Toxoplasma gondii-induced region-specific disintegration in glutamatergic neurotransmission is linked to cognitive impairments in mice

Chronic infection with the protozoan parasite <i>Toxoplasma gondii</i> (<i>T</i>. <i>gondii</i>) elicits distinct alterations in both the immune and nervous system of the host. Previous studies correlated the persistent neuroinflammatory response triggered by chronic <i>T</i>. <i>gondii</i> infection to specific behavioral alterations. Here, we causally link chronic cerebral <i>T</i>. <i>gondii</i> infection to cognitive and motor impairments in mice, as well as to the altered brain glutamatergic signaling in hippocampus, striatum, and cortex. By combining synaptic composition analysis assessed via flow synaptometry with the standard sulfadiazine treatment, we demonstrated the regional specificity of the detected alterations of cerebral <i>T</i>. <i>gondii</i> infection. Importantly, our behavioral analysis exposed the restoration of behavioral flexibility in shifting between goal-directed and habitual action control, with more motorically demanding skills such as social novelty recognition and locomotion being only partially restored. We argue that the revealed regional effects of both <i>T</i>. <i>gondii</i> and sulfadiazine treatment may be a key factor accounting for treatment-resistant behavioral traits.