Serotonergic modulation of the ventral pallidum by 5HT1A, 5HT5A, 5HT7 AND 5HT2C receptors

Introduction: Serotonin's involvement in reward processing is controversial. The large number of serotonin receptor sub-types and their individual and unique contributions have been difficult to dissect out, yet understanding how specific serotonin receptor sub-types contribute to its effects on areas associated with reward processing is an essential step. Methods: The current study used multi-electrode arrays and acute slice preparations to examine the effects of serotonin on ventral pallidum (VP) neurons. Approach for statistical analysis: extracellular recordings were spike sorted using template matching and principal components analysis, Consecutive inter-spike intervals were then compared over periods of 1200 seconds for each treatment condition using a student’s t test. Results and conclusions: Our data suggests that excitatory responses to serotonin application are pre-synaptic in origin as blocking synaptic transmission with low-calcium aCSF abolished these responses. Our data also suggests that 5HT1a, 5HT5a and 5HT7 receptors contribute to this effect, potentially forming an oligomeric complex, as 5HT1a antagonists completely abolished excitatory responses to serotonin application, while 5HT5a and 5HT7 only reduced the magnitude of excitatory responses to serotonin. 5HT2c receptors were the only serotonin receptor sub-type tested that elicited inhibitory responses to serotonin application in the VP. These findings, combined with our previous data outlining the mechanisms underpinning dopamine's effects in the VP, provide key information, which will allow future research to fully examine the interplay between serotonin and dopamine in the VP. Investigation of dopamine and serotonins interaction may provide vital insights into our understanding of the VP's involvement in reward processing. It may also contribute to our understanding of how drugs of abuse, such as cocaine, may hijack these mechanisms in the VP resulting in sensitization to drugs of abuse

Correlation between acute ischaemic stroke clot length before mechanical thrombectomy and extracted clot area: Impact of thrombus size on number of passes for clot removal and final recanalization

Introduction: We assessed the correlation between thrombus size before and after mechanical thrombectomy, measured as length by Computed Tomography Angiography/Non-Contrast Computed Tomography (CTA/NCCT) and Extracted Clot Area, ECA, respectively. We also assessed the influence of thrombus size on the number of passes required for clot removal and final recanalization outcome. Materials and methods: Acute ischaemic stroke (AIS) thrombi retrieved by mechanical thrombectomy from 500 patients and data of clot length by CTA/NCCT were collected from three hospitals in Europe. ECA was obtained by measuring the area of the extracted clot. Non-parametric tests were used for data analysis. Results: A strong positive correlation was found between clot length on CTA/NCCT and ECA (rho = 0.619,N = 500, P < 0.0001*). Vessel size influences clot length on CTA/NCCT (H2 = 98.6, P < 0.0001*) and ECA (H2 = 105.6,P < 0.0001*), but the significant correlation between CTA/NCCT length and ECA was evident in all vessels. Poorer revascularisation outcome was associated with more passes (H5 = 73.1, P < 0.0001*). More passes were required to remove longer clots (CTA/NCCT; H4 = 31.4, P < 0.0001*; ECA; H4 = 50.2, P < 0.0001*). There was no significant main association between recanalization outcome and length on CTA/NCCT or ECA, but medium sized clots (ECA 20-40 mm(2)) were associated with least passes and highest revascularisation outcome (N = 500, X-2 = 16.2, P < 0.0001*). Conclusion: Clot length on CTA/NCCT strongly correlates with ECA. Occlusion location influences clot size. More passes are associated with poorer revascularisation outcome and bigger clots. The relationship between size and revascularisation outcome is more complex. Clots of medium ECA take less passes to remove and are associated with better recanalization outcome than both smaller and larger clots

The impact of occlusion location and bridging therapy in patients affected by acute ischemic stroke in determining the total number of passes required to remove the clot and the final revascularization outcome

