Effects of unilateral decortication on β-adrenergic receptors in the remaining cortex and in the hypothalamus of female rats

Many experiments have been performed to evaluate the physiological role of catecholaminergic mechanisms of gonadotropin release. The purpose of the present study was to determine the concentration of β-adrenoreceptors in the remaining (right) cerebral cortex and in right and left hypothalamic halves of hemi-decorticated female rats which exhibited elevated plasma gonadotropin levels as observed previously. The density of β-receptors was measured using a high-affinity β-adrenergic ligand, iodocyanopindolol (ICYP). Scatchard estimates were obtained for maximum binding (B(max) fmol/mg of tissues) from pooled cerebral cortical and hypothalamic tissue of animals under several experimental conditions after hemi-decortication and sham operation. There was an increase in β-adrenoreceptor density in the remaining (right) cerebral cortex at all times examined in hemi-decorticate in comparison with the sham-operated animals (7 days, +10.9%; 21 days, +8.4%; 90 days, +22%; and 90 days plus ovariectomy, +34.8%). The number of β-adrenoreceptors in the right hypothalamic half in hemi-decorticates decreased at 21 days (-42.20%) and then increased at 90 days (+76.63%) and 90 days plus ovariectomy (+51.75%) when compared with the left hypothalamic half. At the same time there were no significant changes in the sham-operated animals when comparing the receptor density in the right and left hypothalamic halves, respectively. Thus, our results suggest a direct adrenergic pathway by which the left cortex can influence the right cortex and a crossed pathway to the contralateral hypothalamus changing adrenergic activity which can alter the β-adrenergic receptor binding capacity in the hypothalamus.

Effect of an acute β-adrenergic blockade on exercise intensity corresponding to the lactate minimum

β-Adrenoreceptor blockade is reported to impair endurance, power output and work capacity in healthy subjects and patients with hypertension. The purpose of this study was to investigate the effect in eighth athletic males of an acute β-adrenergic blockade with propranolol on their individual power output corresponding to a defined lactate minimum (LM). Eight fit males (cyclist or triathlete) performed a protocol to determine the power output corresponding to their individual LM (defined from an incremental exercise test after a rapidly induced exercise lactic acidosis). This protocol was performed twice in a double-blind randomized order by each athlete first ingesting propranolol (80mg) and in a second trial a placebo, 120 minutes respectively prior to the test sequence. The blood lactate concentration obtained 7 minutes after anaerobic exercise (a Wingate test) was significantly lower after acute β-adrenergic blockade (8.6 ± 1.6mM) than under the placebo condition (11.7 ± 1.6mM). The work rate at the LM was lowered from 215.0 ± 18.6 to 184.0 ± 18.6 watts and heart rate at the LM was reduced from 165 ± 1.5 to 132 ± 2.2 beats/minute as a result of the blockade. There was a non-significant correlation (r = 0.29) between the power output at the LM with and without acute β-adrenergic blockade. In conclusion, since the intensity corresponding to the LM is related to aerobic performance, the results of the present study, are able to explain in part, the reduction in aerobic power output produced during β-adrenergic blockade.

Obesity does not lead to imbalance between myocardial phospholamban phosphorylation and dephosphorylation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Role of cholinergic and adrenergic pathways of the medial septal area in the control of water intake and renal excretion in rats

In this study, we investigated an interaction between noradrenergic and cholinergic pathways of the medial septal area (MSA) on the control of water intake and urinary electrolyte excretion by means of injection of their respective agonists. Noradrenaline (a nonspecific α-adrenergic agonist) and clonidine (an α2-adrenergic agonist), but not phenylephrine (an α1-adrenergic agonist), induced natriuresis and kaliuresis. α-Adrenergic activation had no effect on the natriuresis and kaliuresis induced by carbachol (a cholinergic agonist) and it inhibited the antinatriuresis and antikaliuresis induced by isoproterenol (a ß-adrenergic agonist). Interactions related to volume excretion are complex. α-Adrenergic activation induced a mild diuresis and inhibited the antidiuresis induced by isoproterenol, but phenylephrine combined with carbachol induced antidiuresis. The water intake induced by carbachol was inhibited by clonidine and noradrenaline, but not phenylephrine. These results show an asymmetry in the interaction between α-adrenergic and cholinergic receptors concerning water intake and electrolyte excretion. © 1992.

