Chronic administration of caffeine to common snails increased the rate of formation of a conditioned defensive reflex. When daily caffeine injections were given immediately after the training procedure, the conditioned defensive reflex was acquired more quickly than when caffeine injections were given before the training procedure started. Chronic caffeine administration to both trained and untrained snails led to depolarization changes in the membrane potential and reductions in the threshold potential of defensive behavior command neurons in common snails. Comparative studies showed that addition of caffeine to the solution bathing the mollusk nervous system resulted in decreases in the threshold potential of command neurons in both intact and trained snails; there was, however, no change in the membrane resting potential.

Two types of neurons exhibiting various reactions to application of antibodies against S100 protein in the washing solution were revealed in the nervous system of Helix lucorum snails. After treatment with antibodies against S100 protein the frequency of action potential generation decreased in spontaneously active B1, B3, B17, and PPa6 cells, but increased in B4 and B6 cells. The effect of antibodies against S100 was less pronounced in the solution of potentiated antibodies against this protein. After pre-exposure of ganglia in the solution of potentiated water the effect of antibodies against S100 protein decreased to a lesser extent. No significant changes were revealed in the membrane resting potential of cells. Combination treatment with antibodies and potentiated antibodies against S100 protein increased the threshold of action potential generation in B1 and B17 cells. Our results indicate that potentiated antibodies against S100 protein specifically modulate the activity of nerve cells.

We report here a study of the effects of blockade of protein synthesis with anisomycin during reactivation of a contextual conditioned reflex in the common snail. The amplitudes of the defensive reactions of snails to standard tactile stimulation before training were identical in two conditions: 1) testing of responses of snails fixed by the shell to a plastic ball floating in water and 2) on the surface of the terrarium glass. After applying electric shocks to the snails' skin for 5 days, a significant difference in responses reflecting the formation of a contextual conditioned reflex was seen in only one of the contexts. Placing trained snails in the same context (reminding) two days after training with simultaneous injection of anisomycin led to significant weakening of training, while control injections of physiological saline produced no such changes. These data suggest that the mechanisms of memory consolidation after training and reminding are not identical.

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The actions of the neuroleptic chlorpromazine (CPZ) and the neurotoxin 5,6-dihydroxytryptamine (5,6-DHT) on defensive reactions, locomotion, formation of long-term sensitization, and the electrical characteristics of command neurons in the common snail were compared. Prolonged (chronic) treatment with CPZ led to a significant increase in the pneumostoma closure time, as well as changes in motor behavior, with a decrease in the rate of locomotion. Administration of 5,6-DHT in small daily doses for one week was accompanied by gradual decreases in the rate of locomotion of the snails, which persisted for one week. A similar effect was seen after administration of the same total dose of neurotoxin, 30 mg/kg, as a single injection. Administration of CPZ prevented the formation of long-term sensitization, as did treatment with 5,6-DHT. The procedures of treatment with CPZ, long-term sensitization, long-term sensitization followed by CPZ, and acquisition of long-term sensitization on the background of treatment with CPZ gave a locomotion speed which was directly proportional to the length of the sole. No such relationship was seen during the acquisition of long-term sensitization on the background of treatment with 5,6-DHT. Electrophysiological studies showed that chronic CPZ led to a depolarization shift in the membrane potential and a decreased action potential generation threshold in command neurons, which also occurred on treatment with 5,6-DHT. It is concluded that the actions of the neuroleptic CPZ on defensive behavior and locomotion in the common snail, as well as on the electrical characteristics of identified neurons, were similar to the toxic actions of serotonin.

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We studied the effect of antibodies to Ca(2+)-binding protein S100 in a dilution of 10(-12) (LAT-S100) on the development of long-term sensitization in Helix lucorum, a neurobiological model of anxious and depressive states. After administration of LAT-S100 preventing the development of long-term sensitization before training, the membrane and threshold potentials in command neurons regulating defense behavior decreased less markedly than during long-term sensitization. It is assumed that the "protective" effect is associated with mechanisms of long-term potential maintenance and changes in intra- and extracellular balance of Ca(2+)-binding protein S100.