Purpose Our purpose was to assess the impact of occlusion location in patients suffering from Acute Ischemic Stroke (AIS) on the total number of passes (attempts) necessary to retrieve the clot and on final revascularization outcome. Moreover, we analysed the impact of bridging-therapy, i.e. the concomitant use of IV tPA (intravenous tissue plasminogen activator) and mechanical thrombectomy (MT) on the different categories of occlusion locations. Methods 550 mechanically extracted thrombi were collected from four partner hospitals: Beaumont (Dublin) Sahlgrenska (Gothenburg), National Institute of Clinical Neurosciences (Budapest) and Metropolitan Hospital (Piraeus). In the vast majority of the cases (311 patients, 56.5%) the thrombus was located in the Middle Cerebral Artery (MCA), followed by Carotid Terminus/Internal Carotid Artery (ICA) in 89 cases (16.2%) and by vertebral/basilar artery (45 patients, 8.2%). In 65 cases (11.8%) a tandem occlusion, i.e. the occlusion of both ICA and MCA was found, while a dual occlusion occurred in 26 cases (4.7%). 248 patients (45.1%) underwent bridging-therapy, while 291 patients (52.9%) were treated with MT alone. For 11 patients (2%) we have no information whether tPA was administered or not. Recanalization rate was defined by using the modified Thrombolysis In Cerebral Infarction (mTICI) score. Non-parametric Kruskal-Wallis test using IBM SPSS-25 software was used for statistical analysis. Results Occlusion location had a significant impact on the total number of passes required to retrieve the clot as well as on final revascularization outcome. The cases with tandem and dual occlusion showed higher number of procedural passes and lower percentage of complete revascularizations (mTICI=3, Table 1). Bridging-therapy did not significantly reduce the total number of passes or improve the recanalization rates for patients with singular occlusion. On the other hand, bridging-therapy significantly lowered the total number of passes to remove the clot in patients with dual and tandem occlusion (N=87, mean for MT+tPA= 2.63±1.73, MT alone=3.80±2.14, H1=7.608, p=0.006*), but had no statistically significant effect on the final mTICI score (N=87, H1=0.266, p=0.606). Conclusion This study suggests that occlusion location significantly influences the total number of procedural passes in MT procedures as well as the final revascularization outcome. Furthermore, bridging-therapy lowers the number of procedural passes in cases of tandem and dual occlusion without having significant effect on final mTICI score. Funding: Science Foundation Ireland (Grant Number 13/RC/2073) and Cerenovus.Science Foundation Ireland (Grant Number 13/RC/2073) and Cerenovus.non-peer-reviewe

Histological characterization of white clots retrieved by mechanical thrombectomy from acute ischemic stroke patients

Introduction: Advances in mechanical thrombectomy have created the unique opportunity to study the acute ischemic stroke clot material. However, there is a lack of uniformity in the histopathologic characterization of thrombi. Many clots are mainly red in colour and predominantly composed of Red Blood Cells and Fibrin. In this context, white clots represent a less common entity and their histological composition is largely unknown. We investigated the histopathological features of 21 white clots retrieved by thrombectomy. To our knowledge, this is the first series reported to date. Methods: Twenty one mechanically extracted white thrombi were collected from two partner hospitals: Beaumont Hospital and Sahlgrenska University Hospital. Clots were immediately formalin-fixed and subsequently embedded in paraffin. For each case, serial sections of 3-µm thickness were cut and stained with Hematoxylin & Eosin and Martius Scarlett Blue (MSB) for the identification of main clot components. The MSB-stained slide underwent whole slide scanning (Olympus VS120) and histologic quantification was performed using Orbit Image Analysis Software (Orbit Image Analysis, Idorsia Ltd.). Von Kossa staining was performed to confirm calcification when suspected. The presence of specific components was assessed by immunostaining for platelets (CD42b), von Willebrand Factor (vWF) and fatty-acid binding protein (FABP4) for adipocytes. Results: The quantification identified the Platelets as the major component in white clots accounting for up to 90% of their composition. The main components showed mean values of 75.67% for Platelets, 13.36% for Fibrin, 5.07% for Red Blood cells and 3.75% for White Blood Cells Immunostaining confirmed the presence of CD42b and vWF in all cases. Collagen and calcification were present in one case. Interestingly, adipocytes represented the main component in two cases. Conclusions: Platelets are the key component of white clots . Calcification and adipocytes are also found occasionally. Increased levels of platelets and calcium confer resistance to thrombolysis and may render clots stiffer and less accessible for stent retrievers leading to low recanalization rates. The presence of adipocytes may represent a histological marker of fat embolism when suspected or a vulnerable atherosclerotic plaque, especially if associated with collagen.Science Foundation Ireland (Grant Number 13/RC/2073) and Industrial partners Cerenovu

Novel human acute ischemic stroke blood clot analogs for in vitro thrombectomy testing

BACKGROUND AND PURPOSE: Previous studies have successfully created blood clot analogs for in vitro endovascular device testing using animal blood of various species. Blood components vary greatly among species; therefore, creating clot analogs from human blood is likely a more accurate representation of thrombi formed in the human vasculature. MATERIALS AND METHODS: Following approval from the Mayo Clinic institutional review board, human whole-blood and platelet donations were obtained from the blood transfusion service. Twelve clot analogs were created by combining different ratios of red blood cells + buffy coat, plasma, and platelets. Thrombin and calcium chloride were added to stimulate coagulation. Clot composition was assessed using histologic and immunohistochemical staining. To assess the similarities of mechanical properties to patient clots, 3 types of clot analogs (soft, elastic, and stiff) were selected for in vitro thrombectomy testing. RESULTS: The range of histopathologic compositions produced is representative of clots removed during thrombectomy procedures. The red blood cell composition ranged from 8.9% to 91.4%, and fibrin composition ranged from 3.1% to 53.4%. Platelets (CD42b) and von Willebrand Factor ranged from 0.5% to 47.1% and 1.0% to 63.4%, respectively. The soft clots had the highest first-pass effect and successful revascularization rates followed by the elastic and stiff clots. Distal embolization events were observed when clot ingestion could not be achieved, requiring device pullback. The incidence rate of distal embolization was the highest for the stiff clots due to the weak clot/device integration. CONCLUSIONS: Red blood cell–rich, fibrin-rich, and platelet-rich clot analogs that mimic clots retrieved from patients with acute ischemic stroke were created in vitro. Differing retrieval outcomes were confirmed using in vitro thrombectomy testing in a subset of clots.This work was supported by the National Institutes of Health grant No. R01 NS105853, the European Regional Development Fund and Science Foundation Ireland grant No. 13/RC/2073, and Enterprise Ireland (IP20190865).peer-reviewe

