Patients with an anxiety disorder often display aberrancies in sensing the internal state of the body. Interoception is activated for example by mild hypercapnia during CO2 inhalation due to homeostatic disturbances of the body eliciting anxiety and even panic-like behaviours across species. Yet, although altered interoception is increasingly recognized as an important component of anxiety disorders, its underlying neural mechanisms remain little understood. Here, we aimed to elucidate whether trait anxiety levels affect the engagement of the anxiety network in response to CO2 challenge. Mice selectively bred for high (HAB) and normal (NAB) anxiety-related behavior were exposed to CO2-enriched air. In the test arena, CO2 exposure caused a reduction in locomotor activity of both mouse lines with greater effects in HABs. Furthermore, CO2 inhalation elicited anxiogenic effects in HABs. Using immediate early gene mapping neuronal activation patterns were investigated in key brain areas of the anxiety neurocircuitry including subregions of the amygdala, prefrontal cortex and stress centres. First data indicate that CO2 exposure engages the paraventricular hypothalamus and insula with increased activation of the latter in HAB as compared with NAB mice. Furthermore, sex-dimorphic effects were revealed upon CO2 inhalation. Taken together, the present findings demonstrate increased CO2 sensitivity in individuals with high trait anxiety, thus, highly reflecting patient subgroups. The increased engagement of the insula cortex for the processing of interoceptive signals in high-trait anxiety may represent a potential biomarker for stratifying patient subgroups and, thus, optimizing individualized therapeutic interventions.Supported by the Austrian Science Fund FWF FG 18-B.