| 1. |
- Bodelsson, Mikael, et al.
(författare)
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Cooling augments contractile response to 5-hydroxytryptamine via an endothelium-dependent mechanism
- 1989
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Ingår i: Blood Vessels. - 0303-6847. ; 26:6, s. 347-359
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Tidskriftsartikel (refereegranskat)abstract
- The interaction between cooling and vasoactive substances, e.g. 5-hydroxytryptamine (5-HT), plays an important role in the pathophysiology of cold-induced vasospasm. Our objective was to study the effect of cooling on the 5-HT vascular response, classify the involved 5-HT receptors, and to analyze the role of the endothelium. Ring segments from the rat jugular vein, a preparation without alpha-adrenergic receptors, were suspended in organ baths to record the circular motor activity. The temperature was initially 37 degrees C and was thereafter either continuously lowered to 10 degrees C or kept constant at different temperatures within this range. 5-HT at low concentrations (10(-11) to 3 x 10(-8) M) induced relaxation at 37 degrees C in segments precontracted by prostaglandin F2 alpha. The relaxation was recognized to be mediated via an endothelium-dependent 5-HT1-like receptor mechanism presumably involving the release of endothelium-derived relaxing factor (EDRF). Cooling to 29 and 20 degrees C diminished the relaxation, probably due to an attenuated release of EDRF. 5-HT at concentrations of more than 10(-8) M induced a contraction in all vessels at 37 degrees C mediated via a 5-HT2 receptor. An increased 5-HT-induced contraction was seen at temperatures below 37 degrees C in vessels with an intact endothelium. Endothelial denudation diminished the cold-induced enhancement of the contraction to 5-HT. These studies suggest that endothelial mechanisms contribute to a cold-induced augmented response to 5-HT.
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| 2. |
- Hardebo, Jan Erik, et al.
(författare)
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Endothelin is a potent constrictor of human intracranial arteries and veins
- 1989
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Ingår i: Blood Vessels. - 0303-6847. ; 26:5, s. 249-253
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Tidskriftsartikel (refereegranskat)abstract
- Endothelin, a peptide produced in endothelial cells, was found to be a potent constrictor of human pial arteries through a direct, slow action on the smooth muscle cell, with a pD2 value of 8.54. It was less potent as a constrictor in pial veins (pD2 7.80) and in branches of the middle meningeal artery and superficial temporal artery (pD2 7.61 and 7.77). The major component of the contractile response in the arteries comprises an effect on potential-operated calcium channels, as evidenced by tests with nimodipine. Endothelin may regulate intracranial vessels tonically during physiological as well as pathophysiological conditions.
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| 3. |
- Johansson, B, et al.
(författare)
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Responses of smooth muscle to quick load change studied at high time resolution
- 1978
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Ingår i: Blood Vessels. - 0303-6847. ; 15:1-3, s. 65-82
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Tidskriftsartikel (refereegranskat)abstract
- Quick-release and quick-stretch experiments have been performed on preparations of smooth muscle from rat portal vein and rabbit urinary bladder. The low equivalent mass of the isotonic lever (8 mg) implied that inertial oscillations were limited to the first 5-10 msec after the load step. The high time resolution achieved in this way enabled us to separate three components in the length response to a step change in force: (1) an immediate passive elastic recoil, (2) an isotonic velocity transient lasting 50-75 msec and (3) shortening of the contractile element after its full adjustment to the new load. The maximal series elastic recoil was about 10% of the total muscle length in portal vein but only some 3% in urinary bladder. Stiffness of series elasticity increased in proportion to force and was about 3 times higher in bladder than in portal vein at any force level. Force-velocity relations for loads less than Po could be fitted to Hill's equation; Vmax in 4 AC-stimulated portal veins was 0.53 +/- 0.03 muscle lengths/sec and in 8 K+-activated bladder preparations 0.18 +/- 0.01 muscle lengths/sec. Application of loads greater than Po produced rates of lengthening greater than expected from an extrapolation of Hill's hyperbola. The nature of the transient component is discussed in the light of recent studies of force and velocity transients in skeletal muscle.
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| 4. |
- Owman, Christer
(författare)
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Peptidergic vasodilator nerves in the peripheral circulation and in the vascular beds of the heart and brain
- 1990
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Ingår i: Blood Vessels. - 0303-6847. ; 27:2-5, s. 73-93
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Tidskriftsartikel (refereegranskat)abstract
- This overview focusses on the ubiquitous presence of immunohistochemically visible peptidergic nerves with vasodilatory function. The nerve fibres are primarily related to the parasympathetic system (vasoactive intestinal polypeptide or VIP), the sympathetic system including the adrenal medulla (enkephalins) and to the sensory system (substance P as well as calcitonin gene-related peptide, CGRP). Substance P and probably also CGRP seem to be the mediators of antidromic vasodilatation. Enkephalins appear to be released both from nerve endings and from the adrenomedullary cells. The vasodilatory nerve fibres in the heart distribute both to the coronary vessels and to functionally important parts of the myocardium, where interesting relations exist between the peptidergic flow regulation and contractile force. In the brain the sensory and parasympathetic pathways for VIP and substance P/CGRP have recently been mapped in detail, and a new peptidergic intracranial ganglion has been discovered. The selective electrical stimulation of the sensory and postganglionic parasympathetic fibres, respectively, in the brain circulation has been found to evoke a pronounced flow increase which does not appear to involve cholinergic mediation. There is also experimental evidence that the mentioned systems of fibres may interact with each other and with the sympathetic nervous system by way of neuronal cross-talk.
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| 5. |
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