Doses Of Acetylcholine Research Articles

Effects of radial artery spasm prophylaxis on intracoronary vasomotor responses during acetylcholine spasm provocation testing

BackgroundInvasive coronary angiography via the radial approach is commonly performed following radial artery spasm prophylaxis (RASP). It is however unknown, whether RASP influences the results of coronary spasm provocation testing performed after diagnostic angiography. We aimed to investigate the effects of RASP on vasomotor responses during intracoronary acetylcholine (ACh) testing. MethodsWe retrospectively screened 372 consecutive patients (51 % female, mean age 61 ± 11 years) with angina and non-obstructive coronary arteries, who underwent intracoronary provocation with ACh according to a standardized protocol. During testing, dose-dependent clinical discomfort and concomitant ischemic electrocardiographic changes were recorded in addition to visual reductions of epicardial lumen diameters. Of these patients, 156 (42 %) received RASP (i.e. 200 μg nitroglycerin and 2.5 mg verapamil), while no RASP was administered in 216 (58 %) patients. Both groups were compared regarding age, sex, cardiovascular risk factors and ACh-test results. ResultsACh provocation testing revealed a pathological test result in 71 patients (46 %) with RASP and 103 patients (48 %) without (p = 0.752) [epicardial spasm: in 20 patients (28 %) with RASP and 42 patients (41 %) without (p = 0.120); microvascular spasm: in 51 patients (72 %) with RASP and 61 patients (59 %) without (p = 0.362)]. Overall, RASP did not significantly alter coronary artery vasomotor responses, neither regarding the frequency (p = 0.752) or type of coronary spasm (microvascular vs. epicardial; p = 0.108) nor regarding the ACh dose leading to spasm (p = 0.151). ConclusionsRASP does not significantly affect coronary vasomotor responses to ACh, suggesting that radial artery spasm prophylaxis can be routinely administered even in patients in whom intracoronary spasm testing is performed.

Sex-differences in ANOCA patients undergoing invasive coronary function testing: preliminary results from the Dutch national NL-CFT registry

Abstract Background The majority of patients with angina and non-obstructive coronary arteries (ANOCA) are women. In most of these patients coronary vasomotor dysfunction, consisting of coronary vasospasm and coronary microvascular dysfunction (CMD), are identified through invasive coronary function testing (CFT). To acknowledge possible sex differences in clinical characteristics and in the entities of coronary vasomotor dysfunction more data are needed. Therefore, this study presents data from one centre participating in the Dutch national CFT (NL-CFT) registry in order to investigate sex differences in patients with a clinical indication for CFT. Methods This retrospective cohort study included 285 consecutive ANOCA patients undergoing clinically indicated CFT, using the Doppler wire or the bolus thermodilution method, from November 2016 till June 2023. CFT consisted of incremental doses of intracoronary acetylcholine (ACh) for the diagnosis of coronary vasospasm and intracoronary adenosine for the diagnosis of CMD defined as abnormal coronary flow reserve (CFR) and/or microvascular resistance (MR). Results In total, 285 patients of which 233 (82%) women and 52 (18%) men were included. Women were significantly younger (56 vs 59 yrs.; p=0.046), had less diabetes (6% vs 23% p<0.001), less prior PCI (12% vs 27%; p=0.019) and less statin use (39% vs 60%; p=0.006), and more often migraine at some point in their life (38% vs 9%; p<0.001). The prevalence of coronary vasomotor dysfunction (77% vs 65%, p=0.086), epicardial spasm (26% vs 31%, p=0.500), microvascular spasm (35% vs 23%, p=0.104), and CMD (35% vs 27%, p=0.304), was not significantly different between women and men. However, a trend was seen towards a higher prevalence of coronary vasomotor dysfunction, microvascular spasm and CMD in women. In total, 29% of women had an abnormal CFR compared to 16% of men (p=0.065) and an abnormal MR was seen in 11% of women and 12% of men (p=0.938). Cardiovascular risk factors were similar between women and men with epicardial spasm. In patients with microvascular spasm women had less prior PCI (p=0.025) and more migraine (p=0.005), in CMD patients women had less diabetes (p=0.002) and hypercholesterolemia (p=0.044) and more migraine (p=0.006). Conclusion In the NL-CFT registry study including ANOCA patients with a clinical indication for CFT women were younger, had less prior PCI and, diabetes and more often migraine. A trend towards a higher prevalence of coronary vasomotor dysfunction, microvascular spasm and CMD was found in women. Furthermore, our results suggest that men with CMD or microvascular spasm have a different cardiovascular risk profile compared to women, which might suggest different optimal tailored treatment for men compared to women. * Upon acceptance for presentation at the ESC Congress, all patients from the Dutch NL-CFT registry will be incorporated into this analysis, resulting in a study population of approximately 1200 individuals.

Safety and Usefulness of Intracoronary Acetylcholine 200 μg Into the Left Coronary Artery as Vasoreactivity Testing: Comparisons With Intracoronary Acetylcholine Maximum 100 μg.

