0000000000042581
AUTHOR
Edward Carmeliet
Differential electrophysiologic and inotropic effects of phenylephrine in atrial and ventricular heart muscle preparations from rats.
Stimulation of alpha 1-adrenoceptors evokes a different pattern of inotropic responses in atrial and ventricular heart muscle preparations from rats. The inotropic effects are accompanied by different changes in membrane potential. In an attempt to clarify the question whether or to which extent these events are causally related, the effects of phenylephrine on force of contraction, transmembrane potential, Ca2+ current (ICa) and K+ currents were comparatively studied in either tissue. In atrial preparations, phenylephrine 10 mumol/l caused an increase in force of contraction, a marked prolongation of the action potential duration and a depolarization of the membrane at rest. In the ventric…
Depolarization-induced influx of sodium in response to phenylephrine in rat atrial heart muscle.
1. The effects of alpha 1-adrenoceptor stimulation on transmembrane potential, currents and ion fluxes were investigated in multicellular preparations and/or single cells obtained from the left atrium of rat hearts. 2. In multicellular preparations, phenylephrine caused a concentration-dependent positive inotropic effect, an increase in action potential duration, and a decrease in resting potential; the effects were antagonized by phentolamine. 3. In the presence of phenylephrine (100 mumol/1), two levels of resting potential were observed when the preparations were, alternately, electrically stimulated or kept at rest (-74 +/- 1 mV during activity and -62 +/- 4 mV at rest; mean +/- S.E.M.;…