Octopamine plays important roles as a neurotransmitter and hormone in invertebrates. The functions of octopamine are also similar to noradrenaline in mammals, which mobilizes the body and the nervous system for action. Octopamine is found only in trace amounts in mammals. 

Discovery 

Octopamine was discovered by Vittoro Erspamer from the salivary glands of the octopus in 1948.Octopamine is involved in various behaviors such as flying, egg laying, and jumping in arthropods.In insects, octopamine was found to be equivalent to noradrenaline and regulates aggression.

Properties

Mr. 153.18. Octopamine hydrochloride is soluble in water at 18.96mg/mL.

Synthesis and release

Gene, mRNA, and precursor

The first step in octopamine synthesis is the conversion of tyrosine to tyramine by tyrosine decarboxylase (TDC). Tyramine is then converted to octopamine by tyramine β-hydroxylase (TβH) .Tissue distribution of mRNA Two subtypes of the TDC gene were cloned in the Drosophila (dTdc1 and dTdc2).dTdc1 is primarily expressed in nonneural abdominal organs.dTdc2 is expressed in the central nervous system that innervates the female reproductive tract.TβH mRNA and TβH were expressed in the brains of honey bees.Regulation of synthesis and release The regulatory mechanism of octopamine metabolism has not been well documented.

Biological functions

Octopamine regulates aggression and energydemanding behaviors such as flying, egg laying, and jumping in invertebrates. Octopamine stimulates light production in the firefly.The injection of octopamine into a lobster and crayfish induces limb and abdomen extension.Octopamine controls starvation resistance in Drosophila. In Drosophila, octopamine drives aversive and appetitive learning through the β adrenergic-like receptor.Octopaminergic antagonists impair appetitive visual learning in honey bees.

Clinical implications

Octopamine increases in urine samples when the animal was treated with monoamine oxidase inhibitors in humans, rats, and rabbits.

Use for diagnosis and treatment

Octopamine is used as a sympathomimetic drug sold under the trade names Epirenor, Norden, and Norfen. Recently, it has been suggested that octopamine may provide therapeutic applications in hepatocellular carcinoma and nonalcoholic fatty liver disease.