Corticospinal inhibition investigated in relation to upper extremity motor function in cervical spinal cord injury

OBJECTIVE

Corticospinal inhibitory mechanisms are relevant to functional recovery but remain poorly understood after spinal cord injury (SCI). Post-injury characteristics of contralateral silent period (CSP), a measure of corticospinal inhibition evaluated using transcranial magnetic stimulation (TMS), is inconsistent in literature. We envisioned that investigating CSP across muscles with varying degrees of weakness may be a reasonable approach to resolve inconsistencies and elucidate the relevance of corticospinal inhibition for upper extremity function following SCI.

METHODS

We studied 27 adults with chronic C1-C8 SCI (age 48.8 ± 16.1 years, 3 females) and 16 able-bodied participants (age 33.2 ± 11.8 years, 9 females). CSP characteristics were assessed across biceps (muscle power = 3-5) and triceps (muscle power = 1-3) representing stronger and weaker muscles, respectively. We assessed functional abilities using the Capabilities of the Upper Extremity Test (CUE-T).

RESULTS

Participants with chronic SCI had prolonged CSPs for biceps but delayed and diminished CSPs for triceps compared to able-bodied participants. Early-onset CSPs for biceps and longer, deeper CSPs for triceps correlated with better CUE-T scores.

CONCLUSIONS

Corticospinal inhibition is pronounced for stronger biceps but diminished for weaker triceps muscle in SCI indicating innervation relative to the level of injury matters in the study of CSP.

SIGNIFICANCE

Nevertheless, corticospinal inhibition or CSP holds relevance for upper extremity function following SCI.

Bacterial urine profile and optimal urine specimen collection timing in asymptomatic chronically catheterized adults with spinal cord injuries and disorders

BACKGROUND

Adults with spinal cord injuries and disorders (SCI/D) require chronic indwelling catheterization which is associated with an increased risk of catheter-associated (CA) adverse events.

METHODS

We studied urine samples (culture and urinalysis) from 2 cohorts of chronically catheterized males with SCI/D. Cohort 1 included 28 participants; 3 samples per patient were collected (before, after, and 7 days after catheter change). Cohort 2 included 21 participants; 7 samples per patient were collected (before, immediately after, 30 minutes, 1 hour, 1 day, 2 days, and 7 days after catheter change).

RESULTS

A statistically significant decrease in the post catheter change percentage of "significant cultures" was found in both our cohorts (P<.05). Additionally, our second cohort demonstrated a significant decrease in the number of organisms growing at 100.000 cfu/mL (median=-1, mean=-1.5, P=.0006) and in urinalysis bacterial numbers (median=-0.5, mean=-1, P=.006) from pre- to 1-hour post catheter removal.

CONCLUSIONS

Although there appears to be an improvement of organism burden seen after catheter change, this is only temporary, and its significance in chronically catheterized patients is still unknown. Our second cohort demonstrated an optimal time for sample collection at the 1-hour post-catheter change sample, but further research is required for the extrapolation of these findings.

An End-User's Personal Perspective on the Need of Consumer Involvement in Research

There is growing understanding that the consumer's voice in research needs to be stronger. Translational research studies need consumer inclusion in order to be effectively implemented. This narrative article provides the perspective of a Veteran with spinal cord injury (SCI) who is an active member of several study teams and serves as a Consumer Advocate, providing the voice of the person with SCI. Factors that drive people to develop new research ideas are considered. Consumer involvement offers helpful insight into project outcomes that are valuable to the end-user. It is also recognized that data can be interpreted in several different ways depending on the observer. Including the consumer in a research project enables another interpretation, creating a more complete evaluation. Participating in health research is becoming a new standard for persons with many different illnesses and diseases. Greater things are accomplished by physicians, healthcare scientists, engineers, and healthcare consumers interacting together to increase both the quality of research projects and the quality of life for everyone involved, especially the person with the disorder. There will be more acceptance of ideas or projects when consumers are involved from the early steps and learn how the process works from beginning to end.

Safety and efficacy of transcranial direct current stimulation in upper extremity rehabilitation after tetraplegia: protocol of a multicenter randomized, clinical trial

STUDY DESIGN

A multisite, randomized, controlled, double-blinded phase I/II clinical trial.

