The role of dopamine in Toxoplasma-induced behavioural alterations in mice: an ethological and ethopharmacological study

Abstract

Toxoplasma gondii, a cosmopolitan protozoan parasite, is known to induce behavioural alterations in rodents and may exert an effect on human personality and behaviour. The mechanism of parasite-induced alterations in host behaviour has not been described, but it was hypothesized that development of Toxoplasma tissue cysts in the brain could affect the dopaminergic neuromodulatory system. In this study, we tested the effect of latent Toxoplasma infection on mouse behaviour associated with activity of the dopaminergic system, i.e. locomotion in a novel environment and exploration test. Additionally, we examined the behavioural response of Toxoplasma-infected mice to a selective dopamine uptake inhibitor, GBR 12909. In both genders, Toxoplasma infection decreased locomotion in the open field. Infected females displayed an increased level of exploration in the holeboard test. GBR 12909 induced suppression in holeboard-exploration in the infected males, but had an opposite effect on the controls. These results suggest an association between Toxoplasma gondii infection and changes in the dopaminergic neuromodulatory system.

Toxoplasma gondii infection and behaviour – location, location, location?

“…infected) neurones. A link between dopamine and behaviour changes in infected rodents is supported by experiments in which the dopamine antagonists haloperidol and GBR12909 were found to prevent the behavioural alterations in T. gondii-infected rats and suppress changes in hole-board exploration with infection in male mice, respectively (Skallová et al, 2006;Webster et al, 2006).…”

Congenital Infection of Mice with Toxoplasma gondii Induces Minimal Change in Behavior and No Change in Neurotransmitter Concentrations

“…This makes repetition of his experiments and interpretation of the results impossible. Results from Skallová et al (2006) suggested that male mice may be more susceptible to subtle neurotransmitter changes than female mice; however, they did not examine neurotransmitter concentration in the brains of mice used in their study. Numerous other mouse behavioral studies cite Stibbs (1985) for his research demonstrating increased dopamine levels in the brains of mice chronically or acutely infected with T. gondii.…”

Toxoplasma gondii and Schizophrenia: A Relationship That Is Not Ruled Out

“…As already noted, some experimental animal and human studies concluded that behavioral changes may be explained by increased dopamine levels in the parasitized brain, and that these disorders could largely be resolved by administration of a dopaminergic receptor antagonist (e.g., haloperidol) or dopamine reuptake inhibitor (e.g., GBR-12909) [96,114,115]. It is therefore possible that dopamine represents the link between toxoplasmosis and schizophrenia [97].…”