We retrospectively analyzed the usefulness and safety of intracoronary acetylcholine (ACh) 200 μg into the left coronary artery (LCA) as vasoreactivity testing compared with intracoronary ACh 100 μg. We recruited 1433 patients who had angina-like chest pain and intracoronary ACh testing in the LCA, including 1234 patients with a maximum ACh 100 μg and 199 patients with a maximum ACh 200 μg. ACh was injected in incremental doses of 20/50/100/200 μg into the LCA. Positive spasm was defined as ≥ 90% stenosis, usual chest pain, and ischemic electrocardiogram (ECG) changes. The incidence of coronary constriction ≥ 90%, usual chest pain, and ischemic ECG changes with a maximum ACh of 100 μg was markedly higher than that with a maximum ACh of 200 μg. The frequency of unusual chest pain in patients with a maximum ACh of 200 μg was higher than that in those with a maximum ACh of 100 μg (13% vs. 3%, p < 0.001). In patients with rest angina, positive spasm of maximum ACh 100 μg was significantly higher than that of maximum ACh 200 μg, whereas there was no difference regarding positive spasm in patients with atypical chest pain between the two ACh doses. Major complications (1.38% vs. 1.51%, p = 0.8565) and the occurrence of paroxysmal atrial fibrillation (1.81% vs. 2.63%, p = 0.6307) during ACh testing in the LCA were not different between the two maximum ACH doses. Intracoronary ACh 200 μg into the LCA is clinically useful and safe for vasoreactivity testing when intracoronary ACh 100 μg dose not provoke spasms.

TCT-856 Evaluating the Diagnostic Validity of Incremental Acetylcholine Doses for Inducing Coronary Artery Spasm in Angina With Nonobstructive Coronary Arteries

TCT-856 Evaluating the Diagnostic Validity of Incremental Acetylcholine Doses for Inducing Coronary Artery Spasm in Angina With Nonobstructive Coronary Arteries

Abstract Mo056: Cholinergic Activation Suppresses Optogenetic Stimulation of Intrinsic Cardiac Catecholaminergic Neurons in Perfused Mouse Hearts

Balance of cholinergic and catecholaminergic activation is necessary to maintain heart health. Interrogating the acute interaction of these autonomic pathways can be done using optogenetics via selective expression of channelrhodopsin (ChR2) within intrinsic cardiac neurons. We tested the hypothesis that cholinergic activation via exogenous acetylcholine (ACh) would suppress the beta-adrenergic heart rate (HR) acceleration induced by tyrosine hydroxylase (TH) neuron stimulation, with the prominence of AV block increasing with increased ACh concentration. ECGs were recorded during perfused heart studies using wild-type (WT) mice and transgenic mice that selectively expressed ChR2 in TH neurons that secrete norepinephrine (NE). HR responses were measured for WT while increasing [NE] and for TH by illuminating the right atrium (465nm, microLED) at a range duty cycles and frequencies. Duty cycles (at 5Hz) increasing from 5-50% caused proportional increases in HR however HR was unstable at duty cycles &gt;30%. At 20% duty cycle, HR increased by 39.43±6.79% (n=6). HR increased sigmoidally at frequencies from 2.5-15Hz (with 30ms pulse width) but HR was unstable at 15Hz. At 10Hz, heart rate increased by 64.24±13.47% (n=4). When comparing HR increases for TH (n=5) and WT+NE (n=4), optogenetic activation resulted in similar maximum HRs but drastically different rise times (7.6±1.25 vs 46.43±5.01 beats/sec, respectively). HR suppression at increasing doses of ACh was measured while perfusing WT hearts with NE and photostimulating TH hearts. The addition of ACh caused beta-adrenergic HR increases to diminish, eventually reaching below baseline HR. In WT+NE animals this occurred at 400nM ACh and in TH animals this did not occur until 1800nM ACh. As ACh increased in TH animals, onset of AV block occurred sooner and more prominently. In conclusion, optogenetic activation of TH neurons caused rapid HR acceleration that was suppressed by ACh at concentrations much higher than that required to suppress acceleration during NE perfusion. AV block also occurred more rapidly during TH neuron activation as [ACh] increased, demonstrating a time-dependent effect in the interaction of cholinergic and catecholaminergic activation.

The bottlenose dolphin (Tursiops truncatus): A novel model for studying healthy vascular aging

