Brain chemistry altered by T. gondii
21 Dec 2011 by Evoluted New Media
Brain parasite Toxoplasma gondii directly alters the brain chemistry by affecting dopamine levels say researchers, who believe their work could shed light on treating neurological conditions like schizophrenia, ADHD and Parkinson’s disease.
Researchers from the University of Leeds have shown for the first time that T. gondii found in the brain of mammals can affect dopamine levels. It causes the production and release of many times the normal amount of dopamine – a natural neurotransmitter – in infected brain cells.
Mammalian dopaminergic cells infected with T. gondii enhanced the levels of potassium-induced release of dopamine several-fold, and there was a direct correlation between the number of infected cells and quantity of dopamine released.
“Based on these analyses, it was clear that T. gondii can orchestrate a significant increase in dopamine production in neural cells,” said Dr Glenn McConkey from the faculty of biological sciences.
Immunostaining of rodent brain sections with dopamine antibodies showed intense staining of encysted parasites.
The parasite manipulates the rodent’s brain in order to help them complete their life cycle – infected mice and rats lose their innate fear of cats, increasing the likelihood that they will be caught and eaten, enabling the parasite to return to its main host.
This work – published in Plos One – could be relevant in interpreting reports of psychobehavioural chances in toxoplasmosis-infected humans.
“Humans are accidental hosts to T. gondii and the parasites could end up anywhere in the brain, so human symptoms of toxoplasmosis infection may depend on where parasite ends up,” said McConkey. “This may explain the observed statistical link between incidences of schizophrenia and toxoplasmosis infection.”
Toxoplasmosis – found in cat faeces and raw and undercooked infected meat – is relatively common, with between 10 and 20% of the population estimated to carry the parasite as cysts. The parasite infects the brain by forming a cyst within its cells and produces tyrosine hydroxylase, which is needed to make dopamine – McConkey’s group found that the parasite actually encodes the enzyme for producing dopamine in its genome.
The group’s next experiments will investigate how the parasite enzyme triggers dopamine production and how this may change behaviour.
The neurotropic parasite Toxoplasma gondii increases dopamine metabolism
