6-OHDA Lesioned Rats Research Articles

Effects of bromelain on striatal neuroinflammation in rat model of Parkinsonism

Background: Neuroinflammation alters the microenvironment in certain areas of the brain resulting in the development of Parkinson's disease (PD). Mechanisms involving cytokine and non-cytokine induced pathways are activated in the inflammatory response following injury. The proteolytic activity of bromelain appears to eliminate receptors on immune cells that respond to pro-inflammatory signals. This raises the question of whether manipulation of the inflammatory response pathways could lead to a beneficial intervention for PD. In this study, we investigated the effect of bromelain exposure on pro-inflammatory cytokine concentration and microglial activation in a parkinsonian rat model. Methods: Nigrostriatal dopamine neurons were lesioned by stereotaxic injection of the neurotoxin, 6-OHDA, into the medial forebrain bundle (MFB) of male Sprague-Dawley rats with weight ranging from 230- 250 g. The anti-inflammatory drug bromelain was used to treat a subset of the rats before or 24 h post 6-OHDA lesion. The systemic blood concentration of neutrophils and platelets was measured along with plasma and striatal concentrations of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α. In addition, the densities of CD11b and CD86 cells were differently quantified as a measure of glial cell activation. ResultsPre-treatment with bromelain decreased the plasma concentration of neutrophils and platelets in 6-OHDA lesioned rats. The bromelain treatments (Pre and Post) decreased the plasma concentration of TNF-α and IL-1β. Pre-treatment with bromelain further resulted in the suppression of both systemic pro-inflammatory cytokines and microgliosis. Post-surgical bromelain treatment significantly resulted in the alleviation of systemic pro-inflammatory cytokines. ConclusionEarly treatment with bromelain may slow the progression of PD by attenuating the inflammatory response associated with the disease. The present results suggest that bromelain may be considered for further clinical study and perhaps use as prophylactic treatment for patients with PD.

Nigrostriatal dopamine depletion promoted an increase in inhibitory markers (parvalbumin, GAD67, VGAT) and cold allodynia

Pain constitutes the major non-motor symptom in Parkinson’s disease (PD). Its mechanism is still poorly understood although an increase in excitation or a decrease in inhibition have been reported in preclinical studies. The aim of this study was to investigate gamma aminobutyric acid (GABA) inhibition in the 6-hydroxydopamine (6-OHDA) PD rat model. Therefore, the expression of three inhibitory markers parvalbumin, glutamate decarboxylase 67 (GAD67) and vesicular GABA transporter (VGAT) was evaluated, besides cold allodynia, in bilateral 6-OHDA lesioned rat. There was a significant increase in the expression of the three markers labeling within the spinal dorsal horn (SDH) of 6-OHDA lesioned rats. In parallel, there was also an increase of the excitatory marker protein kinase C gamma (PKCγ) . PKCγ cells have a crucial role in pain chronicity and are regulated by GABAergic influences. Central dopamine depletion induced an increase in excitation as reveled by an increase in cFOS expression upon acetone stimulus and the presence of cold allodynia. In addition, dopamine depletion induced increased expression in inhibitory markers, which may reflect a disinhibition or a decreased inhibition in 6-OHDA lesioned rats.

