eISSN: 1509-572x
ISSN: 1641-4640
Folia Neuropathologica
Current issue Archive Manuscripts accepted About the journal Special Issues Editorial board Reviewers Abstracting and indexing Subscription Contact Instructions for authors Ethical standards and procedures
Editorial System
Submit your Manuscript
SCImago Journal & Country Rank
vol. 61
Original paper

Exercise attenuates neuronal degeneration in Parkinson’s disease rat model by regulating the level of adenosine 2A receptor

Ruizhi Li
Shasha Jin
Jiangen He
Yanxia Peng
Longfei Wei
Lei Gu

Department of Physical Therapy, Beijing Xiaotangshan Hospital, Beijing, China
Department of Sports Rehabilitation, Beijing Xiaotangshan Hospital, Beijing, China
Folia Neuropathol 2023; 61 (2): 217-223
Online publish date: 2023/02/16
Article file
- Exercise.pdf  [0.11 MB]
Get citation
PlumX metrics:


Parkinson’s disease (PD) is a chronic degeneration of dopaminergic neurons which decrease the level of dopamine in the substantia nigra [2]. Parkinson’s disease is characterised by classical symptoms such as tremor, bradykinesia, and rigidity, which is also associated with cognitive dysfunction [6]. Parkinson’s disease is associated with a number of pathogenic pathways including aggregation of α-synuclein (α-syn) in the neurons, contributes to the activation of inflammatory mediators and oxidative stress leads to neurodegeneration [17].
The literature reveals that adenosine A2 receptor (AA2) emerged as a promising target for the management of PD, antagonists of which reverse the altered motor and non-motor function in PD rats [5]. Moreover, AA2 receptor regulation also emerges for the beneficial effect of neuronal dysfunction such as Alzheimer’s disease, stress disorders and epilepsy [24]. AA2 receptor modulation reported for α-syn-mediated neurotoxicity, which alters the synaptic function leads to neuronal death [18]. AA2 receptor regulation stimulates aggregation of α-syn, activates the microglia which stimulates the neuronal inflammatory pathway by regulating TLR-2 pathway, which leads to neuronal death [16].
There are several therapies conventionally used for the management of PD which modulates the motor function and reduces the progression of disease. However, these medicines also have a number of limitations. It is well documented that exercise improves multiple organ functions, which protects PD clinically [1]. Reported studies suggest that exercise promotes motor function by improving the level of dopamine and protects dopaminergic neurons [21]. Exercise downregulates the expression of AA2 receptor, which is reported to alter the neurochemical level in the brain tissue [22]. Exercise promotes the level of dopamine in striatum, which could improve the motor function [8]. Thus, the present report evaluates the effect of exercise against PD.

Material and methods

Sprague Dawley rats (either sex, age: 8 weeks, 250-300 gm) were housed under standard environmental conditions (22 ±2°C, humidity 55-60%, light-dark cycle of 12 hours each) and fed with standard pellet diet and water. The protocol was reviewed and approved by the Beijing Xiaotangshan Hospital animal ethical committee, JN. No. 202001230b0601211.
All the animals were separated into two different groups like the control group (n = 6), PD groups (n = 18) which received rotenone (1 mg/kg) s.c. every 48 h for 18 days for the induction of PD [13]. PD groups were further separated into three groups such as the negative control group which did not receive any treatment or exercise for next 2 weeks; the exercise-treated group received two weeks’ exercise after the induction of PD; the AA2 group received exercise along with CGS 21680 (adenosine A2A receptor agonist; Sigma-Aldrich Ltd., USA; 0.5 mg/kg, i.p.) for a period of two weeks after the induction of PD (Fig. 1).
Treadmill exercise
Rodent treadmill was used to provide exercise training to the rats for a period of 14 days after the confirmation of PD. Training was provided for 40 min every day with an inclination of 0 degree at a speed of 8 m/min, i.e. first 5 min at a speed of 2 m/min, next 5 min at 5 m/min and last 30 min at a speed of 8 m/min. Biochemical, neuronal and behaviour activities were estimated within 48 h after the last session of exercise.
Estimation of motor function
Motor function and muscle balance were estimated using the rotarod apparatus. All the animals were mounted on the apparatus which rotates at a speed of 18 RPM and time to fall was recorded as the latency period.
Behavioural studies
Apomorphine-induced rotation behaviour was assessed to determine the lesions of the dopaminergic system in PD rats. Apomorphine depletes the dopamine level which alters the number of rotations in PD rats. Contralateral rotation was induced by the administration of 3 mg/kg, s.c. and changes in behaviour were monitored for the duration of 1 h.
Morris Water Maze test
Cognitive function in rats was estimated using the Morris Water Maze (MWM) test as per previously published reports [25]. MWM apparatus’ dimensions are as follows: circular pool: 120 cm; height: 50 cm; and depth: 30 cm. The pool was separated into four different quadrants and a platform was placed in one quadrant, trials were given on 5 consecutive days. The platform was removed on the 6th day and the time spent in the target quadrant was observed.
Preparation of brain tissue homogenate
Brain was isolated from each animal after sacrificing them and brain tissue was homogenized in pH = 7.4, 0.1 M phosphate buffer. Brain tissue was centrifuged at 3000 rpm for 15 min and supernatant was separated to determine the neurochemical and biochemical estimation.
Estimation of dopamine and glutamate
The levels of glutamate and dopamine were estimated in the brain tissue homogenate using their respective assay kits as per the directions given by the manufacturer of kits.
Estimation of inflammatory cytokines and oxidative stress parameters
The level of interleukin (IL)-1β, IL-6, and tumor necrosis factor α (TNF-α) was estimated in the tissue homogenate of Parkinson’s disease rat using the ELISA kit as per the direction given by the manufacturer of the kit. Oxidative stress parameters such as lipid peroxidation (LPO) and reduced glutathione (GSH) were determined in brain tissue homogenate of the PD rat. The malondialdehyde (MDA) level was estimated in the brain tissue as per Ohkawa method at 532 nm. GSH content was determined in the hippocampal tissue by estimating the absorbance at 412 nm.
Statistical analysis
Data are expressed as mean ±SD (n = 6). One-way analysis of variance (ANOVA) followed by post-hoc Tukey test was used to compare the various groups. P < 0.05 was considered statistically significant.


