Dr Barron's experiments are providing insights into
both drug addictions and the sophisticated bee
brain.

A study of the effects of low doses of cocaine on foraging honey bees has helped animal behaviour experts better understand the surprisingly sophisticated bee brain, and drawn parallels between how humans and bees respond to this addictive drug.

The research, led by Dr Andrew Barron of Macquarie University's Centre for the Integrative Study of Animal Behaviour and involving researchers from the Australian National University and the University of Illinois, has been released in the Journal of Experimental Biology.

Knowing that foraging honey bees, like humans, are strongly motivated by rewards, Barron set out to test the hypothesis that honey bees are also vulnerable to cocaine - a drug known to be highly rewarding and reinforcing when taken by humans in low doses.

It has never before been proven that cocaine can be rewarding to insects. In fact, cocaine is a powerful insect neurotoxin produced by the coca bush in high doses to protect it from leaf-munching bugs by acting as a natural poison.

It is bees' sophisticated behaviour and love of rewards that made them the obvious choice for Barron's study. By monitoring their dance communication system, Barron could tell what the bees were ‘thinking' about the reward they had just collected far more easily than if he were studying other insects with less complex patterns of behaviour.

"You could be forgiven for thinking that humans and honey bees don't have a lot in common, but as it turns out there is one thing that drives us both to behave the way we do - our love of rewards," Barron said.

"When foraging honey bees discover a particularly good source of pollen or nectar, they fly back to the hive and perform a symbolic dance for their nest-mates - this is a specialised form of communication to tell their nest mates about the rewards they have found. What they're really saying is ‘I've found it, it's this good and it's over there'."

Barron administered the drug non-invasively by applying a tiny drop of cocaine solution to the bees' backs. Low doses caused the bees to dance more vigorously when they returned to their hive. Interestingly, although the drug increased the rate and likelihood of bees dancing after foraging, it did not otherwise increase locomotor activity (i.e. the bees did not become hyperactive as a result of the drug).

The cocaine affected the ‘reward processing' part of the forager bees' brains, triggering a brain chemical called octopamine (similar to dopamine in humans). This caused the bees to overestimate the value of the pollen and nectar they had collected and resulted in a more vigorous dance.

Once he established that the honey bees were responding to the cocaine in a similar way to humans, Barron looked at whether withholding the drug resulted in a withdrawal-like response.

"We tested the bees' ability to learn and distinguish between two different scents," he said.

"There was no impact on learning performance as long as the drug treatments were maintained, but if treatment ceased the bees had difficulty learning the task - similar to humans going into withdrawal."

Barron said the next stage of his research would focus on bees' tolerance and sensitivity to the drug.

"Our early work in this area suggests that the bees are becoming tolerant extremely quickly. We want to understand how this tolerance changes the gene expression in the bees' brains," he said.

"What we're doing essentially is using cocaine as a tool to better understand how these tiny but quite complex brains function."

Barron added that the research could also ultimately result in honey bees being used as a more ethical alternative to rats and mice in drug-related experiments.