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Iyer V, Venkiteswaran K, Savaliya S, Lieu CA, Handly E, Gilmour TP, Kunselman AR, Subramanian T. The cross-hemispheric nigrostriatal pathway prevents the expression of levodopa-induced dyskinesias. Neurobiol Dis 2021; 159:105491. [PMID: 34461264 PMCID: PMC8597404 DOI: 10.1016/j.nbd.2021.105491] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 08/17/2021] [Accepted: 08/25/2021] [Indexed: 11/29/2022] Open
Abstract
Parkinson's disease (PD) is a neurodegenerative movement disorder that is routinely treated with levodopa. Unfortunately, long-term dopamine replacement therapy using levodopa leads to levodopa-induced dyskinesias (LID), a significant and disabling side-effect. Clinical findings indicate that LID typically only occurs following the progression of PD motor symptoms from the unilateral (Hoehn and Yahr (HY) Stage I) to the bilateral stage (HY Stage II). This suggests the presence of some compensatory interhemispheric mechanisms that delay the occurrence of LID. We therefore investigated the role of interhemispheric connections of the nigrostriatal pathway on LID expression in a rat model of PD. The striatum of one hemisphere of rats was first injected with a retrograde tracer to label the ipsi- and cross-hemispheric nigrostriatal pathways. Rats were then split into groups and unilaterally lesioned in the striatum or medial forebrain bundle of the tracer-injected hemisphere to induce varying levels of hemiparkinsonism. Finally, rats were treated with levodopa and tested for the expression of LID. Distinct subsets emerged from rats that underwent the same lesioning paradigm based on LID. Strikingly, non-dyskinetic rats had significant sparing of their cross-hemispheric nigrostriatal pathway projecting from the unlesioned hemisphere. In contrast, dyskinetic rats only had a small proportion of this cross-hemispheric nigrostriatal pathway survive lesioning. Crucially, both non-dyskinetic and dyskinetic rats had nearly identical levels of ipsi-hemispheric nigrostriatal pathway survival and parkinsonian motor deficits. Our data suggest that the survival of the cross-hemispheric nigrostriatal pathway plays a crucial role in preventing the expression of LID and represents a potentially novel target to halt the progression of this devastating side-effect of a common anti-PD therapeutic.
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Affiliation(s)
- Vishakh Iyer
- Department of Neurology and Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA, United States of America
| | - Kala Venkiteswaran
- Department of Neurology and Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA, United States of America
| | - Sandip Savaliya
- Department of Neurosurgery, The Pennsylvania State University College of Medicine, Hershey, PA, United States of America
| | - Christopher A Lieu
- Department of Neurology and Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA, United States of America
| | - Erin Handly
- Department of Neurology and Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA, United States of America
| | - Timothy P Gilmour
- Department of Electrical Engineering, John Brown University, Siloam Springs, AR, United States of America
| | - Allen R Kunselman
- Department of Public Health Sciences, The Pennsylvania State University College of Medicine, Hershey, PA, United States of America
| | - Thyagarajan Subramanian
- Department of Neurology and Neural and Behavioral Sciences, The Pennsylvania State University College of Medicine, Hershey, PA, United States of America.
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Knowing Your Beans in Parkinson's Disease: A Critical Assessment of Current Knowledge about Different Beans and Their Compounds in the Treatment of Parkinson's Disease and in Animal Models. PARKINSON'S DISEASE 2019; 2019:1349509. [PMID: 31781363 PMCID: PMC6875167 DOI: 10.1155/2019/1349509] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 09/21/2019] [Accepted: 10/03/2019] [Indexed: 01/07/2023]
Abstract
This review contains a critical appraisal of current knowledge about the use of beans in both animal models and patients with Parkinson's disease (PD). The potential beneficial effects of beans in PD are increasingly being touted, not only in scientific journals but also by the lay media. While there is a long tradition in Ayurvedic medicine of prescribing extracts from Mucuna pruriens (MP), whose seeds contain 5% L-3,4-dihydroxyphenylalanin (L-DOPA), many other beans also contain L-DOPA (broad beans, common beans, and soybeans) or have other ingredients (coffee and cocoa) that may benefit PD patients. Indeed, bean-derived compounds can elicit neuroprotective effects in animal models of PD, while several studies in human PD patients have shown that motor performance can improve after ingestion of bean extracts. However, there are several arguments countering the view that beans serve as a natural therapy for PD: (i) the results from animal PD models are not necessarily directly applicable to humans; (ii) beans have many bioactive ingredients, some of which can be harmful in large doses; (iii) studies in human PD patients are scarce and only report on the effects of single doses or the administration of bean extract over short periods of time; and (iv) no data on long-term efficacy or side effects of bean therapy are available. Therefore, reservations about the use of beans as a "natural" therapy for PD seem to be justified.