Exercise protects synaptic density in a rat model of Parkinson's disease

BackgroundParkinson's disease (PD) is characterized by Lewy body and neurite pathology associated with dopamine terminal dysfunction. Clinically, it is associated with motor slowing, rigidity, and tremor. Postural instability and pain are also features. Physical exercise benefits PD patients - possibly by promoting neuroplasticity including synaptic regeneration. ObjectivesIn a parkinsonian rat model, we test the hypotheses that exercise: (a) increases synaptic density and reduces neuroinflammation and (b) lowers the nociceptive threshold by increasing μ-opioid receptor expression. MethodsBrain autoradiography was performed on rats unilaterally injected with either 6-hydroxydopamine (6-OHDA) or saline and subjected to treadmill exercise over 5 weeks. [3H]UCB-J was used to measure synaptic vesicle glycoprotein 2A (SV2A) density. Dopamine D2/3 receptor and μ-opioid receptor availability were assessed with [3H]Raclopride and [3H]DAMGO, respectively, while neuroinflammation was detected with the 18kDA translocator protein (TSPO) marker [3H]PK11195. The nociceptive threshold was determined prior to and throughout the exercise protocol. ResultsWe confirmed a dopaminegic deficit with increased striatal [3H]Raclopride D2/3 receptor availability and reduced nigral tyrosine hydroxylase immunoreactivity in the ipsilateral hemisphere of all 6-OHDA-injected rats. Sedentary rats lesioned with 6-OHDA showed significant reduction of ipsilateral striatal and substantia nigra [3H]UCB-J binding while [3H]PK11195 showed increased ipsilateral striatal neuroinflammation. Lesioned rats who exercised had higher levels of ipsilateral striatal [3H]UCB-J binding and lower levels of neuroinflammation compared to sedentary lesioned rats. Striatal 6-OHDA injections reduced thalamic μ-opioid receptor availability but subsequent exercise restored binding. Exercise also raised thalamic and hippocampal SV2A synaptic density in 6-OHDA lesioned rats, accompanied by a rise in nociceptive threshold. ConclusionThese data suggest that treadmill exercise protects nigral and striatal synaptic integrity in a rat lesion model of PD - possibly by promoting compensatory mechanisms. Exercise was also associated with reduced neuroinflammation post lesioning and altered opioid transmission resulting in an increased nociceptive threshold.

Roles of Motor Cortex Neuron Classes in Reach-Related Modulation for Hemiparkinsonian Rats.

Disruption of the function of the primary motor cortex (M1) is thought to play a critical role in motor dysfunction in Parkinson’s disease (PD). Detailed information regarding the specific aspects of M1 circuits that become abnormal is lacking. We recorded single units and local field potentials (LFPs) of M1 neurons in unilateral 6-hydroxydopamine (6-OHDA) lesion rats and control rats to assess the impact of dopamine (DA) cell loss during rest and a forelimb reaching task. Our results indicated that M1 neurons can be classified into two groups (putative pyramidal neurons and putative interneurons) and that 6-OHDA could modify the activity of different M1 subpopulations to a large extent. Reduced activation of putative pyramidal neurons during inattentive rest and reaching was observed. In addition, 6-OHDA intoxication was associated with an increase in certain LFP frequencies, especially those in the beta range (broadly defined here as any frequency between 12 and 35 Hz), which become pathologically exaggerated throughout cortico-basal ganglia circuits after dopamine depletion. Furthermore, assessment of different spike-LFP coupling parameters revealed that the putative pyramidal neurons were particularly prone to being phase-locked to ongoing cortical oscillations at 12–35 Hz during reaching. Conversely, putative interneurons were neither hypoactive nor synchronized to ongoing cortical oscillations. These data collectively demonstrate a neuron type-selective alteration in the M1 in hemiparkinsonian rats. These alterations hamper the ability of the M1 to contribute to motor conduction and are likely some of the main contributors to motor impairments in PD.

Fluoxetine tunes the abnormal hippocampal oscillations in association with cognitive impairments in 6-OHDA lesioned rats

Cognitive decline is a common clinical symptom in Parkinson’s disease (PD) patients. Fluoxetine (FLU), a selective serotonin reuptake inhibitor, can improve cognitive deficits in demented patients. The present study investigated the effects of FLU on spatial learning and memory cognitions in 6-OHDA lesioned rats. Morris water maze (MWM) test showed that FLU significantly improved spatial cognitive deficits in rats with unilateral 6-OHDA injection at 4 and 7 weeks after 6-OHDA injection. Electrophysiological recordings demonstrated that the number and duration of high voltage spindles(HVSs)in the ipsilateral hippocampus of 6-OHDA lesioned rats were decreased by the administration of FLU. Furthermore, the spectral analysis of per frequency revealed increases in δ and θ rhythm power and decreases in α, β and γ rhythm power in the ipsilateral hippocampus of 6-OHDA lesioned rats in contrast to the saline-treated rats. Acute FLU treatment can reduce δ and θ rhythm power, and enhance α, β and γ rhythm power in the ipsilateral hippocampus of 6-OHDA lesioned rats. These findings suggest that FLU improves impaired cognition by tuning oscillatory activities in the hippocampus of 6-OHDA lesioned rats.

