[Variability of the electrical activity of Helix pomatia neurons PPa2]

Transitions of electrical activity were studied in the PPa2 neuron of the snail Helix pomatia. The PPa2 neuron was found to display either spontaneous beating or slow bursting activity. The amplitude of the membrane potential waves during slow bursting activity varied within 1-5 mV and durations of the burst of the action potential and interburst interval were 50-150 s. Spontaneous transition of the activity from beating to slow bursting could occur for about tens of minutes. Such a transition could be also evoked by the action of a water-soluble fraction of the snail brain homogenate. Artificial polarization of the membrane altered the frequency of the membrane potential wave. Under voltage clamp conditions no oscillations of the membrane current were observed in the PPa2 neuronal membrane. It is suggested that electrical activity of the PPa2 neuron is of endogenous nature. It can be controlled by substances similar to neurotransmitters or neurohormones secreted by other neurons.