Electrical and mechanical activity of the longitudinal muscle of the anterior mesenteric artery of the domestic fowl

The electrical activity and changes in tension of the longitudinal muscle of the anterior mesenteric artery (LMAMA) of the domestic fowl were recorded simultaneously using the sucrose-gap method.2. Spontaneous activity consisted of recurring contractions each accompanied by a burst of action potentials.3. In quiescent preparations, brief electrical stimuli, acetylcholine, or barium chloride produced contractions with the appearance of action potentials. Larger concentrations of barium chloride or acetylcholine produced depolarization and action potentials ceased although contraction was maintained. Whenever depolarization without action potentials occurred, it was associated with a smooth contraction, whereas action potentials were always accompanied by small rapid contractions super-imposed upon the main contraction.4. When the tone was raised with barium chloride (and in the presence of hyoscine) continuous action potentials occurred; under these circumstances brief electrical stimuli or noradrenaline produced relaxation, cessation of action potentials, and hyperpolarization.