Histamine Activates the Chloride Current in Cardiac Ventricular Myocytes

Histamine Activation of I Cl . Exposure of enzymatically dispersed guinea pig ventricular myocytes to histamine evoked a time‐independent background current that was measured using the whole cell patch‐clamp technique. This current was observed when Na + currents were inactivated by membrane potential, and Ca 2+ and K + currents were blocked by channel antagonists and impermeant ions. Alterations of the CI − gradient caused a shift of the reversal potential of the histamine‐induced current expected for a CI − current. The histamine‐induced CI − current was attenuated by concurrent exposure of cells to acetylcholine, the H 2 receptor antagonist cimetidine, and adenosine. In current‐clamp experiments, histamine‐induced changes in the action potential and resting membrane potential were dependent upon the CI − gradient across the membrane. The characteristics of the histamine‐induced CI − current resemble those of the CI − current, I Cl elicited by isoproterenol, forskolin, adenosine 3′,5′‐cyclic monophosphate (cAMP), and cAMP‐dependent protein kinase in this preparation. It is concluded that histamine activates a similar CI − conductance in guinea pig ventricular myocytes through a cAMP‐dependent pathway. ( J Cardiovasc Electrophysiol, Vol 1, pp. 309–317, 1990 )