Real-time characterization of chemical threat agent aerosols for improvement of inhalation studies.

OBJECTIVES: Deliberate or accidental release of chemical treat agents in the aerosol form can cause an inhalation hazard. Since the relationship between aerosol properties and health hazards is poorly understood, research into the toxicological consequences of exposure to aerosols is needed. The aim of the present study was to improve the characterization of particles for inhalation studies. METHODS: Several aerosol measurement technologies were compared for their potential to physically and chemically characterize particles in the inhalation size range in real-time. For that purpose, we compared the performance of an aerodynamic particle sizer (APS), a scanning mobility particle sizer (SMPS) and an electrical low-pressure impactor (ELPI) in an experimental set-up in which particles were generated by a Collison nebulizer and subsequently delivered into a nose-only inhalation exposure system. RESULTS: We found that more than 95% of the number of particles, equating to more than 83% of the mass generated by the 6-jet Collison nebulizer, were below 0.5 µm. To characterize the entire size range, the APS as single detector has only limited value, therefore the addition of supplementary instrumentation such as the SMPS or the ELPI is required. After real-time measurements in the size range of 30 nm to 10 µm, ex-situ chromatographic chemical analysis is essential for quantification of the delivered mass concentration. CONCLUSIONS: In summary, the present work demonstrates the utility of the ELPI technology, in combination with off-line analysis, for characterizing aerosols with various size, shape, charge, and composition. This makes the aerosol generation and analysis suite described a promising tool for quantitative inhalation exposure studies.

Multiple analysis techniques were applied for real-time aerosol characterizationAerosol size distributions are characterized for inhalation exposure studies.Analytical analysis following ELPI measurements is essential for mass quantification.

A delayed treatment model for the evaluation of scopolamine for VX nerve agent intoxication.

Most research on medical countermeasures for nerve agent exposure assumes a military scenario, in which (autoinjector) treatment is envisaged to be available immediately. In a civilian setting however, treatment is delayed until arrival of first-aid responders. This may significantly affect treatment efficacy and the requirements for secondary intensive care. The aim of the current study was to develop a guinea pig model to evaluate the efficacy of delayed treatment following nerve agent exposure. We identified a trigger-to-treat based on a progressive stage of the toxidrome following VX exposure, which was associated with the subsiding of clonic movements. This paradigm resulted in treatment consistently being administered between 15 and 25 min post-exposure. Using the model, we investigated the potential for the anticholinergic scopolamine to act as a delayed treatment either as a standalone treatment, or as an adjunct to delayed treatment with Standard of Care (SOC), containing atropine, 2-PAM, and midazolam. The study provides a framework for a small animal model for evaluating the efficacy of treatment administered at a specific stage of the toxidrome, when immediate treatment is absent. As an adjunct, scopolamine treatment did not result in improved survival, but did show a beneficial effect on recovery, in terms of general posture. As a standalone treatment, scopolamine showed a significant, dose-responsive, beneficial effect on survival and recovery. These promising results warrant additional studies to investigate which observed physiological improvements are relevant for the recovery process and residual injury.

Pharmacokinetics and efficacy of atropine sulfate/obidoxime chloride co-formulation against VX in a guinea pig model.

Nerve agent exposure is generally treated by an antidote formulation composed of a muscarinic antagonist, atropine sulfate (ATR), and a reactivator of acetylcholinesterase (AChE) such as pralidoxime, obidoxime (OBI), methoxime, trimedoxime or HI-6 and an anticonvulsant. Organophosphates (OPs) irreversibly inhibit AChE, the enzyme responsible for termination of acetylcholine signal transduction. Inhibition of AChE leads to overstimulation of the central and peripheral nervous system with convulsive seizures, respiratory distress and death as result. The present study evaluated the efficacy and pharmacokinetics (PK) of ATR/OBI following exposure to two different VX dose levels. The PK of ATR and OBI administered either as a single drug, combined treatment but separately injected, or administered as the ATR/OBI co-formulation, was determined in plasma of naïve guinea pigs and found to be similar for all formulations. Following subcutaneous VX exposure, ATR/OBI-treated animals showed significant improvement in survival rate and progression of clinical signs compared to untreated animals. Moreover, AChE activity after VX exposure in both blood and brain tissue was significantly higher in ATR/OBI-treated animals compared to vehicle-treated control. In conclusion, ATR/OBI has been proven to be efficacious against exposure to VX and there were no PK interactions between ATR and OBI when administered as a co-formulation.

