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Ferreira AFF, Ulrich H, Feng ZP, Sun HS, Britto LR. Neurodegeneration and glial morphological changes are both prevented by TRPM2 inhibition during the progression of a Parkinson's disease mouse model. Exp Neurol 2024; 377:114780. [PMID: 38649091 DOI: 10.1016/j.expneurol.2024.114780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 04/11/2024] [Accepted: 04/15/2024] [Indexed: 04/25/2024]
Abstract
Parkinson's disease (PD) is a neurodegenerative disease characterized by dopaminergic neuron death and neuroinflammation. Emerging evidence points to the involvement of the transient receptor potential melastatin 2 (TRPM2) channel in neuron death and glial activation in several neurodegenerative diseases. However, the involvement of TRPM2 in PD and specifically its relation to the neuroinflammation aspect of the disease remains poorly understood. Here, we hypothesized that AG490, a TRPM2 inhibitor, can be used as a treatment in a mouse model of PD. Mice underwent stereotaxic surgery for 6-hydroxydopamine (6-OHDA) administration in the right striatum. Motor behavioral tests (apomorphine, cylinder, and rotarod) were performed on day 3 post-injection to confirm the PD model induction. AG490 was then daily injected i.p. between days 3 to 6 after surgery. On day 6, motor behavior was assessed again. Substantia nigra (SNc) and striatum (CPu) were collected for immunohistochemistry, immunoblotting, and RT-qPCR analysis on day 7. Our results revealed that AG490 post-treatment reduced motor behavior impairment and nigrostriatal neurodegeneration. In addition, the compound prevented TRPM2 upregulation and changes of the Akt/GSK-3β/caspase-3 signaling pathway. The TRPM2 inhibition also avoids the glial morphology changes observed in the PD group. Remarkably, the morphometrical analysis revealed that the ameboid-shaped microglia, found in 6-OHDA-injected animals, were no longer present in the AG490-treated group. These results indicate that AG490 treatment can reduce dopaminergic neuronal death and suppress neuroinflammation in a PD mouse model. Inhibition of TRPM2 by AG490 could then represent a potential therapeutical strategy to be evaluated for PD treatment.
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Affiliation(s)
- Ana Flavia F Ferreira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil; Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada.
| | - Henning Ulrich
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Zhong-Ping Feng
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Hong-Shuo Sun
- Department of Physiology, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada; Department of Surgery, Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Luiz Roberto Britto
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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Airavaara M, Parkkinen I, Konovalova J, Albert K, Chmielarz P, Domanskyi A. Back and to the Future: From Neurotoxin-Induced to Human Parkinson's Disease Models. ACTA ACUST UNITED AC 2020; 91:e88. [PMID: 32049438 DOI: 10.1002/cpns.88] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Parkinson's disease (PD) is an age-related neurodegenerative disorder characterized by motor symptoms such as tremor, slowness of movement, rigidity, and postural instability, as well as non-motor features like sleep disturbances, loss of ability to smell, depression, constipation, and pain. Motor symptoms are caused by depletion of dopamine in the striatum due to the progressive loss of dopamine neurons in the substantia nigra pars compacta. Approximately 10% of PD cases are familial arising from genetic mutations in α-synuclein, LRRK2, DJ-1, PINK1, parkin, and several other proteins. The majority of PD cases are, however, idiopathic, i.e., having no clear etiology. PD is characterized by progressive accumulation of insoluble inclusions, known as Lewy bodies, mostly composed of α-synuclein and membrane components. The cause of PD is currently attributed to cellular proteostasis deregulation and mitochondrial dysfunction, which are likely interdependent. In addition, neuroinflammation is present in brains of PD patients, but whether it is the cause or consequence of neurodegeneration remains to be studied. Rodents do not develop PD or PD-like motor symptoms spontaneously; however, neurotoxins, genetic mutations, viral vector-mediated transgene expression and, recently, injections of misfolded α-synuclein have been successfully utilized to model certain aspects of the disease. Here, we critically review the advantages and drawbacks of rodent PD models and discuss approaches to advance pre-clinical PD research towards successful disease-modifying therapy. © 2020 The Authors.
