Robust disease module mining via enumeration of diverse prize-collecting Steiner trees.

MOTIVATION: Disease module mining methods (DMMMs) extract subgraphs that constitute candidate disease mechanisms from molecular interaction networks such as protein-protein interaction (PPI) networks. Irrespective of the employed models, DMMMs typically include non-robust steps in their workflows, i.e. the computed subnetworks vary when running the DMMMs multiple times on equivalent input. This lack of robustness has a negative effect on the trustworthiness of the obtained subnetworks and is hence detrimental for the widespread adoption of DMMMs in the biomedical sciences. RESULTS: To overcome this problem, we present a new DMMM called ROBUST (robust disease module mining via enumeration of diverse prize-collecting Steiner trees). In a large-scale empirical evaluation, we show that ROBUST outperforms competing methods in terms of robustness, scalability and, in most settings, functional relevance of the produced modules, measured via KEGG (Kyoto Encyclopedia of Genes and Genomes) gene set enrichment scores and overlap with DisGeNET disease genes. AVAILABILITY AND IMPLEMENTATION: A Python 3 implementation and scripts to reproduce the results reported in this article are available on GitHub: https://github.com/bionetslab/robust, https://github.com/bionetslab/robust-eval. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

A Real-World Rheumatology Registry and Research Consortium: The German RheumaDatenRhePort (RHADAR) Registry.

Real-world data are crucial to continuously improve the management of patients with rheumatic and musculoskeletal diseases (RMDs). The German RheumaDatenRhePort (RHADAR) registry encompasses a network of rheumatologists and researchers in Germany providing pseudonymized real-world patient data and allowing timely and continuous improvement in the care of RMD patients. The RHADAR modules allow automated anamnesis and adaptive coordination of appointments regarding individual urgency levels. Further modules focus on the collection and integration of electronic patient-reported outcomes in between consultations. The digital RHADAR modules ultimately allow a patient-centered adaptive approach to integrated medical care starting as early as possible in the disease course. Such a closed-loop system consisting of various modules along the whole patient pathway enables comprehensive and timely patient management in an unprecedented manner.

Probing the interplay between geometric and electronic-structure features via high-harmonic spectroscopy.

We present molecular-frame measurements of the recombination dipole matrix element (RDME) in CO2, N2O, and carbonyl sulfide (OCS) molecules using high-harmonic spectroscopy. Both the amplitudes and phases of the RDMEs exhibit clear imprints of a two-center interference minimum, which moves in energy with the molecular alignment angle relative to the laser polarization. We find that whereas the angle dependence of this minimum is consistent with the molecular geometry in CO2 and N2O, it behaves very differently in OCS; in particular, the phase shift which accompanies the two-center minimum changes sign for different alignment angles. Our results suggest that two interfering structural features contribute to the OCS RDME, namely, (i) the geometrical two-center minimum and (ii) a Cooper-like, electronic-structure minimum associated with the sulfur end of the molecule. We compare our results to ab initio calculations using time-dependent density functional theory and present an empirical model that captures both the two-center and the Cooper-like interferences. We also show that the yield from unaligned samples of two-center molecules is, in general, reduced at high photon energies compared to aligned samples, due to the destructive interference between molecules with different alignments.

Genetic and phenotypic overlap of specific obsessive-compulsive and attention-deficit/hyperactive subtypes with Tourette syndrome.

BACKGROUND: The unique phenotypic and genetic aspects of obsessive-compulsive (OCD) and attention-deficit/hyperactivity disorder (ADHD) among individuals with Tourette syndrome (TS) are not well characterized. Here, we examine symptom patterns and heritability of OCD and ADHD in TS families. METHOD: OCD and ADHD symptom patterns were examined in TS patients and their family members (N = 3494) using exploratory factor analyses (EFA) for OCD and ADHD symptoms separately, followed by latent class analyses (LCA) of the resulting OCD and ADHD factor sum scores jointly; heritability and clinical relevance of the resulting factors and classes were assessed. RESULTS: EFA yielded a 2-factor model for ADHD and an 8-factor model for OCD. Both ADHD factors (inattentive and hyperactive/impulsive symptoms) were genetically related to TS, ADHD, and OCD. The doubts, contamination, need for sameness, and superstitions factors were genetically related to OCD, but not ADHD or TS; symmetry/exactness and fear-of-harm were associated with TS and OCD while hoarding was associated with ADHD and OCD. In contrast, aggressive urges were genetically associated with TS, OCD, and ADHD. LCA revealed a three-class solution: few OCD/ADHD symptoms (LC1), OCD & ADHD symptoms (LC2), and symmetry/exactness, hoarding, and ADHD symptoms (LC3). LC2 had the highest psychiatric comorbidity rates (⩾50% for all disorders). CONCLUSIONS: Symmetry/exactness, aggressive urges, fear-of-harm, and hoarding show complex genetic relationships with TS, OCD, and ADHD, and, rather than being specific subtypes of OCD, transcend traditional diagnostic boundaries, perhaps representing an underlying vulnerability (e.g. failure of top-down cognitive control) common to all three disorders.

