Ionic mechanisms underlying modulating effects of serotonin on acetylcholine-induced responses in Helix pomatia neurons

The ionic mechanisms underlying modulatory effects of serotonin on acetylcholine response in identified and nonidentified Helix pomatia neurons were investigated using voltage-clamping techniques at the neuronal membrane. External application of serotonin to the membrane of neurons responding to application of acetylcholine depending on Na super(+) depolarization reduced membrane conductivity during response to acetylcholine without changing reversal potential of acetylcholine-induced current. Serotonin brought about a shift in reversal potential and an increase in the acetylcholine-induced current in those neurons where this response was associated with changed permeability at the membrane to certain types of ions.