Magic Mushroom Drug Evolved to Mess with Insect Brains

There’s something odd about the many species of magic mushrooms: they’re not related to each other.

Usually, you’d expect such a complex and powerful chemical as psilocybin – the magical ingredient — to be produced by a closely related group of organisms whose common ancestor discovered it once.

But not in this case. Scores of mushroom species – one even lichenized — from five different distantly-related families make it. A team of American scientists wondered about that and had a hunch about why it might be.

Although mushroom-making fungi, considered sophisticated and complicated for the fungal world — have only rarely been caught sharing DNA this way, the fact that they have made an exception for these genes implies psilocybin is a seriously hot item.

In humans, psilocybin is converted to psilocin on ingestion, which activates one of the same receptors as feel-good neurotransmitter serotonin and produces the wild effects for which the drug is known. Serotonin, incidentally, is the same molecule on which antidepressant serotonin-reuptake inhibitors like Prozac act. However, serotonin is not the private preserve of humans. All animals with left-right symmetry – including insects — produce serotonin, as well as some plants and fungi.

A plant has an apparent motive for stockpiling a chemical arsenal: salad bar prevention. But what about mushrooms? The majority of psilocybin-producing mushrooms are either wood or dung decayers. In those environments, they are not only being eaten by insects but also competing with them for food. Termites are major fungal competitors inside decaying logs, but a variety of other wood- and dung-eating insects compete with fungi for food.

Psilocybin may help tilt the playing field in the fungus’s favor by causing insects to, I don’t know, maybe blank on what they went in that log for again? Another serotonin antagonist to a receptor called 5HT-2A causes Drosophila fruit flies to somehow neglect to eat the fruit they’re sitting on. Whatever they’re experiencing, though, is unlikely to be fun. Insects lack the dopamine-based reward systems also triggered by many of the drugs that make them so pleasurable and addictive to humans (although psilocybin acts on serotonin receptors and is non-addictive).

Read the full article at Scientific American