Nerve agent-induced seizures can cause varying degrees of neuropathology depending on level of poisoning and duration of seizing. The intention of this review was to validate a novel approach for establishing effective treatment regimens against soman poisoning. Identification of seizure controlling sites in the forebrain of rats poisoned by soman was made by means of lesions, and the anticonvulsive properties of a number of relevant drugs were tested by microinfusions into the identified areas. By using these procedures, procyclidine emerged as the most potent drug. Its potency was confirmed in systemic studies and is further enhanced when combined with levetiracetam. Acute treatment with a combination of HI-6, levetiracetam and procyclidine (procyclidine regimen) can effectively manage supralethal poisoning by any of the classical nerve agents. Extended treatment with the procyclidine regimen is able to terminate residual "silent", local epileptiform activity in the severely poisoned rats. Evident advantages are seen when the same regimen exerts both powerful anticonvulsant and neuroprotectant efficacies. According to the results presented, the new strategy for establishing therapies against soman-induced seizures appears to be valid.

Compounds that cause powerful sensory irritation to humans were reviewed by the Scientific Advisory Board (SAB) of the Organisation for the Prohibition of Chemical Weapons (OPCW) in response to requests in 2014 and 2017 by the OPCW Director-General to advise which riot control agents (RCAs) might be subject to declaration under the Chemical Weapons Convention (the "Convention"). The chemical and toxicological properties of 60 chemicals identified from a survey by the OPCW of RCAs that had been researched or were available for purchase, and additional chemicals recognised by the SAB as having potential RCA applications, were considered. Only 17 of the 60 chemicals met the definition of a RCA under the Convention. These findings were provided to the States Parties of the Convention to inform the implementation of obligations pertaining to RCAs under this international chemical disarmament and non-proliferation treaty.

AbstractAdvances across the chemical and biological (life) sciences are increasingly enabled by ideas and tools from sectors outside these disciplines, with information and communication technologies playing a key role across 21stcentury scientific development. In the face of rapid technological change, the Organisation for the Prohibition of Chemical Weapons (OPCW), the implementing body of the Chemical Weapons Convention (“the Convention”), seeks technological opportunities to strengthen capabilities in the field of chemical disarmament. The OPCW Scientific Advisory Board (SAB) in its review of developments in science and technology examined the potential uses of emerging technologies for the implementation of the Convention at a workshop entitled “Innovative Technologies for Chemical Security”, held from 3 to 5 July 2017, in Rio de Janeiro, Brazil. The event, organized in cooperation with the International Union of Pure and Applied Chemistry (IUPAC), the National Academies of Science, Engineering and Medicine of the United States of America, the Brazilian Academy of Sciences, and the Brazilian Chemical Society, was attended by 45 scientists and engineers from 22 countries. Their insights into the use of innovative technological tools and how they might benefit chemical disarmament and non-proliferation informed the SAB’s report on developments in science and technology for the Fourth Review Conference of the Convention (to be held in November 2018), and are described herein, as are recommendations that the SAB submitted to the OPCW Director-General and the States Parties of the Convention. It is concluded that technologies exist or are under development that could be used for investigations, contingency, assistance and protection, reducing risks to inspectors, and enhancing sampling and analysis.

The threat of chemical warfare agents like nerve agents requires life saving measures of medical pretreatment combined with treatment after exposure. Pretreatment (pyridostigmine) may cause some side effects in a small number of individuals. A comprehensive research on animals has been performed to clarify effects on behavior. The results from these studies are far from unambiguous, since pyridostigmine may produce adverse effects on behavior in animals in relatively high doses, but not in a consistent way. Other animal studies have examined the potential of drugs like physostigmine, galantamine, benactyzine, trihexyphenidyl, and procyclidine, but they all produce marked behavioral impairment at doses sufficient to contribute to protection against a convulsant dose of soman. Attempts have also been made to develop a combination of drugs capable of assuring full protection (prophylaxis) against nerve agents. However, common to all combinations is that they at anticonvulsant doses cause behavioral deficits. Therefore, the use of limited pretreatment doses may be performed without marked side effects followed by post-exposure therapy with a combination of drugs.

