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The role of the subthalamic nucleus in L-DOPA induced dyskinesia in 6-hydroxydopamine lesioned rats.

Aristieta A, Azkona G, Sagarduy A, Miguelez C, Ruiz-Ortega JÁ, Sanchez-Pernaute R, Ugedo L - PLoS ONE (2012)

Bottom Line: Our results show that chronic L-DOPA treatment does not modify the abnormal STN activity induced by the 6-hydroxydopamine lesion of the nigrostriatal pathway in this model.We did not find any correlation between the abnormal involuntary movement (AIM) scores and the electrophysiological parameters of STN neurons recorded 24 h or 20-120 min after the last L-DOPA injection, except for the axial subscores.In addition, STN lesion decreased the anti-dyskinetogenic effect of buspirone in a reciprocal manner.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa, Spain.

ABSTRACT
L-DOPA is the most effective treatment for Parkinson's disease (PD), but prolonged use leads to disabling motor complications including dyskinesia. Strong evidence supports a role of the subthalamic nucleus (STN) in the pathophysiology of PD whereas its role in dyskinesia is a matter of controversy. Here, we investigated the involvement of STN in dyskinesia, using single-unit extracellular recording, behavioural and molecular approaches in hemi-parkinsonian rats rendered dyskinetic by chronic L-DOPA administration. Our results show that chronic L-DOPA treatment does not modify the abnormal STN activity induced by the 6-hydroxydopamine lesion of the nigrostriatal pathway in this model. Likewise, we observed a loss of STN responsiveness to a single L-DOPA dose both in lesioned and sham animals that received daily L-DOPA treatment. We did not find any correlation between the abnormal involuntary movement (AIM) scores and the electrophysiological parameters of STN neurons recorded 24 h or 20-120 min after the last L-DOPA injection, except for the axial subscores. Nonetheless, unilateral chemical ablation of the STN with ibotenic acid resulted in a reduction in global AIM scores and peak-severity of dyskinesia. In addition, STN lesion decreased the anti-dyskinetogenic effect of buspirone in a reciprocal manner. Striatal protein expression was altered in dyskinetic animals with increases in ΔFosB, phosphoDARPP-32, dopamine receptor (DR) D3 and DRD2/DRD1 ratio. The STN lesion attenuated the striatal molecular changes and normalized the DRD2/DRD1 ratio. Taken together, our results show that the STN plays a role, if modest, in the physiopathology of dyskinesias.

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Schematic representation of experimental design and groups.At the beginning of the study, animals received a vehicle or 6-OHDA injection into the right medial forebrain bundle and were screened by amphetamine-induced rotations 2 weeks later. Rats were treated daily with saline or L-DOPA injections (6 mg/kg plus 12 mg/kg benserazide) for 21 days. AIMs were rated 2–3 days per week (testing sessions are marked in black). Experiment 1: After the chronic treatment was completed, L-DOPA was administered twice per week, and electrophysiological experiments were performed. All animals were perfused transcardially and processed for histology. Experiment 2: After the last testing session (day 21), the animals received a vehicle (in white) or ibotenic acid (in red) injection into the right STN. After a second period of L-DOPA treatment and AIMs rating (in black) animals were killed and the striata were dissected and frozen for western blot, and STN was postfixed for histology. Experiment 3: After chronic treatment and AIMs rating (in black), animals were killed and striata removed and frozen for western blot analysis.
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pone-0042652-g001: Schematic representation of experimental design and groups.At the beginning of the study, animals received a vehicle or 6-OHDA injection into the right medial forebrain bundle and were screened by amphetamine-induced rotations 2 weeks later. Rats were treated daily with saline or L-DOPA injections (6 mg/kg plus 12 mg/kg benserazide) for 21 days. AIMs were rated 2–3 days per week (testing sessions are marked in black). Experiment 1: After the chronic treatment was completed, L-DOPA was administered twice per week, and electrophysiological experiments were performed. All animals were perfused transcardially and processed for histology. Experiment 2: After the last testing session (day 21), the animals received a vehicle (in white) or ibotenic acid (in red) injection into the right STN. After a second period of L-DOPA treatment and AIMs rating (in black) animals were killed and the striata were dissected and frozen for western blot, and STN was postfixed for histology. Experiment 3: After chronic treatment and AIMs rating (in black), animals were killed and striata removed and frozen for western blot analysis.