Exercise ameliorates the motor behaviour
Motor function was estimated in rotenone-induced PD rats treated with exercise and CGS 21680 using the rotarod apparatus and apomorphine-induced rotation behaviour as shown in Figure 2A, B. Effect of exercise was determined by the number of falls per min using the rotarod apparatus. There was a significant increase in the number of falls per min (rotarod apparatus) and total net rotations per 40 min (apomorphine-induced rotation behaviour) in the negative control group compared to the control group of rats. The exercise group had a significantly (p < 0.01) reduced number of falls per min and total net rotations per 40 min than the negative control group, however treatment with CGS 21680 reverses the positive effect of exercise in PD rats.
Exercise ameliorates cognitive dysfunction
Effect of exercise and CGS 21680 was estimated on learning and memory (cognitive function) in rotenone-induced PD rats using Morris water maze apparatus. Percentage of time spent in the target quadrant and the number of crossings was reduced and escape latency was enhanced in the negative control group compared to the control group of rats. It was observed that exercise increases the time spent in the target quadrant and the number of crossings and decreases escape latency in rotenone-induced PD rats. However, treatment with CGS 21680 reverses the effect of exercise on PD rats (Fig. 3).
Exercise ameliorates the level of neurochemicals
The level of neurochemicals such as dopamine and glutamate was estimated in the brain tissue of exercise- and CGS 21680-treated PD rats as shown in Figure 4. There was a significant reduction in the level of dopamine and the level of glutamate increases in brain tissue of the negative control group compared to the control group of rats. The glutamate level was reduced, and the dopamine level was improved significantly in tissue homogenate of the exercise-treated group compared to the negative control group. Treatment with CGS 21680 reverses the positive effect of exercise against PD.
Exercise ameliorates inflammatory cytokines
Inflammatory cytokines such as IL-1β, IL-6 and TNF-α were estimated in the tissue homogenate of exercise- and CGS 21680-treated PD rats using ELISA method. The inflammatory cytokine level was significantly enhanced in brain tissue of PD rats compared to the control group. However, exercise ameliorates the altered expression of cytokines in brain tissue of PD rats and CGS 21680 treatment reverses the effect of exercise in PD rats (Fig. 5).
Exercise ameliorates oxidative stress
Oxidative stress parameters such as MDA and GSH level were estimated in brain tissue of exercise- and CGS 21680-treated PD rats as shown in Figure 6. The level of GSH was reduced and the MDA level was increased in the tissue homogenate of the negative control group compared to the control group of rats. There was an increase in GSH and a decrease in the level of MDA in the brain tissue homogenate of the exercise group compared to the negative control group. Treatment with CGS 21680 significantly reverses the effect of exercise on the level of MDA and SOD in brain tissue of PD rats.