Early Detection of Exposure to Toxic Chemicals Using Continuously Recorded Multi-Sensor Physiology.

Early detection of exposure to a toxic chemical, e.g., in a military context, can be life-saving. We propose to use machine learning techniques and multiple continuously measured physiological signals to detect exposure, and to identify the chemical agent. Such detection and identification could be used to alert individuals to take appropriate medical counter measures in time. As a first step, we evaluated whether exposure to an opioid (fentanyl) or a nerve agent (VX) could be detected in freely moving guinea pigs using features from respiration, electrocardiography (ECG) and electroencephalography (EEG), where machine learning models were trained and tested on different sets (across subject classification). Results showed this to be possible with close to perfect accuracy, where respiratory features were most relevant. Exposure detection accuracy rose steeply to over 95% correct during the first five minutes after exposure. Additional models were trained to correctly classify an exposed state as being induced either by fentanyl or VX. This was possible with an accuracy of almost 95%, where EEG features proved to be most relevant. Exposure detection models that were trained on subsets of animals generalized to subsets of animals that were exposed to other dosages of different chemicals. While future work is required to validate the principle in other species and to assess the robustness of the approach under different, realistic circumstances, our results indicate that utilizing different continuously measured physiological signals for early detection and identification of toxic agents is promising.

Comparative physiology and efficacy of atropine and scopolamine in sarin nerve agent poisoning.

Anticholinergic treatment is key for effective medical treatment of nerve agent exposure. Atropine is included at a 2 mg intramuscular dose in so-called autoinjectors designed for self- and buddy-aid. As patient cohorts are not available, predicting and evaluating the efficacy of medical countermeasures relies on animal models. The use of atropine as a muscarinic antagonist is based on efficacy achieved in studies in a variety of species. The dose of atropine administered varies considerably across these studies. This is a complicating factor in the prediction of efficacy in the human situation, largely because atropine dosing also influences therapeutic efficacy of oximes and anticonvulsants generally part of the treatment administered. To improve translation of efficacy of dosing regimens, including pharmacokinetics and physiology provide a promising approach. In the current study, pharmacokinetics and physiological parameters obtained using EEG and ECG were assessed in naïve rats and in sarin-exposed rats for two anticholinergic drugs, atropine and scopolamine. The aim was to find a predictive parameter for therapeutic efficacy. Scopolamine and atropine showed a similar bioavailability, but brain levels reached were much higher for scopolamine. Scopolamine exhibited a dose-dependent loss of beta power in naïve animals, whereas atropine did not show any such central effect. This effect was correlated with an enhanced anticonvulsant effect of scopolamine compared to atropine. These findings show that an approach including pharmacokinetics and physiology could contribute to improved dose scaling across species and assessing the therapeutic potential of similar anticholinergic and anticonvulsant drugs against nerve agent poisoning.

Treatment efficacy in a soman-poisoned guinea pig model: added value of physostigmine?

Current treatment of organophosphate poisoning is insufficient, and survivors may suffer from long-lasting adverse effects, such as cognitive deficits and sleep-wake disturbances. In the present study, we aimed at developing a guinea pig model to investigate the benefits of immediate and delayed stand-alone therapy on the development of clinical signs, EEG, heart rate, respiration and AChE activity in blood and brain after soman poisoning. The model allowed the determination of the therapeutic effects at the short-term of obidoxime, atropine and physostigmine. Obidoxime exerted the highest therapeutic efficacy at administration of the lowest dose (3.1 mg/kg i.m.), whereas two higher doses (9 and 18 mg/kg) were less effective on most parameters. Addition of atropine at 0.03 and 3 mg/kg (i.m.) to the treatment did not improve the therapeutic effects of obidoxime alone. Physostigmine (0.8 mg/kg im) at 1 min after poisoning increased mortality. Two lower doses (0.1 and 0.3 mg/kg i.m.) showed improvements on all parameters but respiration. The middle dose was most effective in preventing seizure development and therefore assessed as the most efficacious dose. Combined treatment of obidoxime and physostigmine shortened the duration of seizures, if present, from up to 80 min to ~10-15 min. In practice, treatment will be employed when toxic signs appear, with the presence of high levels of AChE inhibition in both blood and brain. Administration of physostigmine at that moment showed to be redundant or even harmful. Therefore, treatment of OP poisoning with a carbamate, such as physostigmine, should be carefully re-evaluated.