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Asakawa T, Fang H, Sugiyama K, Nozaki T, Hong Z, Yang Y, Hua F, Ding G, Chao D, Fenoy AJ, Villarreal SJ, Onoe H, Suzuki K, Mori N, Namba H, Xia Y. Animal behavioral assessments in current research of Parkinson's disease. Neurosci Biobehav Rev 2016; 65:63-94. [PMID: 27026638 DOI: 10.1016/j.neubiorev.2016.03.016] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 03/22/2016] [Accepted: 03/22/2016] [Indexed: 12/21/2022]
Abstract
Parkinson's disease (PD), a neurodegenerative disorder, is traditionally classified as a movement disorder. Patients typically suffer from many motor dysfunctions. Presently, clinicians and scientists recognize that many non-motor symptoms are associated with PD. There is an increasing interest in both motor and non-motor symptoms in clinical studies on PD patients and laboratory research on animal models that imitate the pathophysiologic features and symptoms of PD patients. Therefore, appropriate behavioral assessments are extremely crucial for correctly understanding the mechanisms of PD and accurately evaluating the efficacy and safety of novel therapies. This article systematically reviews the behavioral assessments, for both motor and non-motor symptoms, in various animal models involved in current PD research. We addressed the strengths and weaknesses of these behavioral tests and their appropriate applications. Moreover, we discussed potential mechanisms behind these behavioral tests and cautioned readers against potential experimental bias. Since most of the behavioral assessments currently used for non-motor symptoms are not particularly designed for animals with PD, it is of the utmost importance to greatly improve experimental design and evaluation in PD research with animal models. Indeed, it is essential to develop specific assessments for non-motor symptoms in PD animals based on their characteristics. We concluded with a prospective view for behavioral assessments with real-time assessment with mobile internet and wearable device in future PD research.
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Affiliation(s)
- Tetsuya Asakawa
- Department of Neurosurgery, Hamamatsu University School of Medicine, Hamamatsu-city, Shizuoka, Japan; Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu-city, Shizuoka, Japan.
| | - Huan Fang
- Department of Pharmacy, Jinshan Hospital of Fudan University, Shanghai, China
| | - Kenji Sugiyama
- Department of Neurosurgery, Hamamatsu University School of Medicine, Hamamatsu-city, Shizuoka, Japan
| | - Takao Nozaki
- Department of Neurosurgery, Hamamatsu University School of Medicine, Hamamatsu-city, Shizuoka, Japan
| | - Zhen Hong
- Department of Neurology, Huashan Hospital of Fudan University, Shanghai, China
| | - Yilin Yang
- The First People's Hospital of Changzhou, Soochow University School of Medicine, Changzhou, China
| | - Fei Hua
- The First People's Hospital of Changzhou, Soochow University School of Medicine, Changzhou, China
| | - Guanghong Ding
- Shanghai Key Laboratory of Acupuncture Mechanism and Acupoint Function, Fudan University, Shanghai, China
| | - Dongman Chao
- Department of Neurosurgery, The University of Texas McGovern Medical School,Houston, TX, USA
| | - Albert J Fenoy
- Department of Neurosurgery, The University of Texas McGovern Medical School,Houston, TX, USA
| | - Sebastian J Villarreal
- Department of Neurosurgery, The University of Texas McGovern Medical School,Houston, TX, USA
| | - Hirotaka Onoe
- Functional Probe Research Laboratory, RIKEN Center for Life Science Technologies, Kobe, Japan
| | - Katsuaki Suzuki
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu-city, Shizuoka, Japan
| | - Norio Mori
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu-city, Shizuoka, Japan
| | - Hiroki Namba
- Department of Neurosurgery, Hamamatsu University School of Medicine, Hamamatsu-city, Shizuoka, Japan
| | - Ying Xia
- Department of Neurosurgery, The University of Texas McGovern Medical School,Houston, TX, USA.