OBJECTIVE

The purpose of this clinical trial is to evaluate the safety, feasibility and efficacy of pairing noninvasive transcranial direct current stimulation (tDCS) with rehabilitation to promote paretic upper extremity recovery and functional independence in persons living with chronic cervical spinal cord injury (SCI).

SETTING

Four-site trial conducted across Cleveland Clinic, Louis Stokes Veterans Affairs Medical Center of Cleveland and MetroHealth Rehabilitation Rehabilitation Institute of Ohio, and Kessler Foundation of New Jersey.

METHODS

Forty-four adults (age ≥18 years) with tetraplegia following cervical SCI that occurred ≥1-year ago will participate. Participants will be randomly assigned to receive anodal tDCS or sham tDCS given in combination with upper extremity rehabilitation for 15 sessions each over 3-5 weeks. Assessments will be made twice at baseline separated by at least a 3-week interval, once at end-of-intervention, and once at 3-month follow-up.

PRIMARY OUTCOME MEASURE(S)

Primary outcome measure is upper extremity motor impairment assessed using the Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP) scale. Functional abilities will be assessed using Capabilities of Upper Extremity-Test (CUE-T), while functional independence and participation restrictions will be evaluated using the self-care domain of Spinal Cord Independent Measure (SCIM), and Canadian Occupational Performance Measure (COPM).

SECONDARY OUTCOME MEASURES

Treatment-associated change in corticospinal excitability and output will also be studied using transcranial magnetic stimulation (TMS) and safety (reports of adverse events) and feasibility (attrition, adherence etc.) will also be evaluated.

TRIAL REGISTRATION

ClincalTrials.gov identifier NCT03892746. This clinical trial is being performed at four sites within the United States: Cleveland Clinic (lead site), Louis Stokes Cleveland Veterans Affairs Medical Center (VAMC) and MetroHealth Rehabilitation Institute in Ohio, and Kessler Foundation in New Jersey. The U.S. Army Medical Research Acquisition Activity, 820 Chandler Street, Fort Detrick MD 21702-5014 is the awarding and administering acquisition office.

Wheelchair Mobility-Related Injuries Due to Inadvertent Lower Extremity Displacement on Footplates: Analysis of the FDA MAUDE Database From 2014 to 2018

OBJECTIVES

The aims of the study were to assess reports of wheelchair mobility-related injuries from inadvertent lower extremity displacement (ILED) on footplates, which were submitted to the Food and Drug Administration Manufacturer and User Facility Device Experience (MAUDE) database during 2014-2018, characterize injury types, and evaluate MAUDE data quality.

METHODS

A systematic MAUDE database review was performed. Annual reports were searched using keywords: (a) "power wheelchair" and "injury" and (b) "mechanical (also known as manual) wheelchair" and "injury." Reports related to injuries from ILED on the footplate were reviewed.

RESULTS

Reports of 1075 wheelchair injuries were found across the review period. Twenty nine (3%) met our inclusion criteria. The most common source of reports was "manufacturer." The wheelchair was unavailable for evaluation in 55.17% of reports. Manufacturers' submission dates (number of days that passed after they were notified) ranged from 3 to 159. Reported injuries decreased by 60% from 2014 to 2018. The end user used a power wheelchair for all but one report. The most common injuries were single fractures, multiple fractures, wounds/cuts/infections, and amputations (in order of incidence). The most common mechanism was the foot slipping off the footplate during wheelchair mobility.

CONCLUSIONS

We observed inherent weaknesses in the MAUDE database reporting process and a concerning level of reporting bias. Although there were limited reports of injuries related to ILED on the footplate during wheelchair mobility, the injuries reported were significant. More standardized reporting of the mechanism and impact of these injuries is needed to better inform wheelchair design, prescription, and patient/family education.

