromospheres’ Transplant Reduces Nociception in Hemiparkinsonian Rats

The present study evaluates the possible antinociceptive effect of chromosphere transplants in rats injected with 6-hydroxydopamine (6-OHDA), a model of Parkinson’s disease. Male adult Wistar rats received 40μg/0.5μl of 6-OHDA or 0.5μl of vehicle into the left substantia nigra (SNc). Rats were evaluated for mechanical allodynia, cold allodynia, thermal hyperalgesia and formalin. Rats with altered nociceptive threshold were transplanted with chromospheres. After transplant, rats were evaluated every week. Our results confirm that 6-OHDA injection into rat’s SNc reduces mechanical, thermal, and chemical thresholds. Interestingly, chromospheres’ transplant reverted 6-OHDA-induced allodynia and hyperalgesia. The antinociceptive effect induced by chromospheres was dopamine D2- and opioid-receptor dependent since sulpiride or naltrexone reverted its effect.