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Langston JL, Adkins AL, Moran AV, Rockwood GA, Deford MS. Effects of sarin on the operant behavior of guinea pigs. Neurotoxicol Teratol 2005; 27:841-53. [PMID: 16046097 DOI: 10.1016/j.ntt.2005.06.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 06/20/2005] [Accepted: 06/21/2005] [Indexed: 11/22/2022]
Abstract
The present study evaluated the dose-response effects of subacute exposure to sublethal doses of the organophosphorus (OP) chemical warfare nerve agent (CWNA) sarin (GB) on the operant behavior of guinea pigs. Dietary restricted guinea pigs, trained to respond for food under a progressive ratio (PR) schedule of reinforcement, were injected five times per week (Monday-Friday) for 2 weeks with fractions (0.1, 0.2, and 0.4) of the established LD(50) of GB (42 microg/kg). Changes in body weight, whole blood (WB) acetylcholinesterase (AChE) levels, and operant performances were monitored over the 2 weeks of GB exposure and for an additional 2 weeks following the termination of exposures. There were dose-related changes in body weight and WB AChE levels throughout the exposure and post-exposure periods. Several parameters of PR performance were disrupted during exposure to 0.4 LD50 GB, however, concurrent weight loss indicated the presence of overt toxicity. PR performance recovered following the termination of exposures. Lower doses (0.1 and 0.2 LD50) of GB failed to produce reliable effects on operant performance during the exposure period. Overall responding decreased during exposure to 0.4 LD50 GB, resulting in reduced response rates and break points. The decrease in overall response rates was attributed to an increase in pausing since there was no decrease in running rate. Motor effects of 0.4 LD50 GB were evident as an increase in the proportion of lever press durations > or = 1.0 s. In the present study, doses of GB lower than 0.4 LD50 produced no marked alteration of operant performance in guinea pigs, although WB AChE levels were maximally inhibited to 20% of control.
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Affiliation(s)
- Jeffrey L Langston
- Drug Assessment Division, US Army Medical Research Institute of Chemical Defense, MCMR-UV-DA, Aberdeen Proving Ground, MD 21010-5400, USA.
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Prendergast MA, Terry AV, Buccafusco JJ. Effects of chronic, low-level organophosphate exposure on delayed recall, discrimination, and spatial learning in monkeys and rats. Neurotoxicol Teratol 1998; 20:115-22. [PMID: 9536457 DOI: 10.1016/s0892-0362(97)00098-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Chronic exposure to low levels of organophosphate (OP) compounds impairs acetylcholine (ACh) degradation by acetylcholinesterase (AChE) and, in humans, may produce lasting neurotoxicity affecting cognitive function. The present studies examined the ability of such exposure to impair performance of well-learned cognitive tasks in two species, nonhuman primates and rats. During 25 days of exposure to a 0.01 mg/kg dose of the OP diisopropylfluorophosphate (DFP), mature adult monkeys were not impaired in their performance of a well-learned delayed matching-to-sample task (DMTS). However, erythrocyte AChE activity was reduced from predrug levels by 76.26 +/- 3.33% by 14 days after the initiation of DFP administration. Following titration of DFP to a 0.015 mg/kg dose for 15 days, DMTS performance remained at or above baseline levels. DMTS accuracy was moderately, but not significantly, reduced after titration to a dose of 0.02 mg/kg. However, decrements were associated with mild, overt symptoms of OP toxicity and performance returned to baseline levels after withdrawal from OP exposure. In rats, chronic exposure to a low-dose regimen of DFP (0.25 mg/kg/day for 14 days) impaired the ability to initially learn a spatial navigation task, but did not impair performance of previously learned stimulus discrimination and spatial navigation tasks. These data indicate that performance of memory tasks dependent upon reference concepts is not impaired by OP exposure regimens that impair acquisition of novel cognitive tasks prior to the onset of overt toxicity.
