Isolation and identification of leukocyte populations in intracranial blood collected during mechanical thrombectomy.

Using standard techniques during mechanical thrombectomy, the Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) protocol (NCT03153683) isolates intracranial arterial blood distal to the thrombus and proximal systemic blood in the carotid artery. We augmented the current protocol to study leukocyte subpopulations both distal and proximal to the thrombus during human stroke (n = 16 patients), and from patients with cerebrovascular disease (CVD) undergoing angiography for unrelated conditions (e.g. carotid artery stenosis; n = 12 patients). We isolated leukocytes for flow cytometry from small volume (<1 mL) intracranial blood and systemic blood (5-10 mL) to identify adaptive and innate leukocyte populations, in addition to platelets and endothelial cells (ECs). Intracranial blood exhibited significant increases in T cell representation and decreases in myeloid/macrophage representation compared to within-patient carotid artery samples. CD4+ T cells and classical dendritic cells were significantly lower than CVD controls and correlated to within-patient edema volume and last known normal. This novel protocol successfully isolates leukocytes from small volume intracranial blood samples of stroke patients at time of mechanical thrombectomy and can be used to confirm preclinical results, as well as identify novel targets for immunotherapies.

Smoking-Induced Sex Differences in Clinical Outcomes in Patients Undergoing Mechanical Thrombectomy for Stroke.

OBJECTIVE: Ischemic stroke is the fifth leading cause of death in the United States. Smoking accelerates the onset of stroke by 10 years. The effects of smoking status on percent change in National Institutes of Health Stroke Scale (NIHSS) score, infarct volume, and edema volume were examined following mechanical thrombectomy for large vessel occlusion in patients with acute ischemic stroke. METHODS: Subjects (N = 90; >18 years old) were divided into 3 groups based on smoking status: current smokers, previous smokers (defined as having quit >6 months before the ischemic event), and nonsmokers. Percent change in NIHSS score was defined as score at admission minus score at discharge divided by score at admission and was used as a predictor of functional outcome. Linear regression analysis was performed based on infarct or edema volume versus percent change in NIHSS score and separated by sex. RESULTS: Consistent with previous findings, smokers experienced a stroke 10 years earlier than nonsmokers (P = 0.004). Statistically significant linear regressions existed between infarct volume or edema volume in relation to worsening change in NIHSS score with female smokers only. Stroke-induced tissue damage, as measured by magnetic resonance imaging or computed tomography, was predictive of functional recovery only in female smokers. CONCLUSIONS: These findings are valuable for patient counseling, particularly for women, for smoking cessation.

Intracranial VCAM1 at time of mechanical thrombectomy predicts ischemic stroke severity.

BACKGROUND: Emergent large vessel occlusion (ELVO) strokes are devastating ischemic vascular events for which novel treatment options are needed. Using vascular cell adhesion molecule 1 (VCAM1) as a prototype, the objective of this study was to identify proteomic biomarkers and network signaling functions that are potential therapeutic targets for adjuvant treatment for mechanical thrombectomy. METHODS: The blood and clot thrombectomy and collaboration (BACTRAC) study is a continually enrolling tissue bank and registry from stroke patients undergoing mechanical thrombectomy. Plasma proteins from intracranial (distal to clot) and systemic arterial blood (carotid) were analyzed by Olink Proteomics for N=42 subjects. Statistical analysis of plasma proteomics used independent sample t tests, correlations, linear regression, and robust regression models to determine network signaling and predictors of clinical outcomes. Data and network analyses were performed using IBM SPSS Statistics, SAS v 9.4, and STRING V11. RESULTS: Increased systemic (p<0.001) and intracranial (p=0.013) levels of VCAM1 were associated with the presence of hypertension. Intracranial VCAM1 was positively correlated to both infarct volume (p=0.032; r=0.34) and edema volume (p=0.026; r=0.35). The %∆ in NIHSS from admittance to discharge was found to be significantly correlated to both systemic (p=0.013; r = -0.409) and intracranial (p=0.011; r = -0.421) VCAM1 levels indicating elevated levels of systemic and intracranial VCAM1 are associated with reduced improvement of stroke severity based on NIHSS from admittance to discharge. STRING-generated analyses identified biologic functional descriptions as well as function-associated proteins from the predictive models of infarct and edema volume. CONCLUSIONS: The current study provides novel data on systemic and intracranial VCAM1 in relation to stroke comorbidities, stroke severity, functional outcomes, and the role VCAM1 plays in complex protein-protein signaling pathways. These data will allow future studies to develop predictive biomarkers and proteomic targets for drug development to improve our ability to treat a devastating pathology.

