Treatment of rabbits with thyroxine 1 mg/kg daily for three to six days produced a hyperthyroid state as evidenced by increase in the heart rate and PBI. The hyperthyroid animals exhibited a significant shortening of the atrial refractory period. Beta adrenergic receptor blocking agents, propranolol (l0(-6)M pronethalol (5 X 10(-5)M) or MJ-1999 (5 X 10(-4)M), completely blocked the shortening of the atrial refractory period produced by the treatment with thyroxin, and with norepinephrine. Consequently, the shortening of the atrial refractory period of rabbits treated with thyroxin appears to bs mediated through stimulation of the beta adrenergic receptor in the heart. From these results, it may be concluded that the stimulation of the beta adrenergic receptor plays an important role in the alteration of cardiac function found in hyperthyroidism, and that the beta adrenergic blocking agents may be useful in treatment of the cardiac complications of hyperthyroidism.
Adrenergic beta-Antagonists/pharmacology ; Animals ; Female ; Heart Atria/*drug effects/physiopathology ; Hyperthyroidism/chemically induced/*physiopathology ; Male ; Rabbits ; Sympatholytics/*pharmacology ; Thyroxine

OBJECTIVETo study the interactions between Ligusticum chuanxiong Hort extract and cardiac muscle membrane receptors.

METHODThe cell membrane of rabbit cardiac muscle was fixed on silicon to make cell membrane stationary phase (CMSP), and then the interactions were studied by comparing the retention characteristics of the extracts from different solvents with those of the antagonists or activators corresponding to known receptors in cardiac muscle membrane, and by competition effect on the retention characteristics of extracts when adding the antagonists or activators into the mobile phase.

RESULTWater extract and ethanol extract both had retentions on CMSP; the retention characteristics of water extract could be affected when water extract was in competition with the antagonists for alpha receptor, and could not be affected when with the activator beta1 receptor.

CONCLUSIONIt is possible that some components in water extract may combine with alpha receptor and no component with beta1 receptor, and that some components in ethanol extract may combine with cardiac muscle cell membrane. The process between active components and receptors in vivo can be imitated through the interactions between drugs and CMSP. The method provides references for the resolution of two applications: to screen the active components from Chinese medicine, and to figure out the type of receptors involved.

Adrenergic alpha-Agonists ; metabolism ; Adrenergic alpha-Antagonists ; metabolism ; Adrenergic beta-Agonists ; metabolism ; Adrenergic beta-Antagonists ; metabolism ; Animals ; Cell Membrane ; metabolism ; Chromatography, High Pressure Liquid ; methods ; Drugs, Chinese Herbal ; isolation & purification ; pharmacology ; Female ; Ligusticum ; chemistry ; Male ; Myocytes, Cardiac ; cytology ; metabolism ; Plants, Medicinal ; chemistry ; Protein Binding ; Rabbits ; Receptors, Adrenergic, alpha ; metabolism ; Receptors, Adrenergic, beta ; metabolism

OBJECTIVETo observe the effects of combined beta(1) adrenergic receptor (AR) antagonist with beta(2)AR agonist therapy on cardiac function and cardiomyocyte apoptosis in heart failure rats.

METHODSHeart failure was induced by isoproterenol and rats were randomly divided into metoprolol group (50 mg/kg twice daily/gavage, n = 11), combined treatment group (fenoterol 125 microg/kg and metoprolol 50 mg/kg twice daily/gavage, n = 11) and placebo group (saline, n = 10), another normal 9 male Wistar rats served as control group. After 8 weeks' treatment, cardiac function, apoptosis index (AI), Caspase-3 activity, expression levels of bcl-2 and bax protein, organ weight/body weight and collagen volume fraction (CVF) were evaluated.

RESULTS(1) Left ventricular end diastolic dimension, left ventricular end systolic dimension and E/A ratio were significantly increased and fractional shortening, ejection fraction significantly reduced post isoproterenol (all P < 0.05 vs. control) and these changes were significantly attenuated by metoprolol alone (all P < 0.05 vs. placebo) and further attenuated by the metoprolol and fenoterol combination therapy (all P < 0.05 vs. placebo and metoprolol). (2) Left ventricular weight to body weight ratio, lung weight to body weight ratio and CVF were also significantly reduced in metoprolol and combined treatment group than those in placebo group (all P < 0.01). (3) Compared with placebo group, AI and Caspase-3 activity were significantly lower in metoprolol group (all P < 0.01 vs. placebo) and further reduced in combined treatment group (all P < 0.01 vs. metoprolol). (4) The expression level of bax protein was significantly lower in metoprolol group while bcl-2/bax significantly higher than those in placebo group. These changes were more significant in combined treatment group (all P < 0.01 vs. metoprolol).

