Acute levodopa dosing around-the-clock ameliorates REM sleep without atonia in hemiparkinsonian rats

Exploring the Causal Relationship Between Migraine and Insomnia Through Bidirectional Two-Sample Mendelian Randomization: A Bidirectional Causal Relationship

Introduction

The intricate relationship between migraine and insomnia has been a subject of great interest due to its complex mechanisms. Despite extensive research, understanding the causal link between these conditions remains a challenge.

Material and Methods

This study employs a bidirectional Mendelian randomization approach to investigate the causal relationship between migraine and insomnia. Risk loci for both conditions were derived from large-scale Genome-Wide Association Studies (GWAS). The primary method of Mendelian Randomization utilized in this study is the Inverse Variance Weighted (IVW) method.

Results

Our findings indicate a bidirectional causal relationship between migraine and insomnia. In the discovery set, migraine had a significant effect on insomnia (OR=1.02, 95% CI=1.02 (1.01-1.03), PIVW=5.30E-04). However, this effect was not confirmed in the validation set (OR=1.03, 95% CI=1.03 (0.87-1.21), PIVW=0.77). Insomnia also had a significant effect on migraine (OR=1.02, 95% CI=1.02 (0.01-1.03), PIVW=2.67E-08), and this effect was validated in the validation set (OR=2.30, 95% CI=2.30 (1.60-3.30), PIVW=5.78E-06).

Conclusion

This study provides meaningful insights into the bidirectional causality between migraine and insomnia, highlighting a complex interplay between these conditions. While our findings advance the understanding of the relationship between migraine and insomnia, they also open up new avenues for further research. The results underscore the need for considering both conditions in clinical and therapeutic strategies.

Pharmacological interventions targeting α-synuclein aggregation triggered REM sleep behavior disorder and early development of Parkinson's disease

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by elevated motor behaviors and dream enactments in REM sleep, often preceding the diagnosis of Parkinson's disease (PD). As RBD could serve as a biomarker for early PD developments, pharmacological interventions targeting α-synuclein aggregation triggered RBD could be applied toward early PD progression. However, robust therapeutic guidelines toward PD-induced RBD are lacking, owing in part to a historical paucity of effective treatments and trials. We reviewed the bidirectional links between α-synuclein neurodegeneration, progressive sleep disorders, and RBD. We highlighted the correlation between RBD development, α-synuclein aggregation, and neuronal apoptosis in key brainstem regions involved in REM sleep atonia maintenance. The current pharmacological intervention strategies targeting RBD and their effects on progressive PD are discussed, as well as current treatments for progressive neurodegeneration and their effects on RBD. We also evaluated emerging and potential pharmacological solutions to sleep disorders and developing synucleinopathies. This review provides insights into the mechanisms and therapeutic targets underlying RBD and PD, and explores bidirectional treatment effects for both diseases, underscoring the need for further research in this area.

The cross-hemispheric nigrostriatal pathway prevents the expression of levodopa-induced dyskinesias

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.

Therapeutic Effect of Levodopa/Carbidopa/Entacapone on Sleep Disturbance in Patients with Parkinson's Disease

Objective

To investigate the efficacy of levodopa/carbidopa/entacapone (LCE) at bedtime for treating sleep disturbance in patients with Parkinson’s disease (PD) with motor fluctuations.

Methods

Participants included 128 PD patients with motor fluctuations. All patients were assessed for motor, nonmotor, and sleep-specific symptoms using the United Parkinson’s Disease Rating Scale (UPDRS), the Korean version of the Nonmotor Symptom Scale, the Parkinson’s Disease Sleep Scale (PDSS), the Epworth Sleepiness Scale, and the Rapid Eye Movement Sleep Behavior Disorder Screening Questionnaire (RBDSQ). We compared the baseline characteristics of patients with sleep disturbance (PDSS score < 120) and those without sleep disturbance (PDSS score ≥ 120). Thirty-nine patients with sleep disturbance who agreed to take LCE at bedtime completed 3-month follow-ups. We analyzed changes in the scores of motor, nonmotor, and sleep symptom scales over the 3 months.

Results

PD patients with sleep disturbance were at more advanced disease stages and had more severe motor, nonmotor, and sleep symptoms than those without sleep disturbance. Patients who took LCE at night showed improvements in motor (UPDRS part III, p = 0.007) and sleep symptoms (total PDSS, p < 0.001). Sleep features that benefitted from LCE included not only nocturnal motor components but also insomnia (PDSS items 2 and 3, p = 0.005 and p < 0.001) and rapid eye movement behavior disorder (PDSS item 6, p = 0.002; and RBDSQ, p < 0.001).

Conclusion

The use of LCE at bedtime may be a useful treatment for sleep disturbance in advanced PD patients with motor fluctuations.