The effects of manganese and barium on the cardiac pacemaker current, if, in rabbit sino-atrial node myocytes

Experientia. 1991 May 15;47(5):449-52. doi: 10.1007/BF01959940.


The isolation of ionic fluxes contributing to electric currents through cell membranes often requires block of other undesired components which can be achieved, among others, by divalent cations. Mn2+ and Ba2+ are often used, for example, to block Ca and K currents. Here we have investigated the effects of these two cations on the properties of the hyperpolarization-activated pacemaker current if, in rabbit sino-atrial node myocytes, as obtained by voltage clamp analysis. We find that 2 mM Mn2+ shifts the if activation curve by 3.2 +/- 0.3 mV towards more positive values. However, when 1 mM Ba2+ is also added, the positive shift is more than halved (1.3 +/- 0.2 mV). We find, too, that in the absence of blocking cations the ACh-induced if inhibition is slightly higher than in their presence. These results indicate that the alteration of if kinetic properties by Ba2+ plus Mn(2+)-containing solutions is minimal.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylcholine / administration & dosage
  • Animals
  • Barium / administration & dosage
  • Barium / pharmacology*
  • Biotransformation
  • Dose-Response Relationship, Drug
  • Manganese / administration & dosage
  • Manganese / pharmacology*
  • Membrane Potentials / drug effects*
  • Myocardium / cytology
  • Pacemaker, Artificial*
  • Rabbits
  • Sinoatrial Node / drug effects*


  • Barium
  • Manganese
  • Acetylcholine