A treatment regimen consisting of HI-6, levetiracetam, and procyclidine (termed the triple regimen) has previously been shown to work as a universal therapy against soman poisoning in rats, since it has capacities to function as both prophylactic and therapeutic measure. The purpose of the present study was to examine whether the triple regimen may have antidotal efficacy against intoxication by other classical nerve agents than soman. The treatment was given 1 and 5 min after exposure to a supralethal dose of nerve agents, and the results showed that the triple regimen successfully prevented or terminated seizures and preserved the lives of rats exposed to 5×LD50 of soman, sarin, cyclosarin, or VX, but solely 3×LD50 of tabun was managed by this regimen. To meet the particular antidotal requirements of tabun, the triple regimen was reinforced with obidoxime and was made to a quadruple regimen that effectively treated rats intoxicated by 5×LD50 of tabun. The rats recovered very well and the majority gained pre-exposure body weight within 7 days. Neuropathology was seen in all groups regardless of whether the rats seized or not. The most extensive damage was produced by sarin and cyclosarin. Differentiation between the nerve agents' potency to cause lesions was probably seen because the efficacious treatments ensured survival of supralethal poisoning. A combination of 2 oximes and 2 anticonvulsants may be a prerequisite to counteract effectively high levels of poisoning by any classical nerve agent.

During the establishment of a research branch, all relevant matters encountered will be of interest to study. After having acquired a body of basal knowledge, it becomes possible to derive ideas or hypotheses for further elaboration of information. The purpose of the present study was to show that therapies for nerve agent poisoning based on specific neuropharmacological approaches can have greater probability for being successful than treatment regimens based on fragmental research or serendipitous discoveries. By following the guidelines for research in experimental epilepsy, neuronal target areas for nerve agents have been identified through lesion studies, and critical receptors for pharmacological treatment have been specified through microinfusion studies of rats. Subsequent experimentations have shown that the results achieved from microinfusion studies are transferable to systemic administration. It is demonstrated that a treatment regimen developed through the novel approach is more efficacious than regimens derived from conventional research on countermeasures. A therapy consisting of HI-6, levetiracetam, and procyclidine that has been worked out along the new lines, exerts powerful anticonvulsant capacity and appears to have universal utility as a stand-alone therapy against soman intoxication in rats. It would be of great interest to examine whether the latter findings can be expanded to other animal species than rats and other classical nerve agents than soman.

Four medical therapies previously shown to exert varying degrees of protection against a convulsant dose of soman were assessed for potential behavioral side effects in a novelty test. In Experiment 1, HI-6 (1-[([4-(aminocarbonyl)pyridino] methoxy)methyl]-2-[(hydroxyimino)methyl]pyridinium) (125 mg/kg), scopolamine (1 mg/kg), physostigmine (0.1 mg/kg), levetiracetam (50 mg/kg), and procyclidine (20 mg/kg) were tested separately. In Experiment 2, the combination of HI-6, scopolamine, and physostigmine (termed the physostigmine regimen) or HI-6, levetiracetam, and procyclidine (termed the procyclidine regimen) were tested. In Experiment 3, the metabotropic glutamate modulators DCG-IV ((2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine) (4 mg/kg) and MPEP (2-Methyl-6-(phenylethynyl)pyridine hydrochloride) (30 mg/kg) were tested separately or each drug in combination with HI-6 and procyclidine (termed the DCG-IV regimen and the MPEP regimen, respectively). The results showed that the physostigmine and procyclidine regimens both produced severe cognitive impairment (lack of preference for novelty) and reduced locomotor and rearing activities. The DCG-IV and MPEP regimens caused milder deficits on the same behavioral measures. Some relations were seen between prophylactic capacity and degree of behavioral side effects. Only HI-6 or levetiracetam had no adverse effects on behavior. DCG-IV or MPEP produced some impairment, whereas the detrimental effects of scopolamine or procyclidine were pronounced. The relatively high dose of procyclidine (anticholinergic and antiglutamatergic) needed for prophylactic efficacy may have played a major role for the side effects of the regimens in which the drug was used. It was concluded that behavioral side effects are inevitable for potent prophylactic therapies against soman intoxication.

Current treatment of nerve agent poisoning with ionotropic drugs proves inadequate, and alternative treatment strategies are searched for. Based on positive findings with metabotropic glutamate modulators in microinfusion studies, the present study was initiated to examine anticonvulsant effects of MPEP (2-Methyl-6-(phenylethynyl)pyridine hydrochloride), a metabotropic glutamate receptor 5 antagonist, and DCG-IV ((2S,2′R,3′R)-2-(2′,3′-dicarboxycyclopropyl)glycine), a metabotropic glutamate receptor 2/3 agonist, when administered systemically in combinations with HI-6 (1-[([4-(aminocarbonyl)pyridino]methoxy)methyl]-2-[(hydroxyimino)methyl]pyridinium) and procyclidine or HI-6 and levetiracetam relative to the combination of HI-6, procyclidine, and levetiracetam. The results showed that MPEP or DCG-IV combined with HI-6 and procyclidine resulted in substantial antidotal efficacy when administered 20min after onset of seizures elicited by soman. MPEP or DCG-IV combined with HI-6 and levetiracetam did not terminate seizures and preserve lives. When given 20min before challenge with soman, DCG-IV in combination with HI-6 and procyclidine provided protection, whereas MPEP combined with HI-6 and procyclidine did not. Combinations with metabotropic glutamate receptor modulators did not achieve the same high level of antidotal efficacy as the combination of HI-6, procyclidine, and levetiracetam. MPEP alone inhibited pseudocholinesterase activity in the brain markedly. A positive correlation was found between latency to seizure onset or full protection and level of pseudocholinesterase activity in brain. MPEP and DCG-IV can serve as effective anticonvulsants against nerve agent poisoning when combined with HI-6 and procyclidine. Metabotropic glutamate receptor modulators may represent an alternative or supplement to treatment with ionotropic drugs.