Contact transfer risk from fentanyl-contaminated RSDL® Kit.

The RSDL® (Reactive Skin Decontamination Lotion) Kit contains a lotion-impregnated sponge extensively studied for the removal or neutralization of chemical warfare agents from skin. Pilot investigation of efficacy with industrial threat compounds noted that synthetic opioid fentanyl citrate was removed by the RSDL Kit but not chemically inactivated by the lotion. This implies that after use the RSDL Kit will contain intact fentanyl, which may pose a dermal health hazard if the fentanyl is then transferred to skin after use without proper handling. This in vitro investigation studied the contaminated RSDL Kit using three different concentrations of fentanyl with a skin contact time of 15 min under direct interaction from passive contact, light touch, and leaning with one hand. It was demonstrated that the expected transfer of fentanyl from contaminated RSDL depends on 1) the concentration of fentanyl and 2) the area of the exposed surface. From a toxicological perspective, the contact risk of fentanyl under the conditions tested can be considered low but not absent. The present study determined that a contaminated RSDL Kit, used for removal of fentanyl, should be handled with proper care. Use of protective gloves in operational use and washing skin afterwards is advised to prevent undesired contamination.

Pharmacokinetics of Three Oximes in a Guinea Pig Model and Efficacy of Combined Oxime Therapy.

Organophosphorus nerve agents (NA) inhibit acetylcholinesterase (AChE) which results in the over-stimulation of both the central and peripheral nervous systems, creating a toxic syndrome that can be lethal if left untreated (Cannard, 2006). It is standard practice to treat Sarin (GB) intoxication with an oxime, an antimuscarinic such as atropine and an anticonvulsant. Three common oximes are available: HI-6, Pralidoxime (2-PAM) and Obidoxime (Obi), all possess a nucleophile that can break the NA-AChE covalent bond. However, each oxime's efficacy profile against various agents is different (Thiermann and Worek, 2018). In an effort to broaden therapeutic efficacy against a range of possible NA's, consideration should be given to the use of two oximes in combination. Using a guinea pig model, the first arm of this study was to determine the pharmacokinetics (PK) of HI-6 DMS, 2-PAM chloride and Obi chloride (at autoinjector equivalent doses) following intramuscular (i.m.) co-administration along with atropine to replicate either a single isometrically scaled dose (referred to in this study as a single autoinjector equivalent) of 2-PAM (and equimolar doses of Obi and HI-6) or double doses (referred to in this study as two autoinjector equivalents). The second arm of the study evaluated the efficacy of Obi and 2-PAM individually at a single or double autoinjector dose and also in combination against GB exposure. Pharmacokinetic profiles of each oxime were evaluated for both arms of the study and no significant change in parameters were reported. Improved cholinesterase reactivation was observed in a dose dependent manner with combined therapy showing similar reactivation to individual oximes alone at a two autoinjector equivalent dose. Seizure activity was reduced when combined oxime therapy was administered. This improvement was also reflected in the Racine seizure index score assigned at the end of the experimental period. To the best of our knowledge, this study is the first to evaluate and compare the pharmacokinetics of three oximes and the combination of two oximes (2-PAM and Obi) administered in naïve animals or those exposed to GB. Combined oxime therapy (Obi and 2-PAM) resulted in improved seizure control, increased cholinesterase reactivation peripherally and centrally and improved behavioral signs (Racine score). This study provides evidence that combination of oximes is effective, does not result in adverse events and that the pharmacokinetics of each oxime are not affected when administered in combination.

Long-term cognitive deficits accompanied by reduced neurogenesis after soman poisoning.

