Membrane current oscillation

The Oscillation of Membrane Potential or Membrane Current Kohji Maeda and Sorin Kihara... 

The oscillation of membrane current or membrane potential is well-known to occur in biomembranes of neurons and heart cells, and a great number of experimental and theoretical studies on oscillations in biomembranes as well as artificial membranes [1,2] have been carried out from the viewpoint of their biological importance. The oscillation in the membrane system is also related to the sensing and signal transmission of taste and olfaction. Artificial oscillation systems with high sensitivity and selectivity have been pursued in order to develop new sensors [3-8]. 

Two aqueous phases separated by a liquid membrane, EM, of nitrobenzene, NB, were layered in a glass tube, which was equipped with Pt counterelectrodes in W1 and W2 and reference electrodes in three phases as in Eq. (1). Reference electrodes set in W1 and W2 were Ag/AgCl electrodes, SSE, and those in LM were two tetraphenylborate ion selective electrodes [26,27], TPhBE, of liquid membrane type. The membrane current, /wi-w2 was applied using two Pt electrodes. The membrane potential, AFwi-wi recorded as the potential of SSE in W2 vs. that in W1. When a constant current of 25 /aA cm was applied from W1 to W2 in the cell given as Eq. (1), the oscillation of membrane potential was observed as shown in curve 1 of Fig. 1. The oscillation of AFwi-wi continued for 40 to 60 min, and finally settled at ca. —0.40 V. 

B. Oscillation of Membrane Current Under an Applied Membrane Potential [24,25]... 

Curve 1 in Fig. 5 gives an example of the oscillation of membrane current observed with the liquid membrane system as in Eq. (3) by applying a constant AFwi-w2 of —0.48 V and measuring the time course of the current through the LM, /wi-w2- The cell used was the same as that used for the measurement of the potential oscillation, except a tetraphenyl-arsonium ion selective electrode [26,27], TPhAsE, was employed as a reference electrode in LM of NB ... 

Similarly to the induction or the inhibition of the current oscillation at a biomembrane with a sodium channel, the current oscillation at the liquid membrane (without any channel proteins) caused by the transfer of Na can be induced by acetylcholine ion, Ach, or inhibited by such rather hydrophobic ions as alkylammonium and glutamate ions. 

The above-mentioned results on the voltammograms indicate that the condition available for the oscillation of the membrane current resembles closely that for the appearance of the maximum. 

In the following, a unique oscillation of membrane current observed with a liquid membrane system by the present authors [32,37], which has characteristics similar to those of the oscillation at a biomembrane with so-called sodium channel , will be introduced as an example, and the mechanisms for the oscillation will be clarified by using VCTIES, taking into consideration ion transfer reactions and adsorptions at two W/M interfaces in the membrane system. In this connection, various oscillations other than this example and the elucidation of their mechanisms were described elsewhere [32,37,38]. 

---