Effects of beta-amyloid (25-35) on learning in the common snail.

The effects of neurotoxic beta-amyloid fragment (25-35) on the formation of behavioral sensitization and a conditioned defensive reflex to food were studied. Administration of beta-amyloid (25-35) to common snails before the start of training led to a significant reduction in sensitization of the defensive reaction, weakening of the formation of the conditioned defensive reflex to food, and impairment of memory. These impairments to behavioral plasticity may be mediated by changes in synaptic plasticity previously observed in the presence of beta-amyloid.

Recording of spontaneous oscillations in the procerebrum of the terrestrial snail Helix during free behavior.

The procerebrum is the central component of the olfactory analyzer in terrestrial snails and slugs; spontaneous rhythmic oscillations have been recorded in this structure, but their role in the mechanisms of odor perception and recognition has yet to be clarified. The present report describes a method for recording total electrical activity from the procerebrum in vivo and demonstrates changes in spontaneous rhythmic oscillations in the procerebrum of the snail Helix in response to olfactory stimulation. Recording of total electrical activity from the snail procerebrum in conditions of free behavior demonstrated a significant reduction in the frequency and an increase in the amplitude of spontaneous oscillations in the procerebrum in the first 10 sec after presentation of the odor of cineole at low concentration, which corresponds to the time required for performance of the olfactory tentacle withdrawal reaction. Presentation of the odor at high concentration resulted in a significant increase in the amplitude of spontaneous oscillations in the procerebrum over the time interval 11-20 sec after odor presentation and a tendency to a decrease in the frequency, which correlates with an increase in the time required for the olfactory tentacle withdrawal reaction. These data suggest an implicit relationship between the amplitude and frequency of oscillations in odor recognition.

[Beta-amyloid peptide influences behavioral plasticity in terrestrial snail].

Influence of neurotoxic fragment of beta-amyloid peptide (25-35) on Helix lucorum behavioral plasticity (sensitization and food-aversion learning) was investigated. After beta-amyloid peptide (25-35) injection a significant reduction of behavioral long-term sensitization was observed. It was found, that beta-amyloid peptide (25-35) may interfere with associative learning and memory. Our results clearly demonstrate that beta-amyloid peptide (25-35) may play a significant role in behavioral plasticity by chronically eliminating certain underlying forms of synaptic plasticity.

[Recording of spontaneous oscillations in the procerebrum of terrestrial mollusk Helix in free behavior].

Procerebrum is the central part of the olfactory system in terrestrial snails. Spontaneous rhythmic oscillations were described in this structure. The role of these oscillations in the mechanisms of odor perception and discrimination is unknown yet. Electrical activity of the Helix procerebrum was recorded in vivo. Changes in spontaneous rhythmic oscillations in response to olfactory stimulation were observed. Within the first 10 s after odor application (cineole) in low concentration, a statistically significant decrease in the frequency and increase in the amplitude of procerebrum oscillations were revealed in freely behaving animals. Timing of those changes corresponded to the time of defensive reaction realization of the tentacle withdrawal. The increase in the amplitude and a tendency to a decrease in the frequency of oscillations in response to odor application in high concentration were observed in time period 11-20 s, which corresponded to an increased duration of tentacle withdrawal. The results suggest an implicit relation of the amplitude and frequency of oscillations in odor perception and discrimination.