MUSHROOMS AND HALLUCINATIONS

"Magic mushrooms"can cause hallucinations when ingested. What's the chemical process that causes this reaction?

Liberty cap is one of the mushrooms that contains psilocybin. The drug over­activates cerebral neurons.

Time distorts. Emotions intensify. Senses overload. These are just some of the mind ­altering effects people may experience after ingesting "shrooms" - specifically, liberty caps or other mushrooms that belong to the Psilocybe genus.

But why these mushrooms and not,say, shiitake,portobello or chanterelles? It's because Psilocybe mushrooms contain a substance called psilocybin,a psychoactive compound. Once ingested, psilocybin is absorbed into the bloodstream and then carried to the liver, where it is transformed into psilocin, the chemical responsible for the psychedelic side effects.

Biochemically speaking, psilocin is somewhat like serotonin, a neurotransmitter that helps to regulate moods. Serotonin moves through the brain via neurons: When one neuron releases serotonin, it  moves across a synapse, then is captured by receptors on another neuron. However, psilocin can bind to the receptors used by serotonin, imitating it sufficiently to spontaneously activate neurons in the frontal lobe, causing distorted mental and emotional reactions

It's possible that psilocin also may restrict blood flow to parts of the brain and weaken communication between several brain centers, although it's unknown whether this contributes to the mushrooms' intoxicating effects.

Although psilocybin and psilocin are classified as Schedule I (illegal) drugs in the United States,"magic mushrooms" are relatively harmless. Addiction is rare, and since a fatal dose is 1,000 times greater than the effective dose, the risk of overdosing is extremely low. However, some users can experience a "bad trip" characterized by panic­related anxiety.

In "Science Illustrated", September/October 2012, p.6. Adapted and illustrated to be posted by Leopoldo Costa.