A Pilot Study on the Effects of a 3%, 5%, and 7% CO2 Challenge on Wistar Kyoto Rats

Most people who experience trauma do not go on to develop PTSD. This statistic supports a diathesis model in which vulnerabilities exist that predispose a limited number of individuals to develop PTSD following trauma exposure. Behavioral inhibition (BI) is the consistent temperamental tendency to avoid novel social and non-social situations, and in humans, BI is associated with an increased risk for PTSD. Previously, we compared human BI females to non-inhibited (NI) females with a 7% CO2 challenge or room air control. BI females showed reduced parasympathetic activation independent of condition, suggesting a hypervigilant vulnerability in anticipation of a stressor regardless of whether the stressor was delivered. The Wistar Kyoto (WKY) rat strain has been studied extensively as a model of BI and stress vulnerability. Most of these studies have focused on learning-related abnormalities, primarily exaggerated avoidance acquisition and resistance to extinguishing the avoidance response compared to Sprague Dawley (SD) rats, even when the aversive stimulus is intermittently delivered. The current study compared WKY and SD rats in a plethysmograph when challenged with 3%, 5%, and 7% CO2. Preliminarily, WKY rats appear to have a reduced frequency of breathing, tidal volume, and minute ventilation response to 3%, 5%, and 7% CO2 challenge, indicative of a decreased sensitivity to CO2. These findings highlight potentially critical physiological differences in the WKY rat’s sensitivity to a stressor such as CO2. Additional studies are necessary to elucidate the neural mechanisms underlying the differences in CO2 sensitivity in WKY rats. (Supported by the Wisconsin Space Consortium Early-Stage Investigator Grant, ESI24_2-0 to SJT.) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.