Development of Foot Displacement Detection Algorithm for Power Wheelchair Footplate Pressure and Positioning

Inadvertent lower extremity displacement (ILED) puts the feet of power wheelchair (PWC) users at great risk of traumatic injury. Because disabled individuals may not be aware of a mis-positioned foot, a real-time system for notification can reduce the risk of injury. To test this concept, we developed a prototype system called FootSafe, capable of real-time detection and classification of foot position. The FootSafe system used an array of force-sensing resistors to monitor foot pressures on the PWC footplate. Data were transmitted via Bluetooth to an iOS app which ran a classifier algorithm to notify the user of ILED. In a pilot trial, FootSafe was tested with seven participants seated in a PWC. Data collected from this trial were used to test the accuracy of classification algorithms. A custom figure of merit (FOM) was created to balance the risk of missed positive and false positive. While a machine-learning algorithm (K nearest neighbors, FOM=0.78) outperformed simpler methods, the simplest algorithm, mean footplate pressure, performed similarly (FOM=0.62). In a real-time classification task, these results suggest that foot position can be estimated using relatively few force sensors and simple algorithms running on mobile hardware.Clinical Relevance- Foot collisions or dragging are severe or life-threatening injuries for people with spinal cord injuries. The FootSafe sensor, iOS app, and classifier algorithm can warn the user of a mis-positioned foot to reduce the incidence of injury.

Development of Predictive Informatics Tool Using Electronic Health Records to Inform Personalized Evidence-Based Pressure Injury Management for Veterans with Spinal Cord Injury

BACKGROUND

Pressure injuries (PrI) are serious complications for many with spinal cord injury (SCI), significantly burdening health care systems, in particular the Veterans Health Administration. Clinical practice guidelines (CPG) provide recommendations. However, many risk factors span multiple domains. Effective prioritization of CPG recommendations has been identified as a need. Bioinformatics facilitates clinical decision support for complex challenges. The Veteran's Administration Informatics and Computing Infrastructure provides access to electronic health record (EHR) data for all Veterans Health Administration health care encounters. The overall study objective was to expand our prototype structural model of environmental, social, and clinical factors and develop the foundation for resource which will provide weighted systemic insight into PrI risk in veterans with SCI.

METHODS

The SCI PrI Resource (SCI-PIR) includes three integrated modules: (1) the SCIPUDSphere multidomain database of veterans' EHR data extracted from October 2010 to September 2015 for ICD-9-CM coding consistency together with tissue health profiles, (2) the Spinal Cord Injury Pressure Ulcer and Deep Tissue Injury Ontology (SCIPUDO) developed from the cohort's free text clinical note (Text Integration Utility) notes, and (3) the clinical user interface for direct SCI-PIR query.

RESULTS

The SCI-PIR contains relevant EHR data for a study cohort of 36,626 veterans with SCI, representing 10% to 14% of the U.S. population with SCI. Extracted datasets include SCI diagnostics, demographics, comorbidities, rurality, medications, and laboratory tests. Many terminology variations for non-coded input data were found. SCIPUDO facilitates robust information extraction from over six million Text Integration Utility notes annually for the study cohort. Visual widgets in the clinical user interface can be directly populated with SCIPUDO terms, allowing patient-specific query construction.

CONCLUSION

The SCI-PIR contains valuable clinical data based on CPG-identified risk factors, providing a basis for personalized PrI risk management following SCI. Understanding the relative impact of risk factors supports PrI management for veterans with SCI. Personalized interactive programs can enhance best practices by decreasing both initial PrI formation and readmission rates due to PrI recurrence for veterans with SCI.

Initial assessment and management of respiratory infections in persons with spinal cord injuries and disorders in the COVID-19 era

As the COVID-19 pandemic unfolds, emergency department (ED) personnel will face a higher caseload, including those with special medical needs such as persons living with spinal cord injuries and disorders (SCI/D). Individuals with SCI/D who develop COVID-19 are at higher risk for rapid decompensation and development of acute respiratory failure during respiratory infections due to the combination of chronic respiratory muscle paralysis and autonomic dysregulation causing neurogenic restrictive/obstructive lung disease and chronic immune dysfunction. Often, acute respiratory infections will lead to significant mucus production in individuals with SCI/D, and aggressive secretion management is an important component of successful medical treatment. Secretion management techniques include nebulized bronchodilators, chest percussion/drainage techniques, manually assisted coughing techniques, nasotracheal suctioning, and mechanical insufflation-exsufflation. ED professionals, including respiratory therapists, should be familiar with the significant comorbidities associated with SCI/D and the customized secretion management procedures and techniques required for optimal medical management and prevention of respiratory failure. Importantly, protocols should also be implemented to minimize potential COVID-19 spread during aerosol-generating procedures.