To date, treatment of organophosphate (OP) poisoning shows several shortcomings, and OP-victims might suffer from lasting cognitive deficits and sleep-wake disturbances. In the present study, long-term effects of soman poisoning on learning ability, memory and neurogenesis were investigated in rats, treated with the anticholinergic atropine and the oxime HI-6 for reactivation of soman-inhibited acetylcholinesterase. We also investigated whether sub-chronic treatment with the reported neurogenesis enhancer olanzapine would stimulate neurogenesis and possibly normalize the anticipated long-term deleterious effects of soman intoxication. Animals were treated with HI-6 (125 mg/kg i.p.), followed after 30 min by soman (200 microg/kg s.c.) and atropine sulphate (16 mg/kg i.m.) 1 min thereafter. Soman poisoning led to an elevation of extracellular acetylcholine levels to 1500% over baseline values as assessed by striatal microdialysis. Brain acetylcholinesterase was inhibited over 95%. This was accompanied by short recurrent seizures lasting for 40 min. Osmotic minipumps releasing olanzapine (7.5 mg/kg/day) or vehicle were subcutaneously implanted 24 h post-intoxication. After drug delivery for 4 weeks, newborn cells were BrdU labeled. Learning and memory performance were assessed 8 weeks after soman poisoning, followed by analysis of surviving newborn cells (BrdU) and neurogenesis (doublecortin, DCX). Eight weeks after soman-intoxication a significantly impaired learning ability was found that was paralleled by significantly lower numbers of DCX-positive cells but no changes in the number of BrdU-labeled cells. Apparently, the present Olanzapine regime was ineffective. We conclude that soman poisoning has long lasting effects on learning ability, a finding that was accompanied by impaired neurogenesis. Although we confirm a correlation between impaired neurogenesis and cognitive deficits, establishing the true causal relationship between these processes in OP exposed animals awaits future research.

Efficacy of atropine sulfate/obidoxime chloride co-formulation against sarin exposure in guinea pigs.

The efficacy and pharmacokinetics of the aqueous co-formulation contents of the Trobigard™ (atropine sulfate, obidoxime chloride) auto-injector were evaluated in a sarin exposed guinea pig model. Two subcutaneous (sc) sarin challenge doses were evaluated in guinea pigs instrumented with brain and heart electrodes for electroencephalogram (EEG) and electrocardiogram (ECG). Sarin challenge doses were chosen to reflect exposure subclasses with sublethal (moderate to severe clinical signs) and lethal consequences. The level of protection of intramuscular human equivalent doses of the co-formulation was defined by (1) the mitigation of signs and symptoms at a sublethal level and (2) the increase of survival time at the supralethal sarin dose levels. Pharmacokinetics of both atropine sulfate and obidoxime were proportional at 1 and 3 human equivalent doses, and only a small increase in heart rate was observed briefly as a side effect. At both sarin challenge doses, 54 µg/kg and 84 µg/kg, the co-formulation treatment was effective against sarin-induced effects. Survival rates were improved at both sarin challenge levels, whereas clinical signs and changes in EEG activity could not in all cases be effectively mitigated, in particular at the supralethal sarin challenge dose level. Reactivation of sarin inhibited cholinesterase was observed in blood, and higher brain cholinesterase activity levels were associated with a better clinical condition of the co-formulation treated animals. Although the results cannot be directly extrapolated to the human situation, pharmacokinetics and the effects over time related to plasma levels of therapeutics in a freely moving guinea pig could aid translational models and possibly improve prediction of efficacy in humans.

Potentiation of antiseizure and neuroprotective efficacy of standard nerve agent treatment by addition of tariquidar.

Organophosphate (OP) induced seizures are commonly treated with anticholinergics, oximes and anticonvulsants. Inhibition of P-glycoprotein (PgP) has been shown to enhance the efficacy of nerve agent treatment in soman exposed rats. In the present study, the promising effects of the PgP inhibitor tariquidar were investigated in more detail in rats s.c. exposed to 150 µg/kg soman. Treatment with HI-6 and atropine sulfate (125 and 3 mg/kg i.m respectively) was administered 1 min after exposure. Diazepam (0.5 mg/kg i.m.) and/or tariquidar (7.5 mg/kg i.v.) were included either at 1 min or 40 min following onset of seizures. Animals that received tariquidar, in addition to HI-6 and atropine, at 1 min, displayed a rapid normalization of EEG activity and cessation of seizure-associated behaviour. This improvement by addition of tariquidar was even more substantial in animals that also received diazepam, either immediately or delayed. Animals exhibiting lower intensity seizures displayed less severe neuropathology (neuronal loss, microglia activation and astrogliosis), primarily in the piriform cortex, and to a lesser extent amygdala and entorhinal cortex. The present findings suggest that the interaction of tariquidar with atropine may be the decisive factor for enhanced treatment efficacy, given that atropine was previously found to be a PgP substrate. A more thorough understanding of the interactions of nerve agent antidotes, in particular the actions of central anticholinergics with benzodiazepines, could contribute to a future optimization of treatment combinations, particularly those aimed at later stage medical interventions.