Changes in Angioarchitecture After Stereotactic Radiosurgery for Dural Arteriovenous Fistula.

INTRODUCTION: Dural arteriovenous fistulae (DAVF) are intracranial vascular abnormalities encountered in neurosurgery practice. Treatment options are microsurgical disconnection, endovascular embolization and/or radiosurgery. Past studies have reported the efficacy, safety, and predictors of success of radiosurgery. In this study, we investigated the angioarchitecture of fistulae at the time of radiosurgery and how the anatomy changed in the time after treatment based on angiogram follow-ups. METHODS: A retrospective analysis was performed on patients with angiographic diagnosis of DAVF treated with Gamma Knife radiosurgery (GKRS) between 2013 and 2018. Data collection included demographics, symptoms, grading scores, vascular anatomy, radiation data, treatment strategy, angiographic results, and length of patient follow-up. RESULTS: Our study reports data on 10 patients with a total of 14 fistulae. On follow-up angiography, 8 (57%) had complete occlusion of the fistula with a median time to follow up of 19.5 months. The remaining 6 (43%) were deemed as near-complete occlusion of fistula with a median time to follow up of 12.0 months. Time from radiosurgery to angiogram revealing incomplete vs. angiogram revealing complete obliteration was significantly different (p=0.045). Nearly all AVFs had decreased feeders over time after treatment with only one AVF developing an additional feeder post-treatment. Arterial feeders, drainage site, sex, Borden type, lesion volume and treatment volume had no predictive value of obliteration outcome. CONCLUSIONS: This study provides data on the angioarchitecture of fistulae treated with GKRS and also serves as an extension of previous studies reporting the safety and efficacy of GKRS treatment for DAVF in a specific patient population.

Proteomic changes in intracranial blood during human ischemic stroke.

BACKGROUND: Since 2015, mechanical thrombectomy has been the standard treatment for emergent large vessel occlusion ischemic stroke. OBJECTIVE: To investigate, using the previously published Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC) protocol (clinicaltrials.gov NCT03153683), how the protein expression of a patient's intracranial blood during ischemic stroke compares with the protein expression of their systemic arterial blood in order to better understand and treat stroke. METHODS: Plasma samples from 25 subjects underwent proteomic analysis, where intracranial protein expression was compared with systemic protein levels. Data including sex, comorbidities, infarct volume, and infarct time were included for each subject. RESULTS: A majority of important proteins had a lower expression in intracranial blood than in systemic arterial blood. Proteins with the most significant changes in expression were: endopeptidase at -0.26 (p<0.0001), phospholipid transfer protein (PLTP) at -0.26 (p=0.0005), uromodulin (UMOD) at -0.14 (p=0.002), ficolin-2 (FCN2) at -0.46 (p=0.005), C-C motif chemokine 19 (CCL19) at -0.51 (p<0.0001), C-C motif chemokine 20 (CCL20) at -0.40 (p<0.0001), fibroblast growth factor 21 at -0.37 (p=0.0002), and C-C motif chemokine (CCL23) at -0.43 (p=0.0003). CONCLUSIONS: Evaluation of proteomic changes in the intravascular space of a cerebral infarct in progress in human subjects suggested that changes in proteins such PLTP, fetuin-B (FETUB), and FCN2 may be involved in atherosclerotic changes, and chemokines such as CCL23 are known to play a role in the Th2 autoimmune response. These data provide a scientific springboard for identifying clinically relevant biomarkers for diagnosis/prognosis, and targets for much needed neuroprotective/neuroreparative pharmacotherapies.

Perlecan Domain-V Enhances Neurogenic Brain Repair After Stroke in Mice.

The extracellular matrix fragment perlecan domain V is neuroprotective and functionally restorative following experimental stroke. As neurogenesis is an important component of chronic post-stroke repair, and previous studies have implicated perlecan in developmental neurogenesis, we hypothesized that domain V could have a broad therapeutic window by enhancing neurogenesis after stroke. We demonstrated that domain V is chronically increased in the brains of human stroke patients, suggesting that it is present during post-stroke neurogenic periods. Furthermore, perlecan deficient mice had significantly less neuroblast precursor cells after experimental stroke. Seven-day delayed domain V administration enhanced neurogenesis and restored peri-infarct excitatory synaptic drive to neocortical layer 2/3 pyramidal neurons after experimental stroke. Domain V's effects were inhibited by blockade of α2ß1 integrin, suggesting the importance of α2ß1 integrin to neurogenesis and domain V neurogenic effects. Our results demonstrate that perlecan plays a previously unrecognized role in post-stroke neurogenesis and that delayed DV administration after experimental stroke enhances neurogenesis and improves recovery in an α2ß1 integrin-mediated fashion. We conclude that domain V is a clinically relevant neuroprotective and neuroreparative novel stroke therapy with a broad therapeutic window.

