Evaluation of the tyrosine and dopamine serum level in experimental infected BALB/c mice with chronic toxoplasmosis

Background Toxoplasma parasite alters the transduction of neurotransmitter signals and leads to changes in the level of brain neurotransmitters including tyrosine and dopamine, so, behavior changes can occur in infected hosts. Based on this concept, this study was conducted for evaluation of the tyrosine and dopamine serum level in infected mice with chronic toxoplasmosis. Materials and methods Toxoplasma gondii (Prugniaud strain II) was injected intra-peritoneal into BALB/c mice to induce chronic toxoplasmosis. Modified agglutination test (MAT), polymerase chain reaction (PCR), and microscopic methods were conducted to confirm the induction of chronic toxoplasmosis. The infected mice sera were separated at days 40, 50, 60, 70, and 80 for evaluation of tyrosine and dopamine serum level using High-performance Liquid Chromatography (HPLC). Results Microscopic methods confirmed the formation of the Toxoplasma cysts in mice tissues. Inducing chronic toxoplasmosis is also confirmed by MAT, PCR and histological methods. HPLC results indicated a decrease in serum tyrosine level at days 40 in infected mice in comparison to control and the levels were too low to be measured at other times. However, a significantly high serum dopamine level was observed that gradually increased after parasite inoculation. Conclusions No detection of tyrosine level in most of the sample groups is probably related to the very low concentration of tyrosine in sera. However, low concentration of tyrosine at days 40 and increase of dopamine in most of the sample groups suggests the production of dopamine from tyrosine due to the presence of Toxoplasma in infected mice.