Dietary Zinc Modulates Matrix Metalloproteinases in Traumatic Brain Injury.

Animal models of mild traumatic brain injury (mTBI) provide opportunity to examine the extent to which dietary interventions can be used to improve recovery after injury. Animal studies also suggest that matrix metalloproteinases (MMPs) play a role in tissue remodeling post-TBI. Because dietary zinc (Zn) improved recovery in nonblast mTBI models, and the MMPs are Zn-requiring enzymes, we evaluated the effects of low- (LoZn) and adequate-Zn (AdZn) diets on MMP expression and behavioral responses, subsequent to exposure to a single blast. MMP messenger RNA expression in soleus muscle and frontal cortex tissues were quantified at 48 h and 14 days post-blast. In muscle, blast resulted in significant upregulation of membrane-type (MT)-MMP, MMP-2, tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 at 48 h post-injury in rats consuming AdZn. At 14 days post-blast, there were no blast or dietary effects observed on MMP levels in muscle, supporting the existence of a Zn-responsive, functional repair and remodeling mechanism. In contrast, blast resulted in a significant downregulation of MT-MMP, TIMP-1, and TIMP-2 and a significant upregulation of MMP-3 levels at 48 h post-injury in cortex tissue, whereas at 14 days post-blast, MT-MMP, MMP-2, and TIMP-2 were all downregulated in response to blast, independent of diet, and TIMP-1 were significantly increased in rats fed AdZn diets despite the absence of elevated MMPs. Because the blast injuries occurred while animals were under general anesthesia, the increased immobility observed post-injury in rats consuming LoZn diets suggest that blast mTBI can, in the absence of any psychological stressor, induce post-traumatic stress disorder-related traits that are chronic, but responsive to diet. Taken together, our results support a relationship between marginally Zn-deficient status and a compromised regenerative response post-injury in muscle, likely through the MMP pathway. However, in neuronal tissue, changes in MMP/TIMP levels after blast indicate a variable response to marginally Zn-deficient diets that may help explain compromised repair mechanism(s) previously associated with the systemic hypozincemia that develops in patients with TBI.

Correlations between acetylcholinesterase inhibition, acetylcholine levels and EEG changes during perfusion with neostigmine and N6-cyclopentyladenosine in rat brain.

Organophosphate poisoning can result in seizures and subsequent neuropathology. In order to improve treatment strategies in organophosphate intoxication, the relationship between acetylcholinesterase inhibition, extracellular levels of acetylcholine, and electroencephalogram (EEG) changes was investigated during local perfusion of the reversible acetylcholinesterase inhibitor neostigmine in the hippocampus and striatum of freely moving rats. Acetylcholinesterase activity and acetylcholine levels were measured by microdialysis, and EEG signals were recorded from an electrode placed near the microdialysis probe. A non-linear relationship between the acetylcholinesterase activity and the extracellular amount of acetylcholine was found, the latter being approximately three times higher in the striatum than in the hippocampus upon infusion with 10(-4) M neostigmine. Highly accumulated extracellular acetylcholine significantly correlated with significant relative power increases of the EEG-gamma2-band and a significant relative power decrease in the beta2-band. Co-infusion of the adenosine A1 agonist N6-cyclopentyladenosine partly prevented acetylcholine accumulation, rendered both powers towards control values, and abolished the acetylcholine-EEG correlation. In view of the latter relationship, it is concluded that prevention of acetylcholine accumulation as a concept for neuroprotection in case of organophosphate poisoning, is worth to be further investigated.

Nanometric MIL-125-NH2 Metal-Organic Framework as a Potential Nerve Agent Antidote Carrier.

The three-dimensional (3D) microporous titanium aminoterephthalate MIL-125-NH2 (MIL: Material of Institut Lavoisier) was successfully isolated as monodispersed nanoparticles, which are compatible with intravenous administration, by using a simple, safe and low-cost synthetic approach (100 °C/32 h under atmospheric pressure) so that for the first time it could be considered for encapsulation and the release of drugs. The nerve agent antidote 2-[(hydroxyimino)methyl]-1-methyl-pyridinium chloride (2-PAM or pralidoxime) was effectively encapsulated into the pores of MIL-125-NH2 as a result of the interactions between 2-PAM and the pore walls being mediated by π-stacking and hydrogen bonds, as deduced from infrared spectroscopy and Monte Carlo simulation studies. Finally, colloidal solutions of MIL-125-NH2 nanoparticles exhibited remarkable stability in different organic media, aqueous solutions at different pH and under relevant physiological conditions over time (24 h). 2-PAM was rapidly released from the pores of MIL-125-NH2 in vitro.

