[2 types of neurons differing in their plastic properties: study of ionic mechanisms].

Plasticity ionic mechanisms of 2 types of neurones identified in the brain of snail Helix pomatia: habituating and non-habituating to rhythmic intracellular stimulation by DC pulses were studied. It has been shown that the development of habituation is due to entering of Ca2+ into the cell and by its activation of Ca-dependent K-conductivity of the membrane, leading to hyperpolarization, decrease of input resistance and elimination of spike response to stimulation. Depression of Ca-dependent K-conductivity by quinine totally blocks the ability of the neurons to habituate to stimulation. The data obtained on non-habituating neurons testify that their non-habituation to intracellular stimulation results from their absence or weak manifestation of Ca-dependent K-conductivity in their membrane. Ca2+ entering non-habituating cells during electrical stimulation may have depolarizing and facilitating effects.