A treatment regimen consisting of HI-6, scopolamine, and physostigmine (termed the physostigmine regimen) has been based on the serendipitous discovery that it exerts powerful antidotal effects against high levels of soman poisoning if it is administered 1 min after exposure. A medical therapy with corresponding efficacy, but without the time limitation of the latter regimen, has been developed through studies of microinfusions of anticonvulsants into seizure controlling sites in the forebrain of rats. From these studies procyclidine emerged as the most potent anticonvulsant, and its potency was further enhanced when being combined with the antiepileptic levetiracetam during systemic administration. In the present study, the capacity of HI-6, levetiracetam, and procyclidine (termed the procyclidine regimen) was tested against that of the physostigmine regimen. The results showed that both regimens were very effective against supralethal doses of soman (3, 4, 5 × LD₅₀) when given 1 and 5 min after intoxication. When the treatments were administered 10 and 14 or 20 and 24 min after soman exposure, only the procyclidine regimen was able to terminate seizures and preserve lives. When used as prophylactic therapies, both regimens protected equally well against seizures, but only the procyclidine regimen provided neuroprotection. The procyclidine regimen has apparently capacities to serve as a universal therapy against soman intoxication in rats.

Microinfusion of anticonvulsants into the perirhinal cortex through 1 guide cannula in each hemisphere only invades a small area of this seizure controlling site in rats exposed to soman. The purpose of the present study was to examine whether infusions made through 2 cannulas in each perirhinal cortex may produce more efficacious anticonvulsant action against soman intoxication than the use of 1 cannula only in rats infused with the ionotropic antagonists procyclidine and caramiphen or the metabotropic glutamate modulators DCG-IV and MPEP. The results showed that the mere presence of indwelling double cannulas caused proconvulsant effect in response to subsequent systemic administration of soman. Both the control and caramiphen groups with double cannulas had significantly shorter latencies to seizure onset than the corresponding groups with single cannula. Procyclidine resulted in anticonvulsant efficacy, even in rats with double cannulas. In rats that received twin infusions of DCG-IV or MPEP, the anticonvulsant impact was very high, inasmuch as a majority of the rats in each group was protected against seizure activity. Drugs possessing powerful anticonvulsant potency can apparently counteract the proconvulsant effect of double cannulas, and some can even gain enhanced anticonvulsant capacity when invading a larger area of the perirhinal cortex. Perirhinal EEG recordings (electrodes in indwelling cannulas) in a separate set of rats not exposed to soman or drugs showed no differences in basal electrical activity (total power 0.5-25Hz or the theta band 4-12Hz) between groups with single or double cannulas. The intrinsic excitability and synaptic connectivity of the perirhinal cortex may be associated with the proconvulsant impact observed in rats with double cannulas when exposed to soman.

More effective countermeasures against nerve-agent poisoning are needed, because current ones do not protect sufficiently, particularly the central nervous system (CNS). The purpose of the present study was to make a comparison of the antidotal capabilities of atropine/obidoxime/diazepam (termed the obidoxime regimen), atropine/HI-6 (1-[([4-(aminocarbonyl)pyridinio]methoxy)methyl]-2-[(hydroxyimino)methyl]pyridinium)/avizafone (termed the HI-6 regimen), and scopolamine/HI-6/physostigmine (termed the physostigmine regimen) against various doses of soman (2, 3, 4 x LD50 ). The results showed that each regimen administered twice (1 min and 5 min after exposure) effectively prevented or terminated epileptiform activity within 10 min. However, the regimens differed markedly in life-saving properties with the physostigmine regimen ranking highest followed in descending order by the HI-6 and obidoxime regimens. Pretreatment with pyridostigmine increased the potency of the HI-6 regimen, but not the obidoxime regimen. The latter regimen administered thrice (1 min, 5 min, and 9 min after exposure) did not compensate for the insufficiency. In half of the rats that lived for 7 days, neuropathology was unexpectedly observed predominantly in the left hemisphere unrelated to whether they seized or not. Local glutamatergic excitotoxic activity may occur even if manifest toxic signs are absent. The physostigmine regimen has excellent antidotal capacity, but the very narrow therapeutic window (< 10 min) makes it unsuitable for use in the field. The HI-6 regimen appears to constitute an efficacious therapy against lower doses of soman (2 and 3 x LD50).

