Serotonin-containing nerves in Torpedo electric organ.

Studies on fluorescent histochemical localization of monoamines in strips of connective tissue teared off the electric organ of Torpedo marmorata revealed an extensive system of yellow fluorescent nerve fibres. No green fluorescent (catecholamine-containing) axons were found in this region. The significance of the presence of indole-containing axons in the connective tissue of the electric organ is in accordance with previous findings on a high level of serotonin in the Torpedo electric organ and contradicts the general assumption that the electric tissue is a source of purely cholinergic nerve endings.