CONCLUSIONSbeta(1)AR antagonist in combination with beta(2)AR agonist further improved the cardiac function and prevented cardiac remodeling compared with using beta(1)AR antagonist alone in heart failure rats. Downregulated bax and upregulated bcl-2/bax expressions might contribute to the observed beneficial therapy effects by reducing cardiomyocyte apoptosis in these animals.

Adrenergic beta-1 Receptor Antagonists ; Adrenergic beta-2 Receptor Agonists ; Adrenergic beta-Agonists ; pharmacology ; therapeutic use ; Adrenergic beta-Antagonists ; pharmacology ; therapeutic use ; Animals ; Apoptosis ; drug effects ; Drug Therapy, Combination ; Heart Failure ; drug therapy ; Male ; Myocytes, Cardiac ; cytology ; Rats ; Rats, Wistar ; Ventricular Remodeling

To evaluate the effects of left ventricular contractility on the changes of average image intensity (AII) of the myocardial integrated backscatter (IB) and cyclic variation in IB (CVIB), 7 adult mongrel dogs were studied. The magnitude of AII and CVIB were measured from myocardial IB carves before and after dobatamine or propranolol infusion. Dobutamine or propranolol did not affect the magnitude of AII (13.8 +/- 0.7 vs 14.7 +/- 0.5, P > 0.05 or 14.3 +/- 0.5 vs 14.2 +/- 0.4, P > 0.05). However, dobutamine produced a significant increase in the magnitude of CVIB (6.8 +/- 0.3 vs 9.5 +/- 0.6, P < 0.001) and propranolol induced significant decrease in the magnitude of CVIB (7.1 +/- 0.2 vs 5.2 +/- 0.3, P < 0.001). The changes of the magnitude of AII and CVIB in the myocardium have been demonstrated to reflect different myocardial physiological and pathological changes respectively. The alteration of contractility did not affect the magnitude of AII but induced significant change in CVIB. The increase of left ventricular contractility resulted in a significant rise of the magnitude of CVIB and the decrease of left ventricular contractility resulted in a significant fall of the magnitude of CVIB.
Adrenergic beta-Agonists ; pharmacology ; Adrenergic beta-Antagonists ; pharmacology ; Animals ; Coronary Circulation ; Dobutamine ; pharmacology ; Dogs ; Echocardiography ; methods ; Hemodynamics ; drug effects ; Myocardial Contraction ; drug effects ; physiology ; Propranolol ; pharmacology ; Systole ; Ventricular Function, Left ; physiology

Effects of beta-adrenergic blockers and related agents were investigated on experimental convulsions of chicks induced with strychnine, pentylenetetrazol or electroshock and on thiopental sleeping time of rabbits. Convulsions of chicks due to strychnine were significantly inhibited by all beta-adrenergic blockers except dichloroisopreterenol. Propranolol inhibited electroshock convulsion as well, but none of the blockers inhibited pentylenetetrazol convulsion. Furthermore, the mortality of chicks due to large dose of pentylenetetrazol was greatly increased by treatment of beta-adrenergic blockers. Pindolol alone showed diazepam-like anticonvulsive effect against low doses of pentylenetetrazol. Pretreatment with beta-adrenergic blockers caused a marked increase in thiopental sleeping time in rabbits. Prolongation of thiopental sleep due to propranolol was abolished by premedication of animals with reserpine or tranylcypromine. Thiopental sleeping time was prolonged by Zizyphus extract, though less effective than beta-adrenergic blockers. It is felt that the anticonvulsive or sleep enhancing effect of beta-adrenergic blocking agents has an intimate relationship with endogenous adrenergic amines and the receptors.
Adrenergic beta-Antagonists/pharmacology* ; Anesthesia ; Animal ; Anticonvulsants* ; Blood Pressure/drug effects ; Chickens ; Convulsions/chemically induced ; Heart Rate/drug effects ; Male ; Propranolol/pharmacology* ; Rabbits ; Strychnine/antagonists & inhibitors ; Thiopental

AIMTo investigate the role of overexpression of beta2-adrenoceptor on contraction in cardiac myocytes isolated from failure hearts of rats and primarily analyses its mechanisms.

METHODSPrimarily cultured cardiac myocytes were infected with adenovirus containing the sequence for human beta2-adrenoceptors. The expression of beta2-adrenoceptors was tested by Western blot. The contraction amplitudes induced by isoprenaline stimulation were measured.