Aging is the primary non-modifiable risk factor for the development of cardiovascular diseases (CVD). CVD are often preceded by arterial dysfunction, including endothelial dysfunction and aortic stiffening. Our preliminary results suggest that the circulating milieu is associated with differences in arterial function in young and mid-life/older (ML/O) adults. Moreover, incubation of mouse arteries with serum from young and ML/O adult humans can directly transfer arterial aging phenotypes for endothelial function and aortic stiffness. These results suggest that age-related changes in the circulating milieu are an underlying mechanism of age-related arterial dysfunction. Dolphins are mammals that have evolutionary adapted to diving, with constant cycles of tissue hypoxia/reoxygenation and disturbed shear stress -- exposures which cause arterial dysfunction in humans. Dolphins also have long lifespans and are relatively free of CVD. Taken together, dolphins may be a unique model of healthy vascular aging, with possible applications to clinical medicine. PURPOSE: To determine if the serum of bottlenose dolphins ( Tursiops truncatus) induces the same arterial aging phenotypes as the serum of age-equivalent humans. Methods: Common carotid arteries and aorta rings from young (Y; 5 mo) and old (O; 25 mo) wildtype female (F) and male (M) C57BL/6N mice were exposed ex vivo for 24 and 48h, respectively, to 5% sex-matched adult dolphin serum. Dolphin serum of Y (17 ± 4 years; n = 16: 5F / 11 M) and ML/O (29 ± 2 years; n = 4: 1F/3M) adults was obtained from the National Marine Mammal Tissue Bank. Endothelial function was assessed as carotid artery endothelium-dependent dilation (EDD) in response to increasing doses of acetylcholine. Aortic stiffness was measured as elastic modulus, a measure of intrinsic mechanical wall stiffness. Dolphin serum-mediated responses in mouse arteries were compared with that of adult human serum data (Y, 24 ± 1 years, n=10: 5F/5M; ML/O, 67 ± 3 years, n=10: 5F/5M). Differences were assessed via 2-way ANOVAs; within species post hoc analyses conducted between age groups. Results: Endothelial Function. Peak EDD in Y mouse carotid arteries was lower following exposure to serum from ML/O adult humans (ML/O, 78 ± 2 v. Y, 92 ± 2%; P &lt; 0.001) and higher in O mouse carotid arteries after exposure to Y adult serum (92 ± 2 vs. 73 ± 5%, P = 0.001). In contrast, EDD was similarly high across all groups following dolphin serum exposure (³ 93% peak EDD), independent of the age of the serum donor or the mouse arteries (Y v. ML/O serum donor in Y arteries, P = 0.773; in O mouse arteries, P = 0.942). Aortic Stiffness. Stiffness in Y aortic rings was ~60% higher following exposure to ML/O adult human serum (P = 0.001 v. Y adult serum). In O mouse aortic rings, stiffness was 25% lower after exposure to Y adult serum (P = 0.044 v. ML/O adult serum). In contrast, stiffness was similar across all groups following dolphin serum exposure, independent of age of the serum donor or the arteries (Y v. ML/O serum donor in Y aortic rings, P = 0.974; in O aortic rings P = 0.157). CONCLUSIONS: The circulating milieu of bottlenose dolphins may be geroprotective, which could serve as a model to investigate mechanisms and potential therapies for preventing adverse vascular aging and promoting CV health and longevity in humans. FUNDING: R21 AG078408 &amp; MSCA-IF-2019:892267. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of Myocardial Infarction-induced Heart Failure on Diaphragm Arteriolar Vasorelaxation

INTRODUCTION: Diaphragm atrophy and contractile dysfunction are prevalent in heart failure (HF), diminishing physical capacity and quality of life. The delivery of blood flow and oxygen necessary to support the metabolic demand of contractions is largely governed by the resistance vasculature (i.e., arterioles) with the endothelium playing a central role in arteriolar vasorelaxation. Adequate perfusion and blood flow distribution, and thus resistance vessel vasodilation, is a major determinate of diaphragm contractile function. While the mechanistic bases of HF-induced diaphragm dysfunction continue to be elucidated, the impact of HF on diaphragm vasomotor control has not been investigated. METHODS: Adult (6 mo) Sprague-Dawley rats (n=7) were divided into two groups: 1) Healthy Control (HC; n=4) and 2) MI-induced heart failure (HF; n=3). First-order arterioles (1A) from the medial costal diaphragm were isolated, cannulated, and pressurized at 90 cmH2O and allowed to equilibrate for 60 min to develop spontaneous tone. Thereafter, endothelium-dependent and -independent vasorelaxation responses to cumulative doses of acetylcholine (ACh; 10−9 to 10−4M) and sodium nitroprusside (SNP; 10−9 to 10−4M) were determined. RESULTS: There were no differences in spontaneous development (%) or maximal diameter (μm) between HC (20 ± 4%; 178 ± 11 μm) and HF (18 ± 2%; 184 ± 29 μm) diaphragm 1As ( P &gt; 0.05). Maximal ACh-mediated relaxation (%) was significantly reduced in HF rats compared to HC rats (52 ± 2 versus 68 ± 5%; P &lt; 0.05). Maximal endothelial-independent vasorelaxation with SNP, was not different between HC and HF rats (71 ± 3 versus 73 ± 1%; P &gt; 0.05). CONCLUSION: The preliminary data herein demonstrate that HF impaired endothelial function and vasomotor function in the medial costal diaphragm resistance vasculature. This suggests that, in HF, there may be a redistribution of blood flow to less effcient regions of the diaphragm (e.g., ventral costal) to sustain contractile function and compensate for the diminished medial costal vasomotor function demonstrated herein. Studies including a larger sample size are warranted to investigate the impact of HF on regional blood flow distribution and resistance vessel function in the diaphragm. Such investigations would yield novel mechanistic insights into HF-induced diaphragm dysfunction. National Institute of Aging 1R15AG078060, Ruth L. Kirschstein National Research Service Awards from the National Heart, Lung, and Blood Institute 1F31HL167618-01, and Sustained Momentum for Investigators with Laboratories Established (SMILE) Grants at Kansas State University. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Sulforaphane improves vasodilatory reactivity in diaphragm arterioles from rats with pulmonary hypertension