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Johnston TM, Fox SH. Symptomatic Models of Parkinson's Disease and L-DOPA-Induced Dyskinesia in Non-human Primates. Curr Top Behav Neurosci 2015; 22:221-35. [PMID: 25158623 DOI: 10.1007/7854_2014_352] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Models of Parkinson's disease (PD) can be produced in several non-human primate (NHP) species by applying neurotoxic lesions to the nigrostriatal dopamine pathway. The most commonly used neurotoxin is MPTP, a compound accidentally discovered as a contaminant of street drugs. Compared to other neurotoxins, MPTP has the advantage of crossing the blood-brain barrier and can thus be administered systemically. MPTP-lesioned NHPs exhibit the main core clinical features of PD. When treated with L-DOPA, these NHP models develop involuntary movements resembling the phenomenology of human dyskinesias. In old-world NHP species (macaques, baboons), choreic and dystonic dyskinesias can be readily distinguished and quantified with specific rating scales. More recently, certain non-motor symptoms relevant to human PD have been described in L-DOPA-treated MPTP-NHPs, including a range of neuropsychiatric abnormalities and sleep disturbances. The main shortcomings of MPTP-NHP models consist in a lack of progression of the underlying neurodegenerative lesion, along with an inability to model the intracellular protein-inclusion pathology typical of PD. The strength of MPTP-NHP models lies in their face and predictive validity for symptomatic treatments of parkinsonian motor features. Indeed, these models have been instrumental to the development of several medical and surgical approaches that are currently applied to treat PD.
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Affiliation(s)
- Tom M Johnston
- Toronto Western Research Institute, University of Toronto, Toronto Western Hospital, 399, Bathurst St, Toronto, ON, M5T 2S8, Canada
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Fox SH, Brotchie JM, Johnston TM. Primate Models of Complications Related to Parkinson Disease Treatment. Mov Disord 2015. [DOI: 10.1016/b978-0-12-405195-9.00021-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Schaeffer E, Pilotto A, Berg D. Pharmacological strategies for the management of levodopa-induced dyskinesia in patients with Parkinson's disease. CNS Drugs 2014; 28:1155-84. [PMID: 25342080 DOI: 10.1007/s40263-014-0205-z] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
L-Dopa-induced dyskinesias (LID) are the most common adverse effects of long-term dopaminergic therapy in Parkinson's disease (PD). However, the exact mechanisms underlying dyskinesia are still unclear. For a long time, nigrostriatal degeneration and pulsatile stimulation of striatal postsynaptic receptors have been highlighted as the key factors for the development of LID. In recent years, PD models have revealed a wide range of non-dopaminergic neurotransmitter systems involved in pre- and postsynaptic changes and thereby contributing to the pathophysiology of LID. In the current review, we focus on therapeutic LID targets, mainly based on agents acting on dopaminergic, glutamatergic, serotoninergic, adrenergic, and cholinergic systems. Despite a large number of clinical trials, currently only amantadine and, to a lesser extent, clozapine are being used as effective strategies in the treatment of LID in clinical settings. Thus, in the second part of the article, we review the placebo-controlled trials on LID treatment in order to disentangle the changing scenario of drug development. Promising results include the extension of L-dopa action without inducing LID of the novel monoamine oxidase B- and glutamate-release inhibitor safinamide; however, this had no obvious effect on existing LID. Others, like the metabotropic glutamate-receptor antagonist AFQ056, showed promising results in some of the studies; however, confirmation is still lacking. Thus, to date, strategies of continuous dopaminergic stimulation seem the most promising to prevent or ameliorate LID. The success of future therapeutic strategies once moderate to severe LID occur will depend on the translation from preclinical experimental models into clinical practice in a bidirectional process.
