Effects of 5,7-dihydroxytryptamine on an identified 5-hydroxytryptamine-containing neurone in the central nervous sytem of the snail Helix pomatia.
1. The effect of 5,7-dihydroxytryptamine (5,7-DHT) on an identified 5-hydroxytryptamine (5-HT)-containing neurone in the CNS of the snail was studied by histochemical, biochemical and electrophysiological methods. 2. Low concentrations of 5,7-DHT decreased the endogenous 5-HT content of the neurone without affecting the amino acids, while relatively large amounts of the drug proportionately lowered 5-HT and in addition slightly decreased the tryptophan and methionine content of the cell. 3. 5,7-DHT blocked the uptake of [3H]-5-HT into the neurone; the close analogue 5,6-DHT was more potent. 4. As well as slightly influencing the accumulation of [3H]-tryptophan by the neurone 5,7-DHT inhibited the metabolism of this amino acid to form 5-HT, probably by affecting the enzyme tryptophan-hydroxylase. 5. 5,7-DHT produced a postsynaptic blockade of transmission from the neurone by blocking the 5-HT receptors of the follower neurones. This effect appeared to be specific for 5-HT receptors. 6. The data support the idea that 5,7-DHT is neurotoxic for indoleamine-containing neurones.
D000200:Action Potentials / Q000187:drug effects; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002490:Central Nervous System / Q000166:cytology*; D006372:Helix, Snails / Q000502:physiology*; D066298:In Vitro Techniques; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism / Q000502:physiology*; D012908:Snails / Q000502:physiology*; D013997:Time Factors; D014363:Tryptamines / Q000494:pharmacology*; D014364:Tryptophan / Q000378:metabolism
D000596:Amino Acids; D014363:Tryptamines; D012701:Serotonin; D014364:Tryptophan