Disfunção miocárdica e alterações no trânsito de cálcio intracelular em ratos obesos

Abstract Background: Several mechanisms have been proposed to contribute to cardiac dysfunction in obesity models, such as alterations in calcium (Ca2+) handling proteins and β-adrenergic receptors. Nevertheless, the role of these factors in the development of myocardial dysfunction induced by obesity is still not clear. Objective: The purpose of this study was to investigate whether obesity induced by hypercaloric diets results in cardiac dysfunction. Furthermore, it was evaluated whether this functional abnormality in obese rats is related to abnormal Ca2+ handling and the β-adrenoceptor system. Methods: Male 30-day-old Wistar rats were fed with standard food (C) and a cycle of five hypercaloric diets (Ob) for 15 weeks. Obesity was defined as increases in body fat percentage in rats. Cardiac function was evaluated by isolated analysis of the left ventricle papillary muscle under basal conditions and after inotropic and lusitropic maneuvers. Results: Compared with the control group, the obese rats had increased body fat and glucose intolerance. The muscles of obese rats developed similar baseline data, but the myocardial responsiveness to post-rest contraction stimulus and increased extracellular Ca2+ were compromised. There were no changes in cardiac function between groups after β-adrenergic stimulation. Conclusion: Obesity promotes cardiac dysfunction related to changes in intracellular Ca2+ handling. This functional damage is probably caused by reduced cardiac sarcoplasmic reticulum Ca2+ ATPase (SERCA2) activation via Ca2+ calmodulin kinase. (Arq Bras Cardiol 2011; 97(3) : 232-240).

Age-Related Maximum Heart Rate Among Ischemic and Nonischemic Heart Failure Patients Receiving beta-Blockade Therapy

Background: Equations to predict maximum heart rate (HRmax) in heart failure (HF) patients receiving beta-adrenergic blocking (BB) agents do not consider the cause of HF. We determined equations to predict HRmax in patients with ischemic and nonischemic HF receiving BB therapy. Methods and Results: Using treadmill cardiopulmonary exercise testing, we studied HF patients receiving BB therapy being considered for transplantation from 1999 to 2010. Exclusions were pacemaker and/or implantable defibrillator, left ventricle ejection fraction (LVEF) >50%, peak respiratory exchange ratio (RER) <1.00, and Chagas disease. We used linear regression equations to predict HRmax based on age in ischemic and nonischemic patients. We analyzed 278 patients, aged 47 +/- 10 years, with ischemic (n = 75) and nonischemic (n = 203) HF. LVEF was 30.8 +/- 9.4% and 28.6 +/- 8.2% (P = .04), peak VO2 16.9 +/- 4.7 and 16.9 +/- 5.2 mL kg(-1) min(-1) (P = NS), and the HRmax 130.8 +/- 23.3 and 125.3 +/- 25.3 beats/min (P = .051) in ischemic and nonischemic patients, respectively. We devised the equation HRmax = 168 - 0.76 x age (R-2 = 0.095; P = .007) for ischemic HF patients, but there was no significant relationship between age and HRmax in nonischemic HF patients (R-2 = 0.006; P = NS). Conclusions: Our study suggests that equations to estimate HRmax should consider the cause of HF. (J Cardiac Fail 2012;18:831-836)

Spironolactone prevents alterations associated with cardiac hypertrophy produced by isoproterenol in rats: involvement of serum- and glucocorticoid-regulated kinase type 1

