Clostridioides difficile colonization is not mediated by bile salts and requires Stickland fermentation of proline in an in vitro model of infection.

Treatment with antibiotics is a major risk factor for Clostridioides difficile infection, likely due to depletion of the gastrointestinal microbiota. Two microbiota-mediated mechanisms thought to limit C. difficile colonization include conversion of conjugated primary bile salts into secondary bile salts toxic to C. difficile growth, and competition between the microbiota and C. difficile for limiting nutrients. Using a continuous flow model of the distal colon, we investigated how treatment with six clinically-used antibiotics influenced susceptibility to C. difficile infection in 12 different microbial communities cultivated from healthy individuals. Antibiotic treatment reduced microbial richness; disruption varied by antibiotic class and microbiota composition, but did not correlate with C. difficile susceptibility. Antibiotic treatment also disrupted microbial bile salt metabolism, increasing levels of the primary bile salt, cholate, and decreasing levels of the secondary bile salt, deoxycholate. However, decreased levels of deoxycholate did not correlate with increased C. difficile susceptibility. Further, bile salts were not required to inhibit C. difficile colonization. We tested whether amino acid fermentation contributed to persistence of C. difficile in antibiotic-treated communities. C. difficile mutants unable to use proline as an electron acceptor in Stickland fermentation due to disruption of proline reductase (Δ prdB ) had significantly lower levels of colonization than wild-type strains in four of six antibiotic-treated communities tested. This data provides further support for the importance of bile salt-independent mechanisms in regulating colonization of C. difficile . IMPORTANCE: C. difficile is one of the leading causes of hospital-acquired infections and antibiotic-associated diarrhea. Several potential mechanisms through which the microbiota can limit C. difficile infection have been identified and are potential targets for new therapeutics. However, it is unclear which mechanisms of C. difficile inhibition represent the best targets for development of new therapeutics. These studies demonstrate that in a complex in vitro model of C. difficile infection, colonization resistance is independent of microbial bile salt metabolism. Instead, the ability of C. difficile to colonize is dependent upon its ability to metabolize proline, although proline-dependent colonization is context-dependent and is not observed in all disrupted communities. Altogether, these studies support the need for further work to understand how bile-independent mechanisms regulate C. difficile colonization.

Identification of Simplified Microbial Communities That Inhibit Clostridioides difficile Infection through Dilution/Extinction.

The gastrointestinal microbiome plays an important role in limiting susceptibility to infection with Clostridioides difficile To better understand the ecology of bacteria important for C. difficile colonization resistance, we developed an experimental platform to simplify complex communities of fecal bacteria through dilution and rapidly screen for their ability to resist C. difficile colonization after challenge, as measured by >100-fold reduction in levels of C. difficile in challenged communities. We screened 76 simplified communities diluted from cultures of six fecal donors and identified 24 simplified communities that inhibited C. difficile colonization in vitro Sequencing revealed that simplified communities were composed of 19 to 67 operational taxonomic units (OTUs) and could be partitioned into four distinct community types. One simplified community could be further simplified from 56 to 28 OTUs through dilution and retain the ability to inhibit C. difficile We tested the efficacy of seven simplified communities in a humanized microbiota mouse model. We found that four communities were able to significantly reduce the severity of the initial C. difficile infection and limit susceptibility to disease relapse. Analysis of fecal microbiomes from treated mice demonstrated that simplified communities accelerated recovery of indigenous bacteria and led to stable engraftment of 19 to 22 OTUs from simplified communities. Overall, the insights gained through the identification and characterization of these simplified communities increase our understanding of the microbial dynamics of C. difficile infection and recovery.IMPORTANCEClostridioides difficile is the leading cause of antibiotic-associated diarrhea and a significant health care burden. Fecal microbiota transplantation is highly effective at treating recurrent C. difficile disease; however, uncertainties about the undefined composition of fecal material and potential long-term unintended health consequences remain. These concerns have motivated studies to identify new communities of microbes with a simpler composition that will be effective at treating disease. This work describes a platform for rapidly identifying and screening new simplified communities for efficacy in treating C. difficile infection. Four new simplified communities of microbes with potential for development of new therapies to treat C. difficile disease are identified. While this platform was developed and validated to model infection with C. difficile, the underlying principles described in the paper could be easily modified to develop therapeutics to treat other gastrointestinal diseases.

Excerpts from the documents of Mexican positions and recommendations in cardiovascular diseases and COVID-19.

