Since its discovery in the 18th century, cocaine has been a scourge of western society. Strongly stimulating human reward centres in low doses, cocaine is extremely addictive and can be fatal in high doses. But this potent compound did not evolve to ensnare humans in addiction. Andrew Barron from Macquarie University, Australia, explains that cocaine is a powerful insect neurotoxin, protecting coca bushes from munching insects without rewarding them. Knowing that foraging honey bees are strongly motivated by rewards (they dance in response to the discovery of a rewarding nectar or pollen supply) and that this behaviour is controlled by similar mechanisms to the ones that leave humans vulnerable to cocaine addiction, Barron and Gene Robinson from the University of Illinois at Urbana-Champaign wondered whether bees may be vulnerable to cocaine's allure at the right dose. Teaming up with Ryszard Maleszka at the Australian National University, Barron set about testing how honeybees respond to cocaine. They publish their results on 26th December 2008 in The Journal of Experimental Biology at http://jeb.biologists.org.
Setting up his hives on a farm just outside Canberra, Barron trained the insects to visit a feeder stocked with a sugar solution. Then he gently applied a tiny drop of cocaine solution to the insect's back, and waited to see how enthusiastically the foraging insects danced when returning to the hive. Amazingly, low doses of the drug stimulated the insects to dance extremely vigorously. They behaved as if the sucrose solution was of a much higher quality than it really was. The cocaine seemed to be hitting the insects' reward centres, but were they really responding to the drug like humans or was the drug stimulating some other aspect of the insects' behaviour to look as if they were becoming addicted?
Working with a team of undergraduate students, Barron tested whether cocaine stimulated
|Contact: Kathryn Phillip|
The Company of Biologists