We investigated the toxic effects of the chemical warfare nerve agent (CWNA) soman (GD) on the respiratory dynamics of guinea pigs following microinstillation inhalation exposure. Male Hartley guinea pigs were exposed to 841 mg/m3 of GD or saline for 4 min. At 24 and 48 h post GD exposure, respiratory dynamics and functions were monitored for 75 min after 1 h of stabilization in a barometric whole-body plethysmograph. GD-exposed animals showed a significant increase in respiratory frequency (RF) at 24 h postexposure compared to saline controls.The 24-h tidal volume (TV) increased in GD-exposed animals during the last 45 min of the 75-min monitoring period in the barometric whole-body plethysmograph. Minute ventilation also increased significantly at 24 h post GD exposure. The peak inspiratory flow (PIF) increased, whereas peak expiratory flow (PEF) decreased at 24 h and was erratic following GD exposure. Animals exposed to GD showed a significant decrease in expiratory(Te) and inspiratory time (Ti). Although end inspiratory pause (EIP) and end expiratory pause (EEP) were both decreased 24 h post GD exposure, EEP was more evident. Pause (P) decreased equally during the 75-min recording in GD-exposed animals, whereas the pseudo lung resistance (Penh) decreased initially during the monitoring period but was near control levels at the end of the 75-min period. The 48-h respiratory dynamics and function parameter were lower than 24 post GD exposures. These results indicate that inhalation exposure to soman in guinea pigs alters respiratory dynamics and function at 24 and 48 h postexposure

While assessing the methylphosphonothioic acid S-(2-(bis(1-methylethyl)amino)ethyl)O-ethyl ester (VX) induced respiratory toxicity and evaluating therapeutics against lung injury, we observed that the animals were experiencing abnormal swelling in the abdominal area. Nerve agent has been known to increase salivary, nasal and gastrointestinal secretion and cause diarrhea. This study was initiated to investigate the effect of VX on the gastrointestinal tract (GI) since abdominal pathology may affect breathing and contribute to the on going respiratory toxicity. The mid-abdominal diameter and the size of the lower left abdomen was measured before and after 27.3 mg/m3 VX exposure by microinstillation and at 30 min intervals up to 2 h post-VX exposure. Both VX and saline exposed animals exhibited a decrease in circumference of the upper abdomen, although the decrease was slightly higher in VX-exposed animals up to 1 h. The waist diameter increased slightly in VX-exposed animals from 60 to 90 min post-VX exposure but was similar to saline controls. The lower left abdomen near to the cecum, 6 cm below and 2cm to the right of the end of the sternum, showed an increase in size at 30-60 min that was significantly increased at 90-120 min post-VX exposure. In addition, VX-exposed animals showed loose fecal matter compared to controls. Necropsy at 24h showed an increased small intestine twisting motility in VX-exposed animals. Body tissue AChE assay showed high inhibition in the esophagus and intestine in VX-exposed animals indicating that a significant amount of the agent is localized to the GI following microinstillation exposure. These results suggest that microinstillatipn inhalation VX exposure induces gastrointestinal disturbances similar to that of irritable bowel syndrome and bloating.