Genome-wide association study of Tourette's syndrome.

Tourette's syndrome (TS) is a developmental disorder that has one of the highest familial recurrence rates among neuropsychiatric diseases with complex inheritance. However, the identification of definitive TS susceptibility genes remains elusive. Here, we report the first genome-wide association study (GWAS) of TS in 1285 cases and 4964 ancestry-matched controls of European ancestry, including two European-derived population isolates, Ashkenazi Jews from North America and Israel and French Canadians from Quebec, Canada. In a primary meta-analysis of GWAS data from these European ancestry samples, no markers achieved a genome-wide threshold of significance (P<5 × 10(-8)); the top signal was found in rs7868992 on chromosome 9q32 within COL27A1 (P=1.85 × 10(-6)). A secondary analysis including an additional 211 cases and 285 controls from two closely related Latin American population isolates from the Central Valley of Costa Rica and Antioquia, Colombia also identified rs7868992 as the top signal (P=3.6 × 10(-7) for the combined sample of 1496 cases and 5249 controls following imputation with 1000 Genomes data). This study lays the groundwork for the eventual identification of common TS susceptibility variants in larger cohorts and helps to provide a more complete understanding of the full genetic architecture of this disorder.

[Therapy and care of patients with chronic migraine: expert recommendations of the German Migraine and Headache Society/German Society for Neurology as well as the Austrian Headache Society/Swiss Headache Society]. / Therapie und Versorgung bei chronischer Migräne : Expertenempfehlung der Deutschen Migräne- und Kopfschmerzgesellschaft/Deutsche Gesellschaft für Neurologie sowie der Österreichischen Kopfschmerzgesellschaft/Schweizerischen Kopfwehgesellschaft.

Chronic migraine (CM) was first defined in the second edition of the International Headache Society (IHS) classification in 2004. The definition currently used (IHS 2006) requires the patient to have headache on more than 15 days/month for longer than 3 months and a migraine headache on at least 8 of these monthly headache days and that there is no medication overuse. In daily practice the majority of the patients with CM also report medication overuse but it is difficult to determine whether the use is the cause or the consequence of CM. Most the patients also have other comorbidities, such as depression, anxiety and chronic pain at other locations. Therapy has to take this complexity into consideration and is generally multimodal with behavioral therapy, aerobic training and pharmacotherapy. The use of analgesics should be limited to fewer than 15 days per month and use of triptans to fewer than 10 days per month. Drug treatment should be started with topiramate, the drug with the best scientific evidence. If there is no benefit, onabotulinum toxin A (155-195 Units) should be used. There is also some limited evidence that valproic acid and amitriptyline might be beneficial. Neuromodulation by stimulation of the greater occipital nerve or vagal nerve is being tested in studies and is so far an experimental procedure only.

[The value of "migraine surgery". Overview of the pathophysiological concept and current evidence]. / Stellenwert der "Migränechirurgie". Ubersicht über das pathophysiologische Konzept und die aktuelle Datenlage.

Often without sufficient scientific evidence, unconventional methods for migraine treatment are being put forward. Recently a trial using "migraine surgery" has been published. Its design is based on a concept of migraine pathogenesis without any scientific background and includes several severe methodological flaws. In spite of the above, the study is frequently cited in the lay press. The surgical procedure as well as the study are critically discussed.

EFNS guideline on the drug treatment of migraine--revised report of an EFNS task force.

