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This study examined the real-time exposure–response effects of aerosolized carfentanil (CRF) on opioid-induced toxicity, respiratory dynamics and cardiac function in mice. Unrestrained, conscious male CD-1 mice (25–30 g) were exposed to 0.4 or 4.0 mg/m3of aerosolized CRF for 15 min (Ct = 6 or 60 mg min/m3) in a whole-body plethysmograph chamber. Minute volume (MV), core body temperature (Tc), mean arterial blood pressure (MAP) and heart rate (HR) were evaluated in animals exposed to CRF or sterile H2O. Loss of consciousness and Straub tail were observed in before 1 min following initiation of exposure to 6 or 60 mg min/m3of CRF. Clinical signs of opioid-induced toxicity were observed in a dose-dependent manner. Exposure to 6 or 60 mg min/m3of CRF resulted in significant decrease in MV as compared to the controls. MAP, HR andTcdecreased 24 h in animals exposed to either 6 or 60 mg min/m3of CRF as compared to the controls. Post-exposure administration of naloxone (NX, 0.05 mg/kg,i.m.) did not increase the MV of animals exposed to CRF to control levels within 24 h, but decreased clinical signs of opioid-induced toxicity and the duration of respiratory depression. This is the first study to evaluate real-time respiratory dynamics and cardiac function during exposure and up to 24 h post-exposure to CRF. The evaluation of toxicological signs and respiratory dynamics following exposure to CRF will be useful in the development of therapeutic strategies to counteract the ongoing threat of abuse and overuse of opioids and their synthetic variants. [ABSTRACT FROM PUBLISHER]

Acute respiratory dynamics and histopathology of the lungs and trachea following inhaled exposure to ammonia were investigated. Respiratory dynamic parameters were collected from male Sprague–Dawley rats (300–350 g) during (20 min) and 24 h (10 min) after inhalation exposure for 20 min to 9000, 20,000, and 23,000 ppm of ammonia in a head-only exposure system. Body weight loss, analysis of blood cells, and lungs and trachea histopathology were assessed 1, 3, and 24 h following inhalation exposure to 20,000 ppm of ammonia. Prominent decreases in minute volume (MV) and tidal volume (TV) were observed during and 24 h post-exposure in all ammonia-exposed animals. Inspiratory time (IT) and expiratory time (ET) followed similar patterns and decreased significantly during the exposure and then increased at 24 h post-exposure in all ammonia-exposed animals in comparison to air-exposed controls. Peak inspiratory (PIF) and expiratory flow (PEF) significantly decreased during the exposure to all ammonia doses, while at 24 h post-exposure they remained significantly decreased following exposure to 20,000 and 23,000 ppm. Exposure to 20,000 ppm of ammonia resulted in body weight loss at 1 and 3 h post-exposure; weight loss was significant at 24 h compared to controls. Exposure to 20,000 ppm of ammonia for 20 min resulted in increases in the total blood cell counts of white blood cells, neutrophils, and platelets at 1, 3, and 24 h post-exposure. Histopathologic evaluation of the lungs and trachea tissue of animals exposed to 20,000 ppm of ammonia at 1, 3, and 24 h post-exposure revealed various morphological changes, including alveolar, bronchial, and tracheal edema, epithelial necrosis, and exudate consisting of fibrin, hemorrhage, and inflammatory cells. The various alterations in respiratory dynamics and damage to the respiratory system observed in this study further emphasize ammonia-induced respiratory toxicity and the relevance of efficacious medical countermeasure strategies. [ABSTRACT FROM PUBLISHER]

This study examined acute toxicity and lung injury following inhalation exposure to ammonia. Male Sprague-Dawley rats (300–350 g) were exposed to 9000, 20 000, 23 000, 26 000, 30 000 or 35 000 ppm of ammonia for 20 min in a custom head-out exposure system. The exposure atmosphere, which attained steady state within 3 min for all ammonia concentrations, was monitored and verified using a Fourier transform infrared spectroscopy (FTIR) gas analyzer. Animals exposed to ammonia resulted in dose-dependent increases in observed signs of intoxication, including increased chewing and licking, ocular irritation, salivation, lacrimation, oronasal secretion and labored breathing. The LCt50of ammonia within this head-out inhalation exposure model was determined by probit analysis to be 23 672 ppm (16 489 mg/m3) for the 20 min exposure in male rats. Exposure to 20 000 or 23 000 ppm of ammonia resulted in significant body weight loss 24-h post-exposure. Lung edema increased in all ammonia-exposed animal groups and was significant following exposure to 9000 ppm. Bronchoalveolar fluid (BALF) protein concentrations significantly increased following exposure to 20 000 or 23 000 ppm of ammonia in comparison to controls. BAL cell (BALC) death and total cell counts increased in animals exposed to 20 000 or 23 000 ppm of ammonia in comparison to controls. Differential cell counts of white blood cells, neutrophils and platelets from blood and BALF were significantly increased following exposure to 23 000 ppm of ammonia. The following studies describe the validation of a head-out inhalation exposure model for the determination of acute ammonia-induced toxicity; this model will be used for the development and evaluation of potential therapies that provide protection against respiratory and systemic toxicological effects. [ABSTRACT FROM PUBLISHER]

