Local Hemodynamic Changes Research Articles

Manipulation of magnetic nanoparticle retention and hemodynamic consequences in microcirculation: assessment by laser speckle imaging

Magnetic nanoparticles (MNPs) have been proposed for targeted or embolization therapeutics. How MNP retention occurs in circulation may critically determine local hemodynamics, tissue distribution of MNPs, and the therapeutic effects. We attempted to establish a microcirculation model to study the magnetic capture of MNPs in small vessels and to determine the factors affecting MNP retention. Two-dimensional hemodynamic changes in response to magnet-induced MNP retention in the microvessels of the cremaster muscle in vivo were observed in a real-time manner using a laser speckle imaging technique. Changes in tissue perfusion of the cremaster muscle appeared to be closely correlated with the location of the magnet placement underneath the muscle in response to intra-arterial administration of dextran-coated MNPs. Magnet-related retention was observed along the edge of the magnet, as corroborated by the results of histology analysis and microcomputed tomography. In these preparations, tissue iron content almost doubled, as revealed by inductively coupled plasma optical emission spectroscopy. In addition, MNP retention was associated with reduced downstream flow in a dose-dependent manner. Dissipation of MNPs (5 mg/kg) occurred shortly after removal of the magnet, which was associated with significant recovery of tissue flow. However, MNP dissipation did not easily occur after administration of a higher MNP dose (10 mg/kg) or prolonged exposure to the magnetic field. An ultrasound after removal of the magnet may induce the partial dispersion of MNPs and thus partially improve hemodynamics. In conclusion, our results revealed the important correlation of local MNP retention and hemodynamic changes in microcirculation, which can be crucial in the application of MNPs for effective targeted therapeutics.

Non-invasive continuous EEG-fNIRS recording of temporal lobe seizures

Functional near-infrared spectroscopy (fNIRS) is a technique that allows continuous non-invasive monitoring of tissue oxygenation and haemodynamics in the brain. By using combined EEG-fNIRS recordings, we sought to better understand the pathophysiology of temporal lobe seizures. Nine patients (5 males; mean age 35 years; range 11-56 years) with refractory mesial temporal lobe epilepsy underwent combined EEG-fNIRS recordings. Eight complex partial seizures from 3 patients were successfully recorded. All seizures were associated with significant local and remote haemodynamic changes which outlasted the duration of seizures. Over the epileptogenic temporal lobe, increased oxygenation [increase in cerebral blood volume (CBV) and oxyhaemoglobin (HbO), decrease in deoxyhaemoglobin (HbR)] was followed by a deoxygenated state [increase in HbR]. A similar haemodynamic profile was seen over the contralateral temporal lobe (even without evidence of epileptic propagation) though variations generally had lower amplitudes. Heterogeneous haemodynamic changes in remote frontal and/or parietal areas were also noted early on when epileptic activity was limited to the temporal lobe. EEG-fNIRS reveals complex local and remote oxygenation changes during temporal lobe seizures.

Assessment of Network States: Local Hemodynamics

Neural activity utilizes energy resources and requires replenishment of metabolites through vascular dilation. During wake, cortical neurons usually have depolarized membrane potentials and exhibit frequent spontaneous action potentials, requiring an increased metabolic delivery to activated tissue and causing blood vessels to dilate. Quiet sleep (QS) is characterized by alternating membrane potential between a depolarized and hyperpolarized state. The hyperpolarized state has a lower membrane potential and exhibits few action potentials, which may be less metabolically demanding. In order to investigate the relationship between evoked neural and metabolic responses across wake and sleep states, we combined electrical and optical imaging techniques. We implanted rats with screw electrodes to measure evoked response potentials (ERPs), and used a light emitting diode (LED) and photodiode to measure evoked changes in local hemodynamics based on hemoglobin absorption properties. During QS, hemodynamic changes were larger in amplitude compared to wake and rapid eye movement (REM) sleep. In this review, we explore the potential mechanisms for the larger hemodynamic changes. Wake periods may correspond to decreased vessel compliance as they expand to supply tissue with metabolites while sleep periods may decrease metabolic demand and allow vessels to relax and restore compliance.

