Ozone-induced hypothermia and bradycardia in rats and guinea pigs in nose-only or whole-body inhalation systems

1. Ozone (O-3) inhalation induces a hypothermic response in rodents charact erized primarily by core body tempera -ture (T-CO) and heart rate (HR) decr eases. 2. This preliminary study examined T-CO, HR, and electrocardiographic chang es in rats and guinea pigs during whole-body or nose-only exposure to 1 ppm O-18(3). 3. Rats exposed whole-body demonstrated an immediate hypothermic response, while that of the nose-only exposed rats was delayed approximate to 60 min; guinea pigs showed no hypothermic response to O-18(3). 4. O-18 content in lavage fluid samples suggests that dose is greater in no se-only exposures than whole-body exposures, and that guinea pigs received higher doses than rats. 5. These initial findings suggest that dosimetric differences may result fr om differences in species responses and exposure scenarios. (C) 2000 Elsevi er Science Ltd. All rights reserved.