Neurological toxicity and brain injury following vapor inhalation exposure to the chemical warfare nerve agent (CWNA) soman (GD) were examined in untreated non-anesthetized rats. In this study, male Sprague-Dawley rats (300–350 g) were exposed to 600 mg × min/m3of soman or vehicle in a customized head-out inhalation system for 7 min. Convulsant animals were observed for clinical signs and various regions of the brain (dorsolateral thalamus, basolateral amygdala, piriform cortex, and lateral cortex) were collected for pathological observations 24 h post-exposure. Signs of CWNA-induced cholinergic crises including salivation, lacrimation, increased urination and defecation, and tremors were observed in all soman-exposed animals. Soman-exposed animals at 24 h post-exposure lost 11% of their body weight in comparison to 2% in vehicle-exposed animals. Whole blood acetylcholinesterase (AChE) activity was significantly inhibited in all soman-exposed groups in comparison to controls. Brain injury was confirmed by the neurological assessment of hematoxylin-eosin (H&E) staining and microscopy in the piriform cortex, dorsolateral thalamus, basolateral amygdala, and lateral cortex. Severe damage including prominent lesions, edematous, congested, and/or hemorrhagic tissues was observed in the piriform cortex, dorsolateral thalamus, and lateral cortex in soman-exposed animals 24 h post-exposure, while only minimal damage was observed in the basolateral amygdala. These results indicate that inhalation exposure to soman vapor causes neurological toxicity and brain injury in untreated unanesthetized rats. This study demonstrates the ability of the described soman vapor inhalation exposure model to cause neurological damage 24 h post-exposure in rats. [ABSTRACT FROM PUBLISHER]

Respiratory dynamics were investigated in head-out plethysmography chambers following inhalational exposure to soman in untreated, non-anesthetized rats. A multipass saturator cell was used to generate 520, 560 and 600 mg × min/m3of soman vapor in a customized inhalational exposure system. Various respiratory dynamic parameters were collected from male Sprague-Dawley rats (300--350 g) during (20 min) and 24 h (10 min) after inhalational exposure. Signs of CWNA-induced cholinergic crisis were observed in all soman-exposed animals. Percentage body weight loss and lung edema were observed in all soman-exposed animals, with significant increases in both at 24 h following exposure to 600 mg × min/m3. Exposure to soman resulted in increases in respiratory frequency (RF) in animals exposed to 560 and 600 mg × min/m3with significant increases following exposure to 560 mg × min/m3at 24 h. No significant alterations in inspiratory time (IT) or expiratory time (ET) were observed in soman-exposed animals 24 h post-exposure. Prominent increases in tidal volume (TV) and minute volume (MV) were observed at 24 h post-exposure in animals exposed to 600 mg × min/m3. Peak inspiratory (PIF) and expiratory flow (PEF) followed similar patterns and increased 24 h post-exposure to 600 mg × min/m3of soman. Results demonstrate that inhalational exposure to 600 mg × min/m3soman produces notable alterations in various respiratory dynamic parameters at 24 h. The following multitude of physiological changes in respiratory dynamics highlights the need to develop countermeasures that protect against respiratory toxicity and lung injury. [ABSTRACT FROM PUBLISHER]

