Have you ever seen the, in my opinion, wildly entertaining pictures of webs spiders have spun while on marijuana, caffeine, heroine, and ecstasy to name a few of the drugs used? If you haven´t yet, now is the time to turn on your browser and google “spiders on drugs”. Why the NASA, of all the scientific institutions, turned their attention to drugged insects beats me. Certainly space travel can´t be that boring?! But these poor little arachnids and their webs, artistic in some cases, borderline manic in others, are not the only insects science has ever turned into addicts.
In a study in 2009 researchers fed their bees cocaine in order to see if their dancing behavior differed after consumption of the drug. Researchers, and I can attest this from experience, do sometimes get bored in the lab. We then either doodle our days away drawing lab related comics (Beatrice the Biologist, Bird and Moon Comics, PhD comics, just to name a few), read papers outside of their field such as ones about spiders on drugs or play battleship with the pipette tip boxes and another procrastinating colleagues. But feeding honeybees with cocaine isn´t the brainchild of an idling researcher as much as a rational, thinking person might be led to believe.
Cocaine is produced by the coca plant to protect itself from animals, and is – as we sadly hear time and time again on the news, lethal in high doses. So far, so logical. But we also know, perhaps from personal experience (everyone has their own way of dealing with a wild phase), or from reading, word of mouth or however any information on the effect of any drug leaks through society, that cocaine is addictive. So we´ve got this toxic chemical that a plant produces to kill predators – but then it turns out it´s also addictive if they only have a little of it. How does that make sense? This problem is called “paradox of drug reward”. The plant produces a toxin that basically backfires if the animals only eat a little of the plant. Ideas have been thrown about, trying to solve the suicidal plant problem and most of these have relied on the claim that it´s just addictive to mammals, like humans, and not insects.
Then the bee made its entrance onto the scientific stage. Equipped with some pretty sweet dance moves, it lets scientist study the effects of all kinds of drugs, brain modulations and mutations on the bees ability to map out a field of flowers by using the equivalent of The Invertebrate Twist. But not only can they dance a map, these little critters can also tell each other which flower is the best one to fly to. They are able to emphasize the importance of flying to a location through their dancing. It´s like when you just got home from a bar that serves free drinks. You´re very likely to tell your friends that not only do they have to check that bar out, they really, REALLY have to go there. The bar and its drinks-for-free-special activated your own personal reward system, and what´s more rewarding than to share this feeling with your friends? Back to the addictive drugs: they also activate your reward system. And as we have just learned: humans and bees have the same reward system AND they are both able to express their liking of this reward! This similarity is exactly what scientists used to solve the “paradox of drug reward”. Bees were fed dissolved cocaine while they were out looking for pollen and nectar for themselves and their hive. After they learned which flower served as their personal drug dealer, the bees were strapped into tiny harnesses – yes, this is why scientists sometimes have trouble explaining to people what they do without sounding ridiculous – in order to see how well they were able to recognize their be-petaled “dealer”. Would the bees, who had learned to fly to a flower with cocaine be able to remember the location of the flower better than a bee who hadn´t been dealt the drug? After all, cocaine is supposed to hurt insects, such as bees, since a plant certainly wouldn´t evolve to attract the annoying little nibblers. It would be sensible for the bee to avoid a plant that could potentially kill it. But instead of avoiding their potential murderer, the drugged bees went berserk. Once they got back to tell the stories to their furry, winged friends, they went into dance mode – and stayed that way for far longer than the bees who´d been to the same flower, but had not had the dubious honor of being fed with cocaine. The drug was obviously just as rewarding to the drugged bee as to us mammals. Another interesting morsel of information: the bees on cocaine also experienced a stage of withdrawal, possibly accompanied with headaches and nausea for all we know, after their poison of choice was taken from them. One thing we know for sure though: they couldn´t focus on their dance ritual anymore. Their little drug-incited party was over.
But not for the scientists. They were able to show that cocaine changed the signaling in reward learning in an insect model – which is, coincidentally, linked to motor function. The pathway at work here is the “biogenic amine signaling”, and it works the same in humans as in insects, influencing our reward system and controlling our movement. It is the break down of this motor control system that is the terminal downfall of an insect that has the misfortune to munch on the wrong leaf. However, the activation of the reward system, which uses the same pathway, is just a side effect, a tiny hiccup in the grand scheme of the plant for worldwide insect annihilation – or at least some peace and quiet for a while from insects, please.
Paper: Barron, A.B., Maleszka, R., Helliwell, P.G., Robinson, G.E., Effects of cocaine on honey bee dance behavior, Journal of Experimental Biology ,212, 163-168, (2009)
A similar paper on cocaine in Drosophila looping locomotor stereotypes: McClung and Hirsh, 1997: Stereotypic behavioral responses to free-base sensitization to cocaine in Drosophila