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The effects of nicotinamide (Nic) on cardiac contraction force and on slow inward current (Isi) in guinea pigs were studied with atrial strips and voltage clamp techniques. Verapamil (Ver), MnCl2, nifedipine (Nif), and propranolol (Pro) depressed markedly the positive inotropic effect induced by Nic in a noncompetitive manner. The pD2 values of Ver, MnCl2, Nif, and Pro were 6.19, 3.41, 5.00, and 6.43, respectively. The action of Nic was reduced by a low Ca2+ Tyrode solution and disappeared in a Ca(2+)-free solution. Nic 33 mmol.L-1 elevated the Isi from 6.5 +/- 1.3 microA to 10.3 +/- 2.2 microA. The results suggest that Nic promotes the Ca2+ influx and its site of action is different from that of both Pro and the calcium antagonists.
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
January 1971,
Pflugers Archiv : European journal of physiology,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
March 1975,
The Journal of general physiology,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
January 1985,
The American journal of cardiology,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
June 1980,
The Journal of physiology,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
March 1989,
Zhongguo yao li xue bao = Acta pharmacologica Sinica,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
September 1978,
The Journal of physiology,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
February 1988,
Cardiovascular research,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
January 1993,
Yao xue xue bao = Acta pharmaceutica Sinica,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
January 1972,
Pflugers Archiv : European journal of physiology,
X M Mao, and
D M Li, and
C M Zhou, and
X W Wang, and
K J Zhang
March 1985,
Naunyn-Schmiedeberg's archives of pharmacology,