This study evaluated acute toxicity and pulmonary injury in rats at 3, 6 and 24 h after an inhalation exposure to aerosolized O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX). Anesthetized male Sprague-Dawley rats (250-300 g) were incubated with a glass endotracheal tube and exposed to saline or VX (171, 343 and 514 mg×min/m3 or 0.2, 0.5 and 0.8 LCt50, respectively) for 10 min. VX was delivered by a small animal ventilator at a volume of 2.5 ml × 70 breaths/minute. All VX-exposed animals experienced a significant loss in percentage body weight at 3, 6, and 24 h post-exposure. In comparison to controls, animals exposed to 514 mg×min/m3 of VX had significant increases in bronchoalveolar lavage (BAL) protein concentrations at 6 and 24 h post-exposure. Blood acetylcholinesterase (AChE) activity was inhibited dose dependently at each of the times points for all VX-exposed groups. AChE activity in lung homogenates was significantly inhibited in all VX-exposed groups at each time point. All VX-exposed animals assessed at 20 min and 3, 6 and 24 h post-exposure showed increases in lung resistance, which was prominent at 20 min and 3 h post-exposure. Histopathologic evaluation of lung tissue of the 514 mg×min/m3 VX-exposed animals at 3, 6 and 24 h indicated morphological changes, including perivascular inflammation, alveolar exudate and histiocytosis, alveolar septal inflammation and edema, alveolar epithelial necrosis, and bronchiolar inflammatory infiltrates, in comparison to controls. These results suggest that aerosolization of the highly toxic, persistent chemical warfare nerve agent VX results in acute pulmonary toxicity and lung injury in rats. [ABSTRACT FROM AUTHOR]

This study characterizes the development of a head-out inhalation exposure system for assessing respiratory toxicity of vaporized chemical agents in untreated, non-anesthetized rats. The organophosphate diisopropyl fluorophosphate (DFP) induces classical cholinergic toxicity following inhalation exposure and was utilized to validate the effectiveness of this newly designed inhalation exposure system. A saturator cell apparatus was used to generate DFP vapor at 9750, 10 950, 12 200, 14 625 and 19 500 mg × min/m3 which was carried by filtered nitrogen into a glass mixing tube, where it combined with ambient air before being introduced to the custom-made glass exposure chamber. Male Sprague-Dawley rats (250-300 g) were restrained in individual head-out plethysmography chambers, which acquired respiratory parameters before, during and after agent exposure. All animals were acclimated to the exposure system prior to exposure to reduce novel environment-induced stress. The LCt50, as determined by probit analysis, was 12 014 mg × min/m3. Weight loss in exposed animals was dose-dependent and ranged from 8 to 28% of their body weight 24 h after exposure. Increased salivation, lacrimation, urination, defecation (SLUD) and mild muscular fasciculation were observed in all DFP-exposed animals during and immediately following exposure. In all exposed animals, DFP vapor produced significant inhibition of acetylcholinesterase (AChE) activity in cardiac blood, bronchoalveolar lavage fluid (BALF), whole brain and lung tissue as well as alterations in tidal volume and minute volume. These studies have provided valuable information leading to the initiation of studies evaluating inhalational toxicity and treatments following exposure to the more lethal and potent chemical warfare nerve agents. [ABSTRACT FROM AUTHOR]

We evaluated the efficacy of aerosolized acetylcholinesterase (AChE) reactivator oxime MMB-4 in combination with the anticholinergic atropine sulfate for protection against respiratory toxicity and lung injury following microinstillation inhalation exposure to nerve agent soman (GD) in guinea pigs. Anesthetized animals were exposed to GD (841 mg/m3, 1.2 LCt50) and treated with endotracheally aerosolized MMB-4 (50 µmol/kg) plus atropine sulfate (0.25 mg/kg) at 30 sec post-exposure. Treatment with MMB-4 plus atropine increased survival to 100% compared to 38% in animals exposed to GD. Decreases in the pulse rate and blood O2 saturation following exposure to GD returned to normal levels in the treatment group. The body-weight loss and lung edema was significantly reduced in the treatment group. Similarly, bronchoalveolar cell death was significantly reduced in the treatment group while GD-induced increase in total cell count was decreased consistently but was not significant. GD-induced increase in bronchoalveolar protein was diminished after treatment with MMB-4 plus atropine. Bronchoalveolar lavage AChE and BChE activity were significantly increased in animals treated with MMB-4 plus atropine at 24 h. Lung and diaphragm tissue also showed a significant increase in AChE activity in the treatment group. Treatment with MMB-4 plus atropine sulfate normalized various respiratory dynamics parameters including respiratory frequency, tidal volume, peak inspiratory and expiratory flow, time of inspiration and expiration, enhanced pause and pause post-exposure to GD. Collectively, these results suggest that aerosolization of MMB-4 plus atropine increased survival, decreased respiratory toxicity and lung injury following GD inhalation exposure. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in the blood and tissues of animals that are treated with a number of endotracheally aerosolized therapeutics for protection against inhalation toxicity to sarin. Therapeutics included, aerosolized atropine methyl bromide (AMB), scopolamine or combination of AMB with salbutamol, sphingosine 1-phosphate, keratinocyte growth factor, adenosine A1 receptor antisense oligonucleotide (EPI2010), 2,3-diacetyloxybenzoic acid (2,3 DABA), oxycyte, and survanta. Guinea pigs exposed to 677.4 mg/m3 or 846.5 mg/m3 (1.2 LCt50) sarin for 4 min using a microinstillation inhalation exposure technique and treated 1 min later with the aerosolized therapeutics. Treatment with all therapeutics significantly increased the survival rate with no convulsions throughout the 24 h study period. Blood AChE activity determined using acetylthiocholine as substrate showed 20% activity remaining in sarin-exposed animals compare to controls. In aerosolized AMB and scopolamine-treated animals the remaining AChE activity was significantly higher (45-60%) compared to sarin-exposed animals ( p < 0.05). Similarly, treatment with all the combination therapeutics resulted in significant increase in blood AChE activity in comparison to sarin-exposed animals although the increases varied between treatments ( p < 0.05). BChE activity was increased after treatment with aerosolized therapeutics but was lesser in magnitude compared to AChE activity changes. Various tissues showed elevated AChE activity after therapeutic treatment of sarin-exposed animals. Increased AChE and BChE activities in animals treated with nasal therapeutics suggest that enhanced breathing and reduced respiratory toxicity/lung injury possibly contribute to rapid normalization of chemical warfare nerve agent inhibited cholinesterases. [ABSTRACT FROM AUTHOR]