Motor Thalamic Deep Brain Stimulation Alters Cortical Activity and Shows Therapeutic Utility for Treatment of Parkinson’s Disease Symptoms in a Rat Model

Deep brain stimulation (DBS) in Parkinson’s disease (PD) alters neuronal function and network communication to improve motor symptoms. The subthalamic nucleus (STN) is the most common DBS target for PD, but some patients experience adverse effects on memory and cognition. Previously, we reported that DBS of the ventral anterior (VA) and ventrolateral (VL) nuclei of the thalamus and at the interface between the two (VA|VL), collectively VA-VL, relieved forelimb akinesia in the hemiparkinsonian 6-hydroxydopamine (6-OHDA) rat model. To determine the mechanism(s) underlying VA-VL DBS efficacy, we examined how motor cortical neurons respond to VA-VL DBS using single-unit recording electrodes in anesthetized 6-OHDA lesioned rats. VA-VL DBS increased spike frequencies of primary (M1) and secondary (M2) motor cortical pyramidal cells and M2, but not M1, interneurons. To explore the translational merits of VA-VL DBS, we compared the therapeutic window, rate of stimulation-induced dyskinesia onset, and effects on memory between VA-VL and STN DBS. VA-VL and STN DBS had comparable therapeutic windows, induced dyskinesia at similar rates in hemiparkinsonian rats, and adversely affected performance in the novel object recognition (NOR) test in cognitively normal and mildly impaired sham animals. Interestingly, a subset of sham rats with VA-VL implants showed severe cognitive deficits with DBS off. VA-VL DBS improved NOR test performance in these animals. We conclude that VA-VL DBS may exert its therapeutic effects by increasing pyramidal cell activity in the motor cortex and interneuron activity in the M2, with plausible potential to improve memory in PD.

Drug Repurposing Patent Applications October-December 2020.

Drug Repurposing Patent Applications October-December 2020.

Systemic Inflammation Increases the Susceptibility to Levodopa-Induced Dyskinesia in 6-OHDA Lesioned Rats by Targeting the NR2B-Medicated PKC/MEK/ERK Pathway.

Background: The long-term administration of levodopa (L-dopa), the gold-standard treatment for Parkinson's disease (PD), is irreparably associated with L-dopa-induced dyskinesia (LID), which dramatically affects the quality of life of patients. However, the underlying molecular mechanisms of how LID exacerbates remain unknown. Neuroinflammation in the striatum plays an active role in LID. These findings prompt an investigation of non-neuronal mechanisms of LID. This study will examine the effects of systemic inflammation in the development and progression of LID.Methods: To evaluate the possible influence of systemic inflammation in the appearance of LID, the PD rats received an intraperitoneal (IP) injection of various concentrations of lipopolysaccharides (LPS, 1, 2, and 5 mg/kg) or saline. One day later, these PD rats started to receive daily treatment with L-dopa (6 mg/kg) along with benserazide (6 mg/kg) or saline for 21 days, and dyskinesia was evaluated at several time points. Moreover, the activation of microglia and astrocytes and the molecular changes in NR2B and mGLUR5 signaling pathways were measured.Results: We found that systemic inflammatory stimulation with LPS exacerbated the intensity of abnormal involuntary movements (AIMs) induced by L-dopa treatment in 6-hydroxydopamine (6-OHDA) lesioned rats. The LPS injection activated the gliocytes and increased the levels of proinflammatory cytokines in the striatum in LID rats. The PD rats that received the LPS injection showed the overexpression of p-NR2B and NR2B, as well as activated PKC/MEK/ERK and NF-κB signal pathways in response to the L-dopa administration. On the contrary, clodronate-encapsulated liposomes (Clo-lipo), which could suppress the inflammatory response induced by peripheral LPS injection, improved behavioral dysfunction, inhibited neuroinflammation, prevented NR2B overexpression, and decreased the phosphorylation of PKC/MEK/ERK and NF-κB signaling pathways.Conclusion: This study suggests that systemic inflammation, by exacerbating preexisting neuroinflammation and facilitating NR2B subunit activity, may play a crucial role in the development of LID. The administration of Clo-lipo restores the effects of LPS and decreases the susceptibility to LID in 6-OHDA lesioned rats.

