Chronotropic Effects of Norepinephrine and Tyramine

A System Response Analysis

Battersby, Edward J. M.D.
Newman, Elliot V. M.D.

Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee

Received for Publication January 10, 1964.

Circulation Research 15(2):p 112-123, August 1964.

An analog simulation of the chronotropic effects of norepinephrine and tyramine in the canine heart-lung preparation is presented. The temporal aspects of those responses are described in quantitative terms.

Reserpine produced deprivation suprasensitivity to norepinephrine may be considered as a corollary of the system response nonlinearity to that drug.

Discrepancies between tyramine rate responses and the relatively small amounts of norepinephrine released are resolved by the assumption that the receptor space for norepinephrine has a capacitative function and is not in free dilutional equilibrium with the perfusing blood. This mechanism would allow for a unitary explanation of tyramine action based upon competition with norepinephrine for available storage sites.