RESULTSOverexpression of beta2-adrenoceptor increased the content in failure cardiac myocytes. The contraction amplitudes in failure cardiac myocytes were lower than that in the control (P < 0.01). Overexpression of beta2 adrenoceptor improved the contraction of failure cardiac myocytes (P < 0.01, Failure+ Adv.Beta2 group vs. Failure group). Selective beta2-adrenoceptor antagonist ICI 118,551 partially reversed the effects (P < 0.05, Failure+ Adv.beta2 + ICI group vs Failure + Adv.beta2 group), but the contraction amplitudes in this Failure +/- Adv.beta2 + ICI 118,551 group were still higher than that in only heart failure group (P < 0.05). Selective beta1 adrenoceptor antagonist CGP20712A completely inhibited the effects of overexpression of beta2 adrenoceptor on contraction amplitude in failure cardiac myocytes.

CONCLUSIONOverexpression of beta2-adrenoceptors improves the contraction of cardiac myocytes isolated from failure hearts of rats. The effect is related to beta1-adrenoceptor.

Adenoviridae ; genetics ; Adrenergic beta-Antagonists ; pharmacology ; Animals ; Cells, Cultured ; Heart Failure ; metabolism ; physiopathology ; Humans ; Imidazoles ; pharmacology ; Isoproterenol ; pharmacology ; Male ; Myocardial Contraction ; Myocytes, Cardiac ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Adrenergic, beta-2 ; genetics ; metabolism

This study is to explore the possible mechanisms of the antidepressant-like effect of agmatine. By using two traditional "behavior despair" model, tail suspension test and forced swimming test, we examined the effects of some monoamine receptor antagonists (including beta-adrenergic receptor antagonist propranolol, beta-adrenergic receptor antagonist/5-HT1A/1B receptor antagonist pindolol, alpha2-adrenergic receptor antagonists yohimbine and idazoxan and 5-HT3 receptor antagonist tropisetron) on the antidepressant-like action of agmatine in mice. Activity of adenylate cyclase (AC) in the synapse membrane from rat frontal cortex was determined by radioimmunoassay. Single dose of agmatine (5-40 mg x kg(-1), ig) dose-dependently decrease the immobility time in tail suspension test in mice, indicating an antidepressant-like effect. The effect of agmatine (40 mg x kg(-1), ig) was antagonized by co-administration of beta-adrenergic receptor antagonist/5-HT1A/1B receptor antagonist pindolol (20 mg x kg(-1), ip), alpha2-adrenergic receptor antagonists yohimbine (5-10 mg x kg(-1), ip) or idazoxan (4 mg x kg(-1), ip), but not beta-adrenergic receptor antagonist propranolol (5-20 mg x kg(-1), ip) and 5-HT3 receptor antagonist tropisetron (5-40 mg x kg(-1), ip). Agmatine (5-40 mg x kg(-1), ig) also dose-dependently decrease the immobility time in forced swimming test in mice. The effect of agmatine (40 mg x kg(-1), ig) was also antagonized by pindolol (20 mg x kg(-1), ip), yohimbine (5-10 mg x kg(-1), ip), or idazoxan (4 mg x kg(-1), ip). Incubation of agmatine (0.1-6.4 micromol x L(-1)) with the synaptic membrane extracted from rat frontal cortex activated the AC in a dose-dependent manner in vitro. While the effect of agmatine (6.4 micromol x L(-1)) was dose-dependently antagonized by pindolol (1 micromol x L(-1)) or yohimbine (0.25-1 micromol x L(-1)). Chronic treatment with agmatine (10 mg x kg(-1), ig, bid, 2 w) or fluoxetine (10 mg x kg(-1), ig, bid, 2 w) increased the basic activity, as well as the Gpp (NH)p (1-100 micromol x L(-1)) stimulated AC activity in rat prefrontal cortex. These results indicate that regulation on 5-HT1A/1B and alpha2 receptors, and activation AC in the frontal cortex is one of the important mechanisms involving in agmatine's antidepressant-like action.
Adenylyl Cyclases ; metabolism ; Adrenergic alpha-Antagonists ; pharmacology ; Adrenergic beta-Antagonists ; pharmacology ; Agmatine ; administration & dosage ; pharmacology ; Animals ; Antidepressive Agents ; administration & dosage ; pharmacology ; Behavior, Animal ; drug effects ; Depression ; metabolism ; physiopathology ; Dose-Response Relationship, Drug ; Fenclonine ; pharmacology ; Idazoxan ; pharmacology ; Male ; Mice ; Pindolol ; pharmacology ; Random Allocation ; Rats ; Rats, Wistar ; Receptors, Biogenic Amine ; antagonists & inhibitors ; Serotonin 5-HT1 Receptor Antagonists ; Swimming ; Synapses ; enzymology ; Yohimbine ; pharmacology

BACKGROUNDStimulation of the heart beta 3-adrenoceptor (AR) may result in a negative inotropic effect. Being up-regulated, beta 3-AR plays a more important role in the regulation of cardiac function during heart failure. However, the effect of chronic blocking of beta 3-AR on heart failure has not been fully elucidated. In this study, we used a selective beta 3-AR antagonist SR59230A to treat a well defined heart failure rat model chronically, then evaluated its effect on cardiac function and investigated the mechanism.