The recommendations in which the Mexican Society of Cardiology (SMC) in conjunction with the National Association of Cardiologists of Mexico (ANCAM) as well as different Mexican medical associations linked to cardiology are presented, after a comprehensive and consensual review and analysis of the topics related to cardiovascular diseases in the COVID-19 pandemic. Scientific positions are analyzed and responsible recommendations on general measures are given to patients, with personal care, healthy eating, regular physical activity, actions in case of cardio-respiratory arrest, protection of the patient and health personnel as well as precise indications in the use of non-invasive cardiovascular imaging, prescription of medications, care in specific topics such as systemic arterial hypertension, heart failure, arrhythmias and acute coronary syndromes, in addition to emphasizing electrophysiology, interventionism, cardiac surgery and in cardiac rehabilitation. The main interest is to provide the medical community with a general orientation on what to do in daily practice and patients with cardiovascular diseases in the setting of this unprecedented epidemiological crisis of COVID-19.

Se presentan las recomendaciones en las cuales la Sociedad Mexicana de Cardiología (SMC) en conjunto con la Asociación Nacional de Cardiólogos de México (ANCAM), así como diferentes asociaciones médicas mexicanas vinculadas con la cardiología, después de una revisión y análisis exhaustivo y consensuado sobre los tópicos relacionados con las enfermedades cardiovasculares en la pandemia de COVID-19, se analizan posturas científicas y se dan recomendaciones responsables sobre medidas generales a los pacientes, con cuidados personales, alimentación saludable, actividad física regular, acciones en caso de paro cardiorrespiratorio, la protección del paciente y del personal de salud así como las indicaciones precisas en el uso de la imagen cardiovascular no invasiva, la prescripción de medicamentos, cuidados en tópicos específicos como en la hipertensión arterial sistémica, insuficiencia cardiaca, arritmias y síndromes coronarios agudos, además de hacer énfasis en los procedimientos de electrofisiología, intervencionismo, cirugía cardiaca y en la rehabilitación cardiaca. El interés principal es brindar a la comunidad médica una orientación general sobre el quehacer en la práctica cotidiana y pacientes con enfermedades cardiovasculares en el escenario esta crisis epidemiológica sin precedentes de COVID-19.

Cardiac imaging studies in the COVID-19 pandemic.

COVID-19 is an acute respiratory syndrome caused by coronavirus-2 (SARS COV2). The different cardiac imaging methods have issued specific recommendations for the different imaging methods in this pandemic, so it is essential to emphasize the recommendations for carrying out these studies.

El COVID-19 es un síndrome respiratorio agudo ocasionado por el coronavirus-2 (SARS COV2). Los diferentes métodos de imagen cardiaca han dictado recomendaciones específicas de los diferentes métodos de imagen en esta pandemia, por lo que es indispensable recalcar las recomendaciones para la realización de estos estudios.

Estudios de imagen cardiaca en la pandemia COVID-19 / Cardiac imaging studies in the COVID-19 pandemic

Resumen El COVID-19 es un síndrome respiratorio agudo ocasionado por el coronavirus-2 (SARS COV2). Los diferentes métodos de imagen cardiaca han dictado recomendaciones específicas de los diferentes métodos de imagen en esta pandemia, por lo que es indispensable recalcar las recomendaciones para la realización de estos estudios.

Abstract COVID-19 is an acute respiratory syndrome caused by coronavirus-2 (SARS COV2). The different cardiac imaging methods have issued specific recommendations for the different imaging methods in this pandemic, so it is essential to emphasize the recommendations for carrying out these studies.

Extractos de los documentos de posicionamientos y recomendaciones mexicanas en enfermedades cardiovasculares y COVID-19 / Excerpts from the documents of Mexican positions and recommendations in cardiovascular diseases and COVID-19

