[Changes in the input resistance and membrane potential of a neuron developing a trace effect]

Trace effects in the change of spike activity, input resistance (Rinp) and membrane potential of neurons of the mollusk brain were studied in 36 "silent" brain neurons of Limnaea stagnalis in conditions of 20-min intracellular application of sinusoidal current with the threshold frequency 0.1 Hz. Some neurons revealed the effect of facilitation: the rise of activity with membrane depolarization and an increase of Rinp. Other neurons revealed the fall of activity accompanied by hyperpolarization and a decrease of Rinp. The change of Rinp as a trace effect is at its maximum at the frequency of the current used in the intracellular application. This suggests that the neuronal plasticity in "learning" is just based on the Rinp trace effects. Some of the neurons revealed no change in Rinp, membrane polarization or electrical response to applied stimulation. Possible origin of the above effects is discussed.