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Christophe Delaey, Johan Van de Voorde; Pressure-Induced Myogenic Responses in Isolated Bovine Retinal Arteries. Invest. Ophthalmol. Vis. Sci. 2000;41(7):1871-1875.
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purpose. To investigate whether a pressure-induced myogenic vasoconstriction can
be demonstrated in isolated bovine retinal arteries and to determine
the cellular mechanisms involved.
methods. Isolated bovine retinal arteries were mounted on a pressure myograph
without flow and exposed to stepwise increases in intraluminal
pressure. Changes in internal diameter were monitored continuously
using an inverted microscope video system.
results. Bovine retinal arteries showed myogenic tone at pressures higher than
10 mm Hg. This pressure-induced contraction was absent in calcium-free
Krebs–Ringer bicarbonate solution. Inhibition of L-type
voltage-operated calcium channels with nifedipine (1 μM) suppressed
the myogenic contraction. After depolarization of the vascular smooth
muscle cells with a K+ 120 mM solution, a pressure-induced
contraction was still observed, indicating that besides stimulation of
voltage-operated calcium channels, depolarization-independent
mechanisms contribute to the pressure-induced myogenic
conclusions. Isolated bovine retinal arteries spontaneously contract when exposed to
raised intraluminal pressure. This response depends on extracellular
calcium and is blocked by nifedipine. In addition,
depolarization-independent mechanisms seem to be
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