Donald Cheung

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The characteristics of the hyperpolarization response to acetylcholine (ACh) in endothelial cells from the guinea pig coronary artery were studied by microelectrode recording technique. ACh (30 nM to 3 microM) induced membrane hyperpolarization in a dose-dependent manner. The sustenance of the response required the presence of external calcium. The(More)
1. Intracellular electrodes were used to compare the electrical activity of smooth muscle cells from the longitudinal and circular layers of the rabbit duodenum and their responses to stimulation of the intramural nerves. 2. The longitudinal muscle cells had an average membrane potential of 52 mV when measured between slow waves. Spontaneous action(More)
1. The response of rat tail arteries to stimulation of perivascular nerves was studied with intracellular micro-electrodes. 2. E.j.p.s were recorded from all smooth muscle cells. With higher stimulus strength, a slow depolarization that lasted for more than 30 sec also appeared. Repetitive stimulation was more effective in eliciting this slow component than(More)
1. The tunica media of the proximal segments of the pulmonary vein is made up of cardiac muscle cells. The electrical activity of this cardiac portion of the pulmonary vein was studied with intracellular micro-electrodes in isolated preparations. 2. All-or-none action potentials were recorded in all cardiac muscle cells in response to electrical(More)
Acetylcholine (ACh) induces endothelium-dependent hyperpolarization in the rat mesenteric artery in the presence of the nitric oxide synthase inhibitor N omega-nitro-L-arginine. We have now studied the effects of K(+)-channel blockers on the hyperpolarization responses to ACh in resting and norepinephrine-contracted rat mesenteric arteries. We also measured(More)
Acetylcholine (ACh) induced hyperpolarization and relaxation in rat mesenteric arteries contracted with norepinephrine, as indicated from studies with simultaneous microelectrode and tension recordings. We tested whether the hyperpolarization to ACh was modified by induction and depletion of cytochrome P450 enzymes. Enzyme induction by treating the animals(More)
1. The frequency, amplitude and time course of spontaneous excitatory junction potentials (s.e.j.p.s) and their relationship to the time course and amplitude of evoked excitatory junction potentials (e.j.p.s) were examined. 2. The frequency and amplitude of s.e.j.p.s varied dramatically between cells. There was good correlation between their rise and decay(More)
Contraction of the guinea pig saphenous artery induced by stimulation of perivascular nerves consists of an adrenergic and a purinergic component. Neuropeptide Y (NPY) potentiated the neural responses significantly at low stimulation frequencies but not at high frequencies when the contraction was maximal. After blocking the adrenoceptors with phentolamine,(More)
Membrane rectification to depolarization was studied by voltage recording with patch electrodes in freshly isolated cells from the rat tail artery. Injection of depolarizing currents elicited electrotonic potentials that developed with a single-exponential time course (time constant of 94.8 ms). When the cell was depolarized beyond −30 mV, delayed(More)
Neuropeptide Y(NPY) inhibits Ca2+-activated K+ channels reversibly in vascular smooth muscle cells from the rat tail artery. NPY (200 μM) had no effect in the absence of intracellular adenosine 5′triphosphate (ATP) and when the metabolic poison cyanide-M-chlorophenyl hydrozone (10 μM) was included in the intracellular pipette solution. NPY was also not(More)