, 2013) and reduced uptake of the potassium analogue thallium ( Haroon et al., 2012). Another intriguing possibility is that T. gondii may directly activate the dopaminergic system of its host. The T. gondii genome contains an ortholog of tyrosine hydroxylase ( Etkin et al., 2009), the rate-limiting enzyme in dopamine Selleckchem Ponatinib biosynthesis. Brains of infected mice demonstrate increased levels of dopamine and parasitic tyrosine hydroxylase, both of which localize to the cysts themselves ( Prandovszky et al., 2011). As dopamine is known to powerfully potentiate anxiety expression in the amygdala ( de la Mora et al., 2010), the capacity

to augment local dopaminergic signaling could allow T. gondii to inappropriately activate anxiety circuitry even in the absence of a highly specific tropism. This model

is supported by reports that infected rats demonstrate greater activation in amygdalar and hypothalamic nuclei ( House et al., 2011) and that the dopamine receptor antagonist haloperidol suppresses behavioral changes in infected rats ( Webster et al., 2006). As human studies have implicated both amygdalar ( Etkin et al., 2009) and dopaminergic ( Koenen et al., 2009 and Rowe et al., 1998) disruptions in GAD, parasitic neuromodulation in these limbic structures may activate anxiety circuitry and precipitate the development of human GAD. It is important to note that these pathways are shared by both PTSD and GAD and that the association between high T. gondii antibody level category Smoothened antagonist and PTSD approached statistical significance in fully adjusted models. By definition, however, PTSD requires the occurrence of an external, traumatic event to trigger this not outcome in individuals and is therefore less likely to be associated with T. gondii infection compared to GAD, a diagnosis that does not require an exogenous event. Prior studies of the association between T. gondii and depression have been derived primarily from small case-control studies in which subsamples of individuals with depressive disorders

were included secondarily as controls to the primary outcome of interest, e.g., schizophrenia or history of suicidal behavior ( Arling et al., 2009, Cetinkaya et al., 2007, Hamidinejat et al., 2010 and Hinze-Selch et al., 2007). In the study by Groer et al., the authors found that while T. gondii seropositivity was not associated with higher depressive symptoms in their cohort of pregnant women, among those seropositive for T. gondii, IgG titer was positively correlated with the POMS depression (r = 0.37, p < 0.01) subscale score after controlling for age and race ( Groer et al., 2011). More recently, however, Pearce et al. examined the association between T. gondii seropositivity and history of depression as among a U.S. population-based sample of persons age 15–39 years of age using data from the National Health and Nutrition Examination Survey III ( Pearce et al., 2012).