Persistent beta-adrenergic receptor stimulation with isoproterenol is associated with cardiac hypertrophy as well as cardiac synthesis of angiotensin II. Serum- and glucocorticoid-regulated kinase type 1 (SGK-1) is a key mediator in structural, functional and molecular cardiac effects of aldosterone in rats. This study was designed to investigate the cardiac effects of the mineralocorticoid receptor antagonist spironolactone on the response to isoproterenol treatment in rats, as well as the involvement of the main mediator of cellular aldosterone action, SGK-1, in the heart. Male Wistar rats received isoproterenol (3 mg kg-1 day-1) or vehicle for 15 days. Half of the animals in each group were simultaneously treated with spironolactone (200 mg kg-1 day-1). Systolic and diastolic blood pressures were not significantly different among groups. Treatment with spironolactone normalized the increased left ventricular end-diastolic pressure observed in isoproterenol-treated rats. Isoproterenol treatment induced cardiac hypertrophy and increased collagen content, both of which were normalized by spironolactone treatment. The mRNA levels of transforming growth factor beta, connective tissue growth factor, matrix metalloprotease 2, matrix metalloprotease inhibitor 2, tumour necrosis factor a, interleukin 1 beta, p22phox and xanthine dehydrogenase were increased (P < 0.05) in isoproterenol-treated rats, and this effect was prevented by spironolactone (P < 0.05). Spironolactone also reduced the elevated SGK-1 expression in isoproterenol-treated rats. The observed reduction of the principal mediator of aldosterone cellular actions, SGK-1, by spironolactone in hearts from isoproterenol-treated rats suggests a role of mineralocorticoids in the cardiac hypertrophy, fibrosis, inflammation, oxidation and diastolic dysfunction induced by isoproterenol treatment in rats.

REGULATION OF BRAIN NORADRENERGIC-RECEPTOR FUNCTION BY ADRENOCORTICOTROPHIN AND ANTIDEPRESSANT DRUGS (ADRENERGIC RECEPTOR, CYCLIC-AMP, ADENYLATE CYCLASE, IMIPRAMINE, STRESS)

Human behavior appears to be regulated in part by noradrenergic transmission since antidepressant drugs modify the number and function of (beta)-adrenergic receptors in the central nervous system. Affective illness is also known to be associated with the endocrine system, particularly the hypothalamic-pituitary-adrenal axis. The aim of the present study was to determine whether hormones, in particular adrencorticotrophin (ACTH) and corticosterone, may influence behavior by regulating brain noradrenergic receptor function.^ Chronic treatment with ACTH accelerated the increase or decrease in rat brain (beta)-adrenergic receptor number induced by a lesion of the dorsal noradrenergic bundle or treatment with the antidepressant imipramine. Chronic administration of ACTH alone had no effect on (beta)-receptor number although it reduced norepinephrine stimulated cyclic AMP accumulation in brain slices. Treatment with imipramine also reduced the cyclic AMP response to norepinephrine but was accompanied by a decrease in (beta)-adrenergic receptor number. Both the imipramine and ACTH treatments reduced the affinity of (beta)-adrenergic receptors for norepinephrine, but only the antidepressant modified the potency of the neurotransmitter to stimulate second messenger production. Neither ACTH nor imipramine treatment altered Gpp(NH)p- or fluoride-stimulated adenylate cyclase, cyclic AMP, cyclic GMP, or cyclic GMP-stimulated cyclic AMP phosphodiesterase, or the activity of the guanine nucleotide binding protein (Gs). These findings suggested that post-receptor components of the cyclic nucleotide generating system are not influenced by the hormone or antidepressant. This conclusion was verified by the finding that neither treatment altered adenosine-stimulated cyclic AMP accumulation in brain tissue.^ A detailed examination of the (alpha)- and (beta)-adrenergic receptor components of norepinephrine-stimulated cyclic AMP production revealed that ACTH, but not imipramine, administration reduced the contribution of the (alpha)-receptor mediated response. Like ACTH treatment, corticosterone diminished the (alpha)-adrenergic component indicating that adrenal steroids probably mediate the neurochemical responses to ACTH administration. The data indicate that adrenal steroids and antidepressants decrease noradrenergic receptor function by selectively modifying the (alpha)- and (beta)-receptor components. The functional similarity in the action of the steroid and antidepressants suggests that adrenal hormones normally contribute to the maintenance of receptor systems which regulate affective behavior in man. ^

Receptor-specific in vivo desensitization by the G protein-coupled receptor kinase-5 in transgenic mice.