BACKGROUND: Migraine is one of the most frequent disabling neurological conditions with a major impact on the patients' quality of life. OBJECTIVES: To give evidence-based or expert recommendations for the different drug treatment procedures in the particular migraine syndromes based on a literature search and the consensus of an expert panel. METHODS: All available medical reference systems were screened for the range of clinical studies on migraine with and without aura and on migraine-like syndromes. The findings in these studies were evaluated according to the recommendations of the European Federation of Neurological Societies (EFNS) resulting in level A, B, or C recommendations and good practice points. RECOMMENDATIONS: For the acute treatment of migraine attacks, oral non-steroidal antiinflammatory drug (NSAID) and triptans are recommended. The administration should follow the concept of stratified treatment. Before intake of NSAID and triptans, oral metoclopramide or domperidone is recommended. In very severe attacks, intravenous acetylsalicylic acid or subcutaneous sumatriptan are drugs of first choice. Status migrainosus can be treated by cortoicosteroids, although this is not universally held to be helpful, or dihydroergotamine. For the prophylaxis of migraine, betablockers (propranolol and metoprolol) flunarizine, valproic acid, and topiramate are drugs of first choice. Drugs of second choice for migraine prophylaxis include amitriptyline, naproxen, petasites, and bisoprolol.

[Spontaneous pneumothorax--management, therapy]. / Spontáinní pneumotorax--management, terapie.

OBJECTIVE: Spontaneous pneumothorax (SPNO) is a surgical disease, which belongs to surgical emergencies. It is divided into a primary, secundary, katamenial and neonatal. A young and healthy men are affected by primary SPNO, usually on the right side of the thorax, recurrence is common. A secondary SPNO typically occurs in patients between the 5th and 7th decenium. These patients usually suffer from some lung disease. A major complications are more common in this type of pneumothorax. METHODS: At Department of surgery, University Hospital Brno, 73 patients were treated for spontaneous pneumothorax from the January, 2006 till August, 2008. We divided patients in two groups. The first one with primary SPNO, and the second one with secondary SPNO. Hospital stay, age distribution, type of operation, duration of drainage, postoperative complication, histological findings and laterality were followed up retrospectively. RESULTS: In group of primary SPNO, 24 patients were operated without major complication. The most frequent cause was bullate emphysema, hospital stay was 8 days, duration of drainage 6 days. The second group with secondary SPNO, five patients were operated, hospital stay was 16.5 days, duration of drainage 10 days. Haemothorax as a postoperative complication occured in one case. In both groups we proved the bullate emphysema as the most frequent cause, as well as a right - sided involvement. CONCLUSION: Spontaneous pneumothorax is a surgical disease. It's treatment has to be provided by surgeon, if possible by a thoracic specialist. The first occurrence of spontaneous pneumothorax is treated by drainage, the recurrence by operation. The principal is to combine an atypical resection of affected lung with a mechanical pleurodesis. Postoperative complications are not frequent.

Association study between Gilles de la Tourette Syndrome and two genes in the Robo-Slit pathway located in the chromosome 11q24 linked/associated region.

Gilles de la Tourette Syndrome (GTS) is an inherited neuropsychiatric disorder characterized by the presence of motor and phonic tics. Previous genetic studies have identified linkage and association between GTS and the 11q24 chromosomal region. We selected for study, within this region, two possible susceptibility genes for GTS, the ROBO3 and ROBO4 genes. These two genes were selected because of the recent identification of SLITRK1 as a potential susceptibility gene for GTS based on a translocation breakpoint and the further finding of two mutations in the SLITRK1 gene in three patients with GTS. While thus far, the SLITRK1 gene appears to account for only a few cases of GTS, these findings, if confirmed, point to other genes in these pathways that may contribute to GTS. Based on this, we examined two genes in the Slit-Robo pathway involved in cell migration, axonal pathfinding, and/or neuronal differentiation because of their location in 11q24, a region previously identified as linked and associated with GTS. We selected six haplotype tagging single nucleotide polymorphisms (SNPs) for ROBO3 and four for ROBO4 and genotyped them in our sample of trios and sibpair families diagnosed with GTS. Based on 155 nuclear families with 255 affected children, we did not find evidence for association between GTS and either the ROBO3 or ROBO4 genes. Thus, these two genes are unlikely to be the susceptibility genes contributing to GTS on 11q24.

Evaluation and proposal for optimization of neurophysiological tests in migraine: part 2--neuroimaging and the nitroglycerin test.

Neuroimaging methods have been widely used in headache and migraine research. They have provided invaluable information on brain perfusion, metabolism and structure during and outside of migraine attacks, contributing to an improved understanding of the pathophysiology of the disorder. Human models of migraine attacks are indispensable tools in pathophysiological and therapeutic research. This review of neuroimaging methods and the attack-provoking nitroglycerin test is part an initiative by a task force within the EUROHEAD project (EU Strep LSHM-CT-2004-5044837-Workpackage 9) with the objective of critically evaluating neurophysiological tests used in migraine. The first part, presented in a companion paper, is devoted to electrophysiological methods, this second part to neuroimaging methods such as functional magnetic resonance imaging, positron emission tomography and voxel-based morphometry, as well as the nitroglycerin test. For each of these methods, we summarize the results, analyse the methodological limitations and propose recommendations for improved methodology and standardization of research protocols.

