Electrophysiological studies of the effects of 5,6-dihydroxytryptamine on the acquisition of a conditioned defensive reflex in snails.

The role of serotonin in the membrane properties of identified neurons was studied during acquisition of a conditioned defensive reflex. Serotonin deficiency was created using the neurotoxic serotonin analog 5,6-dihydroxytryptamine (5,6-DHT). Injection of 5,6-DHT was found to prevent decreases in the membrane and threshold potentials of command neurons during acquisition of the conditioned reflex as compared with snails given 5,6-DHT without training. Common snails recovered the ability to acquire the conditioned reflex two weeks after a second 5,6-DHT injection.