Analysis of changes in duration of action potential of myocardial cells during local anaphylactic reaction and in response to histamine in guinea pigs

Abstract

The dependence of the duration of the action potential (AP) on the frequency of spontaneous activity during the local anaphylactic reaction (antigen egg albumin, 2·10⁻⁴–2·10⁻⁵ g/ml) and in response to histamine (1·10⁻⁴–1·10⁻⁵ g/ml) was investigated on the right atrial auricle of guinea pigs under the following experimental conditions: in normal Tyrode solution, b) during blocking of the CA channels by verapamil (2–4 mg/liter) or D-600 (0.2–1 mg/liter) and c) during blocking of the potassium channels by tetraethylammonium (10–20 mM). Analysis of interspike interval versus AP during clots revealed a direct prolonged effect of the antigen and histamine on the duration of the AP plateau, which was masked by the positive chronotropic effect of these agents. Relative lengthening of AP took place over the whole range of frequencies. The results confirm the previous hypothesis of activation of the slow Na−Ca channels during the local anaphylactic reaction and in response to the action of histamine on the myocardium.