Understanding rat emotional responses to CO(2)

The aim of this review is to summarize evidence regarding rat emotional experiences during carbon dioxide (CO(2)) exposure. The studies reviewed show that CO(2) exposure is aversive to rats, and that rats respond to CO(2) exposure with active and passive defense behaviors. Plasma corticosterone and bradycardia increased in rats exposed to CO(2). As with anxiogenic drugs, responses to CO(2) are counteracted by the administration of anxiolytics, SRIs, and SSRI’s. Human studies reviewed indicate that, when inhaling CO(2), humans experience feelings of anxiety fear and panic, and that administration of benzodiazepines, serotonin precursors, and SSRIs ameliorate these feelings. In vivo and in vitro rat studies reviewed show that brain regions, ion channels, and neurotransmitters involved in negative emotional responses are activated by hypercapnia and acidosis associated with CO(2) exposure. On the basis of the behavioral, physiological, and neurobiological evidence reviewed, we conclude that CO(2) elicits negative emotions in rats.