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Affiliation(s)
- Mikko Airavaara
- Neuroscience Center, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Ilmari Parkkinen
- Neuroscience Center, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Julia Konovalova
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Katrina Albert
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
| | - Piotr Chmielarz
- Department of Brain Biochemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Andrii Domanskyi
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
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Rosa I, Di Censo D, Ranieri B, Di Giovanni G, Scarnati E, Alecci M, Galante A, Florio TM. Comparison between Tail Suspension Swing Test and Standard Rotation Test in Revealing Early Motor Behavioral Changes and Neurodegeneration in 6-OHDA Hemiparkinsonian Rats. Int J Mol Sci 2020; 21:ijms21082874. [PMID: 32326015 PMCID: PMC7216013 DOI: 10.3390/ijms21082874] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 04/07/2020] [Accepted: 04/16/2020] [Indexed: 12/25/2022] Open
Abstract
The unilateral 6-hydroxydopamine (6-OHDA) model of Parkinson’s disease (PD) is one of the most commonly used in rodents. The anatomical, metabolic, and behavioral changes that occur after severe and stable 6-OHDA lesions have been extensively studied. Here, we investigated whether early motor behavioral deficits can be observed in the first week after the injection of 6-OHDA into the right substantia nigra pars compacta (SNc), and if they were indicative of the severity of the dopaminergic (DAergic) lesion in the SNc and the striatum at different time-points (day 1, 3, 5, 7, 14, 21). With this aim, we used our newly modified tail suspension swing test (TSST), the standard rotation test (RT), and immunohistochemical staining for tyrosine hydroxylase (TH). The TSST, but not the standard RT, revealed a spontaneous motor bias for the 6-OHDA-lesioned rats from the day 1 post-surgery. Both tests detected the motor asymmetry induced by (single and repeated) apomorphine (APO) challenges that correlated, in the first week, with the DAergic neuronal degeneration. The described TSST is fast and easy to perform, and in the drug-free condition is useful for the functional assessment of early motor asymmetry appearing after the 6-OHDA-lesion in the SNc, without the confounding effect of APO challenges.
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Affiliation(s)
- Ilaria Rosa
- Department of Life, Health and Environmental Sciences (MESVA), University of L’Aquila, 67100 L’Aquila, Italy; (D.D.C.); (B.R.); (M.A.); (A.G.); (T.M.F.)
- Correspondence: (I.R.); (G.D.G.)
| | - Davide Di Censo
- Department of Life, Health and Environmental Sciences (MESVA), University of L’Aquila, 67100 L’Aquila, Italy; (D.D.C.); (B.R.); (M.A.); (A.G.); (T.M.F.)
| | - Brigida Ranieri
- Department of Life, Health and Environmental Sciences (MESVA), University of L’Aquila, 67100 L’Aquila, Italy; (D.D.C.); (B.R.); (M.A.); (A.G.); (T.M.F.)
| | - Giuseppe Di Giovanni
- Department of Life, Health and Environmental Sciences (MESVA), University of L’Aquila, 67100 L’Aquila, Italy; (D.D.C.); (B.R.); (M.A.); (A.G.); (T.M.F.)
- Laboratory of Neurophysiology, Department of Physiology and Biochemistry, Faculty of Medicine and Surgery, University of Malta, Msida MSD 2080, Malta
- Correspondence: (I.R.); (G.D.G.)
| | - Eugenio Scarnati
- Department of Biotechnological and Applied Clinical Sciences (DISCAB), University of L’Aquila, 67100 L’Aquila, Italy;
| | - Marcello Alecci
- Department of Life, Health and Environmental Sciences (MESVA), University of L’Aquila, 67100 L’Aquila, Italy; (D.D.C.); (B.R.); (M.A.); (A.G.); (T.M.F.)
- National Institute of Nuclear Physics, Gran Sasso National Laboratories, Assergi, 67100 L’Aquila, Italy
- SPIN-CNR Institute, Department of Physical and Chemical Sciences, 67100 L’Aquila, Italy
| | - Angelo Galante
- Department of Life, Health and Environmental Sciences (MESVA), University of L’Aquila, 67100 L’Aquila, Italy; (D.D.C.); (B.R.); (M.A.); (A.G.); (T.M.F.)
- National Institute of Nuclear Physics, Gran Sasso National Laboratories, Assergi, 67100 L’Aquila, Italy
- SPIN-CNR Institute, Department of Physical and Chemical Sciences, 67100 L’Aquila, Italy
| | - Tiziana Marilena Florio
- Department of Life, Health and Environmental Sciences (MESVA), University of L’Aquila, 67100 L’Aquila, Italy; (D.D.C.); (B.R.); (M.A.); (A.G.); (T.M.F.)
