Dibutyryl cGMP, like acetylcholine, shortens and reduces repolarization and overshoot of the action potential, slightly hyperpolarizes the cell and decreases the force of the contraction in the atrial working muscle. It suggests that cGMP may mediate the action of acetylcholine in the atrial working fibres.

Acetylcholine↗

PubMedDate not supplied

Effect of adenosine on electrical activity in guinea-pig atrium.

Adenosine abolished action potentials and slowed down depolarization in the sinus node cells, and depressed the slow component in the working fibers. Noradrenaline and dibutryl cAMP did not counteract the effects of adenosine in the working myocardium whereas in the pacemaker, dibutryl cAMP alone evoked low frequency spontaneous activity.

Action Potentials↗