Application of the Ugi Multicomponent Reaction in the Synthesis of Reactivators of Nerve Agent Inhibited Acetylcholinesterase.

Recently, a new class of reactivators of chemical warfare agent inhibited acetylcholinesterase (AChE) with promising in vitro potential was developed by the covalent linkage of an oxime nucleophile and a peripheral site ligand. However, the complexity of these molecular structures thwarts their accessibility. We report the compatibility of various oxime-based compounds with the use of the Ugi multicomponent reaction in which four readily accessible building blocks are mixed together to form a product that links a reactivating unit and a potential peripheral site ligand. A small library of imidazole and imidazolium reactivators was successfully synthesized using this method. Some of these compounds showed a promising ability to reactivate AChE inhibited by various types of CWA in vitro. Molecular modeling was used to understand differences in reactivation potential between these compounds. Four compounds were evaluated in vivo using sarin-exposed rats. One of the reactivators showed improved in vivo efficacy compared to the current antidote pralidoxime (2-PAM).

Increasing nerve agent treatment efficacy by P-glycoprotein inhibition.

One of the shortcomings of current treatment of nerve agent poisoning is that not all drugs effectively penetrate the blood-brain barrier (BBB), whereas most nerve agents easily do. P-glycoprotein (Pgp) efflux transporters at the BBB may contribute to this aspect. It was previously shown that Pgp inhibition by tariquidar enhanced the efficacy of nerve agent treatment when administered as a pretreatment. In the present study soman-induced seizures were also substantially prevented when the animals were intravenously treated with tariquidar post-poisoning, in addition to HI-6 and atropine. In these animals, approximately twice as much AChE activity was present in their brain as compared to control rats. The finding that tariquidar did not affect distribution of soman to the brain indicates that the potentiating effects were a result of interactions of Pgp inhibition with drug distribution. In line with this, atropine appeared to be a substrate for Pgp in in vitro studies in a MDR1/MDCK cell model. This indicates that tariquidar might induce brain region specific effects on atropine distribution, which could contribute to the therapeutic efficacy increase found. Furthermore, the therapeutic enhancement by tariquidar was compared to that of the less specific and less potent Pgp inhibitor cyclosporine A. This compound appeared to induce a protective effect similar to tariquidar. In conclusion, treatment with a Pgp inhibitor resulted in enhanced therapeutic efficacy of HI-6 and atropine in a soman-induced seizure model in the rat. The mechanism underlying these effects should be further investigated. To that end, the potentiating effect of nerve agent treatment should be addressed against a broader range of nerve agents, for oximes and atropine separately, and for those at lower doses. In particular when efficacy against more nerve agents is shown, a Pgp inhibitor such as tariquidar might be a valid addition to nerve agent antidotes.

Stress adversely affects efficacy of physostigmine-scopolamine pretreatment against soman in guinea pigs.

During military operations, soldiers may be exposed to mixtures of chemicals and to physical, emotional and psychological stress factors, which all may influence efficacy of any treatment, including the nerve agent pretreatment regimen. The purpose of this study was therefore to investigate the influence of chronic intermittent, variable, unpredictable and uncontrollable stress conditions on the side effects and therapeutic efficacy of the combination of physostigmine (0.025 mg/kg/h) and scopolamine (0.018 mg/kg/h) as a pretreatment against 2 x LD50 soman intoxication in guinea pigs. Stress during pretreatment led to an increase of motor activity and an increase of power in the EEG delta2 frequency band. After chronic stress, exposure of pretreated animals to 2 x LD50 soman resulted in more severe intoxication symptoms, a more persistent effect on the startle response, and considerable more severe and persistent effects on the EEG power-spectrum, indicating irreversible brain damage.

Anti-Parkinson effects of a selective alpha2C-adrenoceptor antagonist in the MPTP marmoset model.

