Real-Time Neurobehavioral Effects of Single and Combined Chemical Exposures Via Inhalation in Rats

Individuals who experience Physiological Episodes (PEs) may present with a broad range of symptoms including the following: tingling and/or weakness of the limbs and extremities, headaches, dizziness, and in some cases, loss of consciousness. A number of chemical contaminants have been identified in the breathing gases onboard U.S. Navy T-45 aircraft and F-18 family of aircraft. Two of those chemicals included trimethylsilanol (TMS) and trichloromethane (TCM)/chloroform. TMS and TCM have been shown to cause anesthetic effects; therefore, concern has been raised that their presence, or combined presence, may be a factor in some of the recent PEs that have been experienced by Navy aircrews. The purpose of this study was to determine if exposure to these two different compounds in combination could cause short-term effects on the brain during exposure (i.e., in real-time) using a rat model. The reason that this is important is because it was determined that low concentrations of chemical contaminants were being detected in cockpit environments, including in the breathing air supplied by the Onboard Oxygen Generating System (OBOGS). Although many of the chemicals were found at very low levels (i.e. lower than what would be expected to cause an effect), it was unclear if a short exposure (i.e. 30 minutes) to a combination of the chemicals, each at a low level, can contribute to the cognitive effects and symptoms observed during PEs. This study determined the exposure-dependent effects of the two chemicals on male Sprague-Dawley rats. In Experiment 1, rats were exposed to low, mid, or high concentrations of TMS and TCM individually for 30 minutes while the animals were undergoing real-time behavioral testing. This process was necessary to determine the effective concentration for each chemical.