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Andreeva-Gateva P, Traikov L, Sabit Z, Bakalov D, Tafradjiiska-Hadjiolova R. Antioxidant Effect of Alpha-Lipoic Acid in 6-Hydroxydopamine Unilateral Intrastriatal Injected Rats. Antioxidants (Basel) 2020; 9:E122. [PMID: 32024109 PMCID: PMC7070677 DOI: 10.3390/antiox9020122] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 01/29/2020] [Accepted: 01/30/2020] [Indexed: 12/13/2022] Open
Abstract
The toxin 6-hydroxydopamine (6-OHDA) is a highly oxidizable dopamine (DA) analog that is widely used for reproducing several cell processes identified in Parkinson's disease (PD). Due to the close similarity of its neurotoxic mechanism to those of DA, it is suitable as a model for testing the effects of potentially neuroprotective drugs. This study aimed to evaluate the effect of alpha-lipoic acid (LA) on brain oxidative stress (OS) in unilateral intrastriatal (6-OHDA) injected rats. Forty male Wistar rats, four months old (220-260 g), were evaluated. Half of them received LA (35 mg/kg i.p.) from the start to the end of the experiment. On day 2 of the trial, ten LA-supplemented rats and ten non-LA-supplemented rats were subjected to the apomorphine test. Brain homogenates were evaluated for thiobarbituric acid-reactive substances (TBARS) and glutathione peroxidase (GPx) activity. The same evaluation procedures were repeated on day 14 with the remaining animals. An increased TBARS level and decreased GPx activity, suggestive for OS, were recorded in homogenates on day 14 vs. day 2 of the experiment in the 6-OHDA treated rats. The simultaneous application of LA mitigated these changes. Our study demonstrates that the low dose of LA could be of value for decreasing the OS of the neurotoxic 6-OHDA, supporting the need for further studies of the benefit of LA treatment in PD.
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Affiliation(s)
- Pavlina Andreeva-Gateva
- Department of Pharmacology and Toxicology, Faculty of Medicine, Medical University-Sofia, 1431 Sofia, Bulgaria
| | - Lubomir Traikov
- Department of Medical Physics and Biophysics, Faculty of Medicine, Medical University-Sofia, 1431 Sofia, Bulgaria
| | - Zafer Sabit
- Department of Pathophysiology, Faculty of Medicine, Medical University-Sofia, 1431 Sofia, Bulgaria
| | - Dimitar Bakalov
- Department of Pathophysiology, Faculty of Medicine, Medical University-Sofia, 1431 Sofia, Bulgaria
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Combination of CDNF and Deep Brain Stimulation Decreases Neurological Deficits in Late-stage Model Parkinson's Disease. Neuroscience 2018; 374:250-263. [PMID: 29408408 DOI: 10.1016/j.neuroscience.2018.01.052] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Revised: 12/22/2017] [Accepted: 01/25/2018] [Indexed: 12/17/2022]
Abstract
Several neurotrophic factors (NTF) are shown to be neuroprotective and neurorestorative in pre-clinical animal models for Parkinson's disease (PD), particularly in models where striatal dopamine neuron innervation partially exists. The results of clinical trials on late-stage patients have been modest. Subthalamic deep brain stimulation (STN DBS) is a proven treatment for a selected group of advanced PD patients. The cerebral dopamine neurotrophic factor (CDNF) is a promising therapeutic protein, but its effects in animal models of late-stage PD have remained under-researched. The interactions of NTF and STN DBS treatments have not been studied before. We found that a nigral CDNF protein alone had only a marginal effect on the behavioral deficits in a late-stage hemiparkinsonian rat model (6-OHDA MFB). However, CDNF improved the effect of acute STN DBS on front limb use asymmetry at 2 and 3 weeks after CDNF injection. STN lesion-modeling chronic stimulation-had an additive effect in reducing front limb use in the cylinder test and apomorphine-induced rotation. The combination of CDNF and acute STN DBS had a favorable effect on striatal tyrosine hydroxylase. This study presents a novel additive beneficial effect of NTF and STN DBS, which might be explained by the interaction of DBS-induced endogenous NTFs and exogenously injected CDNF. SNpc can be reached via similar trajectories used in clinical STN DBS, and this interaction is an important area for future studies.