Resumen Se presentan las recomendaciones en las cuales la Sociedad Mexicana de Cardiología (SMC) en conjunto con la Asociación Nacional de Cardiólogos de México (ANCAM), así como diferentes asociaciones médicas mexicanas vinculadas con la cardiología, después de una revisión y análisis exhaustivo y consensuado sobre los tópicos relacionados con las enfermedades cardiovasculares en la pandemia de COVID-19, se analizan posturas científicas y se dan recomendaciones responsables sobre medidas generales a los pacientes, con cuidados personales, alimentación saludable, actividad física regular, acciones en caso de paro cardiorrespiratorio, la protección del paciente y del personal de salud así como las indicaciones precisas en el uso de la imagen cardiovascular no invasiva, la prescripción de medicamentos, cuidados en tópicos específicos como en la hipertensión arterial sistémica, insuficiencia cardiaca, arritmias y síndromes coronarios agudos, además de hacer énfasis en los procedimientos de electrofisiología, intervencionismo, cirugía cardiaca y en la rehabilitación cardiaca. El interés principal es brindar a la comunidad médica una orientación general sobre el quehacer en la práctica cotidiana y pacientes con enfermedades cardiovasculares en el escenario esta crisis epidemiológica sin precedentes de COVID-19.

Abstract The recommendations in which the Mexican Society of Cardiology (SMC) in conjunction with the National Association of Cardiologists of Mexico (ANCAM) as well as different Mexican medical associations linked to cardiology are presented, after a comprehensive and consensual review and analysis of the topics related to cardiovascular diseases in the COVID-19 pandemic. Scientific positions are analyzed and responsible recommendations on general measures are given to patients, with personal care, healthy eating, regular physical activity, actions in case of cardio-respiratory arrest, protection of the patient and health personnel as well as precise indications in the use of non-invasive cardiovascular imaging, prescription of medications, care in specific topics such as systemic arterial hypertension, heart failure, arrhythmias and acute coronary syndromes, in addition to emphasizing electrophysiology, interventionism, cardiac surgery and in cardiac rehabilitation. The main interest is to provide the medical community with a general orientation on what to do in daily practice and patients with cardiovascular diseases in the setting of this unprecedented epidemiological crisis of COVID-19.

Angiotensin II AT2 Receptors Contribute to Regulate the Sympathoadrenal and Hormonal Reaction to Stress Stimuli.

Angiotensin II, through AT1 receptor stimulation, mediates multiple cardiovascular, metabolic, and behavioral functions including the response to stressors. Conversely, the function of Angiotensin II AT2 receptors has not been totally clarified. In adult rodents, AT2 receptor distribution is very limited but it is particularly high in the adrenal medulla. Recent results strongly indicate that AT2 receptors contribute to the regulation of the response to stress stimuli. This occurs in association with AT1 receptors, both receptor types reciprocally influencing their expression and therefore their function. AT2 receptors appear to influence the response to many types of stressors and in all components of the hypothalamic-pituitary-adrenal axis. The molecular mechanisms involved in AT2 receptor activation, the complex interactions with AT1 receptors, and additional factors participating in the control of AT2 receptor regulation and activity in response to stressors are only partially understood. Further research is necessary to close this knowledge gap and to clarify whether AT2 receptor activation may carry the potential of a major translational advance.

Common variants of the G protein-coupled receptor type 4 are associated with human essential hypertension and predict the blood pressure response to angiotensin receptor blockade.

Non-synonymous GRK4 variants, R65L, A142V and A486V, are associated with essential hypertension in diverse populations. This study replicated the association of GRK4 variants, including GRK4(142V), with human essential hypertension in a Japanese population (n=588; hypertensive, n=486 normotensive controls) and determined whether the presence of GRK4 variants predicted the blood pressure (BP) response to angiotensin receptor blockers (ARBs) in patients with essential hypertension. We analyzed 829 patients and compared the response to ARBs between individuals with no GRK4 variants (n=136) and those with variants at one or any of the three loci (n=693). Carriers of hGRK4(142V) had a greater decrease in systolic BP in response to ARBs than non-carrier hypertensive patients. By contrast, those with variants only at GRK4(486V) were less likely to achieve the BP goal in response to an ARB than those with no variants. These studies showed for the first time the association between GRK4(142V) and a larger decrease in BP with ARBs in hypertensive patients.

Synthesis of photochromic oligophenylenimines: optical and computational studies.

Phenyleneimine oligomers 4,4'-(((1E,1'E)-(((1E,1'E)-(1,4-phenylenebis-(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-4,1-phenylene))bis(methanylyl-idene))-bis(azanylylidene))dianiline (OIC1MS) and 7,7'-(((1E,1'E)-(((1E,1'E)-((9H-fluorene-2,7-diyl)bis(azanylylidene))bis(methanylylidene))bis(2,5-bis(octyloxy)-4,1phenylene))bis- (methanylylidene))bis(azanylylidene))bis(9H-fluoren-2-amine) (OIC2MS) were prepared by means of conventional and mechanochemical synthesis and characterized by FT-IR, 1H- and 13C-NMR techniques. The optical properties of the compounds were studied in solution by using UV-visible spectroscopy, and the optical effects were analyzed as a function of solvent. The results show that OIC2MS exhibits interesting photochromic properties. Furthermore, the structural and electronic properties of the compounds were analyzed by TD-DFT. It was found that the mechanosynthesis is an efficient method for the synthesis of both tetraimines.

