Stephen T. O'Rourke

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The large-conductance, calcium-activated potassium channels (BK, also termed BK(Ca), Slo, or MaxiK) distributed in both excitable and non-excitable cells are involved in many cellular functions such as action potential repolarization; neuronal excitability; neurotransmitter release; hormone secretion; tuning of cochlear hair cells; innate immunity; and(More)
The present study was designed to determine if endogenous calcitonin gene-related peptide (CGRP) affects the process of nitrate tolerance development in blood vessels. Rat aortic rings were suspended in organ chambers and relaxations to nitroglycerin (10(-9) -10(-6) M) were obtained in nitrate tolerant and nontolerant rings contracted with norepinephrine(More)
Angiotensin II (ANG II) increases GABA(B) receptor expression in neuronal cultures from the nucleus tractus solitarii (NTS). In the present study, the chronic effects of ANG II on GABA(B) receptor expression and activity were examined in the NTS of Sprague-Dawley rats. Intracerebroventricular infusion of ANG II caused a significant elevation in blood(More)
The bioassay technique was utilized to quantitate endothelium-derived relaxing factor (EDRF) released from perfused donor segments of control and diabetic rat aorta. In the presence of indomethacin, perfusates of donor segments with endothelium were allowed to superfuse recipient detector rings of normal rat aorta without endothelium. Under basal(More)
Experiments were designed to characterize pre- and postjunctional muscarinic receptors in the canine saphenous vein. In rings contracted by 2-Hz electrical stimulation, acetylcholine produced concentration-dependent relaxations that result from prejunctional inhibition of norepinephrine release from adrenergic nerve endings (prejunctional effect). In(More)
(1) The present study was designed to test the hypothesis that melatonin inhibits nitrate tolerance in coronary arteries. (2) Rings of porcine coronary arteries were suspended in organ chambers for isometric tension recording. Nitrate tolerance was induced by incubating the tissues with nitroglycerin (10(-4) M) for 90 min, followed by repeated rinsing for 1(More)
The peripheral apelin system plays a significant role in cardiovascular homeostasis and in the pathophysiology of cardiovascular diseases. However, the central effect of this neurohormonal system in neural control of cardiovascular function remains poorly understood. Thus, this study was undertaken to evaluate the effect of apelin in the rostral(More)
The effects of several potassium channel blockers on resting vasomotor tone were studied in porcine isolated coronary arteries. Coronary artery rings were suspended in organ baths for isometric tension recording. The nonselective potassium channel blockers tetraethylammonium (TEA 10(-5)-3 x 10(-2) M) and 4-aminopyridine (4-AP 10(-5)-10(-2) M) caused(More)
Increasing evidence indicates that both the angiotensin II (ANG II) and gamma-aminobutyric acid (GABA) systems play a very important role in the regulation of blood pressure (BP). However, there is little information concerning the interactions between these two systems in the nucleus tractus solitarii (NTS). In the present study, we examined the effects of(More)
Previous studies from our laboratory demonstrated that melatonin inhibits nitric oxide (NO)-induced relaxation in porcine coronary arteries. The present study was designed to further characterize the mechanisms underlying this inhibitory effect of melatonin. Western immunoblot studies identified the presence of melatonin type 2 (MT(2)) receptors, but not(More)