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Carbone C, Costa A, Provensi G, Mannaioni G, Masi A. The Hyperpolarization-Activated Current Determines Synaptic Excitability, Calcium Activity and Specific Viability of Substantia Nigra Dopaminergic Neurons. Front Cell Neurosci 2017; 11:187. [PMID: 28701928 PMCID: PMC5487410 DOI: 10.3389/fncel.2017.00187] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 06/16/2017] [Indexed: 12/28/2022] Open
Abstract
Differential vulnerability between Substantia Nigra pars compacta (SNpc) and Ventral Tegmental Area (VTA) dopaminergic (DAergic) neurons is a hallmark of Parkinson’s disease (PD). Understanding the molecular bases of this key histopathological aspect would foster the development of much-needed disease-modifying therapies. Non-heterogeneous DAergic degeneration is present in both toxin-based and genetic animal models, suggesting that cellular specificity, rather than causing factors, constitutes the background for differential vulnerability. In this regard, we previously demonstrated that MPP+, a neurotoxin able to cause selective nigrostriatal degeneration in animal rodents and primates, inhibits the Hyperpolarization-activated current (Ih) in SNpc DAergic neurons and that pharmacological Ih antagonism causes potentiation of evoked Excitatory post-synaptic potentials (EPSPs). Of note, the magnitude of such potentiation is greater in the SNpc subfield, consistent with higher Ih density. In the present work, we show that Ih block-induced synaptic potentiation leads to the amplification of somatic calcium responses (SCRs) in vitro. This effect is specific for the SNpc subfield and largely mediated by L-Type calcium channels, as indicated by sensitivity to the CaV 1 blocker isradipine. Furthermore, Ih is downregulated by low intracellular ATP and determines the efficacy of GABAergic inhibition in SNpc DAergic neurons. Finally, we show that stereotaxic administration of Ih blockers causes SNpc-specific neurodegeneration and hemiparkinsonian motor phenotype in rats. During PD progression, Ih downregulation may result from mitochondrial dysfunction and, in concert with PD-related disinhibition of excitatory inputs, determine a SNpc-specific disease pathway.
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Affiliation(s)
- Carmen Carbone
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy
| | - Alessia Costa
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy
| | - Gustavo Provensi
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy
| | - Guido Mannaioni
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy.,Toxicology Unit, Azienda Ospedaliero-Universitaria CareggiFlorence, Italy
| | - Alessio Masi
- Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), Section of Pharmacology and Toxicology, University of FlorenceFlorence, Italy.,Toxicology Unit, Azienda Ospedaliero-Universitaria CareggiFlorence, Italy
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Penttinen AM, Suleymanova I, Albert K, Anttila J, Voutilainen MH, Airavaara M. Characterization of a new low-dose 6-hydroxydopamine model of Parkinson's disease in rat. J Neurosci Res 2016; 94:318-28. [PMID: 26762168 DOI: 10.1002/jnr.23708] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 12/01/2015] [Accepted: 12/10/2015] [Indexed: 12/21/2022]
Abstract
Intrastriatal administration of 6-hydroxydopamine (6-OHDA) induces partial degeneration of the nigrostriatal pathway, mimicking the pathology of Parkinson's disease (PD). Setting up the partial lesion model can be challenging because a number of experimental settings can be altered. This study compares seven experimental settings in a single study on d-amphetamine-induced rotations, tyrosine hydroxylase (TH)-positive neurites in the striatum, dopamine transporter (DAT)-positive neurites in the striatum, and TH-positive cells in the substantia nigra pars compacta (SNpc) in rats. Moreover, we validate a new algorithm for estimating the number of TH-positive cells. We show that the behavior and immunoreactivity vary greatly depending on the injection settings, and we categorize the lesions as progressive, stable, or regressive based on d-amphetamine-induced rotations. The rotation behavior correlated with the degree of the lesion, analyzed by immunohistochemistry; the largest lesions were in the progressive group, and the smallest lesions were in the regressive group. We establish a new low-dose partial 6-OHDA lesion model in which a total of 6 μg was distributed evenly to three sites in the striatum at a 10° angle. The administration of low-dose 6-OHDA produced stable and reliable rotation behavior and induced partial loss of striatal TH-positive and DAT-positive neurites and TH-positive cells in the SNpc. This model is highly suitable for neurorestoration studies in the search for new therapies for PD, and the new algorithm increases the efficacy for estimating the number of dopamine neurons. This study can be extremely useful for laboratories setting up the partial 6-OHDA model.
