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  • 1
    ISSN: 1432-1912
    Keywords: SHR ; Captopril ; Noradrenaline ; Sympathetic nerve stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the attenuation by captopril of sympathetic neurotransmission in spontaneously hypertensive rats. Captopril (4 mg/kg for 15–17 days or 20 mg/kg for 4 days) was delivered i.v. by osmotic minipump. The higher dose lowered blood pressure, the lower dose did not. Both doses inhibited converting enzyme activity. In the pithed rat, both doses attenuated responses to exogenous noradrenaline and sympathetic nerve stimulation. In isolated tail arteries removed from captopril-treated rats, responses to sympathetic nerve stimulation and exogenous noradrenaline were the same as in controls. Perfusion of the tail artery of control rats with captopril, angiotensin I or angiotensin II had no effect on basal perfusion pressure or on vasoconstriction induced by exogenous noradrenaline or sympathetic nerve stimulation. Our results are consistent with the hypothesis that: 1. the attenuation of sympathetic neurotransmission by captopril depends upon the presence of an intact renin-angiotensin system, and 2. captopril has no direct postsynaptic effect in the isolated tail artery preparation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1912
    Keywords: Nicardipine ; α-Adrenoceptor agonists ; SHR ; Ganglionic blocking agent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Differences in the degree of attenuation by the calcium entry blocker, nicardipine, of the pressor responses to α-1 (phenylephrine) and α-2 (UK 14.304) adrenoceptor agonists was investigated in pentobarbital-anesthetized, normotensive Sprague-Dawley (SD) or Wistar Kyoto (WKY) rats, and spontaneously hypertensive rats (SHR), treated with the ganglionic blocking agent, pentolinium. Following administration of the ganglionic blocking agent, pentolinium, nicardipine produced a significant fall in blood pressure in SHR but not in SD or WKY rats. Nicardipine had no effect on the basal blood pressure of pithed SHR. In rats treated with the ganglionic blocking agent, pentolinium, nicardipine produced parallel shifts to the right in the doseresponse curves for phenylephrine but had no effect on maximal responses to phenylephrine. The decrease in the ED50 of phenylephrine was greater in the SHR than in normotensive rats. Nicardipine produced a decrease in both the ED so and the maximal response to the α-2 adrenoceptor agonist, UK 14.304. The decrease in the maximal response was greater in SHR than in WKY normotensive rats but the change in ED50 for UK 14.304 was greater in WKY than in SHR. SD normotensive rats gave intermediate results. We conclude that the inhibition of α-adrenoceptor-mediated pressor responses by nicardipine is generally more pronounced in SHR than in normotensive rats. This suggests that hypertension may be accompanied by an increase in the sensitivity of peripheral resistance beds to calcium entry blockers.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 334 (1986), S. 37-39 
    ISSN: 1432-1912
    Keywords: Rat ; Tail artery ; Noradrenaline ; Electrical stimulation ; Ageing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied vasoconstrictor responses to noradrenaline and electrical field stimulation in the isolated perfused/superfused tail arteries of rats of 6–7, 16–17 and 30–31 months of age. Maximal vasoconstrictor responses to noradrenaline were the same at all three ages. Sensitivity to noradrenaline and to electrical stimulation were reduced in the 16–17 and 30–31 month old rats. The noradrenaline content of the arteries of the two latter age groups was reduced. We conclude that ageing in this resistance vessel is accompanied by a decrease in the arterial noradrenaline content and in the sensitivity of the artery to noradrenaline.
    Type of Medium: Electronic Resource
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