Amyloid Beta peptides differentially affect hippocampal theta rhythms in vitro.

Soluble amyloid beta peptide (A ß ) is responsible for the early cognitive dysfunction observed in Alzheimer's disease. Both cholinergically and glutamatergically induced hippocampal theta rhythms are related to learning and memory, spatial navigation, and spatial memory. However, these two types of theta rhythms are not identical; they are associated with different behaviors and can be differentially modulated by diverse experimental conditions. Therefore, in this study, we aimed to investigate whether or not application of soluble A ß alters the two types of theta frequency oscillatory network activity generated in rat hippocampal slices by application of the cholinergic and glutamatergic agonists carbachol or DHPG, respectively. Due to previous evidence that oscillatory activity can be differentially affected by different A ß peptides, we also compared Aß 25-35 and Aß 1-42 for their effects on theta rhythms in vitro at similar concentrations (0.5 to 1.0 µ M). We found that Aß 25-35 reduces, with less potency than Aß 1-42, carbachol-induced population theta oscillatory activity. In contrast, DHPG-induced oscillatory activity was not affected by a high concentration of Aß 25-35 but was reduced by Aß 1-42. Our results support the idea that different amyloid peptides might alter specific cellular mechanisms related to the generation of specific neuronal network activities, instead of exerting a generalized inhibitory effect on neuronal network function.

Neutralizing effects of Nectandra angustifolia extracts against Bothrops neuwiedi snake venom.

Leaves extracts and essential oil of Nectandra angustifolia were explored for the first time for neutralization of Bothrops neuwiedi diporus snake venom. The ethanol extract was the most active and inhibited both venom activities (hemolytic and coagulant), while the oil was only active on the coagulant activity. These observations confirmed that certain medicinal plants from Corrientes and Chaco Provinces possess significant snake venom neutralizing capacity and need further examination for their active constituents. Analysis by GC and GC-MS of the essential oil and the enantiomeric excess found for alpha-pinene, beta-pinene and limonene allowed a better characterization of this species.

Angiotensin II AT(1) receptor blockade selectively enhances brain AT(2) receptor expression, and abolishes the cold-restraint stress-induced increase in tyrosine hydroxylase mRNA in the locus coeruleus of spontaneously hypertensive rats.

Spontaneously hypertensive rats, a stress-sensitive strain, were pretreated orally for 14 days with the AT(1) receptor antagonist candesartan before submission to 2 h of cold-restraint stress. In non-treated rats, stress decreased AT(1) receptor binding in the median eminence and basolateral amygdala, increased AT(2) receptor binding in the medial subnucleus of the inferior olive, decreased AT(2) binding in the ventrolateral thalamic nucleus and increased tyrosine hydroxylase mRNA level in the locus coeruleus. In non-stressed rats, AT(1) receptor blockade reduced AT(1) receptor binding in all areas studied and enhanced AT(2) receptor binding in the medial subnucleus of the inferior olive. Candesartan pretreatment produced a similar decrease in brain AT(1) binding after stress, and prevented the stress-induced AT(2) receptor binding decrease in the ventrolateral thalamic nucleus. In the locus coeruleus and adrenal medulla, AT(1) blockade abolished the stress-induced increase in tyrosine hydroxylase mRNA level. Our results demonstrate that oral administration of candesartan effectively blocked brain AT(1) receptors, selectively increased central AT(2) receptor expression and prevented the stress-induced central stimulation of tyrosine hydroxylase transcription. The present results support a role of brain AT(1) and AT(2) receptors in the regulation of the stress response, and the hypothesis that AT(1) receptor antagonists may be considered as potential therapeutic compounds in stress related disorders in addition to their anti-hypertensive properties.

Brain angiotensin II, an important stress hormone: regulatory sites and therapeutic opportunities.