EFNS guidelines on the treatment of cluster headache and other trigeminal-autonomic cephalalgias.

Cluster headache and the other trigeminal-autonomic cephalalgias [paroxysmal hemicrania, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) syndrome] are rare but very disabling conditions with a major impact on the patient's quality of life. The objective of this study was to give evidence-based recommendations for the treatment of these headache disorders based on a literature search and consensus amongst a panel of experts. All available medical reference systems were screened for any kind of studies on cluster headache, paroxysmal hemicrania and SUNCT syndrome. The findings in these studies were evaluated according to the recommendations of the European Federation of Neurological Societies resulting in level A, B or C recommendations and good practice points. For the acute treatment of cluster headache attacks, oxygen (100%) with a flow of at least 7 l/min over 15 min and 6 mg subcutaneous sumatriptan are drugs of first choice. Prophylaxis of cluster headache should be performed with verapamil at a daily dose of at least 240 mg (maximum dose depends on efficacy or tolerability). Although no class I or II trials are available, steroids are clearly effective in cluster headache. Therefore, the use of at least 100 mg methylprednisone (or equivalent corticosteroid) given orally or at up to 500 mg i.v. per day over 5 days (then tapering down) is recommended. Methysergide, lithium and topiramate are recommended as alternative treatments. Surgical procedures, although in part promising, require further scientific evaluation. For paroxysmal hemicranias, indomethacin at a daily dose of up to 225 mg is the drug of choice. For treatment of SUNCT syndrome, large series suggest that lamotrigine is the most effective preventive agent, with topiramate and gabapentin also being useful. Intravenous lidocaine may also be helpful as an acute therapy when patients are extremely distressed and disabled by frequent attacks.

An exploratory study of ferumoxtran-10 nanoparticles as a blood-brain barrier imaging agent targeting phagocytic cells in CNS inflammatory lesions.

BACKGROUND AND PURPOSE: Iron oxide-based contrast agents have been investigated as more specific MR imaging agents for central nervous system (CNS) inflammation. Ferumoxtran-10 is a virus-size nanoparticle, taken up by reactive cells, that allows visualization of the phagocytic components of CNS lesions. Ferumoxtran-10 was compared with standard gadolinium-enhanced MR images in this exploratory trial to assess its potential in evaluation of CNS lesions with inflammatory aspects, including lymphoma, multiple sclerosis (MS), acute disseminated encephalomyelitis (ADEM), and vascular lesions. METHODS: Twenty-three patients with different types of intracranial "inflammatory" lesions underwent standard brain MR with and without gadolinium, followed an average of 10 days later by a ferumoxtran-10 scan. Patients were imaged 24 hours after infusion of 2.6 mg/kg ferumoxtran-10. All MR images were evaluated subjectively by 4 investigators for a difference in enhancement patterns, which could be useful in differential diagnoses. RESULTS: In 5 cases, (one ADEM, 2 stroke, one cavernous venous vascular malformation, one primary central nervous lymphoma) the ferumoxtran-10 scan showed higher signal intensity, larger area of enhancement, or new enhancing areas compared with gadolinium. Most MS patients showed less enhancement with ferumoxtran-10 than with gadolinium. CONCLUSION: Ferumoxtran-10 showed different enhancement patterns in a variety of CNS lesions with inflammatory components in comparison to gadolinium. The impact of timing and therapy need further evaluation to better assess ferumoxtran-10 in addition to gadolinium as contrast agents for use in diagnosis and monitoring therapy in patients with CNS inflammatory lesions.

Blinking and schizotypal thinking.