Results from studies based on microinfusions into seizure controlling brain sites (area tempestas, medial septum, perirhinal cortex, posterior piriform cortex) have shown that procyclidine, muscimol, caramiphen, and NBQX, but not ketamine, exert anticonvulsant effects against soman-induced seizures. The purpose of the present study was to examine whether levetiracetam (Keppra (R)) may enhance the anticonvulsant potency of the above drugs to become optimally effective when used systemically. Levetiracetam has a unique profile in preclinical models of epilepsy and has been shown to increase the potency of other antiepileptic drugs. The rats were pretreated with pyridostigmine (0.1 mg/kg) to enhance survival and received anticonvulsants 20 min after onset of seizures evoked by soman (1.15 x LD50). The results showed that no single drug was able to terminate seizure activity. However, when levetiracetam (LEV; 50 mg/kg) was combined with either procyclidine (PCD; 10 mg/kg) or caramiphen (CMP; 10 mg/kg) complete cessation of seizures was achieved, but the nicotinic antagonist mecamylamine was needed to induce full motor rest in some rats. In a subsequent experiment, rats were pretreated with HI-6 (125 mg/kg) to enhance survival and treatment started 40 min following seizure onset of a soman dose of 1.6 x LD50. LEV (50 mg/kg) combined with either PCD (20 mg/kg) or CMP (20 mg/kg) terminated seizure activity, but the survival rate was considerably higher for LEV + PCD than LEV + CMP. Both therapies could also save the lives of rats that were about to die 5-10 min after seizure onset. Thus, the combination of LEV and PCD or CMP may make up a model of a future autoinjector being effective regardless of the time of application. (C) 2011 Elsevier Inc. All rights reserved.

Acetylcholinesterase inhibitors in combination with an anticholinergic, particularly anticholinergics with antiglutamatergic properties, can effectively protect against nerve agent-induced seizures and lethality. The objective of the present study was to examine potential behavioral side effects of the anticholinesterases physostigmine (0.1 mg/kg), galantamine (3 mg/kg), huperzine (0.5 mg/kg), and donepezil (2.5 mg/kg) alone or each drug in combination with anticholinergic procyclidine (3 mg/kg). The results showed that rats injected intraperitoneally with galantamine displayed a mild cognitive deficit in terms of reduced preference for novelty that was similarly found among animals treated with procyclidine combined with either galantamine or donepezil. Locomotor activity and rearing were radically depressed in all groups treated with anticholinesterases as well as in combination with procyclidine. Reductions in activity were most prominent for rats injected with galantamine alone. Equalizing effects of cholinesterase inhibitors and anticholinergics were absent in the present context. Findings from previous studies that both systemic and local (amygdala) application of physostigmine cause increased fear-motivated freezing response in rats, may explain the marked reductions in activity among the present rats. In view of these findings, use of anticholinesterases (crossing the blood-brain barrier) as prophylactics against nerve agents must be carefully examined to avoid severe side effects.

Examination of critical subreceptors in the seizure controlling perirhinal cortex has revealed that microinfusion of ionotropic glutamatergic antagonists can exert anticonvulsant efficacy against soman-induced seizures. The purpose of the present study was to investigate whether modulators of metabotropic glutamate (mGlu) receptors may ensure anticonvulsant effects when microinfused into the perirhinal cortex. The results showed that the mGlu5 receptor antagonist MPEP hydrochloride (2-Methyl-6-(phenylethynyl)pyridine hydrochloride) and the mGlu2/3 receptor agonist DCG-IV ((2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine) caused full protection against seizures or increased latency to onset of seizures, whereas the mGlu1 receptor antagonist LY367385 ((S)-(+)-alpha-Amino-4-carboxy-2-methylbenzeneacetic acid) did not produce anticonvulsant efficacy in response to systemically administered soman (1.3 x LD(50)). Low doses of the above modulators had no anticonvulsant effects, whereas too high dose of MPEP resulted in proconvulsant effects. The results suggest that the perirhinal cortex is a likely site of cholinergic recruitment of glutamatergic hyperactivity after exposure to a convulsant dose of soman. Modulators of mGlu receptors may represent an alternative or supplement to ionotropic glutamate antagonists as anticonvulsants against nerve agent-evoked seizures.