Current dopamine replacement therapies, in Parkinson's disease (PD), result in aversive side effects and rapid drug dose escalation over time. Therefore, a non-dopaminergic treatment would be an advantageous supplement to lower the dose of dopamine replacement treatment postponing the occurrence of side effects. The noradrenergic system plays an important role in the facilitation or maintenance of the activity of the nigrostriatal dopamine pathways. Here the putative anti-Parkinson effects of the oral selective alpha2C-adrenoceptor antagonist (JNJ27063699 0.1-10mg/kg p.o.) and of vehicle (fruit syrup) were evaluated in the MPTP-marmoset model. Dose-related anti-Parkinson effects were assessed by means of a behavioural rating scale covering parkinsonian symptoms, body weight and body temperature, and two test systems assessing locomotor activity and complex motor skills of hand-eye coordination for controlled movements in MPTP- or saline-pretreated marmosets. JNJ27063699, at the middle and higher doses, consistently improved locomotor activity and hand-eye coordination capabilities, which indicates an improvement in the coordination of motor control -or movements- in MPTP-pretreated monkeys. No additional effects on the parkinsonian symptoms or side effects were observed on other test systems. Overall, the findings link deficit in motor coordination with dysfunctional adrenergic signalling and it suggest that selective alpha2C adrenergic antagonism may contribute to behavioural improvement in the MPTP-monkey model of PD. In multi-drug medication JNJ27063699 might have potential in the treatment of motor deficit in PD.

Timing of decontamination and treatment in case of percutaneous VX poisoning: a mini review.

Low volatile organophosphorous nerve agents such as VX, will most likely enter the body via the skin. The pharmacokinetics of drugs such as oximes, atropine and diazepam, are not aligned with the variable and persistent toxicokinetics of the agent. Repeated administration of these drugs showed to improve treatment efficacy compared to a single injection treatment. Because of the effectiveness of continuous treatment, it was investigated to what extent a subchronic pretreatment with carbamate (pyridostigmine or physostigmine combined with either procyclidine or scopolamine) would protect against percutaneous VX exposure. Inclusion of scopolamine in the pretreatment prevented seizures in all animals, but none of the pretreatments affected survival time or the onset time of cholinergic signs. These results indicate that percutaneous poisoning with VX requires additional conventional treatment in addition to the current pretreatment regimen. Decontamination of VX-exposed skin is one of the most important countermeasures to mitigate the effects of the exposure. To evaluate the window of opportunity for decontamination, the fielded skin decontaminant Reactive Skin Decontaminant Lotion (RSDL) was tested at different times in hairless guinea pigs percutaneously challenged with 4× LD50 VX in IPA. The results showed that RSDL decontamination at 15 min after exposure could not prevent progressive blood cholinesterase inhibition and therefore would still require additional treatment. A similar decontamination regimen with RSDL at 90 min showed that it still might effectively increase the time window of opportunity for treatment. In conclusion, the delay in absorption presents a window of opportunity for decontamination and treatment. The continuous release of VX from the skin presents a significant challenge for efficacious therapy, which should ideally consist of thorough decontamination and continuous treatment.

Non-enzymatic pretreatment of nerve agent (soman) poisoning: a brief state-of-the-art review.

The rapid onset of toxic signs following nerve agent intoxication and the apprehension that current therapy (atropine, oxime, diazepam) may not prevent brain damage, requires supportive pretreatment. Since the current pretreatment drug pyridostigmine fails in protecting brain-AChE, more effective pretreatment is necessary. A main focus of present-day pretreatment research is on bioscavengers, another is on centrally active reversible AChE-inhibitors combined with drugs showing anti-cholinergic, anti-glutamatergic, neuroprotective and non-sedating GABA-ergic activity. Strategies aimed at improving efficacy of pharmacological pretreatment will briefly be discussed. Galantamine, given as a pretreatment or stand-alone therapy, emerged as one of the best medical countermeasures against nerve agent poisoning in guinea pigs. Other preclinical studies demonstrated effective pretreatment consisting of physostigmine combined with procyclidine, scopolamine or bupropion (all single injections), against nerve agent poisoning in guinea pigs. A long sign-free pretreatment with physostigmine (Alzet pump), combined with single injection of procyclidine just before soman poisoning, enhanced the efficacy of a post-poisoning therapy consisting of 3 autoinjector equivalents of HI-6, atropine and diazepam, considerably.