Pulmonary hypertension (PH) is a chronic, progressive disease characterized by pulmonary vascular remodeling, respiratory muscle and cardiac impairments, and exercise intolerance. Specifically, the diaphragm displays compromised contractile and vascular function, precluding it from meeting the increased metabolic demands of PH-induced chronic hyperpnea. Oxidative stress has been implicated in vascular dysfunction and PH pathology, therefore our objective was to target the antioxidant mediator Nrf2 (Nuclear factor erythroid 2-related factor 2) using sulforaphane (SFN) to determine whether this could improve vascular function in the diaphragm. We hypothesized that incubation with SFN would increase vasodilatory responsiveness in diaphragm arterioles from PH rats. Methods: Female Sprague-Dawley rats were administered monocrotaline (MCT; 50 mg/kg, i.p.) to induce PH. Disease progression was monitored via echocardiography. Once animals developed PH (~3 wks), the diaphragm was removed and first-order arterioles from the medial costal diaphragm were isolated, cannulated, and pressurized at 90 cmH2O. After a 60 min equilibration period and spontaneous tone development, endothelium-dependent and -independent vasorelaxation responses to cumulative doses of acetylcholine (ACh) and sodium nitroprusside (SNP) (10−9 to 10−4 M) were determined. These vessels were subsequently incubated with SFN (10 μM, 20 min), then ACh and SNP dose-response measurements were repeated. Results: All PH rats displayed morphometric and echocardiographic criteria for disease (i.e., right ventricular hypertrophy and reduced pulmonary artery acceleration time). Incubation with SFN improved endothelium-dependent and -independent vasodilation (p&lt;0.05). Maximal vasodilatory responses with SFN were 14% and 16% higher for ACh (30±2 vs 34±3%; P=0.02) and SNP (52±2 vs 60±2%; P=0.03), respectively. However, vasodilatory reactivity remains substantially lower than that of healthy animals. Conclusions: These findings suggest that Nrf2 activation using SFN may improve vascular function in the diaphragm with PH. Future investigations will focus on chronic administration of SFN to PH rats to determine the therapeutic potential of this compound in vivo. The results of these studies provide insight into novel pharmacological strategies to improve diaphragm vascular and contractile function, with the potential to help mitigate dyspnea and exercise intolerance and enhance life quality for PH patients. Sustained Momentum for Investigators with Laboratories Established Grants (TIM &amp; DCP); National Institute on Aging 1R15AG078060 (BJB &amp; DCP); Ruth L. Kirschstein National Research Service Awards 1F31HL167618-01 (AGH) and 1F31HL170643-01 (KMS). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Comparison of the Diagnostic Yield of Intracoronary Acetylcholine Infusion and Acetylcholine Bolus Injection Protocols During Invasive Coronary Function Testing

Coronary endothelial dysfunction (CED) and coronary artery spasm (CAS) are causes of angina in patients with no obstructive coronary arteries (ANOCA). Both can be diagnosed by invasive coronary function testing (ICFT) using Acetylcholine (ACh). This study aimed to evaluate the diagnostic yield of a 3-minute ACh infusion as compared to a 1-minute ACh bolus injection protocol in testing CED and CAS. In total 220 consecutive ANOCA patients underwent ICFT using continuous Doppler flow measurements. Per protocol, 110 patients were tested using 3-minute infusion and thereafter 110 patients using 1-minute bolus injections, due to a protocol change. CED was defined as a <50% increase in coronary blood flow or any epicardial vasoconstriction in reaction to low dose ACh and CAS according to the COVADIS criteria, both with and without T-wave abnormalities, in reaction to high dose ACh. The prevalence of CED was equal in both protocols (78% vs 79%; p=0.869). Regarding the endotypes of CAS according to COVADIS, the equivocal endotype was diagnosed less often in the 3-minutes vs 1-minute protocol (24% vs 44%; p=0.004). Including T-wave abnormalities to the COVADIS criteria resulted in a similar diagnostic yield of both protocols. Hemodynamic changes from baseline to the low or high ACh doses were comparable between the protocols for each endotype. In conclusion, ICFT using 3-minute infusion or 1-minute bolus injections of ACh showed a similar diagnostic yield of CED. When using the COVADIS criteria, a difference in the equivocal diagnosis was observed. Including T-wave abnormalities as diagnostic criterion reclassified equivocal test results into CAS and decreased this difference. For clinical practice, we recommend the inclusion of T-wave abnormalities as diagnostic criterion for CAS and the 1-minute bolus protocol for practicality.

