in asthmatic subjects there is a pronounced diurnal variation in bronchial responsiveness. if this phenomenon is due to variation in factors that control drug delivery, then it should be paralleled by a similar variation in competitive antagonist blockade. in order to study this possibility, we performed the methacholine challenge test and after 45 minutes, administered atropine by inhalation. ...

In asthmatic subjects there is a pronounced diurnal variation in bronchial responsiveness. If this phenomenon is due to variation in factors that control drug delivery, then it should be paralleled by a similar variation in competitive antagonist blockade. In order to study this possibility, we performed the methacholine challenge test and after 45 minutes, administered atropine by inhalat...

INTRODUCTION Heart rate turbulence is a powerful de novo risk predictor for patients surviving acute myocardial infarction. However, little is known about its underlying physiologic mechanism. METHODS AND RESULTS Hypothesizing that heart rate turbulence is barorceptor reflex related, we studied heart rate and blood pressure fluctuations at rest and after systematically introduced ventricular ...

The elasticity of the thoracic aorta was studied in nine dogs instrumented with a pressure microtransducer and two ultrasonic crystals diametrically fixed in the adventitia. Systolic and diastolic changes in pressure and diameter were used to calculate Peterson and incremental elastic moduli. Acute hypertension was induced by infusions of angiotensin performed 1) during the control period, 2) a...

OBJECTIVES In the present study, we evaluated sinus and atrioventricular (AV) node electrophysiology of endurance athletes and untrained individuals before and after autonomic pharmacologic blockade. BACKGROUND Endurance athletes present a higher prevalence of sinus bradycardia and AV conduction abnormalities, as compared with untrained individuals. Previous data from our laboratory suggest t...

Teff, Karen L., and Raymond R. Townsend. Early phase insulin infusion and muscarinic blockade in obese and lean subjects. Am. J. Physiol. 277 (Regulatory Integrative Comp. Physiol. 46): R198–R208, 1999.—The effect of early phase insulin on postprandial levels of insulin, C-peptide, glucose, and glucagon was investigated in lean (n 5 10) and obese (n 5 12) subjects. Subjects underwent four condi...

To investigate the effects of repeated atropine injection on heart rate (HR) variability in resting Thoroughbred horses, two microg/ kg of atropine as parasympathetic nervous blockade was injected intravenously every 6 min to a total of 8 microg/kg after intravenous administration of 0.2 mg/kg of propranolol as sympathetic nervous blockade. We recorded electrocardiograms and obtained the HR, th...

This study was designed to validate the measures of heart period variability for assessing of autonomic nervous system control in calves. Eight calves received an injection of either 0.5 mg/kg atenolol (sympathetic tone blockade), 0.2 mg/kg atropine sulfate (parasympathetic tone blockade), 0.5 mg/kg atenolol + 0.2 mg/kg atropine sulfate (double autonomic blockade) or saline. In the time-domain,...

To evaluate the neural regulation of postprandial somatostatin release we studied the effect of blockade of (a) alpha-adrenergic and beta-adrenergic and (b) cholinergic receptors on the plasma somatostatin, gastrin and insulin responses to a standard meal in two groups of five fasting healthy male volunteers. Thymoxamine (0.1 mg/kg iv over two minutes then 10 mg/hour for two hours) and proprano...

BACKGROUND Survival of post-myocardial infarction patients is related inversely to their levels of very-low-frequency (0.003 to 0.03 Hz) RR-interval variability. The physiological basis for such oscillations is unclear. In our study, we used blocking drugs to evaluate potential contributions of sympathetic and vagal mechanisms and the renin-angiotensin-aldosterone system to very-low-frequency R...