STUDIES ON VERATRUM ALKALOIDS

IX. The Inhibition by Veratrosine of the Cardioaccelerator Action of Epinephrine and of Norepinephrine

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

Veratrosine, a glycosidic Veratrum alkaloid, like its aglycone veratramine, antagonizes the cardioaccelerator action of epinephrine and norepinephrine in the isolated heart of the dog (HLP), in the dog and cat under anesthesia, and in the spinal cat.

The site of action is in the pacemaker of the heart. Atropine does not modify the effect.

While veratramine was shown to act abruptly reaching its maximal effect within three to five minutes, the full veratrosine effect of doses with equivalent potency requires a considerable time to develop, up to 50 minutes in the HLP and fifteen minutes or more in the intact circulation.

The vasopressor action and the positive inotropic action of epinephrine are not abolished by doses of veratrosine which annul the positive chronotropic action.

Restoration of competence in experimental heart failure by epinephrine with and without its positive chronotropic action has been demonstrated by the use of veratrosine.

Given intravenously in doses up to 0.3 mgm. per kgm. veratrosine, contrary to veratramine, has no convulsant properties. In dogs an inconsistent emetic action has been observed with this dose.