Vascular Geometry Change Because of Endovascular Stent Placement for Anterior Communicating Artery Aneurysms

Hemodynamics have been shown to play an important role in the initiation and progress of intracranial aneurysms, and are considered well-related to vascular configuration. The purpose of this study was to quantify the vascular geometry change due to intracranial stent placement and to discuss its potential effects on hemodynamics. Imaging data of patients with wide-neck AcomA aneurysms, treated with stent-assisted coiling between January 2005 and January 2010, were retrospectively analyzed. The angle between the afferent vessels (A1 segment) and the efferent vessels (ipsilateral or contralateral A2 segment) was calculated to determine the exact change in the angle after stent placement. In all 20 patients, the stent caused a distinct change in the geometry of the parent vessel. Stent-related vascular angle change ranged from 7.60 to 74.88°, with an average of 29.95°. In 10 cases, the angle changed by >30°. In the 12 patients with the distal segment of the stent placed in the ipsilateral A2 segment, the mean postoperative A1-A2 angle increased by 27.71 ± 13.17° (from 7.60° to 48.29°). In the other 8 patients with the distal segment of the stent placed in the contralateral A2 segment, the mean postoperative A1-AcomA-A2 angle increased by 33.29 ± 21.89°(from 15.49° to 74.88°). In addition to serving as a scaffold to contain coils, stent placement for AcomA aneurysms has a substantial effect on the vascular geometry, which may result in local hemodynamic changes.

Human pregnancy, a biological paradigm of tolerance and adaptation

This review analyses the changes in immunological tolerance, and the systemic and local hemodynamic changes observed along human pregnancy. To underscore the conceptual importance of tolerance and adaptation the background is provided by the two main advocates of these ideas: Gandhi and Darwin. The cognate factors that determine immunological tolerance (IT), systemic (SA) and local adaptation (LA) are multiple; IT = desensitisation to paternal antigens, absence of HLA-A, roles of HLA-G, natural killer cells and their receptors; SA = decreased vascular resistance, plasma volume expansion, increased cardiac output and plasma renin activity; LA = prostacyclin, nitric oxide, kallikrein-kinin system, vasodilator arm of the renin angiotensin system, vascular endothelial growth factor (VEGF). A possible role of vasodilators in the crucial process of trophoblast invasion and uterine artery transformation is supported. The relevance of an adequate adaptation to pregnancy is highlighted not only by the intragestational complications derived from a defective process, such as intrauterine growth restriction, preterm birth, and preeclampsia -its foremost expression- but also by the long term cardiovascular complications of the mother and her offspring.

El embarazo humano: paradigma biológico de tolerancia y adaptación

This review analyses the changes in immunological tolerance, and the systemic and local hemodynamic changes observed along human pregnancy. To underscore the conceptual importance of tolerance and adaptation the background is provided by the two main advocates of these ideas: Gandhi and Darwin. The cognate factors that determine immunological tolerance (IT), systemic (SA) and local adaptation (LA) are multiple; IT = desensitisation to paternal antigens, absence of HLA-A, roles of HLA-G, natural killer cells and their receptors; SA = decreased vascular resistance, plasma volume expansion, increased cardiac output and plasma renin activity; LA = prostacyclin, nitric oxide, kallikrein-kinin system, vasodilator arm of the renin angiotensin system, vascular endothelial growth factor (VEGF). A possible role of vasodilators in the crucial process of trophoblast invasion and uterine artery transformation is supported. The relevance of an adequate adaptation to pregnancy is highlighted not only by the intragestational complications derived from a defective process, such as intrauterine growth restriction, preterm birth, and preeclampsia -its foremost expression- but also by the long term cardiovascular complications of the mother and her offspring.

