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  • 1
    Electronic Resource
    Electronic Resource
    ELECTROPHYSIOLOGICAL PROPERTIES OF THE RAT MIDDLE CEREBRAL ARTERY AT DIFFERENT LEVELS OF PASSIVE WALL TENSION (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 22 (1995), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Simultaneous measurements of intracellular membrane potential and myogenic tone of proximal segments of the rat middle cerebral artery, mounted in a small vessel myograph, were made at two levels of passive wall tension.2. At low levels of passive tension (less than 0.25mN/mm) vessels had a resting membrane potential of approximately -65mV. Addition of KCl (5–60 mmol/L), BaCl2 (0.01–3 mmol/L) or tetraethylammonium (TEA; 0.1–3 mmol/L) resulted in a concentration-dependent depolarization, to approximately—40 mV, generally associated with a contractile response. After the application of high levels of passive tension (to approximately 2mN/mm maximum) the resting membrane potential of the smooth muscle cells was—40 to—45 mV. This more positive membrane potential was generally associated with an increase in myogenic tone of the vessel. Under these conditions, addition of 5–20 mmol/L KCl resulted in a strong hyperpolarization of the cell along with a concomitant decrease in myogenic tone of the artery. The hyperpolarization and vasorelaxation induced by KCl (5–20 mmol/L) were blocked by BaCl2 (0.5–1 mmol/L).3. While the addition of ryanodine (10 μmol/L) to vessels under low tension had no effect, when added to a vessel under high tension, this agent caused a rhythmic oscillation in membrane potential. This oscillation was augmented by BaCl2 (1mmol/L) and inhibited by nifedipine (10nmol/L) and 4-aminopyridine (1 mmol/L).4. This study suggests that the electrophysiological and mechanical properties of the isolated rat middle cerebral artery depend on the passive resting conditions under which the vessel is studied. The depolarization of membrane potential observed with increased passive tension appears to result from the closure of an inward rectifying K+ channel. These results indicate that the inward rectifying K+ channel plays an important role in regulating vascular reactivity due to its functional dependence on the mechanical status of the blood vessel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1995.tb01926.x
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  • 2
    Electronic Resource
    Electronic Resource
    Spasmolytic effect of cromakalim in dog coronary artery in vitro (1991)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 343 (1991), S. 519-524 
    Details
    ISSN: 1432-1912
    Keywords: Cromakalim ; K+ channels ; Dog coronary artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Isometric force development was measured in isolated ring segments of dog left anterior descending coronary artery to K+ (10–70 mM), U-46619 (0.3–30 nM), endothelin-1 (0.1–30 nM), 5-HT (0.1–30 μM) and angiotensin-II (0.1–30 nM), Compared with the maximum tissue response to a K+ depolarizing solution (100%) there was a marked variation in the maximum response to each spasmogen: K+ (111%), U-46619 (85%), endothelin-1 (48%), 5-HT (49%) and angiotensin-II (15%). In arteries pretreated with cromakalim (0.3–10 μM) the maximum response to all constrictor agents (with the exception of K+) was reduced but the potency was unaffected. Maximum responses to angiotensin-II and 5-HT were affected at concentrations approximately threefold lower than those to endothelin-1 and U-46619. Removal of the endothelium increased the maximum response caused by 5-HT and reduced the potency of cromakalim in inhibiting this contraction. Glyceryl trinitrate and sodium nitroprusside were 100–1000 times more potent than cromakalim although they produced qualitatively similar effects. Cromakalim is an effective spasmolytic against a number of vasoconstrictors in the dog coronary artery. No marked spasmogen selectivity could be identified for Comakalim that was not shown by glyceryl trinitrate or sodium nitroprusside.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169555
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    Paper (German National Licenses)
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