Infection caused by the brain parasite Toxoplasma gondii directly alters the production of dopamine, a vital chemical messenger in the brain, according to rodent research at the University of Leeds.
The parasite is found in 10 to 20 percent of the United Kingdom’s population. This research is the first to show that a parasite in the brain of mammals is capable of affecting dopamine levels.
Although the study was conducted on rodents, research leader Dr. Glenn McConkey of the University’s Faculty of Biological Sciences, believes that the results could offer new insight into treating dopamine-related neurological disorders in humans, including schizophrenia, attention deficit hyperactivity disorder, and Parkinson’s disease.
The study reveals how the parasite, incredibly, influences rodents’ behavior for its own advantage. For example, infected mice and rats lose their natural fear of cats, making them more likely to be caught and eaten, which helps the parasite return to its main host to complete its life cycle.
The researchers also discovered that the parasite triggers the production and release of many times the normal amount of dopamine in infected brain cells.
Dopamine transmits messages in the brain that control aspects of movement, cognition and behavior. It is a key component in the brain’s reward and pleasure centers and helps regulate emotional responses such as fear.
Furthermore, a particular type of dopamine receptor is also associated with sensation-seeking, whereas dopamine deficiency in humans results in Parkinson’s disease.
In previous studies, McConkey’s group discovered that the parasite actually encodes the enzyme for producing dopamine in its genome.
“Based on these analyses, it was clear that T. gondii can orchestrate a significant increase in dopamine production in neural cells,” says McConkey.
“Humans are accidental hosts to T. gondii and the parasite could end up anywhere in the brain, so human symptoms of toxoplasmosis infection may depend on where parasite ends up. This may explain the observed statistical link between incidences of schizophrenia and toxoplasmosis infection.”
McConkey adds that his future research will investigate how the parasite enzyme triggers dopamine production and how this may alter behavior.
Source: University of Leeds