Hello. The chemical structure of psilocybin and psilocin (the active ingredients in magic mushrooms) is similar to the neurotransmitter called serotonin.
In fact, the primary effect of psilocin is on the serotonin receptors. There is also evidence that psilocybin reduces the reuptake of serotonin by neurons in the brain allowing this neurotransmitter more time to act in the synapse. This is how it alters one's feelings and creates euphoria.
So it it the equivalent, you might say, of taking some prozac. :-)
Taking a small amount of these substances would not be expected to cause any brain damage.
Are you experiencing any side effects?