Successful Extracorporeal Membrane Oxygenation (ECMO) Use without Systemic Anticoagulation for Acute Respiratory Distress Syndrome in a Patient with Aneurysmal Subarachnoid Hemorrhage.

Extracorporeal membrane oxygenation (ECMO) is an important life-saving technology for patients with severe acute respiratory distress syndrome (ARDS). Unfortunately, ECMO has been traditionally contraindicated in patients with hemorrhagic neurologic diseases. The recent improvement in ECMO devices, increased utilization and experience with venovenous ECMO technologies among healthcare teams, and the use of ECMO without anticoagulation has expanded the potential populations that may benefit from ECMO. We present a case of successful utilization of venovenous ECMO for severe respiratory failure secondary to ARDS in a patient with aneurysmal subarachnoid hemorrhage and severe, episodic cerebral vasospasm. We also discuss important limitations and considerations for future successful use of ECMO in hemorrhagic stroke. This case report highlights the potential for this life-saving technology in patients with hemorrhagic stroke.

Predictive value of platelet reactivity unit (PRU) value for thrombotic and hemorrhagic events during flow diversion procedures: a meta-analysis.

BACKGROUND AND PURPOSE: Platelet function testing prior to flow diversion procedures, although initially heavily debated, has seen a substantial increase in its adoption to assess the risk of operative and perioperative thrombotic and hemorrhagic events. This meta-analysis was conducted to assess platelet function testing, particularly the VerifyNow Platelet Reactivity Unit (PRU) assay, for a relationship between the reported assay PRU value and thrombotic and hemorrhagic events. MATERIALS AND METHODS: The currently available literature (2013-2018) was surveyed with PubMed and Google Scholar searches. Included studies were those for which there were at least 30 cases during the study period, for which VerifyNow platelet reactivity unit values were obtained prior to the procedures and for which intraoperative and perioperative adverse events were noted. PRU value cut-offs ranging from >200 to >240 comprised the hyporesponse group while values ranging from <60 to <70 comprised the hyper-response group. The data were subject to statistical analysis to assess the relationship between PRU values and thrombotic and hemorrhagic events. The collected data were subsequently statistically analyzed to assess for publication bias. RESULTS: The searches yielded 27 studies, of which 12 met the inclusion criteria for the meta-analysis. The meta-analysis included data from 1464 reported Pipeline cases. The study included 273 men and 1177 women with a mean age across the analyzed procedures of 58 years (range 25-85). After loading with antiplatelet medications, preprocedural platelet hyper-responsiveness was associated with a greater incidence of hemorrhagic events with an increased absolute risk of 12%, but showed no relationship with thrombotic events. Preprocedural platelet hyporesponsiveness was associated with a greater incidence of thrombotic events with an absolute risk of 15%, but showed no relationship with hemorrhagic events. CONCLUSIONS: VerifyNow PRU values that correspond to platelet hyporesponse or hyper-response to dual antiplatelet therapy are associated with a higher risk of thrombotic and hemorrhagic events, respectively. Thus, the PRU value may offer some predictive value for these events.

The Blood And Clot Thrombectomy Registry And Collaboration (BACTRAC) protocol: novel method for evaluating human stroke.

BACKGROUND: Ischemic stroke research faces difficulties in translating pathology between animal models and human patients to develop treatments. Mechanical thrombectomy, for the first time, offers a momentary window into the changes occurring in ischemia. We developed a tissue banking protocol to capture intracranial thrombi and the blood immediately proximal and distal to it. OBJECTIVE: To develop and share a reproducible protocol to bank these specimens for future analysis. METHODS: We established a protocol approved by the institutional review board for tissue processing during thrombectomy (www.clinicaltrials.gov NCT03153683). The protocol was a joint clinical/basic science effort among multiple laboratories and the NeuroInterventional Radiology service line. We constructed a workspace in the angiography suite, and developed a step-by-step process for specimen retrieval and processing. RESULTS: Our protocol successfully yielded samples for analysis in all but one case. In our preliminary dataset, the process produced adequate amounts of tissue from distal blood, proximal blood, and thrombi for gene expression and proteomics analyses. We describe the tissue banking protocol, and highlight training protocols and mechanics of on-call research staffing. In addition, preliminary integrity analyses demonstrated high-quality yields for RNA and protein. CONCLUSIONS: We have developed a novel tissue banking protocol using mechanical thrombectomy to capture thrombus along with arterial blood proximal and distal to it. The protocol provides high-quality specimens, facilitating analysis of the initial molecular response to ischemic stroke in the human condition for the first time. This approach will permit reverse translation to animal models for treatment development.

