Similarity of the effects of training and application of serotonin on the electrical activity of live hippocampal slices from rats.

A pronounced sensitization phase was observed on low-frequency stimulation of hippocampus slices from rats decapitated immediately after training to a conditioned bilateral escape reflex. The same effect was recorded in slices from control animals after brief application of serotonin. Serotonin had significantly smaller effect on the electrical activity of trained animals. Changes in the efficiency of the serotoninergic input to hippocampus neurons are suggested as one of the factors eliciting low-frequency facilitation in trained rats.