Octopamine

Octopamine is a biogenic amine which is closely related to noradrenaline, and has a similar action to dopamine.

Role in invertebrates
Octopamine was first discovered by Italian scientist Vittorio Erspamer in 1948 in the salivary glands of the octopus and has since been found to act as neurotransmitter, neurohormone and neuromodulator in invertebrates. It is widely used in energetically demanding behaviours by all insects, crustaceans (crabs, lobsters, crayfish) and spiders. Such behaviours include flying, egg-laying and jumping.

The best understood role for octopamine is in the locust jump. Here it modulates muscle activity, making the leg muscles contract more effectively. This is at least in part due to an increase in the rate of contraction and of relaxation.

In the honey bee and fruit fly, octopamine has a major role in learning and memory. In the firefly, octopamine release leads to light production in the lantern.

Octopamine also plays a role in mollusks, though the role of octopamine has only been examined in the central nervous system of the model organism, the pond snail.

Heberlein et al have conducted studies of alcohol tolerance in fruit flies; they found that a mutation that caused octopamine deficiency also caused lower alcohol tolerance.

Role in vertebrates
In vertebrates, octopamine also replaces norepinephrine in sympathetic neurons with chronic use of monoamine oxidase inhibitors. It is responsible for the common side effect profile of orthostatic hypotension with these agents.

In mammals, octopamine may mobilise the release of fat from adipocytes (fat cells), and this has led to its promotion on the internet as a slimming aid. However, the released fat is likely to be promptly taken up into other cells, and there is no evidence that octopamine facilitates weight loss. Octopamine may also increase blood pressure significantly when combined with other stimulants, as in some weight loss supplements.

Use in humans
In some countries octopamine is gaining increased commercial interest as an ingredient in benzylpiperazine free 'party pills' due to the fact that in countries such as New Zealand where it is currently legal, BZP faces a probable ban before the end of 2007. It should be noted however that the structure of octopamine falls within the definition of an "amphetamine analogue" in Class C7 of the New Zealand Misuse of Drugs Act, and so would probably be considered an illegal drug if it were tested in court, although no prosecutions involving this compound have been carried out so far.