Hydrodynamic Effects of Compliance Mismatch in Stented Arteries

Cardiovascular diseases are the number one cause of death in the world, making the understanding of hemodynamics and development of treatment options imperative. The most common modality for treatment of occlusive coronary artery diseases is the use of stents. Stent design profoundly influences the postprocedural hemodynamic and solid mechanical environment of the stented artery. However, despite their wide acceptance, the incidence of stent late restenosis is still high (Zwart et al., 2010, "Coronary Stent Thrombosis in the Current Era: Challenges and Opportunities for Treatment," Current Treatment Options in Cardiovascular Medicine, 12(1), pp. 46-57), and it is most prevailing at the proximal and distal ends of the stent. In this work, we focus our investigation on the localized hemodynamic effects of compliance mismatch due to the presence of a stent in an artery. The compliance mismatch in a stented artery is maximized at the proximal and distal ends of the stent. Hence, it is our objective to understand and reveal the mechanism by which changes in compliance contribute to the generation of nonphysiological wall shear stress (WSS). Such adverse hemodynamic conditions could have an effect on the onset of restenosis. Three-dimensional, spatiotemporally resolved computational fluid dynamics simulations of pulsatile flow with fluid-structure interaction were carried out for a simplified coronary artery with physiologically relevant flow parameters. A model with uniform elastic modulus is used as the baseline control case. In order to study the effect of compliance variation on local hemodynamics, this baseline model is compared with models where the elastic modulus was increased by two-, five-, and tenfold in the middle of the vessel. The simulations provided detailed information regarding the recirculation zone dynamics formed during flow reversals. The results suggest that discontinuities in compliance cause critical changes in local hemodynamics, namely, altering the local pressure and velocity gradients. The change in pressure gradient at the discontinuity was as high as 90%. The corresponding changes in WSS and oscillatory shear index calculated were 9% and 15%, respectively. We demonstrate that these changes are attributed to the physical mechanism associating the pressure gradient discontinuities to the production of vorticity (vorticity flux) due to the presence of the stent. The pressure gradient discontinuities and augmented vorticity flux are affecting the wall shear stresses. As a result, this work reveals how compliance variations act to modify the near wall hemodynamics of stented arteries.

Quantification of light reflectance spectroscopy and its application: Determination of hemodynamics on the rat spinal cord and brain induced by electrical stimulation

Two quantification methods for light reflectance spectroscopy (LRS) were developed and validated to determine absolute and relative values of hemodynamic parameters and light scattering, followed by a specific application using in vivo animal experiments. A single-channel LRS system consisted of a light source, CCD-array detector, and a computer along with a bifurcated, 2-mm-diameter optical probe; this system was utilized to perform laboratory tissue phantoms for validation of the algorithms. In the animal study, a multi-channel, multisite approach was used to measure several reflectance spectra from rat brain and spinal cord on both the ipsi-lateral and contra-lateral sides, using thin 800-μm-diameter optic probes. The neuro-hemodynamic changes were induced by 10-V electrical stimulation in rat hind paw. The LRS data of the animals were analyzed using both absolute and relative methods. The results show that the relative method is computation-efficient and offers a quick estimation of changes in oxy-hemoglobin concentration for real-time monitoring. The absolute quantification method, on the other hand, provides us with an accurate computational tool to calculate absolute values of oxy-, deoxy-, total hemoglobin concentrations, and light scattering coefficients. We also observe that the hemodynamic responses in rat spinal cord were delayed with a few seconds and have an overall broader full width at half maximum, as compared to those from rat somatosensory cortex. LRS as a measurement system provides a robust method for studying local hemodynamic changes and a potential technique to investigate hemo-neural mechanisms in pain processing.

Multichannel wearable system dedicated for simultaneous electroencephalography∕near-infrared spectroscopy real-time data acquisitions

Functional neuroimaging is becoming a valuable tool in cognitive research and clinical applications. The clinical context brings specific constraints that include the requirement of a high channel count to cover the whole head, high sensitivity for single event detection, and portability for long-term bedside monitoring. For epilepsy and stroke monitoring, the combination of electroencephalography (EEG) and functional near-infrared spectroscopy (NIRS) is expected to provide useful clinical information, and efforts have been deployed to create prototypes able to simultaneously acquire both measurement modalities. However, to the best of our knowledge, existing systems lack portability, NIRS sensitivity, or have low channel count. We present a battery-powered, portable system with potentially up to 32 EEG channels, 32 NIRS light sources, and 32 detectors. Avalanche photodiodes allow for high NIRS sensitivity and the autonomy of the system is over 24 h. A reduced channel count prototype with 8 EEG channels, 8 sources, and 8 detectors was tested on phantoms. Further validation was done on five healthy adults using a visual stimulation protocol to detect local hemodynamic changes and visually evoked potentials. Results show good concordance with literature regarding functional activations and suggest sufficient performance for clinical use, provided some minor adjustments were made.

Neocortical Interneurons: From Diversity, Strength

Interneurons in the neocortex of the brain are small, locally projecting inhibitory GABAergic cells with a broad array of anatomical and physiological properties. The diversity of interneurons is believed to be crucial for regulating myriad operations in the neocortex. Here, we describe current theories about how interneuron diversity may support distinct neocortical processes that underlie perception.