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Affiliation(s)
- Eva Schaeffer
- Department of Neurodegeneration, Hertie Institute for Clinical Brain Research, University of Tuebingen, Hoppe Seyler-Strasse 3, 72076, Tübingen, Germany
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Modeling dyskinesia in animal models of Parkinson disease. Exp Neurol 2014; 256:105-16. [DOI: 10.1016/j.expneurol.2013.01.024] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 01/12/2013] [Accepted: 01/21/2013] [Indexed: 01/23/2023]
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Del-Bel E, Padovan-Neto FE, Szawka RE, da-Silva CA, Raisman-Vozari R, Anselmo-Franci J, Romano-Dutra AC, Guimaraes FS. Counteraction by nitric oxide synthase inhibitor of neurochemical alterations of dopaminergic system in 6-OHDA-lesioned rats under L-DOPA treatment. Neurotox Res 2013; 25:33-44. [PMID: 23807548 DOI: 10.1007/s12640-013-9406-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 06/12/2013] [Accepted: 06/14/2013] [Indexed: 12/21/2022]
Abstract
Nitric oxide synthase inhibitors reduce L-3, (Del-Bel et al., Cell Mol Neurobiol 25(2):371-392, 2005) 4-dihydroxyphenylalanine (L-DOPA)-induced abnormal motor effects subsequent to depletion of dopaminergic neurons in rodents and non-human primates. The present study used quantitative high-performance liquid chromatography to analyze, for the first time, dopamine metabolism in striatum of rats in order to elucidate the mechanism of action of the nitric oxide synthase inhibitors. Adult male Wistar rats received unilateral microinjection of saline (sham) or 6-hydroxydopamine (6-OHDA-lesioned) in the medial forebrain bundle. Past 3 weeks, rats were treated during 21 days with L-DOPA/benserazide (30 mg/kg/7.5 mg/kg, respectively, daily). On the 22nd day rats received an intraperitoneal (i.p.) injection of either vehicle or 7-nitroindazole, a preferential neuronal nitric oxide synthase inhibitor before L-DOPA. Abnormal involuntary movements and rotarod test were assessed as behavioral correlate of motor responses. Lesion intensity was evaluated through tyrosine hydroxylase immunohystochemical reaction. Dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and an extent of dopamine striatal tissue levels/dopamine metabolism were measured in the striatum. Lesion with 6-OHDA decreased dopamine, DOPAC, and DOPAC/dopamine ratio in the lesioned striatum. L-DOPA treatment induced abnormal involuntary movements and increased DOPAC/dopamine ratio (nearly five times) in the lesioned striatum. L-DOPA-induced dyskinesia was mitigated by 7-nitroindazole, which also decreased dopamine turnover, dopamine and DOPAC levels. Our results revealed an almost two times increase in dopamine content in the non-lesioned striatum of 6-OHDA-lesioned rats. Reduction of striatal DOPAC/dopamine ratio in dyskinetic rats may suggest an increase in the dopamine availability. Our data confirm contribution of nitrergic transmission in the pathogenesis of L-DOPA-induced dyskinesia with potential utilization of nitric oxide synthase inhibitors for treatment.
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Affiliation(s)
- Elaine Del-Bel
- Department of Morphology, Physiology and Pathology, School of Odontology, University of São Paulo, Campus Ribeirão Preto, Av. Café S/N, Ribeirão Preto, SP, 14040-904, Brazil,
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Daneault JF, Carignan B, Sadikot AF, Panisset M, Duval C. Drug-induced dyskinesia in Parkinson's disease. Should success in clinical management be a function of improvement of motor repertoire rather than amplitude of dyskinesia? BMC Med 2013; 11:76. [PMID: 23514355 PMCID: PMC3751666 DOI: 10.1186/1741-7015-11-76] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 03/20/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Dyskinesia, a major complication in the treatment of Parkinson's disease (PD), can require prolonged monitoring and complex medical management. DISCUSSION The current paper proposes a new way to view the management of dyskinesia in an integrated fashion. We suggest that dyskinesia be considered as a factor in a signal-to-noise ratio (SNR) equation where the signal is the voluntary movement and the noise is PD symptomatology, including dyskinesia. The goal of clinicians should be to ensure a high SNR in order to maintain or enhance the motor repertoire of patients. To understand why such an approach would be beneficial, we first review mechanisms of dyskinesia, as well as their impact on the quality of life of patients and on the health-care system. Theoretical and practical bases for the SNR approach are then discussed. SUMMARY Clinicians should not only consider the level of motor symptomatology when assessing the efficacy of their treatment strategy, but also breadth of the motor repertoire available to patients.