Systematic Review of Endovascular, Surgical, and Conservative Options for Infectious Intracranial Aneurysms and Cardiac Considerations.

INTRODUCTION: With rising rates of intravenous drug use, Infectious Intracranial aneurysms (IIAs) are a relevant topic for investigation. We performed a systematic review to better understand current practice patterns and limits of current published literature. METHOD: 131 publications with a total of 499 patients (665 aneurysms) were included. Of the 499 patients, 83 were single case reports, and 20.5% of the total had multiple aneurysms. 35.8% of all aneurysms were ruptured. Of those reporting treatment, options included conservative antibiotic therapy (30.0%), open surgical intervention (31.1%), and endovascular occlusion (31.8%). Chronologically, publication of IIAs has increased. Usage of endovascular therapies has grown, while conservative and surgical management have declined in the literature. Overall, 56.2% of aneurysms for which conservative therapy was initiated eventually either underwent intervention or death of patient occurred. RESULTS: The issue of cardiac valve surgery in relationship to aneurysm therapy was discussed in 20.8% (80 patients) of all 384 infectious endocarditis patients; of which 15.0% (12) underwent valve surgery before aneurysm treatment and 85.0 patients (68)% underwent valve surgery after aneurysm treatment. For 51 of the patients where valve surgery followed aneurysm management, the corresponding aneurysm treatment modality could be determined; 58.8% (30) of whom were managed endovascularly. 32.7% (26) of all cases reporting cardiac surgery details underwent cardiac surgery during their admission with the IIA. CONCLUSIONS: Overall, increasing trend of endovascular management of IIAs is evident, and a strong temporal preference exhibited by providers to perform cardiac surgery subsequently to IIA management.

Expression of Cytokines and Chemokines as Predictors of Stroke Outcomes in Acute Ischemic Stroke.

Introduction: Ischemic stroke remains one of the most debilitating diseases and is the fifth leading cause of death in the US. The ability to predict stroke outcomes within the acute period of stroke would be essential for care planning and rehabilitation. The Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC; clinicaltrials.gov NCT03153683) study collects arterial blood immediately distal and proximal to the intracranial thrombus at the time of mechanical thrombectomy. These blood samples are an innovative resource in evaluating acute gene expression changes at the time of ischemic stroke. The purpose of this study was to identify inflammatory genes and important immune factors during mechanical thrombectomy for emergent large vessel occlusion (ELVO) and which patient demographics were predictors for stroke outcomes (infarct and/or edema volume) in acute ischemic stroke patients. Methods: The BACTRAC study is a non-probability sampling of male and female subjects (≥18 year old) treated with mechanical thrombectomy for ELVO. We evaluated 28 subjects (66 ± 15.48 years) relative concentrations of mRNA for gene expression in 84 inflammatory molecules in arterial blood distal and proximal to the intracranial thrombus who underwent thrombectomy. We used the machine learning method, Random Forest to predict which inflammatory genes and patient demographics were important features for infarct and edema volumes. To validate the overlapping genes with outcomes, we perform ordinary least squares regression analysis. Results: Machine learning analyses demonstrated that the genes and subject factors CCR4, IFNA2, IL-9, CXCL3, Age, T2DM, IL-7, CCL4, BMI, IL-5, CCR3, TNFα, and IL-27 predicted infarct volume. The genes and subject factor IFNA2, IL-5, CCL11, IL-17C, CCR4, IL-9, IL-7, CCR3, IL-27, T2DM, and CSF2 predicted edema volume. The overlap of genes CCR4, IFNA2, IL-9, IL-7, IL-5, CCR3, and IL-27 with T2DM predicted both infarct and edema volumes. These genes relate to a microenvironment for chemoattraction and proliferation of autoimmune cells, particularly Th2 cells and neutrophils. Conclusions: Machine learning algorithms can be employed to develop prognostic predictive biomarkers for stroke outcomes in ischemic stroke patients, particularly in regard to identifying acute gene expression changes that occur during stroke.