Parkinson’s disease is a degenerative disease of the dopaminergic neuron, which is characterized by loss of motor function [2]. There are several pathogenic pathways such as oxidative stress, neuronal apoptosis, inflammatory pathway, and deposition of -syn around the neuron which are involved in development of PD [7]. There are several conventional drugs available for its management, which has several limitations. In the recent era, more clinical concern focuses on quality of life of the patient suffering from chronic disorders including PD. The literature reports that exercise has a beneficial effect on PD as it promotes the mobility and delays the degradation of neurodegeneration in PD [15]. Adenosine A2A receptor activation is reported to be observed in PD, which is responsible for neuronal degeneration and reduction in the level of dopamine in the brain tissue [23]. Moreover, AA2 agonist (CGS 21680) is responsible for activation of inflammation and oxidative stress in PD [10]. However, the exact molecular involvement of the exercise effect on motor function and neurodegeneration in PD is yet to be explored.
Parkinson’s disease is characterized by classical symptoms such as tremor, akinesia, and rigidity, which occur due to the altered motor function because of degeneration of dopaminergic neurons [6]. Motor function such as muscle coordination and locomotor activity is regulated by motor neurons, which is altered in PD [14] and this is supported by data of the study as muscle coordination and locomotor activity are reduced significantly in PD rats. Exercise improves motor function such as locomotor activity and muscle coordination in PD. Adenosine A2 receptor activation are reported to occur in PD [5] and treatment with AA2 antagonist reverses motor and non-motor function in PD. However, data of the present report reveal that treatment with CGS 21680 reverses the effect of exercise on motor and non-motor function in PD rats. Cognitive function such as learning and memory is also altered in PD [9] and the present report reveals that exercise improves it, which is altered due to treatment with CGS 21680.
Neurochemical balance is required for the normal functioning of the nervous system and degeneration of dopaminergic neurons altered the level of neurotransmitters including reduction in the dopamine level and increase in the glutamate level in PD [11]. Data of the present study suggest that exercise attenuates the altered neurochemical level in brain tissue of PD rats, CGS 21680 treatment reverses the beneficial effect of exercise on the level of DA and glutamate in PD rats.
Oxidative stress and inflammatory pathway are involved in the pathogenesis of PD. Lipid peroxidation is an oxidative stress marker by determining the concentration of thiobarbituric acid [19]. LPO impairs the function of the cellular membrane by degrading the membrane due to oxidative degradation of polyunsaturated fatty acids [20]. Oxidative stress is one of the major pathways involved in most of the chronic disorders including PD, which causes neuronal injury in substantia nigra [4], and data of the present report also suggest that oxidative stress is enhanced in PD. Moreover, the level of reduced GSH decreases PD, which causes neuronal loss in the brain tissue [3]. Reduced GSH improves the neuronal capacity to metabolize H2O2, which is responsible for generation of reactive oxygen species [26]. Exercise ameliorates altered oxidative stress parameters in brain tissue of PD and treatment with CGS 21680 reverses the effect of exercise on oxidative stress parameters in PD rats.
Inflammation is involved in neuronal injury including PD, cytokines such as IL-1β, IL-6 and TNF-α are involved majorly in systemic inflammation, which is responsible for the activation of apoptosis [12]. Parkinson’s disease occurs due to neuronal injury in which the inflammatory cytokine level is enhanced, which contributes to neuronal apoptosis in the brain tissue. This is supported by data of the present report and exercise ameliorates the altered level of inflammatory cytokines, which is reversed with CGS 21680 treatment.


All the authors of the presented manuscript are thankful to Beijing Xiaotangshan Hospital for providing necessary facility to conduct the presented work.


