Abstract
1. The inward and outward currents (OXT-currents) responsible for depolarization and hyperpolarization of the neuronal membrane induced by oxytocin (OXT) application to the soma of identified Helix pomatia neurons was investigated with conventional voltage-clamp technique. 2. The inward current (OXT 1-current) was increased in amplitude in low Cl- ions solution. This current associated with neuronal membrane conductance increase. The reversal potential of this current was near −40 mV. Addition to the bath solution of furosemide reversibly blocked the OXTl-current. 3. Two types of neurons were found with a different outward OXT-currents. The first type associated with a neuronal conductance decrease. It's reversal potential was near −40 mV. This current was increased by hyperpolarization and was reversibly blocked by furosemide (OXTZ-current). The second one associated with a conductance increase. It's reversal potential was near −70 mV, and with a 2-fold increase of external K + ions concentration it shifted towards depolarization by 15mV. Addition of TEA was blocked this current (OXT3-current). 4. Extracellular addition of theophylline increased, while imidazole and tolbutamide decreased the amplitude of OXTl-current. The OXT2-current was decreased, while OXT3-current was unchanged, in tolbutamide-containing solution. 5. It is suggested that Helix pomatia neurons have different types of OXT receptors. Activation of some receptors cause an increase or a decrease in the membrane permeability for Cl-ions, probably through the system of cyclic nucleotides, in turn, the activation of another receptor, which increase K + ions permeability probably, without cyclase system activation.
Published Version
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