Infection of male rats with Toxoplasma gondii results in enhanced delay aversion and neural changes in the nucleus accumbens core

Rats infected with the protozoan parasite Toxoplasma gondii exhibit reduced avoidance of predator odours. This behavioural change is likely to increase transmission of the parasite from rats to cats. Here, we show that infection with T. gondii increases the propensity of the infected rats to make more impulsive choices, manifested as delay aversion in an intertemporal choice task. Concomitantly, T. gondii infection causes reduction in dopamine content and neuronal spine density of the nucleus accumbens core, but not of the nucleus accumbens shell. These results are consistent with a role of the nucleus accumbens dopaminergic system in mediation of choice impulsivity and goal-directed behaviours. Our observations suggest that T. gondii infection in rats causes a syndromic shift in related behavioural constructs of innate aversion and making foraging decisions.感染原生动物寄生虫刚地弓形虫（Toxoplasma gondii）的大鼠，其对捕食者气味的规避行为显著减弱。这种行为变化大概率会提升该寄生虫从大鼠向猫的传播效率。本研究发现，刚地弓形虫感染会增强受感染大鼠的冲动选择倾向，该倾向在跨期选择任务中具体表现为延迟厌恶。与此同时，刚地弓形虫感染可使伏隔核核心区（nucleus accumbens core）的多巴胺含量与神经元树突棘密度显著降低，但对伏隔核壳区（nucleus accumbens shell）无此影响。上述结果与伏隔核多巴胺能系统介导选择冲动性与目标导向行为的功能相一致。本研究观察结果表明，大鼠感染刚地弓形虫会使其在先天厌恶与觅食决策相关的行为建构方面出现综合征性偏移。