Local hemodynamic changes caused by main branch stent implantation and subsequent virtual side branch balloon angioplasty in a representative coronary bifurcation

Abnormal blood flow patterns promoting inflammation, cellular proliferation, and thrombosis may be established by local changes in vessel geometry after stent implantation in bifurcation lesions. Our objective was to quantify altered hemodynamics due to main vessel (MV) stenting and subsequent virtual side branch (SB) angioplasty in a coronary bifurcation by using computational fluid dynamics (CFD) analysis. CFD models were generated from representative vascular dimensions and intravascular ultrasound images. Time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and fractional flow reserve (FFR) were quantified. None of the luminal surface was exposed to low TAWSS (<4 dyn/cm(2)) in the nondiseased bifurcation model. MV stenting introduced eccentric areas of low TAWSS along the lateral wall of the MV. Virtual SB angioplasty resulted in a more concentric region of low TAWSS in the MV distal to the carina and along the lateral wall of the SB. The luminal surface exposed to low TAWSS was similar before and after virtual SB angioplasty (rest: 43% vs. 41%; hyperemia: 18% vs. 21%) and primarily due to stent-induced flow alterations. Sites of elevated OSI (>0.1) were minimal but more impacted by general vessel geometry established after MV stenting. FFR measured at a jailed SB was within the normal range despite angiographic stenosis of 54%. These findings indicate that the most commonly used percutaneous interventional strategy for a bifurcation lesion causes abnormal local hemodynamic conditions. These results may partially explain the high clinical event rates in bifurcation lesions.

Quiste óseo aneurismático coexistente con osteosarcoma. Discusión radiopatológica

Aneurysmatic bone cysts are benign lesions of unknown origin. It has been postulated that they might occur in reaction to trauma or to a primary benign (giant cell tumor, chondroblastoma, etc.) or malignant (osteosarcoma) bone tumor that results in local hemodynamic changes. Their malignant transformation is controversial. We present a case of low grade osteosarcoma with a radiologic progression that was indistinguishable from that of an aneurysmatic bone cyst.

Local haemodynamic changes preceding interictal spikes: A simultaneous electrocorticography (ECoG) and near-infrared spectroscopy (NIRS) analysis in rats

The mechanisms that drive neurons to synchronize in epileptic spikes are still subject to debate. In the present study, we used a combination of electrocorticography and near-infrared spectroscopy (ECoG/NIRS) to evaluate haemodynamic changes before, during and after epileptic spikes induced by administration of bicuculline methiodide (BM) onto the sensorimotor cortex in 8 adult Sprague–Dawley rats. Simultaneous ECoG/NIRS signals were recorded during an initial reference period (to measure spontaneous bioelectrical/metabolic activities) and then again 60 min after BM administration. Spikes in the ECoG were detected by an in-house program based on MatLab 7.0. The appearance times of the P1 peaks were used to determine corresponding time periods in the NIRS for further analysis. We observed a pronounced pre-spike modification in the haemodynamics, which became visible latest 5 s before the spike, achieving after some oscillations its minimum at round about the P1 appearance time. The post-spike period was characterized by an initial increase in oxyhaemoglobin (HbO) and total haemoglobin (HbT) to a maximum at about 2 s after the spike followed by a phase of declining oscillations disappearing after 10 to 15 s after the spike. We discuss the mechanisms underlying the haemodynamic and electrical changes that occur before, during and after epileptiform spikes. The haemodynamic changes observed with NIRS and occurring before the spikes constitute a haemodynamic predictor of electrical synchronization of spikes.

Clinical Significance and Technical Assessment of Stent Cell Geometry in Carotid Artery Stenting

Carotid artery stenting has gained popularity due to its minimally invasive approach. However, several design concerns preclude the successful use of carotid stents. Technical issues, such as open versus closed cells, scaffolding, trackability, foreshortening, and changes in local geometry and hemodynamics, affect stent performance. Previous clinical and experimental studies have evaluated current stent models while proposing and testing novel stent designs. This review focuses on the technical aspects of carotid stent design and the clinical significance of key design parameters identified via computational and experimental modeling.

Visualizing localized dynamic changes during epileptic seizure onset in vivo with diffuse optical tomography

Diffuse optical tomography (DOT) is a promising functional imaging modality due to its ability to provide quantitative and dynamic tomographic imaging of brain functions. This pilot study was conducted to demonstrate that DOT can be used to visualize the changes in local hemodynamics during seizures. The focal seizure was induced by microinjection of 10 microl of 1.9 mM GABAA antagonist bicuculline methiodide (BMI) into the left parietal neocortex of male Harlen Sprague-Dawley rats, which was imaged by a multispectral continuous-wave DOT system. Functional images were obtained by our finite element based image reconstruction algorithm. A series of dynamic 2D images were obtained to delineate the time course of concentration changes of oxyhaemoglobin, deoxyhaemoglobin, and total hemoglobin in the rat brain during seizure onset. The BMI induced epileptic foci were localized and observed over time from the images obtained. Our results suggest that diffuse optical tomography may be a promising modality for epilepsy imaging due to its ability to localize epileptic foci as well as its potential to map the functional activity in the area of human cerebral cortex in planning of epilepsy surgery.