Biomarkers for recurrent pressure injury risk in persons with spinal cord injury

Objective: To investigate potential linkages between pressure injury (PrI) recurrence following spinal cord injury (SCI) and muscle-based and circulatory biomarkers, specifically fatty metabolites and inflammatory cytokines. Design: Observational study. Setting: Tertiary Care Center. Participants: 30 individuals with complete or incomplete SCI. Study participants either had never developed a PrI (Group I) or had a history of recurrent PrI (Group II). Interventions: Not applicable. Outcome Measures: Gluteal muscle histology, immunohistochemistry, muscle-based and circulatory fatty metabolites and inflammatory cytokines. Results: Gluteal intramuscular adipose tissue (IMAT) was greater than 15% in most Group II (83%) individuals. Muscle tissue histology confirmed intramuscular structural differences. Fatty acid binding protein 4 (FABP4) and fatty acid binding protein 3 (FABP3) were reliably detected in muscle and blood and significantly correlated with IMAT (P < 0.001). FABP4 was significantly higher in Group II muscle and blood (P < 0.05). FABP3 was significantly higher in Group I muscle (P < 0.05). Circulatory FABP3 levels were lower for Group I. Inflammatory biomarkers were more reliably detected in blood. Colony-Stimulating Factor-1 was slightly higher in Group II muscle. Circulatory interleukin-13 was significantly higher (P < 0.01) in Group I. Vascular endothelial growth factor (VEGF-A) was significantly increased (P < 0.05) in Group I muscle and blood. Conclusion: Identifying individuals with SCI at highest risk for recurrent PrI may impact patient management. IMAT content evaluation illustrates that muscle quality is a key biomarker. Low circulatory inflammatory biomarker expression potentially limits clinical significance for between group differences. Circulatory levels of FABP4 hold great potential as a recurrent PrI risk biomarker.

0644 An Educational and Behavioral Intervention Failed to Improve PAP Use Among Veterans With Spinal Cord Injuries and Diseases: Results of a Randomized Controlled Trial

Introduction

Sleep disordered breathing (SDB) is common among individuals with spinal cord injuries or diseases (SCI/D), many of whom are military Veterans, and physical limitations make use of positive airway pressure (PAP) therapy challenging. This study sought to test the effects of an educational and behavioral intervention to improve PAP adherence among Veterans with SCI/D over the first 3 months of use.

Methods

63 Veterans (mean age=60.7(10.2) years; 92% male) with SCI/D (33 SCI, 30 SCD; 25 cervical involvement; 38 thoracic and below) and SDB (23 with AHI 5-15; 40 with AHI&#8805;15) who received PAP treatment (CPAP or BPAP) were randomly assigned to receive a comprehensive 3-month intervention (INT) or an equal attention control (EAC). INT and EAC both included 1 face-to-face session (week 1) and 5 additional telephone sessions (weeks 2, 3, 4, 8 and 12). Main outcome measures were PAP use over the first 3 months: nights of use, nights of use &#8805;4 hours, and mean hours of use per night. Repeated measures ANCOVA models were used to test the differences between INT and EAC over the first 3 months of treatment.

Results

Number of nights with &#8805;4 hours of use in months 1-3 was 9, 7, and 6 nights in the INT and 8, 5 and 4 nights in the EAC (p’s&#8805;.37), respectively. There were no significant differences between INT and EAC for number of nights with any use (p’s&#8805;.24), or mean hours of use per night (p’s&#8805;.30). All 3 PAP use variables declined over time in both groups.

Conclusion

Sustained use of PAP therapy was difficult to achieve among those with SCI/D, and a 6-session behavioral intervention did not lead to significant improvements in use. Even when relatively high levels of initial use are achieved, this is difficult to sustain over time. Future studies should explore whether SCI/D patients experience significant symptom relief with PAP, and if so, whether home-based interventions or more intensive face-to-face PAP adherence programs will be effective.