Novel Temporary Treatment for a Severe Case of Syndrome of Trephined.

BACKGROUND: Syndrome of the trephined is a unique neurosurgical condition that is seen in patients that have undergone craniectomy. While the symptoms of the condition range from mild to severe, the only definitive treatment for the condition is replacement of the bone flap. This article presents a novel, temporary treatment for syndrome of the trephined in a patient with severe symptoms who was unable to undergo immediate cranioplasty due to infection. CASE DESCRIPTION: A 25-year-old gentleman with a history of trauma resulting in hydrocephalus, craniectomy, and eventually ventriculoperitoneal shunt placement presented with a cranial wound infection requiring removal of his bone flap. While being treated with antibiotics, with his bone flap removed, he developed severe syndrome of the trephined. An emergency bedside procedure was developed and executed to treat his condition. CONCLUSIONS: Treating syndrome of the trephined with an external suction device proved useful and lifesaving fort the patient presented. Such a device can be made with common supplies found within any hospital. The technique used to treat the patient is novel and may be useful for others to consider if ever faced with a similar situation.

Management of antiplatelet therapy in patients undergoing neuroendovascular procedures.

Neuroendovascular techniques for treating cerebral aneurysms and other cerebrovascular pathology are increasingly becoming the standard of care. Intraluminal stents, aneurysm coils, and other flow diversion devices typically require concomitant antiplatelet therapy to reduce thromboembolic complications. The variability inherent with the pharmacodynamic response to common antiplatelet agents such as aspirin and clopidogrel complicates optimal selection of antiplatelet agents by clinicians. This review serves to discuss the literature related to antiplatelet use in neuroendovascular procedures and provides recommendations for clinicians on how to approach patients with variable response to antiplatelet agents, particularly clopidogrel.

The Kentucky Appalachian Stroke Registry (KApSR).

BACKGROUND: The population of rural Kentucky and West Virginia has a disproportionately high incidence of stroke and stroke risk factors. The Kentucky Appalachian Stroke Registry (KApSR) is a novel registry of stroke patients developed to collect demographic and clinical data in real time from these patients' electronic health records. OBJECTIVE: We describe the development of this novel registry and test it for ability to provide the information necessary to identify care gaps and direct clinical management. METHODS: The KApSR was developed as described in this article. To assess utility in patient care, we developed a "Diabetes Quality Assurance Dashboard" by cross-referencing patients in the registry with a diagnosis of ischemic cerebrovascular disease with patients that were tested for hemoglobin A1c (HbA1c) levels, patients with HbA1c levels diagnostic for diabetes mellitus (DM), and patients with an elevated HbA1c that were formally diagnosed with DM. RESULTS: For the 1008 patients treated for ischemic cerebrovascular disease in the year studied, 859 (85%) had their HbA1c tested. Of those, 281 had levels of 6.5 or greater, although only 261 (93%) were discharged with a formal diagnosis of DM. CONCLUSIONS: The KApSR has practical value as a tool to assess a large population of patients quickly for care quality and for research purposes.

Factors Associated with Moyamoya Syndrome in a Kentucky Regional Population.

OBJECTIVES: Our study aimed to report both new and previously identified conditions associated with moyamoya syndrome in a Western population and to present our outcomes after surgical treatment with indirect bypass. METHODS: We performed a retrospective chart review of patients evaluated at our institution from June 2011 to June 2015 who were diagnosed with moyamoya. Data collected include patient demographics, presenting manifestations, vessels involved, comorbid conditions, abnormal laboratory values, treatments administered, and clinical outcomes. RESULTS: Thirty-one patients with moyamoya were enrolled (11 male and 20 female), with 84% Caucasian and 16% African-American. The most common comorbidity was hypertension in 61% of the patients. Coexisting autoimmune conditions were present in 26%, with another 13% having coexisting prothrombotic disorders. Diabetes mellitus was not found to correlate with the Suzuki grade of disease at presentation (P = .30). When noninvasive imaging was performed before the cerebral angiogram, the computed tomography angiography had a false-negative rate of 59%, and magnetic resonance angiography had a false-negative rate of 33%. Twenty-one patients underwent surgical intervention, 2 underwent intracranial stenting, and 19 underwent indirect bypass with encephaloduroarteriosynangiosis. At an average 28-month follow-up, all 15 patients who had an angiogram after intervention showed evidence of neovascularization. CONCLUSIONS: Autoimmune and prothrombotic disorders were found to be comorbid in patients with moyamoya at much higher rates than expected in the general population. Diabetes mellitus was not significantly correlated with Suzuki grade. Angiogram remains an important diagnostic modality when noninvasive imaging is negative for vasculopathy. We demonstrate excellent evidence of revascularization within 1 year with intracranial stenting and indirect bypass.