Sarin is a volatile nerve agent that has been used in the Tokyo subway attack. Inhalation is predicted to be the major route of exposure if sarin is used in war or terrorism. Currently available treatments are limited for effective postexposure protection against sarin under mass casualty scenario. Nasal drug delivery is a potential treatment option for mass casualty under field conditions. We evaluated the efficacy of endotracheal administration of muscarinic antagonist scopolamine, a secretion blocker which effectively crosses the blood-brain barrier for protection against sarin inhalation toxicity. Age and weight matched male Hartley guinea pigs were exposed to 677.4 mg/m3 or 846.5 mg/ m3 (1.2 ×× LCt50) sarin by microinstillation inhalation exposure for 4 min. One minute later, the animals exposed to 846.5 mg/ m3 sarin were treated with endotracheally aerosolized scopolamine (0.25 mg/kg) and allowed to recover for 24 h for efficacy evaluation. The results showed that treatment with scopolamine increased the survival rate from 20% to 100% observed in untreated sarin-exposed animals. Behavioral symptoms of nerve agent toxicity including, convulsions and muscular tremors were reduced in sarin-exposed animals treated with scopolamine. Sarin-induced body weight loss, decreased blood O2 saturation and pulse rate were returned to basal levels in scopolamine-treated animals. Increased bronchoalveolar lavage (BAL) cell death due to sarin exposure was returned to normal levels after treatment with scopolamine. Taken together, these data indicate that postexposure treatment with aerosolized scopolamine prevents respiratory toxicity and protects against lethal inhalation exposure to sarin in guinea pigs. [ABSTRACT FROM AUTHOR]

The efficacy of endotracheal aerosolization of atropine sulfate for protection against soman (GD)-induced respiratory toxicity was investigated using microinstillation technique in guinea pigs. GD (841 mg/m3, 1.3 LCt50 or 1121 mg/m3, 1.7 LCt50) was aerosolized endotracheally to anesthetized male guinea pigs that were treated with atropine sulfate (5.0 mg/kg) 30 s postexposure by endotracheal microinstillation. Animals exposed to 841 mg/m3 and 1121 mg/m3GD resulted in 31 and 13% while treatment with atropine sulfate resulted in 100 and 50% survival, respectively. Cholinergic symptoms and increased body weight loss were reduced in atropine-treated animals compared to GD controls. Diminished pulse rate and blood O2 saturation in GD-exposed animals returned to normal levels after atropine treatment. Increased cell death, total cell count and protein in the bronchoalveolar fluid (BALF) in GD-exposed animals returned to normal levels following atropine treatment. GD exposure increased glutathione and superoxide dismutase levels in BALF and that were reduced in animals treated with atropine. Respiratory parameters measured by whole-body barometric plethysmography revealed that treatment with atropine sulfate resulted in normalization of respiratory frequency, tidal volume, time of expiration, time of inspiration, end expiratory pause, pseudo lung resistance (Penh) and pause at 4 and 24 h post 841 mg/m3 GD exposure. Lung histopathology showed that atropine treatment reduced bronchial epithelial subepithelial inflammation and multifocal alveolar septal edema. These results suggest that endotracheal aerosolization of atropine sulfate protects against respiratory toxicity and lung injury induced by microinstillation inhalation exposure to lethal doses of GD. [ABSTRACT FROM AUTHOR]