Transgenic mice were generated with cardiac-specific overexpression of the G protein-coupled receptor kinase-5 (GRK5), a serine/threonine kinase most abundantly expressed in the heart compared with other tissues. Animals overexpressing GRK5 showed marked beta-adrenergic receptor desensitization in both the anesthetized and conscious state compared with nontransgenic control mice, while the contractile response to angiotensin II receptor stimulation was unchanged. In contrast, the angiotensin II-induced rise in contractility was significantly attenuated in transgenic mice overexpressing the beta-adrenergic receptor kinase-1, another member of the GRK family. These data suggest that myocardial overexpression of GRK5 results in selective uncoupling of G protein-coupled receptors and demonstrate that receptor specificity of the GRKs may be important in determining the physiological phenotype.

G protein beta gamma subunits stimulate phosphorylation of Shc adapter protein.

The mechanism of mitogen-activated protein (MAP) kinase activation by pertussis toxin-sensitive Gi-coupled receptors is known to involve the beta gamma subunits of heterotrimeric G proteins (G beta gamma), p21ras activation, and an as-yet-unidentified tyrosine kinase. To investigate the mechanism of G beta gamma-stimulated p21ras activation, G beta gamma-mediated tyrosine phosphorylation was examined by overexpressing G beta gamma or alpha 2-C10 adrenergic receptors (ARs) that couple to Gi in COS-7 cells. Immunoprecipitation of phosphotyrosine-containing proteins revealed a 2- to 3-fold increase in the phosphorylation of two proteins of approximately 50 kDa (designated as p52) in G beta gamma-transfected cells or in alpha 2-C10 AR-transfected cells stimulated with the agonist UK-14304. The latter response was pertussis toxin sensitive. These proteins (p52) were also specifically immunoprecipitated with anti-Shc antibodies and comigrated with two Shc proteins, 46 and 52 kDa. The G beta gamma- or alpha 2-C10 AR-stimulated p52 (Shc) phosphorylation was inhibited by coexpression of the carboxyl terminus of beta-adrenergic receptor kinase (a G beta gamma-binding pleckstrin homology domain peptide) or by the tyrosine kinase inhibitors genistein and herbimycin A, but not by a dominant negative mutant of p21ras. Worthmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K) inhibited phosphorylation of p52 (Shc), implying involvement of PI3K. These results suggest that G beta gamma-stimulated Shc phosphorylation represents an early step in the pathway leading to p21ras activation, similar to the mechanism utilized by growth factor tyrosine kinase receptors.

Efeitos da Imunocastração e de agonistas beta-adrenérgicos sobre a qualidade da carne de bovinos