Understanding history, and not repeating it. Neuroprotection for acute ischemic stroke: from review to preview.

BACKGROUND: Neuroprotection for ischemic stroke is a growing field, built upon the elucidation of the biochemical pathways of ischemia first studied in the 1970s. Beginning in the early 1990s, means by which to pharmacologically intervene and counteract these pathways have been sought, though with little clinical success. Through a comprehensive review of translations from laboratory to clinic, we aim to evaluate individual mechanisms of action, while highlighting potential barriers to success that will guide future research. METHODS: The MEDLINE database and The Internet Stroke Center clinical trials registry were queried for trials involving the use of neuroprotective agents in acute ischemic stroke in human subjects. For the purpose of the review, neuroprotective agents refer to medications used to preserve or protect the potentially ischemic tissue after an acute stroke, excluding treatments designed to re-establish perfusion. This excludes mechanical or pharmacological thrombolytics, anti-thrombic medications, or anti-platelet therapies. RESULTS: This review summarizes previously trialed neuroprotective agents, including but not limited to glutamate neurotransmission blockers, anti-oxidants, GABA agonists, leukocyte migration blockers, various small cation channel modulators, narcotic antagonists, and phospholipid membrane stabilizers. We outline key biochemical steps in ischemic injury that are the proposed areas of intervention. The agents, time to administration of therapeutic agent, follow-up, and trial results are reported. DISCUSSION: Stroke trials in humans are burdened with a marked heterogeneity of the patient population that is not seen in animal studies. Also, trials to date have included patients that are likely treated at a time outside of the window of efficacy for neuroprotective drugs, and have not effectively combined thrombolysis with neuroprotection. Through an evaluation of the accomplishments and failures in neuroprotection research, we propose new methodologies, agents, and techniques that may provide new routes for success.

Urotensin II acts as a modulator of mesopontine cholinergic neurons.

Urotensin II (UII) is a vasomodulatory peptide that was not predicted to elicit CNS activity. However, because we have recently shown that the urotensin II receptor (UII-R) is selectively expressed in rat mesopontine cholinergic (MPCh) neurons, we hypothesize that UII may have a central function. The present study demonstrates that the UII system is able to modulate MPCh neuron activity. Brain slice experiments demonstrate that UII excites MPCh neurons of the mouse laterodorsal tegmentum (LDTg) by activating a slow inward current. Furthermore, microinfusion of UII into the ventral tegmental area produces a sustained increase in dopamine efflux in the nucleus accumbens, as measured by in vivo chronoamperometry. In agreement with UII activation of MPCh neurons, intracerebroventricular injections of UII significantly modulate ambulatory movements in both rats and mice but do not significantly affect startle habituation or prepulse inhibition. The present study establishes that UII is a neuromodulator that may be exploited to target disorders involving MPCh dysfunction.

Urotensin II modulates rapid eye movement sleep through activation of brainstem cholinergic neurons.

Urotensin II (UII) is a cyclic neuropeptide with strong vasoconstrictive activity in the peripheral vasculature. UII receptor mRNA is also expressed in the CNS, in particular in cholinergic neurons located in the mesopontine tegmental area, including the pedunculopontine tegmental (PPT) and lateral dorsal tegmental nuclei. This distribution suggests that the UII system is involved in functions regulated by acetylcholine, such as the sleep-wake cycle. Here, we tested the hypothesis that UII influences cholinergic PPT neuron activity and alters rapid eye movement (REM) sleep patterns in rats. Local administration of UII into the PPT nucleus increases REM sleep without inducing changes in the cortical blood flow. Intracerebroventricular injection of UII enhances both REM sleep and wakefulness and reduces slow-wave sleep 2. Intracerebroventricular, but not local, administration of UII increases cortical blood flow. Moreover, whole-cell recordings from rat-brain slices show that UII selectively excites cholinergic PPT neurons via an inward current and membrane depolarization that were accompanied by membrane conductance decreases. This effect does not depend on action potential generation or fast synaptic transmission because it persisted in the presence of TTX and antagonists of ionotropic glutamate, GABA, and glycine receptors. Collectively, these results suggest that UII plays a role in the regulation of REM sleep independently of its cerebrovascular actions by directly activating cholinergic brainstem neurons.