Combined application of acetylcholine (ACh) and gamma-aminobutyric acid (GABA) mitigates the effects of water deficit in soybean

Bioregulatory substances, such as acetylcholine (ACh) and γ-aminobutyric acid (GABA), have shown promise in mitigating water deficit effects on plants. Their action on plant physiology, particularly in stomatal regulation and osmoprotection, contributes to enhanced agricultural productivity. Regarding soybean plants, changes in the metabolic profile that could justify the improvement in physiological performance and growth are still unknown. This study investigated the impact of combined ACh:GABA application during soybean V4 and R2 stages using physiological assessments and NMR-based metabolomics. Two equimolar doses (2 and 8 mM) of ACh:GABA were applied to soybean plants subjected to two water regimes: 100 % of field capacity (continuously irrigated) and water deficit (water suspension). Results demonstrated enhanced gas exchange, biomass, and chlorophyll content, alongside favorable enzymatic activity. NMR analysis revealed metabolites countering oxidative stress, supporting osmoprotection, and contributing to soybean development and energy supply. The 8 mM ACh:GABA application notably improved plant performance, showcasing potential for water deficit mitigation in soybeans.

Do changes in intracoronary pressure aid coronary spasm diagnosis using the spasm provocation test?

Although the spasm provocation test (SPT) can diagnose coronary spasms, it would be helpful if it could also predict their occurrence. To investigate whether coronary spasms can be predicted using changes in intracoronary artery pressure measured using a pressure wire during the SPT. Seventy patients underwent SPTs with pressure-wire measurement of intracoronary artery pressure. During each SPT, the pressure wire was advanced into the distal portion of the right coronary artery (RCA) and left anterior descending coronary artery, and the ratio of intracoronary pressure to aortic pressure (Pd/Pa) was monitored. Coronary spasm was defined as an arterial narrowing of > 90% in response to the administration of acetylcholine (ACh), with chest symptoms and/or ischemic electrocardiographic changes. ACh was administered to the RCA at low, moderate, or high doses of 20, 50, or 80 µg, respectively, and to the left coronary artery (LCA) at low, moderate, or high doses of 50, 100, or 200 µg, respectively. Coronary arteries with coronary spasms at low doses of ACh were defined as group L, and those with coronary spasms at moderate or high doses were defined as group MH. Those who did not occur coronary spasms at any ACh dose were designated as group N. Among the 132 coronary arteries assessed using a pressure wire, there were 49 in group N, 25 in group L, and 58 in group MH. Baseline Pd/Pa was the lowest in group L (P = 0.001). The decrease in the Pd/Pa between baseline to low doses of ACh was lower in group MH than in group N (P < 0.001). A receiver-operating characteristics analysis showed that the cutoff baseline Pd/Pa value for predicting group L was 0.95, with a sensitivity of 0.600 (15/25) and a specificity of 0.713 (76/107) and that the cutoff value of Pd/Pa from baseline to low doses of ACh for predicting group MH was -0.04, with a sensitivity of 0.741 (43/58) and a specificity of 0.694 (34/49). These findings suggest that indices of intracoronary pressure during SPT may be useful means for predicting the occurrence of coronary spasms.

Invasive coronary function testing in patients with INOCA - a single center experience

Abstract Background Coronary vasomotion disorders (CVDs) represent a frequent cause of angina in patients with ischemia with non-obstructed coronary arteries (INOCA). Invasive coronary angiography (ICA) often fails to identify patients with vasospastic angina and/or microvascular dysfunction. Purpose Our aim was to describe and characterize CVDs in INOCA patients, using a multi-parametric, invasive, coronary function testing protocol. Methods Patients with INOCA that underwent our protocol for coronary function testing (CFT), between July 2021 and October 2022 were included in this single-center prospective study. The protocol consisted of an invasive assessment of coronary circulation vasorelaxation at rest and during hyperemia, as well as the propensity for coronary vasospasm using increasing doses of intra-coronary acetylcholine. Fractional flow reserve, coronary flow reserve (CFR), and index of microvascular resistance (IMR) were recorded. CVDs were diagnosed based on the criteria proposed by the Coronary Vasomotor Disorders International Study Group. Results A total of 56 patients were included, mean age was 64±12 years and 57.1% were female. At baseline, all patients had either typical angina (82.1%, n=46) or a positive ischemia test (67.9%, n=38). Twenty patients (35.7%) had a history of a previous ICA or computed tomography due to anginal symptoms, while only 8.9% of patients had known structural ischemic heart disease and were subjected to percutaneous coronary intervention. Our CFT protocol was completed in all patients without any serious complications. Isolated epicardial vasospasm was found in 16 (28.6%) patients, isolated coronary microvascular dysfunction (CMD) in 9 (16.1%), and a combination of CMD and coronary vasospasm in 9 (16.1%). Only 1 patient (1.8%) had isolated microvascular spasm. We were able to further identify two distinct endotypes of CMD, using a combined assessment of CFR and IMR, termed structural and functional CMD: Functional CMD - 7 patients (12.5%) had CFR &amp;lt; 2.0 and IMR &amp;lt; 25; Structural CMD - 6 patients (10.7%) had CFR &amp;lt; 2.0 and IMR &amp;gt; 25. Conclusion Coronary vasomotion disorders are a common cause of INOCA. A CFT protocol is safe, can be used in clinical practice, and can provide a definite diagnosis for the underlying cause of angina.

