Study: NCT04058132

Intervention type: DRUG
Group type: OTHER
Intervention: Sildenafil Citrate 50Mg Tab
Description: sildenafil citrate (Viagra®, Pfizer. Inc., NY, NY). Sildenafil citrate is designated chemically as 1-\[\[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1Hpyrazolo\[4,3-d\]pyrimidin-5-yl)-4- ethoxyphenyl\]sulfonyl\]-4-methylpiperazine citrate. Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/mL in water and a molecular weight of 666.7. For this study, we will use 50 mg tablets for the single dose studies.

Intervention type: DRUG
Group type: OTHER
Intervention: Sildenafil Citrate 50Mg Tab
Description: sildenafil citrate (Viagra®, Pfizer. Inc., NY, NY). Sildenafil citrate is designated chemically as 1-\[\[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1Hpyrazolo\[4,3-d\]pyrimidin-5-yl)-4- ethoxyphenyl\]sulfonyl\]-4-methylpiperazine citrate. Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/mL in water and a molecular weight of 666.7. For this study, we will use 50 mg tablets for the single dose studies.

Intervention type: DEVICE
Group type: OTHER
Intervention: functional Near-infrared Spectroscopy (fNIRS)
Description: Functional Near-Infrared Spectroscopy (fNIRS): Functional near-infrared spectroscopy (fNIRS) a noninvasive technique that can measure cerebrovascular reactivity (CVR) will be used to measure regional cerebral blood flow and cerebrovascular reactivity in the brain. The device (fNRIS100, fNIR Device LLC), uses laser emission diodes (730nm and 850nm)which in a headband that is worn on the front of the scalp and forehead. Surrounding detectors a few centimeters away detect the light as it scatters through the underlying tissues. The technique is able to detect changes in the absorption spectrum of the tissue corresponding to the concentrations of oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR), and indicate local perfusion changes. fNIRS will be performed twice at each study visit, once before and once about 45 minutes after single dose administration of sildenafil 50 mg.

Intervention type: DEVICE
Group type: OTHER
Intervention: functional Near-infrared Spectroscopy (fNIRS)
Description: Functional Near-Infrared Spectroscopy (fNIRS): Functional near-infrared spectroscopy (fNIRS) a noninvasive technique that can measure cerebrovascular reactivity (CVR) will be used to measure regional cerebral blood flow and cerebrovascular reactivity in the brain. The device (fNRIS100, fNIR Device LLC), uses laser emission diodes (730nm and 850nm)which in a headband that is worn on the front of the scalp and forehead. Surrounding detectors a few centimeters away detect the light as it scatters through the underlying tissues. The technique is able to detect changes in the absorption spectrum of the tissue corresponding to the concentrations of oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR), and indicate local perfusion changes. fNIRS will be performed twice at each study visit, once before and once about 45 minutes after single dose administration of sildenafil 50 mg.

Intervention type: OTHER
Group type: OTHER
Intervention: Carbon Dioxide (CO2) 5%
Description: Carbon Dioxide (CO2) 5% mixed with room air. Both the fNIRS procedure and one Magnetic Resonance Imaging (MRI) session at visits that include imaging will be done with a hypercapnia challenge for comparison.~CO2 (hypercapnia) challenge is similar to holding one's breath. Participant will wear a nose clip and a mouth breathing apparatus while in the MRI scanner or sitting in a chair during the fNIRS procedure.~During the 7-minute hypercapnia procedure, participants will breathe room air and then switch to room air mixed with 5% CO2, from one to the other for one minute each.

Intervention type: OTHER
Group type: OTHER
Intervention: Carbon Dioxide (CO2) 5%
Description: Carbon Dioxide (CO2) 5% mixed with room air. Both the fNIRS procedure and one Magnetic Resonance Imaging (MRI) session at visits that include imaging will be done with a hypercapnia challenge for comparison.~CO2 (hypercapnia) challenge is similar to holding one's breath. Participant will wear a nose clip and a mouth breathing apparatus while in the MRI scanner or sitting in a chair during the fNIRS procedure.~During the 7-minute hypercapnia procedure, participants will breathe room air and then switch to room air mixed with 5% CO2, from one to the other for one minute each.

Intervention type: OTHER
Group type: OTHER
Intervention: Neuropsychological Assessments
Description: TBI Neuropsychological Assessments: Study participants will be administered a set of Neuropsychological Tests designed by the NINDS Common Data Elements (CDEs) initiative for TBI, in order to provide a comprehensive and broad assessment of deficits commonly found after TBI. We anticipate that the neuropsychological battery will require approximately 1 hour to complete. The measures (pencil and paper exercises, questionnaires, and interview by the examiner) to be administered are: Glasgow Outcome Scale-Extended (GOS-E). Learning trials portion of the California Verbal Learning Test (CVLT-II): The Trail Making Tests A and B (TMT): Subsets of the Wechsler Adult Intelligence Scale (WAIS-IV) (Digit Symbol and Symbol Search): Behavioral Symptoms Inventory-18: Satisfaction with Life Scale (SWLS): Word Reading subtest of Wide Range Achievement Test (WRAT)-4: Rivermead Post-Concussion Symptom Questionnaire.