The authors report no conflict of interest.
1. Ahlskog JE. Does vigorous exercise have a neuroprotective effect in Parkinson disease? Neurology 2011; 77: 288-294.
2. Alexander GE. Biology of Parkinson’s disease: pathogenesis and pathophysiology of a multisystem neurodegenerative disorder. Dialogues Clin Neurosci 2004; 6: 259-280.
3. Aoyama K, Nakaki T. Impaired glutathione synthesis in neurodegeneration. Int J Mol Sci 2013; 14: 21021-21044.
4. Chen X, Guo C, Kong J. Oxidative stress in neurodegenerative diseases. Neural Regen Res 2012; 7: 376-385.
5. Cieślak M, Komoszyński M, Wojtczak A. Adenosine A(2A) receptors in Parkinson’s disease treatment. Purinergic Signal 2008; 4: 305-312.
6. DeMaagd G, Philip A. Parkinson’s disease and its management. Part 1: Disease entity, risk factors, pathophysiology, clinical presentation, and diagnosis. P T 2015; 40: 504-532.
7. Dias V, Junn E, Mouradian MM. The role of oxidative stress in Parkinson’s disease. J Parkinsons Dis 2013; 3: 461-491.
8. El-Ghaiesh SH, Bahr HI, Ibrahiem AT, Ghorab D, Alomar SY, Farag NE, Zaitone SA. Metformin protects from rotenone-induced nigrostriatal neuronal death in adult mice by activating AMPK-FOXO3 signaling and mitigation of angiogenesis. Front Mol Neurosci 2020; 13: 84.
9. Fang C, Lv L, Mao S, Dong H, Liu B. Cognition deficits in Parkinson’s disease: mechanisms and treatment. Parkinsons Dis 2020; 2020: 2076942.
10. Haskó G, Pacher P. A2A receptors in inflammation and injury: lessons learned from transgenic animals. J Leukoc Biol 2008; 83: 447-455.
11. Juárez Olguín H, Calderón Guzmán D, Hernández García E, Barragán Mejía G. The role of dopamine and its dysfunction as a consequence of oxidative stress. Oxid Med Cell Longev 2016; 2016: 9730467.
12. Kany S, Vollrath JT, Relja B. Cytokines in inflammatory disease. Int J Mol Sci 2019; 20: 6008.
13. Lin TW, Kuo YM. Exercise benefits brain function: the monoamine connection. Brain Sci 2013; 3: 39-53.
14. Magrinelli F, Picelli A, Tocco P, Federico A, Roncari L, Smania N, Zanette G, Tamburin S. Pathophysiology of motor dysfunction in Parkinson’s disease as the rationale for drug treatment and rehabilitation. Parkinsons Dis 2016; 2016: 9832839.
15. Mahalakshmi B, Maurya N, Lee SD, Bharath Kumar V. Possible neuroprotective mechanisms of physical exercise in neurodegeneration. Int J Mol Sci 2020; 21: 5895.
16. Merighi S, Nigro M, Travagli A, Pasquini S, Borea PA, Varani K, Vincenzi F, Gessi S. A2A adenosine receptor: a possible therapeutic target for Alzheimer’s disease by regulating NLRP3 inflammasome activity? Int J Mol Sci 2022; 23: 5056.
17. Mosley RL, Benner EJ, Kadiu I, Thomas M, Boska MD, Hasan K, Laurie C, Gendelman HE. Neuroinflammation, oxidative stress and the pathogenesis of Parkinson’s disease. Clin Neurosci Res 2006; 6: 261-281.
18. Morelli M, Carta AR, Jenner P. Adenosine A2A receptors and Parkinson’s disease. Handb Exp Pharmacol 2009; 193: 589-615.
19. Nagababu E, Rifkind JM, Boindala S, Nakka L. Assessment of antioxidant activity of eugenol in vitro and in vivo. Methods Mol Biol 2010; 610: 165-180.
20. Nita M, Grzybowski A. The role of the reactive oxygen species and oxidative stress in the pathomechanism of the age-related ocular diseases and other pathologies of the anterior and posterior eye segments in adults. Oxid Med Cell Longev 2016; 2016: 3164734.
21. Petzinger GM, Holschneider DP, Fisher BE, McEwen S, Kintz N, Halliday M, Toy W, Walsh JW, Beeler J, Jakowec MW. The effects of exercise on dopamine neurotransmission in Parkinson’s disease: targeting neuroplasticity to modulate basal ganglia circuitry. Brain Plast 2015; 1: 29-39.
22. Shen HY, Chen JF. Adenosine A(2A) receptors in psychopharmacology: modulators of behavior, mood and cognition. Curr Neuropharmacol 2009; 7: 195-206.
23. Stockwell J, Jakova E, Cayabyab FS. Adenosine A1 and A2A receptors in the brain: current research and their role in neurodegeneration. Molecules 2017; 22: 676.
24. Tescarollo FC, Rombo DM, DeLiberto LK, Fedele DE, Alharfoush E, Tomé ÂR, Cunha RA, Sebastião AM, Boison D. Role of adenosine in epilepsy and seizures. J Caffeine Adenosine Res 2020; 10: 45-60.
25. Vorhees CV, Williams MT. Morris water maze: procedures for assessing spatial and related forms of learning and memory. Nat Protoc 2006; 1: 848-858.
26. Zorov DB, Juhaszova M, Sollott SJ. Mitochondrial reactive oxygen species (ROS) and ROS-induced ROS release. Physiol Rev 2014; 94: 909-950.
Copyright: © 2023 Mossakowski Medical Research Centre Polish Academy of Sciences and the Polish Association of Neuropathologists. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) License (http://creativecommons.org/licenses/by-nc-sa/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material, provided the original work is properly cited and states its license.
Quick links
© 2023 Termedia Sp. z o.o.
Developed by Bentus.