Mechanisms of Neuromuscular Fatigue Post Stroke

Early Phase 1

Completed

• Conditions: Stroke
• Interventions: Drug: Placebo; Drug: Cyproheptadine; Drug: duloxetine

• Registration Number: NCT01688570
• Lead Sponsor: Medical College of Wisconsin

Brief Summary

While baseline weakness is clearly an important factor that contributes to disability post stroke, neuromuscular fatigue (the acute reduction in force production) of the paretic musculature likely compounds strength deficits and further exacerbates disability. The proposed study aims to improve our understanding of the mechanisms of neuromuscular fatigue in people post stroke in order to optimize strength training. In healthy individuals, both central (neural) and peripheral (muscle) factors are determinants of neuromuscular fatigue, but preliminary data from our laboratory suggests a greater contribution of central components to neuromuscular fatigue in the paretic musculature. Although cortical pathways are clearly disrupted post stroke, it is likely that brainstem pathways, known to have neuromodulatory effects on spinal motor circuitry, are more involved in the sustaining of force in the paretic leg, compared to the non-paretic and control legs. Therefore, the purpose of this proposal is to examine the role of descending neuromodulatory pathways of the brainstem in neuromuscular fatigue post stroke (Aim 1) and to correlate brainstem-related changes in neuromuscular fatigue to walking function (Aim 2). The investigators propose that stroke survivors' decreased capability to sustain force overtime results from the diminished ability of spinal motoneurons to respond to brainstem neuromodulatory inputs (serotonin (5-HT) and norepinephrine (NE)). Aim 1 will quantify stroke-related decreases in motor output sensitivity to a 5-HT and NE reuptake inhibitor (SNRI), serotonin antagonist, or placebo during sub-maximal intermittent fatiguing knee extension contractions. If motoneurons are desensitized to descending monoamines in chronic stroke patients, then they will be less sensitive to the effects of drugs that increase monoamine levels. The investigators predict that in response to the SNRI or serotonin antagonist, the paretic leg will show less change in time to task failure and a smaller reduction in strength as compared to the non-paretic and control legs. For Aim 2, the investigators predict that stroke subjects with the highest walking function will demonstrate the greatest fatigue-related changes in response to the SNRI. This proposal adopts an innovative model of motor impairment post stroke by including the role of subcortical structures in neuromuscular fatigue.

Detailed Description

Not available

Study Timeline

• Study Start: 2011-08
• Study First Submitted: 2012-09-12
• Study First Submitted QC: 2012-09-16
• Study First Posted: 2012-09-20
• Primary Completion: 2015-05
• Study Completion: 2015-05
• Status Verified: 2015-11
• Last Update Submitted: 2015-11-04
• Last Update Posted: 2015-11-05

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 27

Inclusion Criteria

General

• be at least 18 years of age

• Cognitively able to give informed consent Stroke

  -≥ 6 months post diagnosis of unilateral cortical stroke

• residual leg paresis

Exclusion Criteria

General

• chronic low back or hip pain
• major psychiatric disorders (e.g. depression
• substance abuse
• head trauma
• neurodegenerative disorder
• any uncontrolled medical disorder (e.g. hypertension)
• taking any medication or supplement (e.g. St. John's Wort) that has 5-HT or NE mechanisms of action(including Monoamine oxidase inhibitors (MAO) inhibitors)
• narrow angle glaucoma
• chronic liver or kidney disorders Stroke
• history of multiple strokes
• people who are unable to follow 2 step commands
• people who cannot walk ≥ 10 ft without physical assistance.

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Placebo	Placebo	Neuromuscular fatigue testing with placebo dose
Cyproheptadine	Cyproheptadine	Neuromuscular fatigue testing with cyproheptadine dose
Duloxetine	duloxetine	Neuromuscular fatigue testing with duloxetine dose

Primary Outcome Measures

Name	Time	Method
Force generation	At time of each of 4 testing sessions (all sessions within a 2 year period).	Sub-maximal and maximal force measurements will be made during brief contractions during each of the four testing sessions. All sessions will occur at least one week apart and within a total time span of 2 years.

Secondary Outcome Measures

Name	Time	Method
Surface electromyography (EMG)of lower leg muscles.	EMG measurements will be made during each of the four sessions.	Sessions will occur at least a week apart and within a 2 year time span.

Trial Locations

Locations (1)

Medical College of Wisconsin; 🇺🇸 Milwaukee, Wisconsin, United States