Os agonistas beta-adrenérgicos (&beta;AA) são conhecidos por aumentar a hipertrofia muscular e lipólise, neste caso uma maneira de se reduzir o efeito da lipólise seria a imunocastração. Dessa forma, o objetivo deste projeto foi avaliar o efeito dos &beta;AA e da imunocastração sobre a qualidade da carne de bovinos Nelore. Foram utilizados noventa e seis bovinos Nelore, sendo que metade dos animais (n=48) receberam uma dose da vacina de imunocastração, e após 30 dias receberam a segunda dose. A outra metade dos animais (n=48) não recebeu nenhuma dose da vacina. Durante 70 dias os animais foram alimentados com uma dieta padrão composta de 24% volumoso e 76% de concentrado. Após 70 dias de confinamento os animais foram divididos em três grupos, dentro de bloco (peso inicial) e condição sexual e foram alimentados por 30 dias, com umas das seguintes dietas: CON - dieta padrão utilizada na fase anterior, sem a adição de &beta;AA; ZIL - dieta padrão acrescida de 80 mg/dia Cloridrato de Zilpaterol; RAC - dieta padrão acrescida de 300 mg/dia Cloridrato de Ractopamina. Ao final desse período os animais foram abatidos e colhidas amostras do músculo Longissimus dorsi para as avaliações de qualidade de carne, lipídeos totais, perfil de ácidos graxos, análise sensorial do consumidor, perfil morfométrico muscular, expressão dos genes calpaína e calpastatina, comprimento de sarcômero. Para a maioria das características avaliadas não foram observadas interações entre os tratamentos. Ao avaliar o efeito da condição sexual, os animais imunocastrados apresentaram maiores intensidades de cor L, a e b, lipídios totais, ácidos oleico, palmítico e total de monoinsaturados e maior frequência para as fibras oxidativas (FO) e glicolíticas (FG) em relação aos não-castrados. Contudo, os animais não-castrados tiveram uma tendência a apresentarem uma carne mais macia na análise sensorial e obtiveram maior frequência das fibras oxidativasglicolíticas (FOG) em relação aos imunocastrados. Quanto ao efeito dos &beta;AA, o grupo ZIL apresentaram uma carne menos macia na força de cisalhamento, maiores concentrações de ácidos heptadecanoico, linoleico, araquidonico ácido C20:3 N6C8C11C14, ômega 6, maior frequência para as FO e menor para FG em comparação ao grupo RAC e CON. No entanto, os animais do grupo CON e ZIL apresentaram maior área para as FO em comparação ao grupo RAC, enquanto que para as FOG, os animais do grupo CON tiveram maior área do que os animais do grupo RAC e ZIL. Na análise sensorial, os grupos RAC e ZIL receberam menores notas para os atributos textura e qualidade global em relação ao CON. Não foi observado efeito da condição sexual e dos &beta;AA sobre a expressão dos genes e comprimento de sarcômero. Conclui-se que a condição sexual e a suplementação com os &beta;AA podem alterar a qualidade da carne, perfil de ácidos graxos e morfométrico muscular, sem, contudo, alterar a expressão dos genes e do comprimento de sarcômero.

Constitutive glycogen synthase kinase-3α/β activity protects against chronic β-adrenergic remodelling of the heart

Aims - Glycogen synthase kinase 3 (GSK-3) signalling is implicated in the growth of the heart during development and in response to stress. However, its precise role remains unclear. We set out to characterize developmental growth and response to chronic isoproterenol (ISO) stress in knockin (KI) mice lacking the critical N-terminal serines, 21 of GSK-3 and 9 of GSK-3 respectively, required for inactivation by upstream kinases. Methods and results - Between 5 and 15 weeks, KI mice grew more rapidly, but normalized heart weight and contractile performance were similar to wild-type (WT) mice. Isolated hearts of both genotypes responded comparably to acute ISO infusion with increases in heart rate and contractility. In WT mice, chronic subcutaneous ISO infusion over 14 days resulted in cardiac hypertrophy, interstitial fibrosis, and impaired contractility, accompanied by foetal gene reactivation. These effects were all significantly attenuated in KI mice. Indeed, ISO-treated KI hearts demonstrated reversible physiological remodelling traits with increased stroke volume and a preserved contractile response to acute adrenergic stimulation. Furthermore, simultaneous pharmacological inhibition of GSK-3 in KI mice treated with chronic subcutaneous ISO recapitulated the adverse remodelling phenotype seen in WT hearts. Conclusion - Expression of inactivation-resistant GSK-3/does not affect eutrophic myocardial growth but protects against pathological hypertrophy induced by chronic adrenergic stimulation, maintaining cardiac function and attenuating interstitial fibrosis. Accordingly, strategies to prevent phosphorylation of Ser-21/9, and consequent inactivation of GSK-3/, may enable a sustained cardiac response to chronic-agonist stimulation while preventing pathological remodelling. © 2010 The Author.

