STUDIES ON VERATRUM ALKALOIDS. XXXV. THE EFFECT OF VERATRAMINE ON RESPONSES OF SPONTANEOUSLY BEATING GUINEA-PIG ATRIUM PREPARATIONS TO EPINEPHRINE

¹ Department of Pharmacology, Harvard Medical School, Boston, Massachusetts

Epinephrine, 0.01 to 40.0 µg/ml, caused positive chronotropic responses of isolated guinea-pig atrium preparations.

Pretreatment of the preparations with veratramine, 0.1 to 0.8 µg/ml, for 1 hour or more did not affect the height of the response to epinephrine at 32°C, but the effect of the latter drug was less well maintained. At 37°C, veratramine, 0.2 to 0.4 µg/ml, sufficient to cause marked reductions in rate, reduced the peak height of the response to epinephrine, as well as impairing its maintenance.