EFFECTS OF CARNITINE ON THE SPONTANEOUS CONTRACTION AND THE TRANSMEMBRANE POTENTIALS OF THE ISOLATED RABBIT’S ATRIA

Abstract

The effects of carnitine methylester and carnitine chloride on the spontaneous contraction and the transmembrane potential were studied in the isolated rabbit''s atria. The results are summarized as follows: Higher doses of carnitine methylester decreased the rate and amplitude of the spontaneous atrial contraction and shortened the duration and repolarization time of the action potential without affecting the height of the resting and action potentials. The intensity of the effects of carnitine methylester corresponded with about 1/10,000 dose of ACh [acetycholine]. These effects of carnitine methylester were slightly potentiated by the pre-treatment with eserine and were blocked by atropine. The cholinergic effects of carnitine chloride were weaker than those of carnitine methylester. Higher doses of carnitine chloride sometimes increased the atrial rate. The pre-treatment with carnitine methylester or carnitine chloride antagonized the negative inotropic and chronotropic responses and the shortening of the duration of the action potential caused by ACh.