Transcranial cortex stimulation and fMRI: Electrophysiological correlates of dual-pulse BOLD signal modulation

Are the local hemodynamic changes in BOLD-fMRI correlated to increased or decreased neuronal activity or both? We combined transcranial electrical cortex stimulation (TES) with simultaneous fMRI and electromyographic (EMG) recording to study the influence of inhibitory and excitatory neuronal activity on the concomitant BOLD signal change. Unilateral or bilateral TES was applied with a postero-anterior orientation. This activates pyramidal cells transsynaptically and allows for the induction of cortical inhibition and excitation of the pyramidal cell, respectively. In this project interhemispheric inhibition (IHI) served as an in vivo model to investigate electrophysiologically well defined inhibitory and excitatory effects. MethodologyIncluded event-related fMRI, which triggered TES; online recording of the EMG response monitored the inhibitory and excitatory influences on discharging corticospinal neurons. ResultsRevealed that a single suprathreshold stimulus induced a positive BOLD response both in the ipsilateral as well as in the contralateral primary motor cortex (M1). The contralateral co-activation of the homotopic M1 should be a functional correlate of transcallosal connections. If a contralateral conditioning stimulus preceded the test stimulus by 10 ms (IHI), the subsequent ipsilateral BOLD signal was significantly reduced. We find that cortical inhibitory processes are accompanied by attenuation of the local neurovascular signal.

NO counterbalances HO-1 overexpression-induced acceleration of hepatocyte proliferation in mice

The trigger for liver regeneration, including shear stress, has been the subject of ongoing debate. Blood vessel-derived gaseous molecules carbon monoxide (CO) and nitric oxide (NO) regulate vascular tone and play an important role in liver regeneration. In heme oxygenase-1 (HO-1) transgenic mice, it has been shown that CO-mediated impairment of vasorelaxation is an NO-dependent event. We therefore studied liver regeneration in HO-1 overexpressing animals in dependency of NO availability. Mice were subjected to 2/3 hepatectomy and were treated with either cobalt protoporphyrin-IX for induction of CO-liberating HO-1, Nω-nitro-L-arginine methyl ester (L-NAME) for blockade of NO synthase (NOS) or both. Application of molsidomine in L-NAME treated animals served for resubstitution of NO. Vehicle-treated animals served as respective control animals. We examined 5-bromo-2′-deoxyuridine incorporation and proliferating cell nuclear antigen expression as well as HO-1 and NOS-2 protein levels. Intrahepatic red blood cell velocity and volumetric blood flow were evaluated by in vivo fluorescence microscopy as indicators for microvascular shear stress. Hepatic regeneration remained unaffected by L-NAME application for NOS blockade. However, NOS blockade in HO-1 induced animals caused increased 5-bromo-2′-deoxyuridine and proliferating cell nuclear antigen measures of liver regeneration. In parallel, these animals revealed increased velocities and volumetric blood flow in the terminal afferent vessels and postsinusoidal venules. These local hemodynamic changes including enhanced hepatocyte proliferation could be reversed by NO liberation via molsidomine. The present findings stress the role of NO to counterbalance vascular tone in HO-1 overexpressing animals for maintenance of adequate perfusion and salutary shear force within the hepatic microvasculature upon liver resection.

Clinical Use of Functional Magnetic Resonance Imaging: Reflections on the New CPT Codes