Levodopa-Induced Dyskinesia Are Mediated by Cortical Gamma Oscillations in Experimental Parkinsonism.

Levodopa is the most efficacious drug in the symptomatic therapy of motor symptoms in Parkinson's disease (PD); however, long-term treatment is often complicated by troublesome levodopa-induced dyskinesia (LID). Recent evidence suggests that LID might be related to increased cortical gamma oscillations. The objective of this study was to test the hypothesis that cortical high-gamma network activity relates to LID in the 6-hydroxydopamine model and to identify new biomarkers for adaptive deep brain stimulation (DBS) therapy in PD. We recorded and analyzed primary motor cortex (M1) electrocorticogram data and motor behavior in freely moving 6-OHDA lesioned rats before and during a daily treatment with levodopa for 3 weeks. The results were correlated with the abnormal involuntary movement score (AIMS) and used for generalized linear modeling (GLM). Levodopa reverted motor impairment, suppressed beta activity, and, with repeated administration, led to a progressive enhancement of LID. Concurrently, we observed a highly significant stepwise amplitude increase in finely tuned gamma (FTG) activity and gamma centroid frequency. Whereas AIMS and FTG reached their maximum after the 4th injection and remained on a stable plateau thereafter, the centroid frequency of the FTG power continued to increase thereafter. Among the analyzed gamma activity parameters, the fraction of longest gamma bursts showed the strongest correlation with AIMS. Using a GLM, it was possible to accurately predict AIMS from cortical recordings. FTG activity is tightly linked to LID and should be studied as a biomarker for adaptive DBS. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Peripheral benzodiazepine receptor/18kDa translocator protein positron emission tomography imaging in a rat model of acute brain injury.

The activation of microglia in various brain pathologies is accompanied by an increase in the expression of peripheral benzodiazepine receptor/18kDa translocator protein (PBR/TSPO). However, whether activated microglia have a neuroprotective or neurotoxic effect on neurons in the brain is yet to be determined. In this study, we investigated the ability of the novel PBR/TSPO ligand FEPPA to detect activated microglia in an animal model of primary neurotoxic microglia activation. [18F] FEPPA positron emission tomography (PET) imaging was performed before and after intraperitoneal administration of lipopolysaccharide (LPS) (LPS group) or saline (control group) in a unilateral 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson's disease. Images were compared between these groups. After imaging, the brains were collected, and the activated microglia at the disease sites were analyzed by the expression of inflammatory cytokines and immunohistochemistry staining. These results were then comparatively examined with those obtained by PET imaging. In the unilateral 6-OHDA lesion rat model, the PBR/TSPO PET signal was significantly increased in the LPS group compared with the saline group. As the increased signal was observed 4h after the injection, we considered it an acute response to brain injury. In the post-imaging pathological examination, activated microglia were found to be abundant at the site where strong signals were detected, and the expression of the inflammatory cytokines TNF-α and IL-1β was increased. Intraperitoneal LPS administration further increased the expression of inflammatory cytokines, and the PBR/TSPO PET signal increased concurrently. The increase in inflammatory cytokine expression correlated with enhanced signal intensity. PET signal enhancement by PBR/TSPO at the site of brain injury correlated with the activation of microglia and production of inflammatory cytokines. Furthermore, because FEPPA enables the detection of neurotoxic microglia on PET images, we successfully constructed a novel PET detection system that can monitor neurodegenerative diseases.

Early Expression of Neuronal Dopaminergic Markers in a Parkinson's Disease Model in Rats Implanted with Enteric Stem Cells (ENSCs).