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Affiliation(s)
| | - Ilida Suleymanova
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Katrina Albert
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Jenni Anttila
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | | | - Mikko Airavaara
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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Slack K, Billing R, Matthews S, Allbutt HN, Einstein R, Henderson JM. Subtle cardiovascular dysfunction in the unilateral 6-hydroxydopamine-lesioned rat. PARKINSONS DISEASE 2010; 2010:427810. [PMID: 20976085 PMCID: PMC2957224 DOI: 10.4061/2010/427810] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 11/17/2009] [Accepted: 12/30/2009] [Indexed: 11/20/2022]
Abstract
The present study evaluated whether the unilateral 6-hydroxydopamine (6-OHDA) model of Parkinson's disease produces autonomic deficits. Autonomic parameters were assessed by implanting a small radiofrequency telemetry device which measured heart rate variability (HRV), diurnal rhythms of heart rate (HR), core body temperature (cBT) and locomotor activity (LA). Rats then received 6-OHDA lesion or sham surgery. 6-OHDA lesioned rats exhibited head and body axis biases, defective sensorimotor function ("disengage" test), and prominent apomorphine rotation (all P < .05 versus controls). Diurnal rhythm of HR was lower for 6-OHDA lesioned rats (n = 8) versus controls (n = 6; P < .05). Whilst HR decreased similarly in both groups during the day, there was a greater decrease in HR for the 6-OHDA lesioned rats at night (by 38 b.p.m. relative to 17 b.p.m. for controls). LA and cBT did not differ between surgery groups. This study indicates the unilateral 6-OHDA model of PD shows subtle signs of cardiovascular autonomic dysfunction.
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Affiliation(s)
- K Slack
- Department of Pharmacology, Bosch Institute and School of Medical Sciences, University of Sydney, NSW 2006, Australia
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Warraich ST, Allbutt HN, Billing R, Radford J, Coster MJ, Kassiou M, Henderson JM. Evaluation of behavioural effects of a selective NMDA NR1A/2B receptor antagonist in the unilateral 6-OHDA lesion rat model. Brain Res Bull 2008; 78:85-90. [PMID: 18822357 DOI: 10.1016/j.brainresbull.2008.08.023] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The degeneration of the dopaminergic nigrostriatal pathway in Parkinson's disease (PD) is associated with altered transmission at striatal NMDA receptors containing NR2B subunits. We investigated a potential novel therapeutic compound, 4-trifluoromethoxy-N-(2-trifluoromethyl-benzyl)-benzamidine (BZAD-01), a selective NMDA NR1A/2B receptor antagonist for PD and compared it with levodopa, the standard treatment for PD. This study also evaluated whether combining levodopa and BZAD-01 gave better improvements of parkinsonian symptoms. Parkinsonism was induced by microinjection of the toxin, 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle (MFB) of 40 Sprague-Dawley rats. Parkinsonism and the efficacy of drugs were assessed using a battery of behavioural tests including balance beam, apomorphine-induced rotation, body axis bias or "curling", head position bias and disengage sensorimotor latency test. Immunohistochemistry was performed on post-mortem tissue to estimate the loss of dopaminergic neurons. The main effects were that BZAD-01 co-administration prevented chronic levodopa-induced potentiation of apomorphine rotation. However levodopa-treated rats were slower than either controls or BZAD-01-treated rats in the locomotor test. The improvement in the apomorphine rotation test suggests that BZAD-01 may be a useful adjunct to levodopa monotherapy.
