SLOW-WAVE ACTIVITY IN RABBIT JEJUNUM

A study of slow wave activity present in rabbit jejunum was carried out using intracellular recording techniques and the double sucrose-gap apparatus. Two different indications of changes in membrane potential previously postulated to be pacemaker activity were seen. Slow wave activity was dependent on membrane potential, decreasing in amplitude and increasing in frequency with depolarization, and increasing in amplitude with hyperpolarization. There was no significant change in frequency with hyperpolarization. Slow waves could be entrained using short depolarizing pulses. The ionic dependence of slow waves was studied. In 15 mM Na, slow wave activity was maintained and small oscillations were seen with 5 mM Na. Removing K abolished slow wave activity, although Cs could act as a substitute for K. Removing Ca abolished slow wave activity; Sr ions were able to replace Ca in the generation of slow waves. Agents which blocked or reduced the transmembrane flux of Ca ions (Mn, lanthanum and high concentrations of verapamil) produced a decrease in slow wave amplitude and frequency. Small oscillations in membrane potential could be produced in Na-free-40 mM Ca solution following application of short duration depolarizing current pulses. The results obtained could not be readily explained in terms of an oscillating electrogenic Na-K pump. Rather they support the hypothesis of an oscillating ionic conductance change associated with alterations in the distribution of Ca ions across the membrane (Tomita and Watanabe, 1973). © 1979 Springer-Verlag.