Does bridging therapy in mechanical thrombectomy increase recanalization rates in ischemic stroke patients affected by acute large vessel occlusion?

Both intravenous thrombolysis with tissue plasminogen activator (IV-rtPA) and mechanical thrombectomy (MT) increase recanalization rates. We assessed if bridging-therapy (the concomitant use of rtPA and MT) could increase the recanalization rates and reduce the number of procedural passes in patients suffering from acute ischemic stroke (AIS) when compared to MT alone. Analysis of type of device used, stentriever or aspiration catheter, is also reported. 334 mechanically extracted thrombi were collected from two partner hospitals: Beaumont (Dublin) and Sahlgrenska (Gothenburg). 158 patients (47.3%) were treated with bridging-therapy, while 176 (52.7%) underwent MT alone. Recanalization rate was defined by using the modified Thrombolysis In Cerebral Infarction (mTICI) score. Non-parametric Kruskal-Wallis test was used for statistical analysis. Bridging-therapy reduced the total number of passes to remove the clot (mean for MT+rtPA=2.27±2.10, MT alone=2.63±1.88, H1=4.376, p=0.036*). Analysing the device, rtPA lowered the overall number of passes using stentriever devices (mean for MT+rtPA=1.57±1.12, MT alone=2.36±1.48, H1=8.303, p=0.004*), but not for aspiration (mean for MT+rt-PA=1.78±1.22, MT alone=2.03±1.47, for H1=0.795, p=0.372). Also, when using both devices no significant reduction of number of passes was observed (mean for MT+rtPA=3.29±2.90, MT alone=3.83±2.20, H1=3.027, p=0.082). There was no significant effect on final mTICI score using bridging-therapy when compared to MT alone (H1=1.163, p=0.281). This small study suggests that bridging-therapy lowers the number of procedural passes in MT procedures, specifically when using stentriever devices. However, this did not have a significant effect on final mTICI score. Funding: Science Foundation Ireland (Grant Number 13/RC/2073) and Cerenovus.Funding: Science Foundation Ireland (Grant Number 13/RC/2073) and Cerenovus.non-peer-reviewe

High-resolution scanning electron microscopy for the analysis of three-dimensional ultrastructure of clots in acute ischemic stroke

Background: Characterization of acute ischemic stroke (AIS) clots has typically focused on two dimensional histological analysis of the thrombus. The three dimensional (3D) architecture and distribution of components within emboli have not been fully investigated. The aim of this study was to examine the composition and microstructure of AIS clots using histology and serial block-face scanning electron microscopy (SBFSEM). Methods: As part of the multi-institutional STRIP registry, ten consecutive AIS emboli were collected from ten patients treated by mechanical thrombectomy. Histological and immunohistochemical analysis was performed to determine clot composition. SBFSEM was used to assess ultrastructural organization of clots and specific features of individual components. Results: Quantification of Martius Scarlett Blue stain identified fibrin (44.4%) and red blood cells (RBC, 32.6%) as main components. Immunohistochemistry showed a mean platelet and von Willebrand content of 23.9% and 11.8%, respectively. The 3D organization of emboli varied greatly depending on the region analyzed. RBC-rich areas were composed of tightly packed RBC deformed into polyhedrocytes with scant fibrin fibers interwoven between cells. Regions with mixed composition showed thick fibrin fibers along with platelets, white blood cells and RBC clusters. Fibrin-rich areas contained dense fibrin masses with sparse RBC. In three cases, the fibrin formed a grid-like or a sponge-like pattern likely due to thrombolytic treatment. Segmentation showed that fibrin fibers were thinner and less densely packed in these cases. Conclusions: 3D-SEM provides novel and potentially clinically relevant information on clot components and ultrastructure which may help to inform thrombolytic treatment and medical device design.This work was supported by the National Institutes of Health (R01 NS105853), the European Regional Development Fund and Science Foundation Ireland (grant number 13/RC/2073).peer-reviewe