Abstract 13713: Coronary Endothelial Dysfunction and Microvascular Vasospasm in Patients With Postural Orthostatic Tachycardia Syndrome

Background: Postural Orthostatic Tachycardia Syndrome (POTS) is characterized by autonomic dysfunction-related symptoms such as orthostatic intolerance, palpitations, dizziness, and chest pain. The mechanisms driving chest pain in POTS are unclear. Hypothesis: We hypothesized that coronary endothelial dysfunction (ED) and abnormal microvascular reactivity may be a contributor to chest pain in POTS. Methods: Patients (n=6) were diagnosed with POTS or had significant tachycardia despite medical therapy out of 67 patients in our cohort. All patients reported persistent chest pain and were referred for coronary function testing (CFT) to test macro- and micro-vascular function. CFT was performed to test endothelium-dependent and non-endothelium dependent function using graded doses of intracoronary acetylcholine (ACH), and intravenous adenosine (ADO). Coronary Flow Reserve&lt;2.0 and Index of Microvascular Resistance&gt;25 diagnosed coronary microvascular dysfunction. Coronary artery diameter narrowing to ACH (100 mcg) was used to diagnose ED. Epicardial coronary spasm was defined as &gt;90% constriction to ACH. Microvascular spasm was diagnosed by ACH provoked-chest pain and EKG changes in the absence of epicardial spasm. Results: Mean age was 44.1 ± 15.2 years, 67% were female, and all tolerated CFT without complications. POTS symptoms, baseline medications, and CFT results are shown ( Table ). All had an abnormal response to ACH, indicating ED and microvascular spasm. Non-endothelium function was normal in all patients. Anti-anginal medications were changed based on CFT information, with improvement in chest pain with calcium channel blocker use. Conclusion: In all 6 pts, CP was associated with ED and microvascular spasm. Mechanistic links between ED and POTS need further investigation. Given that ED is a prognostic marker associated with recurrent angina hospitalization and events, investigation of therapies that target ED in POTS may be warranted.

Abstract 122: Cerebral Artery Function And Stiffness Is Dependent On Apoe Genotype And Ovariectomy Status In Mice

The major risk factors for late-onset Alzheimer’s Disease (LOAD) include old age, female sex and the APOE4 allele. Post-menopausal females with an APOE4 allele have higher rates of LOAD compared with age-matched males with an APOE4 allele, suggesting an interaction between APOE genotype and estrogen deficiency. Importantly, cerebrovascular dysfunction is a contributor to LOAD risk. However, it is unknown if APOE genotype and estrogen deficiency interact to impact cerebrovascular function.Young female homozygous APOE3 and APOE4 mice (n=4-6 per group; ~6 months old) fed a high-fat, high-cholesterol diet were intact (sham) or ovariectomized (OVX). We assessed endothelium-dependent dilation to increasing doses of acetylcholine (ACh) in pressurized posterior cerebral arteries (PCAs). There was an interaction effect of APOE genotype and OVX status for endothelium-dependent dilation (p=0.03), such that APOE3 -Sham mice had a greater endothelium-dependent dilation compared to the APOE3 -OVX group (70±9.1% vs. 39±7.6%, p=0.003). These differences were mediated by nitric oxide as indicated by the absence of dilation in the presence of N omega-Nitro-L-arginine methyl ester hydrocholoride (L-NAME, Sham: 3.7±3.3% vs OVX: 4.1±4.0%, p= 0.99). In contrast, APOE4 -OVX had preserved endothelium-dependent dilation compared with APOE4 -Sham (49.9±14.8% vs 56.1±9.2%, p=0.8). Endothelium-independent dilation was assessed by the response to increasing doses of sodium nitroprusside and did not differ among groups (all p&gt;0.05). Passive stiffness was measured in isolated PCAs after incubation in a calcium-free solution. For the elastic modulus at low pressures, there was an interaction effect of APOE genotype and OVX status (p=0.03), with APOE4 -OVX having a higher elastic modulus compared to APOE4 -Sham (0.93±0.3 vs. 0.47±0.1, p=0.03). The elastic modulus was similar in APOE3 groups (sham: 0.64±0.01, OVX: 0.62±0.09, p=0.99). Overall, we found that estrogen deficiency impacts cerebral artery endothelial function in APOE3 , but not APO E4 mice, while estrogen deficiency impacts cerebral artery stiffness in APOE4 , but not APOE3 mice. These results shed light on the impact of APOE genotype on the cerebral vasculature, suggesting a potential mechanism for LOAD.