Spontaneous eye blink rate (SBR) is thought to be a biological marker for cerebral dopamine (DA) activity. Accordingly, positive psychotic symptoms have been found to be associated with an increased SBR and negative psychotic symptoms with a decreased SBR. However, modulations of the DA system in patient populations also result from prior neuroleptic treatment. Here, we tested the possible relationship between SBR and positive and negative schizotypal thought. To test the direct influence of DA on SBR in general and as a function of schizotypy, half of a sample of 40 healthy men received levodopa and the other half placebo in a double-blind procedure. SBR did not differ between substance groups suggesting that a pharmacologically induced DA increase in healthy individuals does not generally increase SBR. However, in the levodopa group, increasing SBR correlated with increasing negative schizotypy scores, while no relationship was found between SBR and (1) negative schizotypy in the placebo group, or (2) positive schizotypy in either substance group. We conjecture that a pre-existing hypodopaminergic state in high negative schizotypy scorers, made these individuals susceptible to an increased DA concentration, as it has been observed in Parkinson's disease. Furthermore, the absence of any relationship in the placebo group might suggest that variations in DA concentration as a function of schizotypy are too subtle to influence SBR. Finally, the lack of any association of SBR with positive schizotypy might indicate that SBR and positive schizotypy are mediated by functionally distinct neural circuits.

Ultrasound as a tool to evaluate remission of cutaneous Kaposi's sarcoma.

OBJECTIVE: To evaluate ultrasound measurement of Kaposi's sarcoma (KS) tumour volume for follow-up during therapy. Two-dimensional evaluation of size and description of gross alteration (for example, colour, nodularity, resolution) was used to assess treatment of KS. Flattening of palpable cutaneous KS lesions during anti-KS therapy has not been quantified objectively by a reliable method. METHODS: In six patients with advanced AIDS and KS, a total of 17 cutaneous lesions were evaluated prospectively by ultrasound and surface measurements. KS lesions were examined histologically before and after 12 weeks of chemotherapy with liposomal doxorubicin. RESULTS: In comparison with size reduction, volume measurement showed a more pronounced reduction of tumour volume. The mean tumour volume was reduced by 94% from 451 mm3 +/- 655 mm3 to 66 mm3 +/- 165 mm3 at week 12 (P < 0.001). Histological evaluation of lesions no longer detectable by ultrasound after therapy showed abundant siderophages but no increase in spindle cells and no mitoses. CONCLUSIONS: Our findings suggest that ultrasound is a useful method with which to follow growth and remission of cutaneous KS. In contrast, pigmentation due to iron deposition is unaffected by chemotherapy because, despite histological remission, pigmentation can persist. Though ultrasound cannot replace histologic evaluation for complete response, we suggest the use of ultrasound assessment, thus introducing a more objective criterion than subjective rating of nodularity.

NO synthase blockade induces chaotic cerebral vasomotion via activation of thromboxane receptors.

BACKGROUND AND PURPOSE: Instability of the vascular tone (vasomotion) develops in several cerebrovascular diseases associated with endothelial dysfunction. The aim of the present study was to characterize cerebral vasomotion induced by diminished NO production with quantitative evaluation and chaos analysis. We tested the hypothesis that activation of thromboxane receptors mediates chaotic vasomotion after NO synthase (NOS) inhibition. METHODS: Measurements of vascular tension were carried out in isolated rat middle cerebral arteries. The extent of vasomotion was characterized by tension instability, whereas vasomotion complexity was assessed by chaos analysis. RESULTS: Blocking the basal NO release by N(omega)-nitro-L-arginine (L-NA) induced vasomotion, which was further enhanced and became irregular after UTP administration. The NO donor sodium nitroprusside was able to reverse this effect, and stable steady-state conditions reappeared. The guanylyl cyclase inhibitor 1H-(1,2,4)oxadiazolo[4,3-a]quinoxaline-1-one (ODQ) or coapplication of ODQ and L-NA had an effect identical to that of L-NA alone. Vasoconstriction by K(+) failed to induce vasomotion in intact vessels or in the presence of L-NA or ODQ. The thromboxane receptor antagonist ICI 192605 dose-dependently attenuated the vasomotion induced by L-NA and UTP, and the thromboxane-receptor agonist U-46619 induced significant vasomotion in intact vessels. CONCLUSIONS: The lack of NO in cerebral vessels provokes vulnerability to chaotic vasomotion, which can be triggered by the administration of UTP, whereas excess NO reverses it to stable conditions. The vasomotion after blockade of the NO-cGMP pathway is mediated by activation of thromboxane receptors.

Major role of nitric oxide in the mediation of regional CO2 responsiveness of the cerebral and spinal cord vessels of the cat.