Mentions: The design and timeline of the experiments is shown in Figure 1. Experiment 1. Characterization of the electrophysiological properties of STN neurons in sham and 6-OHDA-lesioned animals treated chronically (3 weeks) with either saline or L-DOPA. Behavioral tests were performed periodically. All the 6-OHDA-lesioned animals treated with L-DOPA included in these experiments developed dyskinesia. Electrophysiological recordings were obtained 24 h after the last dose of the corresponding treatment (saline or L-DOPA). After baseline recordings were acquired, rats received an acute challenge with a standard dose of L-DOPA (6 mg/kg plus benserazide 12 mg/kg, i.p.) and cell recordings were obtained from 20 to 120 min after the drug administration. The groups included in this experiment are referred to as sham saline (n = 9), sham L-DOPA (n = 12), 6-OHDA saline (n = 12) and 6-OHDA L-DOPA (n = 13). Experiment 2. Impact of STN lesion on LID. Two groups of dyskinetic animals received an injection in the STN with ibotenic acid (STN-lesion; n = 14) or Dulbeco's buffer solution (STN-sham; n = 5). Abnormal involuntary movement (AIM) scores were evaluated before and after the STN surgery. At the end of the experiment, 6 rats from the STN-lesion and 5 from the STN-sham group received a single buspirone injection 30 min prior to L-DOPA administration. Experiment 3. Effect of STN lesion on striatal protein expression. For this purpose, animals were killed 1 h after the last saline or L-DOPA injection and the striata were processed for western blot analyses. The groups included in this experiment are referred to as sham L-DOPA (n = 7), 6-OHDA saline (n = 9), 6-OHDA L-DOPA (n = 10) and STN lesion (n = 8 from Experiment 2. Animals tested with buspirone were excluded from this analysis).


The role of the subthalamic nucleus in L-DOPA induced dyskinesia in 6-hydroxydopamine lesioned rats.

Aristieta A, Azkona G, Sagarduy A, Miguelez C, Ruiz-Ortega JÁ, Sanchez-Pernaute R, Ugedo L - PLoS ONE (2012)

Schematic representation of experimental design and groups.At the beginning of the study, animals received a vehicle or 6-OHDA injection into the right medial forebrain bundle and were screened by amphetamine-induced rotations 2 weeks later. Rats were treated daily with saline or L-DOPA injections (6 mg/kg plus 12 mg/kg benserazide) for 21 days. AIMs were rated 2–3 days per week (testing sessions are marked in black). Experiment 1: After the chronic treatment was completed, L-DOPA was administered twice per week, and electrophysiological experiments were performed. All animals were perfused transcardially and processed for histology. Experiment 2: After the last testing session (day 21), the animals received a vehicle (in white) or ibotenic acid (in red) injection into the right STN. After a second period of L-DOPA treatment and AIMs rating (in black) animals were killed and the striata were dissected and frozen for western blot, and STN was postfixed for histology. Experiment 3: After chronic treatment and AIMs rating (in black), animals were killed and striata removed and frozen for western blot analysis.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3412805&req=5

