Abstract
This study is concerned with the mechanism of the inhibition of the tyramine action by reserpine.
It was found that, when the injection of reserpine in cats was preceded by nialamide, the effects of tyramine on blood pressure, cardiac contractility and coatractions of the nictitating membrane were not inhibited but cardiac norepinephrine was reduced. Effects of sympathetic stimulation on heart and nictitating membrane were also diminished. Following a single injection of reserpine the effects of tyramine returned to nornial within 7 days in spite of significantly diminished concentrations of cardiac norepinephrine.
On the basis of these results it is concluded that tyramine acts on receptors which are blocked by reserpine and differ from the norepinephrine receptors. It is suggested that the present classification of sympathomimetic amines as directly and indirectly acting agents needs modification in view of the uncertain mode of action.
Footnotes
- Received October 21, 1963.
- Accepted December 23, 1963.
- The Williams & Wilkins Company
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