Support

VA Rehabilitation Research and Development Service, Merit Review (1RX002116; PI: Badr); NIH/NHLBI K24 HL143055 (Martin).

Management of the Patient with Chronic Spinal Cord Injury

Individuals with spinal cord injuries or disorders (SCI/D), whether of traumatic or nontraumatic cause, require multidisciplinary management by their care team to achieve optimal health outcomes. SCI/D is relatively rare in the general population and primary care providers (PCPs) may not have extensive experience managing people with these disorders. Spinal cord injuries, impair the body's autonomic and biomechanical performance by interrupting the communications to and from major bodily systems. This article provides a framework to help PCPs understand how these changes impact their patient's physiologic function and subsequent risks for health complications with guidance for initial treatment approaches.

Power Wheelchair Footplate Pressure and Positioning Sensor

Power wheelchair users are at risk for severe injuries caused by foot mis-position on the footplate. This can lead to collisions or foot dragging which are severe or lifethreatening injuries for people with spinal cord injuries. The foot cannot be safely immobilized due to tilting pressure relief injuries, therefore, the foot can easily fall into a vulnerable position without the user realizing it. To reduce the likelihood of injury, we have developed a sensor for monitoring foot position in real time, as the wheelchair is driven. The sensor uses an array of force-sensing resistors and infrared distance sensors to detect the pressure and location of the foot within the immediate confines of the footplate. Sensor arrays with 23 force sensors and 14 infrared sensors per foot were fabricated on standard printed circuit boards and encapsulated in a durable thermoplastic urethane for environmental resistance. Fabricated sensors transmitted foot pressures and position data at 10 Hz using a Bluetooth Low Energy radio. An iOS app was developed to notify users of vulnerable foot position. Measured results confirmed the functionality of the system over typical foot pressures, and indicated that the device is ready for next-stage clinical trials with spinal cord injured power wheelchair users.

A Computational, Tissue-Realistic Model of Pressure Ulcer Formation in Individuals with Spinal Cord Injury

People with spinal cord injury (SCI) are predisposed to pressure ulcers (PU). PU remain a significant burden in cost of care and quality of life despite improved mechanistic understanding and advanced interventions. An agent-based model (ABM) of ischemia/reperfusion-induced inflammation and PU (the PUABM) was created, calibrated to serial images of post-SCI PU, and used to investigate potential treatments in silico. Tissue-level features of the PUABM recapitulated visual patterns of ulcer formation in individuals with SCI. These morphological features, along with simulated cell counts and mediator concentrations, suggested that the influence of inflammatory dynamics caused simulations to be committed to "better" vs. "worse" outcomes by 4 days of simulated time and prior to ulcer formation. Sensitivity analysis of model parameters suggested that increasing oxygen availability would reduce PU incidence. Using the PUABM, in silico trials of anti-inflammatory treatments such as corticosteroids and a neutralizing antibody targeted at Damage-Associated Molecular Pattern molecules (DAMPs) suggested that, at best, early application at a sufficiently high dose could attenuate local inflammation and reduce pressure-associated tissue damage, but could not reduce PU incidence. The PUABM thus shows promise as an adjunct for mechanistic understanding, diagnosis, and design of therapies in the setting of PU.

Systemic Evaluation of Electrical Stimulation for Ischemic Wound Therapy in a Preclinical In Vivo Model