pone-0042652-g001: Schematic representation of experimental design and groups.At the beginning of the study, animals received a vehicle or 6-OHDA injection into the right medial forebrain bundle and were screened by amphetamine-induced rotations 2 weeks later. Rats were treated daily with saline or L-DOPA injections (6 mg/kg plus 12 mg/kg benserazide) for 21 days. AIMs were rated 2–3 days per week (testing sessions are marked in black). Experiment 1: After the chronic treatment was completed, L-DOPA was administered twice per week, and electrophysiological experiments were performed. All animals were perfused transcardially and processed for histology. Experiment 2: After the last testing session (day 21), the animals received a vehicle (in white) or ibotenic acid (in red) injection into the right STN. After a second period of L-DOPA treatment and AIMs rating (in black) animals were killed and the striata were dissected and frozen for western blot, and STN was postfixed for histology. Experiment 3: After chronic treatment and AIMs rating (in black), animals were killed and striata removed and frozen for western blot analysis.
Mentions: The design and timeline of the experiments is shown in Figure 1. Experiment 1. Characterization of the electrophysiological properties of STN neurons in sham and 6-OHDA-lesioned animals treated chronically (3 weeks) with either saline or L-DOPA. Behavioral tests were performed periodically. All the 6-OHDA-lesioned animals treated with L-DOPA included in these experiments developed dyskinesia. Electrophysiological recordings were obtained 24 h after the last dose of the corresponding treatment (saline or L-DOPA). After baseline recordings were acquired, rats received an acute challenge with a standard dose of L-DOPA (6 mg/kg plus benserazide 12 mg/kg, i.p.) and cell recordings were obtained from 20 to 120 min after the drug administration. The groups included in this experiment are referred to as sham saline (n = 9), sham L-DOPA (n = 12), 6-OHDA saline (n = 12) and 6-OHDA L-DOPA (n = 13). Experiment 2. Impact of STN lesion on LID. Two groups of dyskinetic animals received an injection in the STN with ibotenic acid (STN-lesion; n = 14) or Dulbeco's buffer solution (STN-sham; n = 5). Abnormal involuntary movement (AIM) scores were evaluated before and after the STN surgery. At the end of the experiment, 6 rats from the STN-lesion and 5 from the STN-sham group received a single buspirone injection 30 min prior to L-DOPA administration. Experiment 3. Effect of STN lesion on striatal protein expression. For this purpose, animals were killed 1 h after the last saline or L-DOPA injection and the striata were processed for western blot analyses. The groups included in this experiment are referred to as sham L-DOPA (n = 7), 6-OHDA saline (n = 9), 6-OHDA L-DOPA (n = 10) and STN lesion (n = 8 from Experiment 2. Animals tested with buspirone were excluded from this analysis).

Bottom Line: Our results show that chronic L-DOPA treatment does not modify the abnormal STN activity induced by the 6-hydroxydopamine lesion of the nigrostriatal pathway in this model.We did not find any correlation between the abnormal involuntary movement (AIM) scores and the electrophysiological parameters of STN neurons recorded 24 h or 20-120 min after the last L-DOPA injection, except for the axial subscores.In addition, STN lesion decreased the anti-dyskinetogenic effect of buspirone in a reciprocal manner.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, Faculty of Medicine and Dentistry, University of the Basque Country, Leioa, Spain.

ABSTRACT
L-DOPA is the most effective treatment for Parkinson's disease (PD), but prolonged use leads to disabling motor complications including dyskinesia. Strong evidence supports a role of the subthalamic nucleus (STN) in the pathophysiology of PD whereas its role in dyskinesia is a matter of controversy. Here, we investigated the involvement of STN in dyskinesia, using single-unit extracellular recording, behavioural and molecular approaches in hemi-parkinsonian rats rendered dyskinetic by chronic L-DOPA administration. Our results show that chronic L-DOPA treatment does not modify the abnormal STN activity induced by the 6-hydroxydopamine lesion of the nigrostriatal pathway in this model. Likewise, we observed a loss of STN responsiveness to a single L-DOPA dose both in lesioned and sham animals that received daily L-DOPA treatment. We did not find any correlation between the abnormal involuntary movement (AIM) scores and the electrophysiological parameters of STN neurons recorded 24 h or 20-120 min after the last L-DOPA injection, except for the axial subscores. Nonetheless, unilateral chemical ablation of the STN with ibotenic acid resulted in a reduction in global AIM scores and peak-severity of dyskinesia. In addition, STN lesion decreased the anti-dyskinetogenic effect of buspirone in a reciprocal manner. Striatal protein expression was altered in dyskinetic animals with increases in ΔFosB, phosphoDARPP-32, dopamine receptor (DR) D3 and DRD2/DRD1 ratio. The STN lesion attenuated the striatal molecular changes and normalized the DRD2/DRD1 ratio. Taken together, our results show that the STN plays a role, if modest, in the physiopathology of dyskinesias.

Show MeSH
Related in: MedlinePlus