Effect of chronic administration of magnesium supplement (magnesium glycinate) on male albino wistar rats’ intestinal (Ileum) motility, body weight changes, food and water intake

Recent researches suggests magnesium as an adjuvant medication for COVID 19 patients. Magnesium relaxes skeletal muscles, an effect when prolonged in intestinal smooth muscles can cause severe discomfort such as bloating, vomiting, constipation and nausea. The objectives of this study was to ascertain if magnesium will cause relaxation of the intestinal (ileum) smooth muscles as it does in skeletal muscles. Also, this research seeks to find out the receptor pathway through which magnesium will alter motility in the gut using acetylcholine, atropine and propranolol. Ten male albino wistar rats (100–150 g) were randomly assigned into two groups (control and magnesium treated) (n = 5). Animals were acclimatized for two weeks before treatment which lasted for 6 weeks. Magnesium treated animals received oral magnesium glycinate (1600 mg/70 kg) daily while control group receive normal saline of equal volume. All animals had free access to food and water ad libitum. Results were analyzed at statistical level of P < 0.05. Body weight changes, food and water intake were not statistically significant. Basal contractions of ileum in magnesium treated group were significantly lower compared to control group. Propranolol significantly increased the percentage relaxation in magnesium treated group compared to the control. Atropine significantly decrease the percentage relaxation in magnesium treated group compared to the control. Higher doses of acetylcholine (10−5 and 10−4) increased the contractions in magnesium treated group. Conclusively, magnesium decreases motility of the intestine through beta adrenergic receptor pathway. Intake of magnesium for long period should be closely monitored to avoid the discomforting symptoms earlier stated.

Glycyrrhizic Acid Inhibits High-Mobility Group Box-1 and Homocysteine-Induced Vascular Dysfunction.

Hyperhomocysteinemia (HHcy) worsens cardiovascular outcomes by impairing vascular function and promoting chronic inflammation via release of danger-associated molecular patterns, such as high-mobility group box-1 (HMGB-1). Elevated levels of HMGB-1 have recently been reported in patients with HHcy. Therefore, targeting HMGB-1 may be a potential therapy to improve HHcy-induced cardiovascular pathologies. This study aimed to further elucidate HMGB-1's role during acute HHcy and HHcy-induced atherogenesis and to determine if inhibiting HMGB-1 with glycyrrhizic acid (Glyz) improved vascular function. Male New Zealand White rabbits (n = 25) were placed on either a standard control chow (CD; n = 15) or atherogenic diet (AD; n = 10) for 4 weeks. Rabbit serum and Krebs taken from organ bath studies were collected to quantify HMGB-1 levels. Isometric tension analysis was performed on abdominal aorta (AA) rings from CD and AD rabbits. Rings were incubated with homocysteine (Hcy) [3 mM] for 60 min to induce acute HHcy or rhHMGB-1 [100 nM]. Vascular function was assessed by relaxation to cumulative doses of acetylcholine. Markers of vascular dysfunction and inflammation were quantified in the endothelium, media, and adventitia of AA rings. HMGB-1 was significantly upregulated in serum (p < 0.0001) and Krebs (p < 0.0001) after Hcy exposure or an AD. Incubation with Hcy (p < 0.0001) or rhHMGB-1 (p < 0.0001) and an AD (p < 0.0001) significantly reduced relaxation to acetylcholine, which was markedly improved by Glyz. HMGB-1 expression was elevated (p < 0.0001) after Hcy exposure and AD (p < 0.0001) and was normalized after Glyz treatment. Moreover, markers of vascular function, cell stress and inflammation were also reduced after Glyz. These results demonstrate that HMGB-1 has a central role during HHcy-induced vascular dysfunction and inhibiting it with Glyz could be a potential treatment option for cardiovascular diseases.

Driver Mutations of Pancreatic Cancer Affect Ca2+ Signaling and ATP Production.

Glandular pancreatic epithelia of the acinar or ductal phenotype may seem terminally differentiated, but they are characterized by remarkable cell plasticity. Stress-induced trans-differentiation of these cells has been implicated in the mechanisms of carcinogenesis. Current consensus links pancreatic ductal adenocarcinoma with onco-transformation of ductal epithelia, but under the presence of driver mutations in Kras and Trp53, also with trans-differentiation of pancreatic acini. However, we do not know when, in the course of cancer progression, physiological functions are lost by mutant acinar cells, nor can we assess their capacity for the production of pancreatic juice components. Here, we investigated whether two mutations-KrasG12D and Trp53R172H-present simultaneously in acinar cells of KPC mice (model of oncogenesis) influence cytosolic Ca2+ signals. Since Ca2+ signals control the cellular handling of digestive hydrolases, any changes that affect intracellular signaling events and cell bioenergetics might have an impact on the physiology of the pancreas. Our results showed that physiological doses of acetylcholine evoked less regular Ca2+ oscillations in KPC acinar cells compared to the control, whereas responses to supramaximal concentrations were markedly reduced. Menadione elicited Ca2+ signals of different frequencies in KPC cells compared to control cells. Finally, Ca2+ extrusion rates were significantly inhibited in KPC cells, likely due to the lower basal respiration and ATP production. Cumulatively, these findings suggest that driver mutations affect the signaling capacity of pancreatic acinar cells even before the changes in the epithelial cell morphology become apparent.