The presence of a brain Angiotensin II (Ang II) system, separated from and physiologically integrated with the peripheral, circulating renin-angiotensin system, is firmly established. Ang II is made in the brain and activates specific brain AT(1) receptors to regulate thirst and fluid metabolism. Some AT(1) receptors are located outside the blood-brain barrier and are sensitive to brain and circulating Ang II. Other AT(1) receptors, located inside the blood-brain barrier, respond to stimulation by Ang II of brain origin. AT(1) receptors in the subfornical organ, the hypothalamic paraventricular nucleus (PVN), and the median eminence are involved in the regulation of the stress response. In particular, AT(1) receptors in the PVN are under glucocorticoid control and regulate corticotrophin-releasing hormone (CRH) formation and release. In the PVN, restraint elicits a fast increase in AT(1) receptor mRNA expression. The expression of paraventricular AT(1) receptors is increased during repeated restraint and after 24 h of isolation stress, and their stimulation is essential for the hypothalamic-pituitary-adrenal axis activation, the hallmark of the stress response. Peripheral administration of an AT(1) receptor antagonist blocks peripheral and brain AT(1) receptors, prevents the sympathoadrenal and hormonal response to isolation stress, and prevents the gastric stress ulcers that are a characteristic consequence of cold-restraint stress. This evidence indicates that pharmacologic inhibition of the peripheral and brain Ang II system by AT(1) receptor blockade has a place in the prevention and treatment of stress-related disorders.

Angiotensin II AT1 and AT2 receptor types regulate basal and stress-induced adrenomedullary catecholamine production through transcriptional regulation of tyrosine hydroxylase.

The sympathoadrenal response to stress includes a profound increase in adrenomedullary catecholamine synthesis driven by stimulation of tyrosine hydroxylase (TH) transcription. We studied the role of Angiotensin II type 1 and 2 (AT(1) and AT(2)) receptors during isolation stress, and under basal conditions. Pretreatment of rats with the AT(1) receptor antagonist candesartan for 14 days prior to isolation completely prevented the stress-induced stimulation of catecholamine synthesis, decreasing tyrosine hydroxylase transcription by preventing the expression of the transcriptional factor, Fos-related antigen 2 (Fra-2). In addition, AT(1) receptor antagonism prevented the stress-induced increase in adrenomedullary AT(2) receptor binding and protein. Treatment of non-stressed, grouped animals under basal conditions with the AT(1) receptor or with PD 123319, an AT(2) receptor antagonist, decreased the adrenomedullary norepinephrine (NE) content and TH transcription. While AT(1) receptor antagonism decreased the levels of Fra-2 and the phosphorylated forms of cAMP responsive element binding protein (pCREB) and EKR2 (p-ERK2, phosphor-p42 MAP kinase), the AT(2) antagonist decreased Fra-2 with no change in the phosphorylation of CREB or EKR2. Our results demonstrate that both adrenomedullary AT(1) and AT(2) receptor types maintain and promote the adrenomedullary catecholamine synthesis and the transcriptional regulation of TH. Instead of opposing effects, however, our results indicate a complex synergistic regulation between the AT(1) and AT(2) receptor types.

Angiotensin II AT1 receptor blockade prevents gastric ulcers during cold-restraint stress.

Cold-restraint stress reduces gastric blood flow and produces acute gastric ulcers. We studied the role of Angiotensin II (Ang II) on gastric blood flow and gastric ulceration during stress. Spontaneously hypertensive rats, a stress-sensitive strain, were pretreated for 14 days with the AT(1) receptor antagonist candesartan before cold-restraint stress. AT(1) blockade increased gastric blood flow 40% to 50%; prevented gastric ulcer formation by 70% to 80%; reduced the increase in adrenomedullary epinephrine and TH mRNA without preventing the stress-induced increase in adrenal corticosterone; decreased the stress-induced expression of tumor necrosis factor alpha (TNF-alpha) and adhesion protein ICAM-1 in arterial endothelium, and neutrophil infiltration in the gastric mucosa; and decreased PGE(2) content. AT(1) receptor blockers prevent stress-induced ulcerations by a combination of gastric blood flow protection, decreased sympathoadrenal activation, anti-inflammatory effects with reduction in TNF-alpha, and ICAM-1 expression, leading to reduced neutrophil infiltration while maintaining the protective glucocorticoid effects and PGE(2) release. Ang II has a crucial role, through stimulation of AT(1) receptors, in the production and progression of stress-induced gastric injury, and AT(1) receptor antagonists could be of therapeutic benefit.

