The presence of tyramine and related monoamines in the nerve cord and some other tissues of the lobster, Homarus americanus.

This report shows the existence of endogenous p-tyramine in the nerve cord and some organs of the lobster. Their concentrations are lower than those of dopamine or 5-hydroxytryptamine. The nerve cord levels of m-tyramine, beta-phenylethylamine and tryptamine are much lower than those of the phenolic or catecholic amines. The finding that the administration of an aromatic-L-amino acid decarboxylase inhibitor leads to a decrease of p-tyramine gives further evidence that this amine is synthesized from p-tyrosine, which is also found in high concentrations in the lobster nerve cord. The widespread distribution of p-tyramine in the nervous system and peripheral tissues of the lobster suggests that this amine may have additional roles rather than functioning only as a precursor of p-octopamine.