#4063 APELIN INCREASES FOREARM BLOOD FLOW IN CHRONIC KIDNEY DISEASE

Abstract Background and Aims Chronic kidney disease (CKD) affects 1 in 10 people and cardiovascular disease is its commonest complication. Despite current standard of care, many patients continue to progress to kidney failure and/or die of cardiovascular disease. Thus, there is an urgent unmet need for new treatments that slow kidney function decline and offer broad cardiovascular protection. The apelin system, comprising the apelin receptor and its two endogenous ligands apelin and elabela, is an attractive therapeutic target for CKD. Apelin is an endothelium-dependent vasodilator and a potent inotrope. Clinical studies show that apelin improves endothelial function in health and heart failure, and pre-clinical studies in models of kidney disease find apelin offers renoprotection. At present, apelin has not been studied in patients with CKD. The aims of this study were to examine the local vascular actions of apelin in CKD. Method Participants with stable, non-diabetic CKD and age- and sex-matched healthy volunteers were recruited to a prospective, randomised, placebo-controlled study. Blood pressure and arterial stiffness (measured using pulse wave velocity) were assessed at baseline. Endothelial function was examined using gold-standard venous occlusion plethysmography. Forearm vasodilatation was measured in response to incremental intra-arterial doses of acetylcholine (7.5, 15 and 30 μg/min, used to assess endothelium-dependent vasodilatation), sodium nitroprusside (1, 2 and 4 μg/min, used to assess endothelium-independent vasodilatation), and pyroglutamated apelin-13 ([Pyr1]apelin-13; 0.3, 1, 3, 10, 30 and 100 nmol/min). Circulating tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) were assessed as measures of endogenous fibrinolysis. Results Fifteen patients with CKD (mean age 55±4 years; 53% male) and 15 healthy volunteers (mean age 51±3 years; 67% male) completed the study. In comparison to healthy volunteers, patients with CKD had a higher blood pressure (mean arterial pressure: 102 mmHg versus 93 mmHg, p&amp;lt;0.05) and increased pulse wave velocity (7.5±2.2 m/s versus 6.0±0.9 m/s, p&amp;lt;0.01). Similar dose-dependent vasodilatation to acetylcholine and sodium nitroprusside was seen in both groups. [Pyr1]apelin-13 increased forearm blood flow by a maximum of ∼30% in both health and CKD (p&amp;lt;0.01 compared to baseline for both) (Figure 1). This response appeared to be dose-dependent. Net tPA antigen release increased 20-70 fold in response to [Pyr1]apelin-13 in both health and CKD, with a trend to a greater release in CKD. There was no change in PAI-1. No relationship was seen between the response to [Pyr1]apelin-13 and kidney function. Conclusion Apelin promotes vasodilatation in optimally managed patients with CKD and may regulate endogenous fibrinolysis. If this effect were maintained in the long-term with systemic apelin treatment, it would be expected to reduce cardiovascular risk. Systemic studies are now justified to investigate the haemodynamic and renal effects of apelin in these patients.

α7 nicotinic receptors play a role in regulation of cardiac hemodynamics.

The α7 nicotinic receptors (NR) have been confirmed in the heart but their role in cardiac functions has been contradictory. To address these contradictory findings, we analyzed cardiac functions in α7 NR knockout mice (α7-/-) in vivo and ex vivo in isolated hearts. A standard limb leads electrocardiogram was used, and the pressure curves were recorded in vivo, in Arteria carotis and in the left ventricle, or ex vivo, in the left ventricle of the spontaneously beating isolated hearts perfused following Langedorff's method. Experiments were performed under basic conditions, hypercholinergic conditions, and adrenergic stress. The relative expression levels of α and β NR subunits, muscarinic receptors, β1 adrenergic receptors, and acetylcholine life cycle markers were determined using RT-qPCR. Our results revealed a prolonged QT interval in α7-/- mice. All in vivo hemodynamic parameters were preserved under all studied conditions. The only difference in ex vivo heart rate between genotypes was the loss of bradycardia in prolonged incubation of isoproterenol-pretreated hearts with high doses of acetylcholine. In contrast, left ventricular systolic pressure was lower under basal conditions and showed a significantly higher increase during adrenergic stimulation. No changes in mRNA expression were observed. In conclusion, α7 NR has no major effect on heart rate, except when stressed hearts are exposed to a prolonged hypercholinergic state, suggesting a role in acetylcholine spillover control. In the absence of extracardiac regulatory mechanisms, left ventricular systolic impairment is revealed.

Biphasic Cholinergic Modulation of Reverberatory Activity in Neuronal Networks

Acetylcholine (ACh) is an important neuromodulator in various cognitive functions. However, it is unclear how ACh influences neural circuit dynamics by altering cellular properties. Here, we investigated how ACh influences reverberatory activity in cultured neuronal networks. We found that ACh suppressed the occurrence of evoked reverberation at low to moderate doses, but to a much lesser extent at high doses. Moreover, high doses of ACh caused a longer duration of evoked reverberation, and a higher occurrence of spontaneous activity. With whole-cell recording from single neurons, we found that ACh inhibited excitatory postsynaptic currents (EPSCs) while elevating neuronal firing in a dose-dependent manner. Furthermore, all ACh-induced cellular and network changes were blocked by muscarinic, but not nicotinic receptor antagonists. With computational modeling, we found that simulated changes in EPSCs and the excitability of single cells mimicking the effects of ACh indeed modulated the evoked network reverberation similar to experimental observations. Thus, ACh modulates network dynamics in a biphasic fashion, probably by inhibiting excitatory synaptic transmission and facilitating neuronal excitability through muscarinic signaling pathways.