Objective: In a systematic preclinical investigation of ischemic wound healing, we investigated the hypothesis that electrical stimulation (ES) promotes the healing of ischemic wounds. Approach: The effects of varying clinically relevant ES variables were evaluated using our modified version of the Gould F344 rat ischemic wound model. Stimulation was delivered using the novel lightweight integrated, single-channel, current-controlled modular surface stimulation (MSS) device. Stepwise variation allowed the effects of five different stimulation paradigms within an appropriate current density range to be studied. Within each group, 8-10 animals were treated for 28 days or until the ischemic wounds were healed and 5 animals were treated for 12 days. Eight rats received sham devices. A quantitative multivariable outcomes assessment procedure was used to evaluate the effects of ES. Results: Ischemic wounds treated with a decreased interpulse interval (IPI) had the highest rate of complete wound closure at 3 weeks. Wounds treated with decreased pulse amplitude (PA) had a lower proportion of closed wounds than sham ischemic wounds and showed sustained inflammation with a lack of wound contraction. Innovation: Our systematic study of varying ES paradigms using the novel MSS device provides preliminary insight into potential mechanisms of ES in ischemic wound healing. Conclusion: Clinically appropriate ES can more than double the proportion of ischemic wounds closed by 3 weeks in this model. Ninety percent of wounds treated with a decreased IPI healed by 21 days compared with only 29% of ischemic wounds treated with decreased PA, which appears to inhibit healing.

Comparison of surface and ultrasound localization to identify forearm flexor muscles for botulinum toxin injections

OBJECTIVE

To determine if ultrasound (US) localization is equivalent to surface landmark localization to identify botulinum toxin injection targets for forearm muscle spasticity.

DESIGN

Observational.

SETTING

Outpatient spasticity clinic in a tertiary care center.

SUBJECTS

Eighteen patients with upper-extremity flexor spasticity that interferes with function were included. Individuals with severe fixed contractures or traumatic injury of the involved forearm were excluded.

METHODS

Flexor pollicis longus, flexor carpi radialis, pronator teres, and flexor digitorum superficialis (FDS) were identified by 2 separate localization techniques: the method of Delagi et al for flexor carpi radialis, pronator teres, and flexor pollicis longus; and a surface landmark technique by Bickerton et al to identify the 4 muscle bellies of FDS. Proximodistal and lateral (radial) coordinates were recorded relative to a landmark line from the medial epicondyle to pisiform bone, and percentage of landmark line distance was calculated. After surface measurements were collected, the best point for injection was determined by using real-time US with a 12-MHz linear transducer. US measurements were recorded by using the same landmark line system.

RESULTS

Localization techniques were compared by using the Wilcoxon signed rank test. One-sample t-tests compared surface-mapped lateral coordinates to US-derived lateral coordinates with controls for multiple testing. Significant differences were observed between surface and US proximodistal and lateral coordinates for several flexor muscles.

CONCLUSIONS

US should be considered as an adjunct for localization in patients with upper-limb spasticity. US can improve accuracy of toxin placement and help to avoid injection into vascular and nerve structures.

Pregnancy-induced alterations of uterine arteriolar reactivity in the rat: observations with a new in vivo microcirculatory preparation

OBJECTIVE

The aim of this study was to compare reactivity of uterine arterioles in vivo between virgin and gravid rats.

STUDY DESIGN

In anesthetized gravid and virgin rats circumferential arterioles were observed by videomicroscopy while vasoactive agonists were suffused over the uterus. Arteriolar diameter changes were compared.

RESULTS

Resting and maximum diameters of circumferential arterioles were significantly larger in pregnant animals. Sensitivity to acetylcholine was greater in pregnant animals than in virgin animals (50% effective concentration, 7.1 +/- 0.17 negative log mol/L vs 6.1 +/- 0.32 negative log mol/L), whereas that to phenylephrine was less (50% effective concentration, 5.3 +/- 0.11 negative log mol/L vs 6.0 +/- 0.17 negative log mol/L). Angiotensin II-induced constriction was significantly reduced in pregnant rats only at lower concentrations. Serotonin significantly dilated arterioles in virgin rats (76% +/- 3% of maximum) but caused significant arteriolar constriction in pregnant animals (65% +/- 4% of maximum).

CONCLUSION

The in vivo uterine microcirculatory preparation allows measurement of resistance vessels in the intact animal. Although these results differ from some previous reports, differences may be attributable to vessel location or to in vivo versus in vitro conditions.

