Ionic mechanisms of the rapid (nicotinic) phase of acetylcholine response in identified Planobarius corneus neurones

Abstract Current responses to acetylcholine (ACh) and to suberyldicholine (D-6) applied from the double-barrelled ionophoretic micropipette were studied in two identified neurones (LPed-2 and LPed-3) isolated from the left pedal ganglion of pulmonate mollusc, Planorbarius corneus . Experiments made with K 2 SO 4 -filled microelectrodes show that in LPed-2 neurone two kinds of cholinoreceptors are involved in the rapid phase of ACh response one of which induces chloride conductance and the other, sodium conductance. The C1 − -dependent component can be separated from the cationic one by C-6 whereas the cationic component can be deparated from the Cl − -dependent one by furosemide. Cl − conductance can be induced selectively by D-6. In the LPed-3 neurone only Cl − conductance increases during rapid phase of ACh response. The reversal potential of Cl − -dependent responses was found to be more negative than the resting potential in experiments made with K 2 SO 4 -filled microelectrodes but less negative than the resting potential in the case of KCl-filled microelectrodes. This difference seems to be due the artificial increase of intracellular chloride concentration.