The serotonin transporter is required for stress-evoked increases in adrenal catecholamine synthesis and angiotensin II AT(2) receptor expression.

High numbers of serotonin transporter (SERT) binding sites and high serotonin (5-HT) content are expressed in the adrenal medulla of wild-type (SERT+/+) mice. Acute restraint stress increases adrenomedullary 5-HT, norepinephrine (NE) and epinephrine (E) release, adrenomedullary tyrosine hydroxylase (TH) mRNA, and angiotensin II AT(2) receptor expression. There are no alterations in adrenal catecholamine content during restraint. In littermate SERT-/- mice, which do not express SERT binding sites, the basal adrenomedullary 5-HT content is significantly reduced and does not increase after stress. The stress-induced increase in plasma E is higher in SERT-/- than in SERT+/+ animals. In SERT-/- mice, the stress-induced increase in expression of TH mRNA does not occur, and as a consequence, adrenal E content decreases, and adrenal E and NE content are lower than that of SERT+/+ mice during restraint. In addition, instead of increased expression, stress induces a profound decrease in the number of adrenomedullary AT(2) receptors in SERT-/- mice. Our results indicate that SERT is necessary for the stress-induced increase in adrenomedullary catecholamine synthesis and AT(2) receptor expression. These data further indicate a close relationship between the adrenomedullary 5-HT and angiotensin II systems, and an important role of adrenomedullary AT(2) receptors in catecholamine synthesis and release during stress.

Atenolol improves ventricular function without changing plasma noradrenaline but decreasing plasma atrial natriuretic factor in chronic heart failure.

1 There is good evidence that beta-blockers improve ventricular function, disease progression and survival in patients with left ventricular systolic dysfunction. The aim of this study was to determine the effects of atenolol therapy on the sympathetic nervous system at rest and after ergometric exercise, on left ventricular function and on baseline plasma atrial natriuretic factor (ANF) in ambulatory patients with chronic heart failure (CHF). 2 Twenty-two patients [left ventricular ejection fraction (LVEF) <36%; New York Heart Association II-III] were studied before atenolol treatment. Because of cardiac events (new Hospital admission or death) only 13 patients completed 1 year of treatment. Baseline noradrenaline (NE) concentrations were similar in patients and controls while ANF was higher in patients than in controls (328 +/- 35 pg ml(-1) vs. 37 +/- 3 pg ml(-1); P<0.01). 3 Patients with events showed higher NE (540 +/- 87 pg ml(-1) vs. 303 +/- 44 pg ml(-1); P<0.01) and ANF (460 +/- 70 pg ml(-1) vs. 291 +/- 44 pg ml(-1); P<0.03) at rest; and greater NE response to exercise (2.003 +/- 525 pg ml(-1) vs. 694 +/- 121 pg ml(-1); P<0.005). Atenolol treatment improved LVEF (19.5 +/- 1.9% vs. 33 +/- 3.9%; P<0.001), increased exercise tolerance (9 +/- 3.2 min vs. 17 +/- 4.8 min; P<0.001) and decreased plasma ANF (292 +/- 42 pg ml(-1) vs. 133 +/- 35 pg ml(-1); P<0.01). 4 Reduced basal dihydroxyphenylglycol (DHPG)/NE ratio (3.4 +/- 0.46 vs. 4.3 +/- 0.35; P<0.01) was observed in patients compared with healthy volunteers. Atenolol increased DHPG plasma levels (1.398 +/- 129 pg ml(-1) vs. 913 +/- 86 pg ml(-1); P<0.005) but the DHPG/NE ratio during exercise was not modified after treatment, suggesting that re-uptake of released NE is not changed by beta-blocker treatment. 5 In conclusion, the fact that atenolol treatment improves ventricular dysfunction and clinical status without changing plasma NE levels in CHF patients, suggests that plasma NE is a poor surrogate measurement for cardiac sympathetic activity in this pathology. In addition, decrease in plasma ANF produced by atenolol treatment may reflect the improvement of ventricular function.

Increased AT(1) receptors in adrenal gland of AT(2) receptor gene-disrupted mice.

