Proconflict effect of carbon dioxide inhalation in rats.

The effect of brief inhalation of carbon dioxide (CO2) was studied in a conflict situation (Vogel test) in the rat. This treatment, which inhibits gamma-aminobutyric acid (GABA)-mediated transmission in rat brain and induces anxiety and panic attacks in humans, elicited a proconflict effect. Exposure of rats for 1 min to CO2 decreased by approximately 40% the number of licking periods in the test. This effect was abolished by prior administration of alprazolam (0.5 mg per kilogram of body mass, i.p.). Although these results may support a role for GABA-mediated transmission in the anxiogenic effect of CO2 inhalation, the possibility that different neurotransmitters other than GABA are involved in the action of CO2 can not be ruled out.