METHODSMale Wistar rats were chosen randomly as controls (n = 8). Isoproterenol induced heart failure rats were randomly divided into ISO group (n = 10) and SR group (n = 10). The ISO group received intraperitoneal injection of 1 ml saline twice a day; the SR group received intraperitoneal injection of SR59230A 85 nmol in 1 ml saline twice a day; and the control group received no treatment. The treatment was started 24 hours after the last isoproterenol injection and continued for 7 weeks. Then we measured the following indexes: the ratio of heart weight to body weight (HW/BW) and the ratio of left ventricular weight to body weight (LVW/BW), collagen volume fraction (CVF), left ventricular end diastolic dimension (LVEDd), left ventricular end systolic dimension (LVESd), ejection fraction (EF), fractional shortening (FS) and the ratio of E wave to A wave (E/A), the mRNA and protein expression of beta 3-AR and eNOS, and cGMP level in the heart.

RESULTSThe ratios HW/BW and LVW/BW were significantly increased in the ISO group compared with the control group (P < 0.01), but they were limited in the SR group (P < 0.05 compared with the ISO group). CVF increased in the ISO group and the SR group (P < 0.01), but it was significantly attenuated in the SR group (P < 0.01). LVEDd, LVESd and E/A ratio were significantly increased in the ISO group compared with the control group (P < 0.01), while EF and FS were significantly decreased (P < 0.01). Compared with the ISO group, the SR group showed that LVEDd, LVESd and E/A ratio were significantly decreased (P < 0.01), whereas EF and FS were significantly increased (P < 0.01). beta(3)-AR and eNOS mRNA and protein in the ISO group were significantly increased when compared with the control group (P < 0.01). These increases were all attenuated in the SR group compared with the ISO group (P < 0.01). The level of cGMP in myocardial tissue was significantly increased in the ISO group compared with the control group (P < 0.01), whereas SR59230A treatment normalized this increment (P < 0.01).

CONCLUSIONSChronic blocking of beta 3-AR could ameliorate cardiac function in heart failure rats and its mechanism involves inhibition of the negative inotropic effect and attenuation of cardiac remodeling.

Adrenergic beta-3 Receptor Antagonists ; Adrenergic beta-Antagonists ; pharmacology ; therapeutic use ; Animals ; Blotting, Western ; Disease Models, Animal ; Echocardiography ; Enzyme-Linked Immunosorbent Assay ; Heart Failure ; drug therapy ; physiopathology ; Male ; Myocardium ; pathology ; Nitric Oxide Synthase Type III ; genetics ; Propanolamines ; pharmacology ; Rats ; Rats, Wistar ; Receptors, Adrenergic, beta-3 ; physiology ; Reverse Transcriptase Polymerase Chain Reaction ; Ventricular Function, Left ; drug effects

Adrenergic beta-Antagonists ; pharmacology ; Animals ; Cardiopulmonary Resuscitation ; Diastole ; drug effects ; Female ; Male ; Natriuretic Peptide, Brain ; blood ; Propanolamines ; pharmacology ; Rabbits ; Ventricular Function, Left ; drug effects

OBJECTIVETo compare the effects of carvedilol, metoprolol and propranolol on myocardial gap junction (GJ) structure in rat with myocardial ischemia and reperfusion injury.

METHODSRats were divided randomly into five groups: sham operation group (SO), myocardial ischemia and reperfusion group (IR), IR + carvedilol group (CV), IR + metoprolol group (MT), and IR + propranolol group (PP). The left anterior descending branch was ligated for 30 minutes and reperfused for 4 hours (IR). After 4 h reperfusion, the distribution and composition of gap junctional connexin 43 (CX43) were observed by immunofluorescence and laser scanning confocal microscopy (LSCM), and the quantification of CX43 was measured by LSCM.

RESULTCompared with SO group, IR resulted in abnormal distribution and composition of CX43-GJ and the impairment of CX43-GJ was significantly attenuated by CV, MT and PP treatments with the best effect observed in CV group (P<0.05 vs. MT and PP).

CONCLUSIONThese results suggest that beta-blockers, especially, carvedilol, could significantly attenuate IR induced CX43-GJ impairment.

Adrenergic beta-Antagonists ; pharmacology ; Animals ; Connexin 43 ; metabolism ; Disease Models, Animal ; Gap Junctions ; drug effects ; Male ; Myocardial Reperfusion Injury ; Myocardium ; metabolism ; Rats ; Rats, Sprague-Dawley