[Variability of the electrical activity of Helix pomatia neuron PPa1].

Transitions of electrical activity were investigated in the PPa1 bursting neuron of the snail Helix pomatia. This neuron was found to exhibit the following modes of the activity: silent, beating, low amplitude and high amplitude bursting ones. The transitions between different modes of electrical activity occur within several hundreds of seconds. Such transitions were demonstrated to be simultaneous with changes in the membrane potential of other neurons. Application of a water-soluble fraction of the snail brain to the neuron evoked transitions of electrical activity similar to those occurring spontaneously. The analysis of the data obtained leads to the hypothesis that the activity of the PPa1 neuron is not of endogenous nature but is due to the action of substances released by other neurons.