Parkinson's Disease (PD) is a common neurodegenerative disorder affecting the dopaminergic (DAergic) system. Replacement therapy is a promising alternative aimed at reconstructing the cytoarchitecture of affected brain regions in PD. Experimental approaches, such as the replacement of DAergic neurons with cells obtained from the Enteric Nervous System (ENS) has yet to be explored. To establish and characterize a cell replacement strategy with ENS Cells (ENSCs) in a PD model in rats. Since ENSCs can develop mature DAergic phenotypes, here we cultured undifferentiated cells from the myenteric plexus of newborn rats, establishing that they exhibit multipotential characteristics. These cells were characterized and further implanted in the Substantia nigra pars compacta (SNpc) of adult rats previously lesioned by a retrograde degenerative model produced by intrastriatal injection of 6-Hydroxydopamine (6-OHDA). DAergic markers were assessed in implants to validate their viability and possible differentiation once implanted. Cell cultures were viable, exhibited stem cell features and remained partially undifferentiated until the time of implant. The retrograde lesion induced by 6-OHDA produced DAergic denervation, reducing the number of fibers and cells in the SNpc. Implantation of ENSCs in the SNpc of 6-OHDAlesioned rats was tracked after 5 and 10 days post-implant. During that time, the implant increased selective neuronal and DAergic markers, Including Microtubule-Associated Protein 2 (MAP-2), Dopamine Transporter (DAT), and Tyrosine Hydroxylase (TH). Our novel results suggest that ENSCs possess a differentiating, proliferative and restorative potential that may offer therapeutic modalities to attenuate neurodegenerative events with the inherent demise of DAergic neurons.

Investigation of nerve pathways mediating colorectal dysfunction in Parkinson's disease model produced by lesion of nigrostriatal dopaminergic neurons.

Gastrointestinal (GI) dysfunction, including constipation, is a common non-motor symptom of Parkinson's disease (PD). The toxin 6-hydroxydopamine (6OHDA) produces the symptoms of PD, surprisingly including constipation, after it is injected into the medial forebrain bundle (MFB). However, the mechanisms involved in PD-associated constipation caused by central application of 6OHDA remain unknown. We investigated effects of 6OHDA lesioning of the MFB on motor performance and GI function. Male Sprague Dawley rats were unilaterally injected with 6OHDA in the MFB. Colorectal propulsion was assessed by bead expulsion after 4weeks and by recording colorectal contractions and propulsion after 5weeks. Enteric nervous system (ENS) neuropathy was examined by immunohistochemistry. When compared to shams, 6OHDA-lesioned rats had significantly increased times of bead expulsion from the colorectum, indicative of colon dysmotility. Administration of the colokinetic, capromorelin, that stimulates defecation centers in the spinal cord, increased the number of contractions and colorectal propulsion in both groups compared to baseline; however, the effectiveness of capromorelin in 6OHDA-lesioned rats was significantly reduced in comparison with shams, indicating that 6OHDA animals have reduced responsiveness of the spinal defecation centers. Enteric neuropathy was observed in the distal colon, revealing that lesion of the MFB has downstream effects at the cellular level, remote from the site of 6OHDA administration. We conclude that there are trans-synaptic effects of the proximal, forebrain, lesion of pathways from the brain that send signals down the spinal cord, at the levels of the defecation centers and the ENS.

Perillyl Alcohol Mitigates Behavioural Changes and Limits Cell Death and Mitochondrial Changes in Unilateral 6-OHDA Lesion Model of Parkinson’s Disease Through Alleviation of Oxidative Stress

