[Effect of application of oxytocin on neurons of Helix pomatia: hyperpolarization effects].

Ionic mechanisms of hyperpolarization induced by oxytocin application on the neuronal membrane of identified neurons of Helix pomatia have been studied under voltage clamp conditions. There are two types of neurons and two types of hyperpolarization, respectively. Hyperpolarization of the first type is due to a decrease in chloride permeability and hyperpolarization of the second type is due to an increase in potassium permeability of the surface neuronal membrane. The reversion potential in the first case was -40 mV and decreased with addition of external solutions of furosemide or tolbutamide. The reversion potential in the second case was -70 mV, and with a 2-fold increase of external potassium concentration it shifted towards depolarization by 15 mV, while tolbutamide addition to the external solution induced no changes. It is supposed that Helix pomatia neurons have different receptors to oxytocin. Activation of some receptors causes a decrease in the membrane permeability for chloride ions, probably, through the system of cyclic nucleotides, while activation of their receptors increases potassium permeability of the surface membrane.