Impairment of Context Memory by β-Amyloid Peptide in Terrestrial Snail

Abstract

We examined influence of the β-amyloid peptide (βAP) (25–35) neurotoxic fragment on Helix lucorum food-aversion learning. Testing with aversively conditioned carrot showed that 2, 5 and 14 days after training the βAP-injected group responded in a significantly larger number of cases and with a significantly smaller latency than the sham-injected control group. The results demonstrate that the AP partially impairs the learning process. In an attempt to specify what component of memory is impaired we compared responses in a context in which the snails were aversively trained, and in a neutral context. It was found that the sham-injected learned snails significantly less frequently took the aversively conditioned food in the context in which the snails were shocked, while the βAP-injected snails remembered the aversive context 2 days after associative training, but were not able to distinguish two contexts 5, and 14 days after training. In a separate series of experiments a specific context was associated with electric shock, and changes in general responsiveness were tested in two contexts several days later. It was found that the βAP-injected snails significantly increased withdrawal responses in all tested contexts, while the sham-injected control animals selectively increased responsiveness only in the context in which they were reinforced with electric shocks. These results demonstrate that the βAP (25–35) interferes with the learning process, and may play a significant role in behavioral plasticity and memory by selectively impairing only one component of memory – the context memory.