[The effect of serotonin precursor 5-hydroxytryptophan and neurotoxic analogue 5,7-dihydroxytryptamine on defensive conditioning in a snail].

This study is devoted to investigation of the influence of precursor of serotonin 5-hydroxytryptophane (5-HTP) and neurotoxic analogue 5,7-dihydroxytryptamine (5,7-DHT) on defensive conditioning and electrical characteristics of command neurones of defensive behaviour after learning. Snails injected with 5-HTP learned faster as compared to control group injected with physiological solution. After the 5,7-DHT injection, snails failed to form the conditioned reflex. Injection of 5-HTP after the preliminary injection of neurotoxin 5,7-DHT restored the capability of snails for learning. Injections of 5-HTP prevented the effect of 5,7-DHT at the behavioural level, but not at the level of electrical characteristics of the command neurones.