In this study, we aim to assess the phytomedicinal potential of perillyl alcohol (PA), a dietary monoterpenoid, in a unilateral 6-hydroxydopamine (6-OHDA) lesion rat model of Parkinson's disease (PD). We observed that PA supplementation alleviated behavioural abnormalities such as loss of coordination, reduced rearing and motor asymmetry in lesioned animals. We also observed that PA-treated animals exhibited reduced oxidative stress, DNA fragmentation and caspase 3 activity indicating alleviation of apoptotic cell death. We found reduced mRNA levels of pro-apoptotic regulator BAX and pro-inflammatory mediators IL18 and TNFα in PA-treated animals. Further, PA treatment successfully increased mRNA and protein levels of Bcl2, mitochondrial biogenesis regulator PGC1α and tyrosine hydroxylase (TH) in lesioned animals. We observed that PA treatment blocked BAX and Drp1 translocation to mitochondria, an event often associated with the inception of apoptosis. Further, 6-OHDA exposure reduced expression of electron transport chain complexes I and IV, thereby disturbing energy metabolism. Conversely, expression levels of both complexes were upregulated with PA treatment in lesioned rats. Finally, we found that protein levels of Nrf2, the transcription factor responsible for antioxidant gene expression, were markedly reduced in cytosolic and nuclear fraction on 6-OHDA exposure, and PA increased expression of Nrf2 in both fractions. We believe that our data hints towards PA having the ability to provide cytoprotection in a hemiparkinsonian rat model through alleviation of motor deficits, oxidative stress, mitochondrial dysfunction and apoptosis.

Frequency-Specific Optogenetic Deep Brain Stimulation of Subthalamic Nucleus Improves Parkinsonian Motor Behaviors.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective therapy for the motor symptoms of Parkinson's disease (PD). However, the neural elements mediating symptom relief are unclear. A previous study concluded that direct optogenetic activation of STN neurons was neither necessary nor sufficient for relief of parkinsonian symptoms. However, the kinetics of the channelrhodopsin-2 (ChR2) used for cell-specific activation are too slow to follow the high rates required for effective DBS, and thus the contribution of activation of STN neurons to the therapeutic effects of DBS remains unclear. We quantified the behavioral and neuronal effects of optogenetic STN DBS in female rats following unilateral 6-hydroxydopamine (6-OHDA) lesion using an ultrafast opsin (Chronos). Optogenetic STN DBS at 130 pulses per second (pps) reduced pathologic circling and ameliorated deficits in forelimb stepping similarly to electrical DBS, while optogenetic STN DBS with ChR2 did not produce behavioral effects. As with electrical DBS, optogenetic STN DBS exhibited a strong dependence on stimulation rate; high rates produced symptom relief while low rates were ineffective. High-rate optogenetic DBS generated both increases and decreases in firing rates of single neurons in STN, globus pallidus externa (GPe), and substantia nigra pars reticular (SNr), and disrupted β band oscillatory activity in STN and SNr. High-rate optogenetic STN DBS can indeed ameliorate parkinsonian motor symptoms through reduction of abnormal oscillatory activity in the STN-associated neural circuit, and these results highlight that the kinetic properties of opsins have a strong influence on the effects of optogenetic stimulation.SIGNIFICANCE STATEMENT Whether STN local cells contribute to the therapeutic effects of subthalamic nucleus (STN) deep brain stimulation (DBS) in Parkinson's disease (PD) remains unclear. We re-examined the role of STN local cells in mediating the symptom-relieving effects of STN DBS using cell type-specific optogenetic stimulation with a much faster opsin, Chronos. Direct optogenetic stimulation of STN neurons was effective in treating the symptoms of parkinsonism in the 6-hydroxydopamine (6-OHDA) lesion rat. These results highlight that the kinetic properties of opsins can have a strong influence on the effects of optogenetic activation/inhibition and must be considered when employing optogenetic to study high-rate neural stimulation.

Long-term, stable, targeted biodelivery and efficacy of GDNF from encapsulated cells in the rat and Goettingen miniature pig brain

Delivering glial cell line-derived neurotrophic factor (GDNF) to the brain is a potential treatment for Parkinson's Disease (PD). Here we use an implantable encapsulated cell technology that uses modified human clonal ARPE-19 ​cells to deliver of GDNF to the brain. In vivo studies demonstrated sustained delivery of GDNF to the rat striatum over 6 months. Anatomical benefits and behavioral efficacy were shown in 6-OHDA lesioned rats where nigral dopaminergic neurons were preserved in neuroprotection studies and dopaminergic fibers were restored in neurorecovery studies. When larger, clinical-sized devices were implanted for 3 months into the putamen of Göttingen minipigs, GDNF was widely distributed throughout the putamen and caudate producing a significant upregulation of tyrosine hydroxylase immunohistochemistry. These results are the first to provide clear evidence that implantation of encapsulated GDNF-secreting cells deliver efficacious and biologically relevant amounts of GDNF in a sustained and targeted manner that is scalable to treat the large putamen in patients with Parkinson's disease.

