TY - JOUR
T1 - Direct cardiac stimulation by arginine vasotocin in bullfrogs (Rana catesbeiana)
AU - Sham, J. S.K.
AU - Sawyer, W. H.
AU - Pang, P. K.T.
PY - 1989
Y1 - 1989
N2 - The antidiuretic and vasopressor effects of arginine vasotocin (AVT) in bullfrogs have been well documented. However, the direct cardiac stimulatory effects of AVT have not been previously reported. We found that AVT stimulates significant increases in heart rate, pulse pressure, and the maximal time derivative of ventricular pressure in anesthetized bullfrogs after the β-adrenergic and muscarinic receptors in the heart were blocked by atropine and propranolol. In spontaneously beating isolated frog atria, AVT increased the beating rate by 20% and the contractile force by 100%. The inotropic effect of AVT was also demonstrated in electrically driven atria and ventricles. Propranolol was ineffective in blocking these cardiac responses in vitro. The Hill coefficients of the concentration-response curves did not differ from unity. In conclusion, AVT possesses both positive chronotropic and inotropic effects in bullfrogs, Rana catesbeiana, probably by direct stimulation of its specific receptors in the heart.
AB - The antidiuretic and vasopressor effects of arginine vasotocin (AVT) in bullfrogs have been well documented. However, the direct cardiac stimulatory effects of AVT have not been previously reported. We found that AVT stimulates significant increases in heart rate, pulse pressure, and the maximal time derivative of ventricular pressure in anesthetized bullfrogs after the β-adrenergic and muscarinic receptors in the heart were blocked by atropine and propranolol. In spontaneously beating isolated frog atria, AVT increased the beating rate by 20% and the contractile force by 100%. The inotropic effect of AVT was also demonstrated in electrically driven atria and ventricles. Propranolol was ineffective in blocking these cardiac responses in vitro. The Hill coefficients of the concentration-response curves did not differ from unity. In conclusion, AVT possesses both positive chronotropic and inotropic effects in bullfrogs, Rana catesbeiana, probably by direct stimulation of its specific receptors in the heart.
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M3 - Article
C2 - 2783536
AN - SCOPUS:0024529465
SN - 0002-9513
VL - 256
SP - 25/1
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 1
ER -