The medial septum is considered to belong to a group of brain structures termed as seizure controlling sites. The septal area is dominated by both cholinergic input and output. The activity of the cholinoceptive neurons in the medial septum can, however, be modified by glutamatergic antagonists and γaminobutyric acid (GABA)ergic agonists in addition to cholinergic antagonists. The purpose of this study was to examine whether a single dose of anticholinergics (atropine, scopolamine, procyclidine), antiglutamatergic drug (ketamine), or GABA enhancing drug (muscimol) microinfused (1 µL) into the medial septum may produce anticonvulsant effects in rats exposed to soman (1.3 x LD 50 subcutaneously). The results showed that infusion of atropine, scopolamine, or procyclidine into the medial septum increased latency to seizure onset, but did not prevent seizures, whereas ketamine and muscimol had no anticonvulsant impact. Repeated microinfusions of atropine into the medial septum after seizure onset

Identification of critical receptors in seizure controlling brain regions may facilitate the development of more efficacious pharmacological therapies against nerve agent intoxication. In the present study, a number of drugs with anticonvulsant potency were microinfused into the perirhinal cortex (PRC) or posterior piriform cortex (PPC) in rats. The drugs used exert cholinergic antagonism (scopolamine), glutamatergic antagonism (ketamine, NBQX), both cholinergic and glutamatergic antagonism (procyclidine, caramiphen), or GABAergic agonism (muscimol). The results showed that in the PRC anticonvulsant efficacy against soman-induced seizures (subcutaneously administered) was achieved by procyclidine or NBQX, but not by ketamine, scopolamine, caramiphen, or muscimol (Experiment 1). Hence, both muscarinic and glutamatergic NMDA receptors had to be antagonized simultaneously or AMPA receptors alone, suggesting increased glutamatergic activation in the PRC before onset of seizures. In the PPC, anticonvulsant effects were assured by scopolamine or muscimol, but not by procyclidine, caramiphen, NBQX, or ketamine (Experiment 2). Thus, muscarinic and GABA(A) receptors appear to be the critical ones in the PPC. Microinfusion of soman into the PRC or PPC resulted in sustained seizure activity in the majority of the rats of both infusion categories. The rhinal structures encompassed in this study apparently have critical functions as both control and trigger sites for nerve agent-evoked seizures.

A group of antiparkinson drugs (benactyzine, biperiden, caramiphen, procyclidine, and trihexyphenidyl) has been shown to possess both anticholinergic and antiglutamatergic properties, making these agents very well suited as anticonvulsants against nerve agents. The first purpose of this study was to make a comparative assessment of the anticonvulsant potencies of the antiparkinson agents when microinfused (1 μl) into the seizure controlling area tempestas (AT) of rats 20 min before subcutaneous injection of soman (100 μg/kg). The second purpose was to determine whether cholinergic and/or glutamatergic antagonism was the effective property. The results showed that only procyclidine (6 μg) and caramiphen (10 μg) antagonized soman-induced seizures. Cholinergic, and not glutamatergic, antagonism was likely the active property, since atropine (100 μg), and scopolamine (1 μg) caused anticonvulsant effects, whereas MK-801 (1 μg), and ketamine (50 μg) did not. Soman (11 nmol) injected into AT resulted more frequently in clonic convulsions than full tonic–clonic convulsions. AT may serve as both a trigger site for soman-evoked seizures and a site for screening anticonvulsant potencies of future countermeasures.

Mapping of trigger sites and/or propagation pathways for soman-induced seizures may provide clues for the designing of anticonvulsant drugs. In the present study, anticonvulsant efficacy against soman intoxication (1.3 x LD50) was examined in rats with either lesion of the perirhinal cortex, posterior piriform cortex, entorhinal cortex, hippocampal region, or amygdala. The results showed that prevention of convulsions or increased latency to onset of convulsions was ensured in rats with perirhinal or piriform cortical lesions, whereas anticonvulsant effects were not achieved in rats with damage to the entorhinal cortex, hippocampal region, or amygdala. The results from the present study suggest that critical structures for induction of seizures after soman exposure are located in the ventrolateral aspect of the forebrain. This suggestion is in compliance with convulsant reactions to microinfusions of soman or VX into ventrolateral brain structures and increased neuronal activity in corresponding structures revealed by c-fos staining in response to soman. Furthermore, results from studies of kindling, lesions, and microinfusion of chemoconvulsants in experimental epilepsy also imply that the perirhinal and piriform cortices are critically involved in seizure control.