Repetitive antidotal treatment is crucial in eliminating eye pathology, respiratory toxicity and death following whole-body VX vapor exposure in freely moving rats.

Exposure to the chemical warfare nerve agent VX is extremely toxic, causing severe cholinergic symptoms. If not appropriately treated, death ultimately ensues. Based on our previously described whole-body vapor exposure system, we characterized in detail the clinical outcome, including respiratory dynamics, typical of whole-body exposure to lethal doses of VX vapor in freely moving rats. We further evaluated the efficacy of two different antidotal regimens, one comprising a single and the other repeated administration of antidotes, in countering the toxic effects of the exposure. We show that a 15 min exposure to air VX concentrations of 2.34-2.42 mg/m3 induced a late (15-30 min) onset of obvious cholinergic signs, which exacerbated over time, albeit without convulsions. Marked eye pathology was observed, characterized by pupil constriction to pinpoint, excessive lacrimation with red tears (chromodacryorrhea) and corneal damage. Respiratory distress was also evident, characterized by a three-fourfold increase in Penh values, an estimate of lung resistance, and by lung and diaphragm histological damage. A single administration of TAB (the oxime TMB-4, atropine and the anticholinergic and antiglutamatergic benactyzine) at the onset of clinical signs afforded only limited protection (66% survival), with clinical deterioration including weight loss, chromodacryorrhea, corneal damage, increased airway resistance and late death. In contrast, a combined therapy of TAB at the onset of clinical signs and repeated administration of atropine and toxogonin (ATOX) every 3-5 h, a maximum of five i.m. injections, led to 100% survival and a prompt recovery, accompanied by neither the above-described signs of eye pathology, nor by bronchoconstriction and respiratory distress. The necessity of recurrent treatments for successful elimination of VX vapor toxicity strongly supports continuous penetration of VX following termination of VX vapor exposure, most likely from a VX reservoir formed in the skin due to the exposure. This, combined with the above-described eye and respiratory pathology and absence of convulsions, are unique features of whole-body VX vapor exposure as compared to whole-body vapor exposure to other nerve agents, and should accordingly be considered when devising optimal countermeasures and medical protocols for treatment of VX vapor exposure.

Sex modulated effects of sarin exposure in rats: Toxicity, hypothermia and inflammatory markers.

This work focused on sex differences in rats exposed to sarin. Females were found to be more sensitive to sarin toxicity (LD50 67 µg/kg) than males (88 µg/kg), showed less acute hypothermic effects than males (at 120 min post sarin, 3.1 ±â€¯1.1 and 4.5 ±â€¯1 °C decrease, respectively), but with a significant slower recovery over days. Females' temperature response to the cholinergic agonist oxotremorine (0.25 mg/kg, im) was more pronounced than that of males (at 30 min, 3.13 ±â€¯0.27 and 2.13 ±â€¯0.19 °C decrease, respectively) and both sexes recovered within 2 h of exposure. 24 h after sarin exposure (80 µg/kg) followed 1 min later by TA treatment (TMB4 7.5 mg/kg and atropine 5 mg/kg) a 255% increase in plasma MCP-1 in males but not in females was recorded. In the brain, TIMP-1 increased 43 fold in females and 25 fold in males, compared to control rats. MCP-1 increased 8 fold in females only. TNFα increased in both sexes, but the increase in female brain was higher than that recorded in males. IL-6 increased in females but not in males. IL-1ß increased in both sexes. This work clearly demonstrates significant sex modulation effects on measures of toxicity, hypothermia and inflammatory markers in brain and plasma 24 h following exposure to sarin. In general, females seem to be more sensitive to the toxicity of sarin, but may be better protected against its brain damage. In light of these and other findings, the efficacy of the various available treatments, as well as those being developed, should be evaluated in both sexes.