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Affiliation(s)
- Jean-François Daneault
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec H3A 2B4, Canada
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The Antiparkinsonian and Antidyskinetic Mechanisms of Mucuna pruriens in the MPTP-Treated Nonhuman Primate. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2012; 2012:840247. [PMID: 22997535 PMCID: PMC3445014 DOI: 10.1155/2012/840247] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/26/2012] [Accepted: 07/27/2012] [Indexed: 12/01/2022]
Abstract
Chronic treatment with levodopa (LD) in Parkinson's disease (PD) can cause drug induced dyskinesias. Mucuna pruriens endocarp powder (MPEP) contains several compounds including natural LD and has been reported to not cause drug-induced dyskinesias. We evaluated the effects of Mucuna pruriens to determine if its underlying mechanistic actions are exclusively due to LD. We first compared MPEP with and without carbidopa (CD), and LD+CD in hemiparkinsonian (HP) monkeys. Each treatment ameliorated parkinsonism. We then compared the neuronal firing properties of the substantia nigra reticulata (SNR) and subthalamic nucleus (STN) in HP monkeys with MPEP+CD and LD+CD to evaluate basal ganglia circuitry alterations. Both treatments decreased SNR firing rate compared to HP state. However, LD+CD treatments significantly increased SNR bursting firing patterns that were not seen with MPEP+CD treatments. No significant changes were seen in STN firing properties. We then evaluated the effects of a water extract of MPEP. Oral MPWE ameliorated parkinsonism without causing drug-induced dyskinesias. The distinctive neurophysiological findings in the basal ganglia and the ability to ameliorate parkinsonism without causing dyskinesias strongly suggest that Mucuna pruriens acts through a novel mechanism that is different from that of LD.
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Pharmacokinetic study of baicalein after oral administration in monkeys. Fitoterapia 2012; 83:532-40. [DOI: 10.1016/j.fitote.2011.12.019] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 12/18/2011] [Accepted: 12/28/2011] [Indexed: 11/18/2022]
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The interhemispheric connections of the striatum: Implications for Parkinson's disease and drug-induced dyskinesias. Brain Res Bull 2011; 87:1-9. [PMID: 21963946 DOI: 10.1016/j.brainresbull.2011.09.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 09/16/2011] [Accepted: 09/19/2011] [Indexed: 11/20/2022]
Abstract
Parkinson's disease (PD) is characterized by loss of nigrostriatal neurons and depletion of dopamine. This pathological feature leads to alterations to basal ganglia circuitry and subsequent motor disability. Pharmacological dopamine replacement therapy with medications such as levodopa ameliorates the symptoms of PD but can lead to motor complications known as drug-induced dyskinesias. We have recently shown that clinically hemiparkinsonian rhesus monkeys do not develop levodopa-induced dyskinesias despite chronic intermittent exposure and significant unilateral loss of nigrostriatal neurons and dopamine. It is currently unclear what mechanisms prevent the onset of dyskinesias in these animals. Based on our study and results from previous lesioning studies in both the rat and monkey models of PD, we hypothesize that one potential mechanism that may prevent the genesis of dyskinesias in these animals is interhemispheric neuromodulation. Two potential interhemispheric connections that may modulate dyskinesias are the interhemispheric nigrostriatal and corticostriatal pathways. Few investigators have examined the interhemispheric nigrostriatal and corticostriatal connections and the functional role they may play in drug-induced dyskinesias in PD. Therefore, in the following review, we assess the neuroanatomical, electrophysiological and behavioral properties of these interhemispheric connections. Future studies evaluating these interhemispheric striatal pathways and the pathophysiological changes that occur to these pathways in the dyskinetic state are warranted to further develop treatments that prevent or mitigate drug-induced dyskinesias in PD.