Role of nitric oxide and cyclooxygenase products in controlling vascular tone in uterine microvessels of rats

The importance of nitric oxide (NO) and dilator prostaglandins in uterine resistance arterioles was investigated. In pentobarbital anaesthetized rats at dioestrus-2, the uterine microcirculation in vivo was transilluminated by a fibreoptic probe and microvessels (circumferential arterioles) viewed by video microscopy. Arteriolar diameters were measured while increasing concentrations of acetylcholine (ACh), serotonin (5-HT), phenylephrine (PE), or angiotensin II (AII) were applied topically (suffused) over the uterus. Agonists were applied alone or with ibuprofen (IBU; cyclooxygenase inhibitor), N omega-nitro-L-arginine (L-NA; nitric oxide synthase inhibitor) or both. Circumferential arterioles were dilated by ACh and 5-HT (10(-8)-10(-4) mol l-1) and constricted by PE (10(-8)-10(-5) mol l-1) and AII (10(-11)-10(-7) mol l-1). Suffusion of L-NA or L-NA with ibuprofen (10(-4) mol l-1 each) abolished ACh-induced dilation; ibuprofen alone blocked dilation at higher ACh concentrations. Serotonin-induced relaxation was significantly attenuated by L-NA alone or in combination with ibuprofen. Vasoconstriction induced by PE was enhanced by L-NA alone and L-NA with ibuprofen, but ibuprofen alone had no effect. In contrast, AII-induced constriction was enhanced significantly by ibuprofen or L-NA and further enhanced when both ibuprofen and L-NA were present. These results suggest that ACh can release either nitric oxide (NO) or cyclooxygenase products to cause uterine arteriolar dilation and that 5-HT-induced uterine microvascular relaxation is mediated via NO only. They also suggest that PE-induced vasoconstriction is attenuated by the release of NO but not cyclooxygenase products and that constrictor responses evoked by AII are attenuated by both NO and dilator prostaglandin release. Thus, both nitric oxide and dilator prostaglandins are important in the control of uterine microvessels.

Calcium-dependent phospholipase A2 mediates the production of endothelium-derived hyperpolarizing factor in perfused rat mesenteric prearteriolar bed

The isolated, perfused rat mesenteric bed releases a cytochrome P450-linked metabolite of arachidonic acid (AA) as endothelium-derived hyperpolarizing factor (EDHF) in response to acetylcholine and histamine. This study assessed the relative contribution of two AA-generating pathways, phospholipase A2 (PLA2) and diacylglycerol (DAG) lipase, to EDHF-mediated dilation of the rat mesenteric bed. We tested the hypothesis that PLA2-mediated release of AA is essential for the production of EDHF. Mesenteric beds were perfused with physiological salt solution (PSS) containing indomethacin and nitro-L-arginine methyl ester to block cyclooxygenase and nitric oxide synthase, respectively, and constricted with cirazoline (an alpha1-adrenoceptor agonist). Bolus applications of acetylcholine and histamine caused dose-dependent dilation of the constricted beds. The 85-kDa PLA2 inhibitor, arachidonyl trifluoromethyl ketone (AACOCF3), at 3 microM, profoundly blunted decreases in perfusion pressure initiated by 1 nmol acetylcholine (94.3+/-1.7%) and by 100 nmol histamine (88.5+/-3.3%) to 9.6+/-7.5 and 8.6+/-6.0%, respectively. AACOCF3 also blocked cirazoline-stimulated release of 6-keto-PG1alpha, but did not alter the vasodilation initiated by sodium nitroprusside (a nitric oxide donor), cromakalim (a K+ channel activator), or by Na+/K+-ATPase activation, as measured by KCl vasodilation in preconstricted beds perfused with K+-free PSS. The 14-kDa PLA2 inhibitor, oleyloxyethyl phosphorylcholine, also blocked EDHF vasodilation and also significantly inhibited K+ channel activity. Neither the Ca2+-independent PLA2 inhibitor, HELSS [E-6-(bromomethylene)-tetrahydro-3-(1-naphthalenyl)-2H-pyran-2-one], nor DAG lipase inhibitor, RHC-80267 [1,6-bis-(cyclohexyloximino-carbonylamino)-hexane] altered EDHF-mediated vasodilation. However, RHC-80267 blocked cirazoline-stimulated release of 6-keto-PGF1alpha. We conclude that Ca2+-dependent PLA2, rather than DAG lipase, generates the AA for the production of EDHF in the perfused rat mesenteric bed.