Neuroprotective effect of regular swimming exercise on calretinin-positive striatal neurons of Parkinsonian rats.

In Parkinson's disease (PD), physical therapy is one of the mainstays of supportive treatment modalities. This study focused on the neuroprotective effect of regular exercise on striatal calretinin positive interneurons in a rat model of PD. 6-hydroxydopamine (6-OHDA) was injected unilaterally into the medial forebrain bundle of Wistar rats. 6-OHDA lesioned (Parkinsonian) and unlesioned (control) rats were divided into sedentary and exercise groups. Exercise groups had daily swimming sessions for 30min for 6 weeks. After 6-OHDA injections, an apomorphine-induced rotation test was performed (0.05mg/kg, subcutaneous) at the 3rd and 6th weeks. At the end of the 6th week, brains were removed following transcardiac perfusion. The brain sections were stained immunohistochemically for tyrosine hydroxylase and calretinin reactivity. The number of rotations was significantly lower in Parkinsonian exercise group compared to Parkinsonian sedentary group at the 6th week (p = 0.024) and there was significant difference between Parkisonian sedentary groups at the 3rd and 6th weeks (p < 0.002). The calretinin positive interneurons significantly increased in the Parkinsonian exercise group compared to Parkinsonian sedentary group (p = 0.0003) and control exercise group (p < 0.0001). To conclude, the swimming exercise led to a striking increment of calretinin positive interneurons in the striatum of Parkinsonian rat. These findings indicated that the neuroprotective mechanism of exercise increased the number of striatal calretinin positive interneurons that might generate new approaches for the mechanism of neuroprotection. We concluded that striatal calretinin positive interneurons have an important role in the neuroprotective mechanisms of exercise in PD.

Ameliorative effects of a phosphodiesterase 10A inhibitor, MR1916 on L-DOPA-induced dyskinesia in parkinsonian rats.

Dopamine replacement therapy using L-3,4-dihydroxyphenylalanine (L-DOPA) is a gold standard treatment in patients with Parkinson's disease (PD); however, chronic administration of L-DOPA causes excessive involuntary movements called L-DOPA-induced dyskinesia. Therefore, the novel pharmacological treatment is needed. We examined the antidyskinetic effect of a phosphodiesterase 10A (PDE10A) inhibitor, MR1916 and a currently available antidyskinetic drug, amantadine in unilateral 6-OHDA lesioned rats exhibited stably dyskinesia after chronic administration of L-DOPA. We also examined the influence of MR1916 and amantadine on the improvement of forelimb akinesia induced by L-DOPA using stepping test in unilateral 6-OHDA lesioned rats. MR1916 (0.03‒0.3mg/kg, po) reduced L-DOPA-induced dyskinesia in a dose-dependent manner and showed significant effects at doses of 0.1 and 0.3mg/kg, while amantadine (40mg/kg, sc) had no remarkable effects. Neither MR1916 (0.03‒0.3mg/kg, po) nor amantadine (40mg/kg, sc) affected the antiparkinsonian effects induced by L-DOPA in unilateral 6-OHDA lesioned rats. These results indicate that MR1916 specifically reduces L-DOPA-induced dyskinesia without affecting the antiparkinsonian effect of L-DOPA in parkinsonian rats.