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Affiliation(s)
- S T Warraich
- Department of Pharmacology, Bosch Institute and School of Medical Sciences, University of Sydney, NSW 2006, Australia
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Chen MT, Morales M, Woodward DJ, Hoffer BJ, Janak PH. In vivo extracellular recording of striatal neurons in the awake rat following unilateral 6-hydroxydopamine lesions. Exp Neurol 2001; 171:72-83. [PMID: 11520122 DOI: 10.1006/exnr.2001.7730] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to further understand the functional effects of dopaminergic input to the dorsal striatum and to compare the effects of dopaminergic lesions in awake and anesthetized animals. We examined the effects of unilateral 6-hydroxydopamine (6-OHDA) lesions of the ascending dopaminergic bundle on the firing properties of dorsal striatal neurons in the awake freely moving rat using chronically implanted microwire electrode arrays. We recorded extracellular activity of striatal neurons under baseline conditions and following the systemic injection of apomorphine in awake and anesthetized subjects. Firing rates were higher in the hemisphere ipsilateral to the 6-OHDA lesion compared to rates of neurons from the contralateral unlesioned hemisphere. Striatal firing rates from sham and no-surgery control rats were, in general, higher than those from the contralateral unlesioned striatum of experimental subjects. Apomorphine (0.05 mg/kg, sc) normalized the differences in firing rates in lesioned animals by increasing firing of neurons within the contralateral unlesioned side, while simultaneously decreasing firing of neurons within the ipsilateral lesioned side. Mean firing rates were substantially higher in awake animals than in subjects anesthetized with chloral hydrate, perhaps reflecting anesthesia-induced decreases in excitatory input to striatal neurons. Chloral hydrate anesthesia decreased firing rates of neurons in the lesioned, unlesioned, and control striata to a similar degree, although absolute firing rates of neurons from the 6-OHDA-lesioned striata remained elevated over all other groups. Unilateral 6-OHDA lesions also altered the pattern of spike output in the awake animal as indicated by an increase in the number of bursts per minute following dopaminergic deafferentation. This and other burst parameters were altered by apomorphine. Our findings show that effects of dopaminergic deafferentation can be measured in the awake behaving animal; this model should prove useful for testing the behavioral and functional effects of experimental manipulations designed to reduce or reverse the effects of dopaminergic cell loss. In addition, these results suggest that the contralateral changes in striatal function which occur in the unilateral dopaminergic lesion model should be considered when evaluating experimental results.
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Affiliation(s)
- M T Chen
- Intramural Research Program, Cellular Neurobiology Branch, National Institute on Drug Abuse, Baltimore, Maryland, USA
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Tirelli E, Heidbreder CA. Anticipatory responding, exclusive drug-context pairing and conditioned effects in sensitization to apomorphine-induced climbing in mice. Prog Neuropsychopharmacol Biol Psychiatry 1999; 23:505-18. [PMID: 10378233 DOI: 10.1016/s0278-5846(99)00012-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
1. The conditioning aspects of contextual sensitization were examined in the case of apomorphine-induced wall-climbing in mice, measuring onset latencies of the pharmacological response and controlling differential habituation to the test context during drug treatment. 2. Sensitization was generated in male out-bred mice which received intermittent i.p. injections of 0.4 mg/kg apomorphine over 9 daily sessions. On day 10, they were tested for contextual sensitization (all mice under apomorphine). On day 14, after 3 sessions of reinstatement, mice were tested for conditioned climbing (all mice under saline). 3. It was found that simultaneous exposure to both apomorphine and the test context facilitated the expression of a full-blown contextual sensitization (some non-contextual sensitization emerging too); importantly, sensitization was accompanied by a progressive shortening of the latencies to climb (before injections); conditioned climbing appeared only in mice pairing the drug with the test context, that response being absent in mice treated outside the context or never exposed to the context. 4. It is likely that contextual sensitization to apomorphine-induced climbing relies on Pavlovian conditioning processes rather than on habituation-related processes.
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Affiliation(s)
- E Tirelli
- University of Liège, Laboratory of Psychopharmacology, Belgium.
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Wynne B, Delius JD. Sensitization to apomorphine in pigeons: unaffected by latent inhibition but still due to classical conditioning. Psychopharmacology (Berl) 1995; 119:414-20. [PMID: 7480521 DOI: 10.1007/bf02245857] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
When administered apomorphine, pigeons exhibit protracted bouts of pecking behavior. This response is subject to sensitization, as it initially increases with repeated drug injections. The hypothesis is examined that the sensitization is due to a Pavlovian conditioning of the drug-induced pecking to the environment in which it first takes effect. In a first experiment, we attempted to suppress this conditioning by extensively pre-exposing the birds to the test environment and saline injections (latent inhibition procedure). As the experiment yielded undiminished sensitization, it cast doubt on the conditioning hypothesis. However, while inhibitory pretraining also proved ineffective in a second experiment, a shortening of response latencies specific to the environment in which the animals had first experienced the apomorphine effect supported the conditioning hypothesis. It is suggested that the absence of latent inhibition may be due to the interference of a context-dependent conditioning effect. A third experiment that examined the hypothesis that the reinforcing properties of apomorphine might be attributable to its well known anorectic properties. The results provided some support for this notion. At the same time, they also confirmed that apomorphine-induced pecking conditions reliably to environmental cues. These cues are then by themselves capable of provoking conditioned pecking.
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Affiliation(s)
- B Wynne
- Universität Konstanz, Germany
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