The role of nitric oxide (NO) in the mediation of cerebrovascular CO2 responsiveness was studied in 10 distinct brain and spinal cord regions of the anesthetized, ventilated, temperature-controlled, normoxic cat. Regional CBF was measured with 15-micron radiolabeled microspheres in hypocapnic, normocapnic, and hypercapnic conditions. CO2 responsiveness of each region was determined from the equation of the best-fit regression lines to the obtained flow values. The effect of altered endothelial and/or neuronal NO synthesis on CO2 responsiveness was studied following either selective blockade of the NO synthase enzyme by N omega-nitro-L-arginine methyl ester (L-NAME; 3 or 30 mg/kg i.v.) or simultaneous administration of L-NAME (3 mg/kg i.v.) and a large dose of the NO precursor L-arginine (30 mg/kg i.v.). Blockade of NO synthesis by 30 mg/kg L-NAME resulted in a significant reduction of the steady-state regional blood flow values and in an almost complete abolition of the CO2 sensitivity in each region studied. Changes of the basal flow values as well as the reduction of the regional CO2 sensitivity were dose dependent. Hypothalamic, sensorimotor cortical, and cerebellar regions were the areas most sensitive to the NO blockade. Impaired CO2 responsiveness following NO synthase inhibition, however, was reversed in these regions by simultaneous administration of a large dose of intravenously injected L-arginine. These findings suggest a major role of nitric oxide in the mediation of regional cerebrovascular CO2 responsiveness in cats.

Interactions between the endothelium-derived relaxing factor/nitric oxide system and the endogenous opiate system in the modulation of cerebral and spinal vascular CO2 responsiveness.

The role of the L-arginine-nitric oxide (NO) system, the role of the endogenous morphine-like substances (endorphins), and the possible interaction between these two systems in the modulation of regional cerebral and spinal CO2 responsiveness was investigated in anesthetized, ventilated, normotensive, normoxic cats. Regional cerebral blood flow was measured with radiolabeled microspheres in hypocapnic, normocapnic, and hypercapnic conditions in nine individual cerebral and spinal cord regions. General opiate receptor blockade by 1 mg/kg naloxone intravenously alone or NO synthase blockade by 3 mg/kg N(omega)-nitro-L-arginine-methyl ester (L-NAME) intravenously alone caused no changes in regional CO2 responsiveness. Combined administration of these two blocking agents in the very same doses, however, resulted in a strong potentiation, with a statistically significant reduction of the CO2 responsiveness observed. Separation of the blood flow response to hypercapnia and hypocapnia indicates that this reduction occurs only during hypercapnia. Specific mu and delta opiate receptors were blocked by 0.5 mg kg(-1) IV beta-funaltrexamine and 0.4 mg kg(-1) IV naltrindole, respectively. The role of specific mu and delta opiate receptors in the NO-opiate interaction was found to be negligible because neither mu nor delta receptor blockade along with simultaneous NO blockade were able to decrease CO2 responsiveness. The current findings suggest a previously unknown interaction between the endothelium-derived relaxing factor/nitric oxide (EDRF/NO) system and the endogenous opiate system in the cerebrovascular bed during hypercapnic stimulation, with the phenomenon not mediated by mu or delta opiate receptors.

Effects of a stable enkephalin analogue, (D-Met2,Pro5)-enkephalinamide, and naloxone on cortical blood flow and cerebral blood volume in experimental brain ischemia in anesthetized cats.

The effects of intracarotid injection of the stable enkephalin analogue (D-Met2,Pro5)-enkephalinamide (ENK) and intravenous administration of naloxone on the cerebrocortical blood flow (dye dilution method) and cerebral blood volume (CBV) (photoelectric method) were investigated during unilateral brain ischemia in anesthetized cats. Both parameters were measured simultaneously in the intact and ischemic (middle cerebral artery occluded) hemispheres. An intracarotid injection of ENK 0.5 mg/kg induced a significant increase in cortical vascular resistance and a -87% decrease in cerebrocortical blood flow from 25 +/- 3 to 4 +/- 3 ml/100 g/min, without CBV alteration in the ischemic hemisphere. Naloxone (1 mg/kg i.v.), on the other hand, induced a marked two-fold increase in cerebrocortical blood flow and a significant elevation of CBV from 5.9 +/- 0.5 to 7.4 +/- 0.7 vol% in the ischemic hemisphere. No change in cerebrocortical blood flow or CBV was observed in the intact hemisphere either after ENK or after naloxone administration. Arterial blood gases and hematocrit remained unchanged. On the basis of the present findings, we conclude that besides other factors, endogenous opioid mechanisms may also participate in ischemic cerebrovascular reactions and the cerebral circulatory effects of naloxone probably reflect its opiate receptor blocking property and not simply its other non-opiate-related actions.