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Gilmour TP, Piallat B, Lieu CA, Venkiteswaran K, Ramachandra R, Rao AN, Petticoffer AC, Berk MA, Subramanian T. The effect of striatal dopaminergic grafts on the neuronal activity in the substantia nigra pars reticulata and subthalamic nucleus in hemiparkinsonian rats. ACTA ACUST UNITED AC 2011; 134:3276-89. [PMID: 21911417 DOI: 10.1093/brain/awr226] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
The electrophysiological correlates of parkinsonism in the basal ganglia have been well studied in patients with Parkinson's disease and animal models. Separately, striatal dopaminergic cell transplantation has shown promise in ameliorating parkinsonian motor symptoms. However, the effect of dopaminergic grafts on basal ganglia electrophysiology has not thoroughly been investigated. In this study, we transplanted murine foetal ventral mesencephalic cells into rats rendered hemiparkinsonian by 6-hydroxydopamine injection. Three months after transplantation, extracellular and local field potential recordings were taken under urethane anaesthesia from the substantia nigra pars reticulata and subthalamic nucleus along with cortical electroencephalograms and were compared to recordings from normal and hemiparkinsonian controls. Recordings from cortical slow-wave activity and global activation states were analysed separately. Rats with histologically confirmed xenografts showed behavioural improvement measured by counting apomorphine-induced rotations and with the extended body axis test. Firing rates in both nuclei were not significantly different between control and grafted groups. However, burst firing patterns in both nuclei in the slow-wave activity state were significantly reduced (P < 0.05) in rats with large surviving grafts, compared to hemiparkinsonian controls. The neuronal firing entropies and oscillations in both nuclei were restored to normal levels in the large-graft group. Electroencephalogram spike-triggered averages also showed normalization in the slow-wave activity state (P < 0.05). These results suggest that local continuous dopaminergic stimulation exerts a normalizing effect on the downstream parkinsonian basal ganglia firing patterns. This novel finding is relevant to future preclinical and clinical investigations of cell transplantation and the development of next-generation therapies for Parkinson's disease that ameliorate pathophysiological neural activity and provide optimal recovery of function.
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Affiliation(s)
- Timothy P Gilmour
- Department of Neurology, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
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Gilmour TP, Lieu CA, Nolt MJ, Piallat B, Deogaonkar M, Subramanian T. The effects of chronic levodopa treatments on the neuronal firing properties of the subthalamic nucleus and substantia nigra reticulata in hemiparkinsonian rhesus monkeys. Exp Neurol 2010; 228:53-8. [PMID: 21146527 DOI: 10.1016/j.expneurol.2010.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 11/12/2010] [Accepted: 12/01/2010] [Indexed: 10/18/2022]
Abstract
Dopamine replacement therapy with levodopa (LD) is currently the most effective pharmacological treatment for Parkinson's disease (PD), a neurodegenerative disorder characterized by dysfunction of basal ganglia electrophysiology. The effects of chronic LD treatments on the electrophysiological activity of the subthalamic nucleus (STN) and the substantia nigra reticulata (SNR) in parkinsonism are not clear. In the present study we examined the effects of chronic LD treatments on the firing rate and firing pattern of STN and SNR neurons in the stable hemiparkinsonian monkey model of PD. We also evaluated local field potentials of both nuclei before and after LD treatments. In a stable hemiparkinsonian state, STN and SNR had a mean firing rate of 42.6 ± 3.5H z (mean ± SEM) and 52.1 ± 5.7 Hz, respectively. Chronic intermittent LD exposure induced marked amelioration of parkinsonism with no apparent drug-induced motor complications. LD treatments did not significantly change the mean firing rate of STN neurons (41.3 ± 3.3 Hz) or bursting neuronal firing patterns. However, LD treatments induced a significant reduction of the mean firing rates of SNR neurons to 36.2 ± 3.3 Hz (p<0.05) and a trend toward increased burstiness. The entropy of the spike sequences from STN and SNR was unchanged by LD treatment, while there was a shift of spectral power into higher frequency bands in the LFPs. The inability of chronic LD treatments to reduce the bursty firing patterns in the STN and SNR should be further examined as a potential pathophysiological mechanism for PD symptoms that are refractory to LD treatments.
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Affiliation(s)
- Timothy P Gilmour
- Department of Neurology, The Pennsylvania State University College of Medicine, Hershey, PA, USA.
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