The primary amine metabolite of sibutramine stimulates lipolysis in adipocytes isolated from lean and obese mice and in isolated human adipocytes

Sibutramine is a satiety-inducing serotonin-noradrenaline reuptake inhibitor that acts predominantly via its primary and secondary metabolites. This study investigates the possibility that sibutramine and/or its metabolites could act directly on white adipose tissue to increase lipolysis. Adipocytes were isolated by a collagenase digestion procedure from homozygous lean (+/+) and obese-diabetic ob/ob mice, and from lean nondiabetic human subjects. The lipolytic activity of adipocyte preparations was measured by the determination of glycerol release over a 2-hour incubation period. The primary amine metabolite of sibutramine M2, caused a concentration-dependent stimulation of glycerol release by murine lean and obese adipocytes (maximum increase by 157 ± 22 and 245 ± 1696, respectively, p < 0.05). Neither sibutramine nor its secondary amine metabolite M1 had any effect on lipolytic activity. Preliminary studies indicated that M2-induced lipolysis was mediated via a beta-adrenergic action. The non-selective beta-adrenoceptor antagonist propranolol (10-6M) strongly inhibited M2-stimulated lipolysis in lean and obese murine adipocytes. M2 similarly increased lipolysis by isolated human omental and subcutaneous adipocytes (maximum increase by 194 ± 33 and 136 ± 4%, respectively, p < 0.05) with EC50 values of 12 nM and 3 nM, respectively. These results indicate that the sibutramine metabolite M2 can act directly on murine and human adipose tissue to increase lipolysis via a pathway involving beta-adrenoceptors. © Georg Thieme Verlag KG Stuttgart.

Adherence, adaptation and acceptance of elderly chronic heart failure patients to receiving healthcare via telephone-monitoring

Background: Although the potential to reduce hospitalisation and mortality in chronic heart failure (CHF) is well reported, the feasibility of receiving healthcare by structured telephone support or telemonitoring is not. Aims: To determine; adherence, adaptation and acceptability to a national nurse-coordinated telephone-monitoring CHF management strategy. The Chronic Heart Failure Assistance by Telephone Study (CHAT). Methods: Triangulation of descriptive statistics, feedback surveys and qualitative analysis of clinical notes. Cohort comprised of standard care plus intervention (SC + I) participants who completed the first year of the study. Results: 30 GPs (70% rural) randomised to SC + I recruited 79 eligible participants, of whom 60 (76%) completed the full 12 month follow-up period. During this time 3619 calls were made into the CHAT system (mean 45.81 SD ± 79.26, range 0-369), Overall there was an adherence to the study protocol of 65.8% (95% CI 0.54-0.75; p = 0.001) however, of the 60 participants who completed the 12 month follow-up period the adherence was significantly higher at 92.3% (95% CI 0.82-0.97, p ≤ 0.001). Only 3% of this elderly group (mean age 74.7 ±9.3 years) were unable to learn or competently use the technology. Participants rated CHAT with a total acceptability rate of 76.45%. Conclusion: This study shows that elderly CHF patients can adapt quickly, find telephone-monitoring an acceptable part of their healthcare routine, and are able to maintain good adherence for a least 12 months. © 2007.

The biology of the glutamatergic system and potential role in migraine

Migraine is a common genetically linked neurovascular disorder. Approximately ~12% of the Caucasian population are affected including 18% of adult women and 6% of adult men (1, 2). A notable female bias is observed in migraine prevalence studies with females affected ~3 times more than males and is credited to differences in hormone levels arising from reproductive achievements. Migraine is extremely debilitating with wide-ranging socioeconomic impact significantly affecting people's health and quality of life. A number of neurotransmitter systems have been implicated in migraine, the most studied include the serotonergic and dopaminergic systems. Extensive genetic research has been carried out to identify genetic variants that may alter the activity of a number of genes involved in synthesis and transport of neurotransmitters of these systems. The biology of the Glutamatergic system in migraine is the least studied however there is mounting evidence that its constituents could contribute to migraine. The discovery of antagonists that selectively block glutamate receptors has enabled studies on the physiologic role of glutamate, on one hand, and opened new perspectives pertaining to the potential therapeutic applications of glutamate receptor antagonists in diverse neurologic diseases. In this brief review, we discuss the biology of the Glutamatergic system in migraine outlining recent findings that support a role for altered Glutamatergic neurotransmission from biochemical and genetic studies in the manifestation of migraine and the implications of this on migraine treatment.