The Effect of Focused Transcranial Magnetic Stimulation on Behavioral Profiles and Motor Cortex Signals in the Animal Model of Parkinsonism

Background: Non-invasive magnetic stimulation therapies have become a widespread neuromodulation method utilized in the treatment of mood disorders. Although these methods have shown efficacy in the treatment of psychiatric disorders such as bipolar affective disorder and depression, a few studies have been done on Parkinson's disease (PD). Objective: This study was executed to demonstrate the effectiveness of focused transcranial magnetic stimulation (fTMS) for the treatment of PD. For this aim, a new stimulation coil design with the semi-hexagonal core was used to concentrate magnetic flux in the particular innervation nucleus. Several TMS protocols were tested to stimulate the STN region of 6-OHDA lesioned rats to determine the most effective treatment. Results: The progress of treatment was investigated by recording and analyzing the neurophysiological activity of the primary motor cortex and locomotor behaviors. After 6-OHDA injection, sharp increases in the energy and power spectral density of beta and low- gamma band were caused. Also, the motor activities of rats reduced, and the degree of catalepsy increased significantly. By completing the proposed 1Hz r-TMS treatment, the amount of energy and power density in these bands diminished and came close to the baseline. Furthermore, debilitating motor fluctuations were reverted considerably. Conclusion: Experimental results reveal that after 40 days of the non-invasive procedure, both oscillatory activity and the locomotor behavior produce remarkable changes. The 1Hz r-TMS showed acceptable performance in a reduction of symptoms in the PD. The outcomes of the animal trials have raised some hopes to employ the findings of this study in human clinical research.

Voltage-Gated Sodium Channels Are Involved in Cognitive Impairments in Parkinson's Disease- like Rats

Cognitive impairment is one of the common non-motor symptoms in Parkinson's disease (PD). The hippocampus is a critical structure for learning and memory processes. The abnormal synaptic plasticity in the hippocampus is suggested to be associated with cognitive dysfunction in PD. Voltage gated sodium channels (VGSCs) are key molecules involved in synaptic transmission in the nervous system. Here, the expression patterns of VGSC subtypes Nav1.1, Nav1.3, Nav1.6 in the hippocampus of 6-hydroxydopamine (6-OHDA) lesioned rats were investigated at different time points after 6-OHDA injection. The results showed that the expression of Nav1.1 was remarkably increased in reactive astrocytes at 28days, whereas was sharply reduced at 49days after 6-OHDA injection. However, the expression of Nav1.6 was not different from the control hippocampus at 28days, but was abundantly increased in neurons of the contralateral and ipsilateral hippocampus at 49days after 6-OHDA injection. Moreover, Nav1.3, a subtype predominantly expressed at embryonic stage, was scatteredly re-expressed in neurons of the CA area in the contralateral and ipsilateral hippocampus at 49days after 6-OHDA injection. Furthermore, spatial learning and memory in 6-OHDA lesioned rats were effectively improved by acute treatment with a VGSCs blocker, phenytoin. These findings suggested that VGSCs may play an important role in the genesis of cognitive deficits in PD.

Levodopa/Benserazide PLGA Microsphere Prevents L-Dopa–Induced Dyskinesia via Lower β-Arrestin2 in 6-Hydroxydopamine Parkinson’s Rats

Prolonged pulsatile administration of Levodopa (L-dopa) can generate L-dopa–induced dyskinesia (LID). Numerous research has reported that continuous dopamine delivery (CDD) was useful in reducing the severity of LID. 6-OHDA lesioned rats were divided into two groups to receive intermittent L-dopa stimulation (L-dopa/benserazide) or Levodopa/benserazide PLGA microsphere (LBPM) for 3 weeks. rAAV (recombinant adeno-associated virus) vector was used to overexpress and ablation of β-arrestin2. We found that LBPM developed less AIM severity compared with standard L-dopa administration, whereas selective deletion of β-arrestin2 in striatum neurons dramatically enhanced the severity of dyskinesia by LBPM. On the contrary, the effects of LBPM in terms of ALO AIM were further relieved by β-arrestin2 overexpression. Furthermore, no significant change in motor behavior was seen either in inhibition or overexpression of β-arrestin2. In short, our experiments provided evidence that LBPM’s prevention of LID behavior was likely due to β-arrestin2, suggesting that a therapy modulating β-arrestin2 may offer a more efficient anti-dyskinetic method with a low risk of untoward effects.