Functional magnetic resonance imaging (fMRI), a noninvasive method for mapping human brain function, was developed 15 years ago. This technique, based on the blood oxygen level dependent (BOLD) contrast, is sensitive to the localized hemodynamic changes that occur with increased neural activity. Over the first decade following this discovery, fMRI was used extensively to map brain activity evoked from sensory, motor, cognitive, and emotional tasks in healthy individuals. More recently, this technique has been applied to further our understanding of neurobehavioral disorders, such as Alzheimer’s disease, epilepsy, brain tumors, stroke, traumatic brain injury, and multiple sclerosis. fMRI has become widespread because it is relatively easy to perform, is reproducible, does not involve the use of exogenous contrast agents, can be performed with the majority of existing MR scanners, and yields superior temporal and spatial resolution relative to other functional imaging techniques (e.g., positron emission tomography). Not surprisingly, some clinicians have appreciated the potential of fMRI as a tool for diagnosis and management of patients. Several professional specialties have begun to apply fMRI techniques to patient care, including clinical neuropsychology, neurology, neuroradiology, neurosurgery, psychiatry, and rehabilitation. The best developed clinical application has involved the use of fMRI in the presurgical mapping of patients with brain tumors and epilepsy. The strength of clinical fMRI research in this area culminated in the approval of fMRI-specific CPT codes (see below), effective January 2007. One of the three approved fMRI codes was specifically designed for clinical neuropsychologists and physicians with education and training in the administration of neurofunctional tests. The advent of CPT codes has raised concerns regarding the appropriate qualifications of clinical neuropsychologists applying fMRI in clinical practice. Regardless of the purpose of study, fMRI is technically challenging with regard to study design, image analysis, and interpretation of findings. The complex nature of this technique increases the risk of over-interpretation or misuse of data when individuals practice this technique without adequate training. To address this concern, Division 40 of the American Psychological Association published a position paper identifying the role of neuropsychologists in clinical fMRI (The Clinical Neuropsychologist, volume 18, 2004). The task force noted that clinical fMRI is a team effort; consequently, clinical neuropsychologists will typically collaborate with professionals with expertise in neuroradiology, neurosurgery, MR physics, and statistical image analysis. Neuropsychologists have extensive training in the development of cognitive tasks and statistical analysis, recognizing the importance of reliability and validity. In clinical practice, neuropsychologists are trained to recognize confounds to assessment of human behavior, interpret findings of cognitive performances, and make appropriate recommendations for treatment. Given the basic, fundamental training in brain-behavior relationships and human behavior, the role of neuropsychology in fMRI is well supported. This paper will first discuss the CPT codes and then provide possible models of education and training that will ensure that the clinical fMRI study is administered and interpreted by a qualified practitioner.

Event‐related functional near‐infrared spectroscopy (fNIRS) based on craniocerebral correlations: Reproducibility of activation?

The purpose of the present study was to assess the retest reliability of cortical activation detected by event-related functional near-infrared spectroscopy (fNIRS) based on craniocerebral correlations. Isolated functional activation was evoked in the motor cortex by a periodically performed finger-tapping task. During 44-channel fNIRS recording, 12 subjects performed 30 trials of right and left index finger tapping in two sessions. The retest interval was set to 3 weeks. Simple correlations of the contrast t-values supplemented by scatterplots, channel-wise intraclass correlation coefficients (ICC), as well as reproducibility indices for the size and the location of the detected activation were calculated. The results at the group level showed sufficient single measure ICCs (up to 0.80) and excellent reproducibility of the size and the location (up to 89% were reproducible). Comparisons of the intersession group amplitudes demonstrate that the fNIRS signals were stable across time in a retest study design: the number of significant differences was less than randomly occurring false-positive activated channels if an alpha level of 5% is chosen. Effect size analyses indicated that the intersession amplitude differences are small (mean < 0.25). For deoxyhemoglobin and oxyhemoglobin distinct statistical power profiles were revealed regarding the activation vs. baseline contrast as well as the intersession amplitude differences, indicating a higher sensitivity of deoxyhemoglobin for local hemodynamic changes. The results suggest that sensorimotor activation assessed by event-related fNIRS based on craniocerebral correlations is sufficiently reproducible at the group level.

The effect of local nitric oxide synthase inhibition on the diameter of pulpal arteriole in dental bond material-induced vasodilation in rat

Local application of dental bond materials can cause pulpal vasodilation and hyperemia. Such local hemodynamic changes may be mediated by alterations in the levels of locally generated nitric oxide (NO). In different species systemic administration of NO synthase inhibitors leads to a decrease in pulpal blood flow. In contrast, the local administration of these inhibitors has not been tested yet. Therefore, the effect of locally blocked NO synthase on the internal diameter of rat pulpal arterioles under basal conditions and immediately after dental bond material application was studied by using vitalmicroscopic technique. The NO synthase blocker ( l-NAME) was locally administered on a thinned dentine layer of the left lower incisor. l-NAME reduced the diameter of the pulpal arteriole both in basal and after bond material-induced hyperaemic conditions. These data suggest that the local formation of NO may have a significant role in the acute vasodilation induced by bond material application and also in maintenance of basal pulpal arteriolar tone.