Drugs online research references
Arzneimittelforschung. 1986 Dec;36(12):1736-9.
Comparison of vasodilating effects of nisoldipine and nifedipine in anesthetized open-chest dogs.
Sakanashi M, Noguchi K, Kato T, Sunagawa R, Nagamine F, Nakasone J.
Hemodynamic effects of nisoldipine (Bay k 5552) were compared with those of nifedipine in anesthetized open-chest dogs. Both nisoldipine and nifedipine produced a fall in aortic pressure and increases in aortic, vertebral and coronary blood flows. After administration of nisoldipine, renal blood flow, heart rate and left ventricular enddiastolic pressure were not changed, but left ventricular dP/dt was increased. After administration of nifedipine, renal blood flow and left ventricular dP/dt were decreased, and left ventricular enddiastolic pressure was elevated. Heart rate was hardly changed. Durations of increases in aortic, vertebral and coronary blood flows were about 3 times longer after nisoldipine than after nifedipine. Percent decrease in coronary vascular resistance was greater and percent decrease in renal vascular resistance was smaller than that in total peripheral vascular resistance with both nisoldipine and nifedipine. Results indicate that nisoldipine and nifedipine produce marked coronary vasoldilation and the vasodilating effect of nisoldipine lasts longer than that of nifedipine.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3566835&dopt=Abstract
Eur J Pharmacol. 1985 Apr 2;110(2):241-6.
Further examination of the effects of ageing on the adrenoceptor responsiveness of the rat vas deferens.
Hyland L, Docherty JR.
Age-related changes in presynaptic alpha 2-adrenoceptors were investigated in prostatic and epididymal portions of vasa deferentia from young adult (2-3 months) and old (24-29 months) Sprague-Dawley rats, using the alpha 2-selective agonists xylazine and clonidine. In prostatic portions the inhibitory effects of clonidine against the isometric contractions to single pulse field stimulation were complicated by a postsynaptic action in old animals, but in epididymal portions in the presence of nifedipine both xylazine and clonidine were 3 times less potent in old rats. However, there were no significant differences between young and old in the potency of xylazine at inhibiting the overflow of tritium or the isometric contraction evoked by 5 Hz stimulation for 3 min in tissues pre-incubated with [3H]noradrenaline. It is suggested that there is reduced responsiveness of presynaptic alpha 2-adrenoceptors in the vas deferens of old rats, but that this can only be demonstrated using a sensitive measure of the presynaptic potency of agonists: the isometric contraction to a single stimulus.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=3987814&dopt=Abstract
Arch Int Pharmacodyn Ther. 1979 Oct;241(2):224-34.
Comparison of the in vitro effects of prazosin, nifedipine, and dihydralazine in isolated human mesenteric and crural vessels.
Pedersen OL, Mikkelsen E, Andersson KE.
The inhibitory and relaxing effects of prazosin, nifedipine, and dihydralazine on contractions induced by noradrenaline (NA), or potassium (K+), were investigated in isolated human crural and mesenteric arteries and veins. Vascular ring preparations were suspended in organ baths and isometric tension was recorded. Prazosin was the most potent of the drugs in counteracting NA-induced contractions in all types of vessels except crural veins, in which the effect of nifedipine was the more pronounced. On K+-induced contractions prazosin was completely devoid of relaxing or inhibitory effects, whereas nifedipine was by far the most effective of the investigated drugs. Nifedipine had a more marked effect in venous than in arterial preparations from the peripheral circulation, but no such difference was seen in mesenteric vessels. Dihydralazine was found to have a very low potency in all types of vessels, and no difference between the effects on arterial and venous preparations was found. The results suggest that the in vitro effects of prazosin, nifedpine, and dihydralazine are different from those observed in vivo. Thus, the balance between the effects on arteries and veins in vitro was quite different from those reported in clinical studies on the three vasodilatators. The results give no support to the hypothesis of an unspecific vasodilatating effect of prazosin. The clinical usefulness of dihydralazine cannot be explained from the poor in vitro effects of the unmetabolized drug.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=526077&dopt=Abstract
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