Intervention type: OTHER
Group type: OTHER
Intervention: Neuropsychological Assessments
Description: TBI Neuropsychological Assessments: Study participants will be administered a set of Neuropsychological Tests designed by the NINDS Common Data Elements (CDEs) initiative for TBI, in order to provide a comprehensive and broad assessment of deficits commonly found after TBI. We anticipate that the neuropsychological battery will require approximately 1 hour to complete. The measures (pencil and paper exercises, questionnaires, and interview by the examiner) to be administered are: Glasgow Outcome Scale-Extended (GOS-E). Learning trials portion of the California Verbal Learning Test (CVLT-II): The Trail Making Tests A and B (TMT): Subsets of the Wechsler Adult Intelligence Scale (WAIS-IV) (Digit Symbol and Symbol Search): Behavioral Symptoms Inventory-18: Satisfaction with Life Scale (SWLS): Word Reading subtest of Wide Range Achievement Test (WRAT)-4: Rivermead Post-Concussion Symptom Questionnaire.

Intervention type: DRUG
Group type: OTHER
Intervention: Gadolinium contrast infusion
Description: Gadolinium contrast infusion: Brain MRI with gadolinium contrast: Dynamic contrast-enhanced (DCE) MRI with intravenous gadolinium-based contrast agents (GBCAs) to measure their transfer rate between intravascular and extravascular compartments as a marker of blood-brain barrier (BBB) permeability. For the DCE sequence, the participant is injected with the contrast agent through a heplock/iv in the scanner and the sequence takes about 15 min. Half-life of gadolinium is about 1 ½ hours and 90-98% clearance from the body in 24 hours in people with normal kidney function.

Intervention type: DRUG
Group type: OTHER
Intervention: Gadolinium contrast infusion
Description: Gadolinium contrast infusion: Brain MRI with gadolinium contrast: Dynamic contrast-enhanced (DCE) MRI with intravenous gadolinium-based contrast agents (GBCAs) to measure their transfer rate between intravascular and extravascular compartments as a marker of blood-brain barrier (BBB) permeability. For the DCE sequence, the participant is injected with the contrast agent through a heplock/iv in the scanner and the sequence takes about 15 min. Half-life of gadolinium is about 1 ½ hours and 90-98% clearance from the body in 24 hours in people with normal kidney function.

Intervention type: PROCEDURE
Group type: OTHER
Intervention: Blood sample collection for research purposes
Description: Serum and plasma (5 ml each) will be collected at at each study visit 10 m or 2 tsp. per visit or up to 40 ml or 8 tsp. over the 180 day course of the study). Samples will be collected by study personnel.

Intervention type: PROCEDURE
Group type: OTHER
Intervention: Blood sample collection for research purposes
Description: Serum and plasma (5 ml each) will be collected at at each study visit 10 m or 2 tsp. per visit or up to 40 ml or 8 tsp. over the 180 day course of the study). Samples will be collected by study personnel.

Intervention type: OTHER
Group type: OTHER
Intervention: Structural brain Magnetic Resonance Imaging (MRI
Description: Structural brain Magnetic Resonance Imaging (MRI): The scanner used is a 3.0 Tesla MR (Model 750, General Electric Healthcare), which is equipped with a high-performance gradient subsystem and a 32-channel head coil (General Electric Healthcare). These scans involve lying still in a scanner for several minutes at a time which is tube shaped, using magnetism to take images of the brain. There is no radiation in MRI. The participants will have up to 3 research brain MRIs. Healthy controls will have 1 MRI session.~Common TBI MRI techniques will be performed. Block-design BOLD fMRI during which there will be a 7 minute hypercapnia challenge will be done to assess brain blood flow and measure cerebral vascular reactivity (CVR).

Intervention type: OTHER
Group type: OTHER
Intervention: Structural brain Magnetic Resonance Imaging (MRI
Description: Structural brain Magnetic Resonance Imaging (MRI): The scanner used is a 3.0 Tesla MR (Model 750, General Electric Healthcare), which is equipped with a high-performance gradient subsystem and a 32-channel head coil (General Electric Healthcare). These scans involve lying still in a scanner for several minutes at a time which is tube shaped, using magnetism to take images of the brain. There is no radiation in MRI. The participants will have up to 3 research brain MRIs. Healthy controls will have 1 MRI session.~Common TBI MRI techniques will be performed. Block-design BOLD fMRI during which there will be a 7 minute hypercapnia challenge will be done to assess brain blood flow and measure cerebral vascular reactivity (CVR).