Angiotensin II (Ang II) AT(2) receptor-gene disrupted mice have increased systemic blood pressure and response to exogenous Angiotensin II. To clarify the mechanism of these changes, we studied adrenal AT(1) receptor expression and mRNA by receptor autoradiography and in situ hybridization in female AT(2) receptor-gene disrupted mice (agtr 2-/-) and wild-type controls (agtr 2+/+). We found high expression of AT(1) receptor binding and mRNA in adrenal zona glomerulosa of female wild-type mice. AT(2) receptors and mRNA were highly expressed in adrenal medulla of wild-type mice, but were not detected in zona glomerulosa. There was no AT(2) receptor binding or mRNA in adrenal glands of AT(2) receptor-gene disrupted mice. In these animals, AT(1) receptor binding and mRNA were increased in adrenal zona glomerulosa and AT(1) receptor mRNA was increased in the adrenal medulla when compared with wild-type animals.The present data support the hypothesis of an interaction or cross talk between AT(2) and AT(1) receptors in adrenal gland. The significant increase in AT(1) receptor expression in the absence of AT(2) receptor transcription may be partially responsible for the increased blood pressure and for the enhanced response to exogenously administered Angiotensin II in this model.

Peripheral administration of an angiotensin II AT(1) receptor antagonist decreases the hypothalamic-pituitary-adrenal response to isolation Stress.

Angiotensin II, which stimulates AT(1) receptors, is a brain and peripheral stress hormone. We pretreated rats with the AT(1) receptor antagonist candesartan for 13 d via sc-implanted osmotic minipumps, followed by 24-h isolation in individual metabolic cages. We measured angiotensin II receptor-type binding and mRNAs and tyrosine hydroxylase mRNA by quantitative autoradiography and in situ hybridization, catecholamines by HPLC, and hormones by RIA. Isolation increased AT(1) receptor binding in hypothalamic paraventricular nucleus as well as anterior pituitary ACTH, and decreased posterior pituitary AVP. Isolation stress also increased AT(1) receptor binding and AT(1B) mRNA in zona glomerulosa and AT(2) binding in adrenal medulla, adrenal catecholamines, tyrosine hydroxylase mRNA, aldosterone, and corticosterone. Candesartan blocked AT(1) binding in paraventricular nucleus and adrenal gland; prevented the isolation-induced alterations in pituitary ACTH and AVP and in adrenal corticosterone, aldosterone, and catecholamines; abolished the increase in AT(2) binding in adrenal medulla; and substantially decreased urinary AVP, corticosterone, aldosterone, and catecholamines during isolation. Peripheral pretreatment with an AT(1) receptor antagonist blocks brain and peripheral AT(1) receptors and inhibits the hypothalamic-pituitary-adrenal response to stress, suggesting a physiological role for peripheral and brain AT(1) receptors during stress and a possible beneficial effect of AT(1) antagonism in stress-related disorders.

Pharmacological involvement of the calcium channel blocker flunarizine in dopamine transmission at the striatum.

Single intrastriatal microinjections of 25, 50 and 100nmol/microl of flunarizine in normal rats produced a dose-dependent turning behavior toward the injected side when they were challenged with apomorphine (1mg/kg, s.c). This effect was seen at 1, 3 and 7 days following administration of the high dose of flunarizine, but had subsided by 24h after administration of the intermediate dose; the low dose was ineffective. However, intrastriatal injection of the high dose of flunarizine resulted in a local lesion and thereafter this dose was not used. A similar dose-response relationship was determined for nifedipine, an L-type calcium channel antagonist. Injection of this antagonist did not result in apomorphine-elicited rotational behavior, reflecting its lack of antidopaminergic action. Intrastriatal injections of haloperidol (5microg/microl), an antagonist of dopamine D(2) receptors, or the sodium channel blocker lidocaine (40microg/microl), were given in order to compare their effects to those observed with flunarizine. Intracerebral injection of haloperidol produced ipsilateral turning in response to systemic administration of apomorphine given 60min after. The same response was obtained with the injection of apomorphine 10min after the injection of intracerebral lidocaine. This effect was no longer apparent 24h after the microinjection of haloperidol and 60min after the injection of lidocaine. In rats rendered hemiparkinsionian by lesioning the nigrostriatal pathway with 6OHDA, intrastriatal microinjection of flunarizine (50nmol/microl) significantly reduced apomorphine (0.2mg/kg, s.c.)-elicited turning behavior towards the non-lesioned side. These results suggest an antidopaminergic effect of flunarizine mediated by antagonistic action of post-synaptic striatal dopamine receptors. However, an action of the drug on sodium channels may not be ruled out. These studies offer additional supporting evidence for the induction or aggravation of extrapyramidal side-effects in patients receiving flunarizine.