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Affiliation(s)
- M A Prendergast
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta 30912, USA
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Raveh L, Grauer E, Grunwald J, Cohen E, Ashani Y. The stoichiometry of protection against soman and VX toxicity in monkeys pretreated with human butyrylcholinesterase. Toxicol Appl Pharmacol 1997; 145:43-53. [PMID: 9221822 DOI: 10.1006/taap.1997.8160] [Citation(s) in RCA: 149] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Bioscavengers of organophophates (OP) have been examined as potential substitutes for the currently approved drug treatment against OP toxicity. The present work was designed to assess the ability of butyrylcholinesterase, purified from human serum (HuBChE), to prevent the toxicity induced by soman and VX in rhesus monkeys. The consistency of the data across species was then evaluated as the basis for the extrapolation of the data to humans. The average mean residence time of the enzyme in the circulation of monkeys following an intravenous loading was 34 hr. High bioavailability of HuBChE in blood (>80%) was demonstrated after intramuscular injection. A molar ratio of HuBChE:OP approximately 1.2 protected against an i.v. bolus injection of 2.1 x LD50 VX, while a ratio of 0.62 was sufficient to protect monkeys against an i.v. dose of 3.3 x LD50 of soman, with no additional postexposure therapy. A remarkable protection was also seen against soman-induced behavioral deficits detected in the performance of a spatial discrimination task. The consistency of the results across several species offers a reliable prediction of both the stoichiometry of the scavenging and the extent of prophylaxis with HuBChE against nerve agent toxicity in humans.
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Affiliation(s)
- L Raveh
- Israel Institute for Biological Research, Ness-Ziona
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Orr JL, Rogers WR, Smith HD. Exposure of baboons to combined 60 Hz electric and magnetic fields does not produce work stoppage or affect operant performance on a match-to-sample task. Bioelectromagnetics 1995; Suppl 3:61-70. [PMID: 8787567 DOI: 10.1002/bem.2250160707] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We examined the effects of combined 60 Hz electric and magnetic field (EMF) exposure on performance of delayed match-to-sample (MTS) procedure involving the flash rate of a light as the stimulus. Six baboons (Papio cynocephalus) fully acquired the task; four others functioned accurately only when cued. All ten subjects were assigned to EMF-exposed or sham-exposed groups of five and were used to test for a work-stoppage effect that was previously observed with initial exposure to electric fields (EF) of 30 or 60 kV/m. Here, we report the results of two experiments, each consisting of 6 week preexposure, exposure, and postexposure periods. We found no evidence of work stoppage with fields of 6 kV/m and 50 microT (0.5 G) or with 30 kV/m and 100 microT (1.0 G). In neither experiment was there evidence of an adverse effect of 60 Hz EMF exposure on MTS performance.
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Affiliation(s)
- J L Orr
- Department of Biosciences and Bioengineering, Southwest Research Institute, San Antonio, Texas 78228-0510, USA
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Blick DW, Murphy MR, Brown GC, Hartgraves SL. Primate performance decrements following acute soman exposure: failure of chemical countermeasures. Pharmacol Biochem Behav 1994; 49:503-10. [PMID: 7862701 DOI: 10.1016/0091-3057(94)90062-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Three experiments are reported: 1) a feasibility study on using laboratory primates repeatedly in behavioral toxicity studies of organophosphate (OP) agents or of chemical countermeasures against OPs; 2) a study of the efficacy of pyridostigmine pretreatment and 2-PAM therapy; and 3) a study to determine the effects of these treatments on soman-induced cholinesterase (ChE) inhibition and its recovery. In rhesus monkeys, three repeated acute low-dose (2.1 to 2.8 micrograms/kg) soman exposures, separated by intervals > 5 weeks, did not change baseline compensatory tracking performance or the soman ED50. Atropine therapy (97 micrograms/kg) alone had no effect on soman ED50. Addition of pyridostigmine pretreatment (150 micrograms/kg) and 2-PAM therapy (17 mg/kg) to atropine therapy increased the soman ED50 for a performance decrement from 2.27 micrograms/kg to 2.58 micrograms/kg, an insignificant protective effect. At the soman ED50 for behavioral decrements, pyridostigmine pretreatment increased the inhibition of serum ChE observed immediately after soman exposure, but reduced the extent of permanent inhibition. The 2-PAM therapy reduced serum ChE inhibition from about 80% to less than 70%. These effects on the time course of ChE inhibition following soman exposure appear to combine additively. These chemical countermeasures do not prevent soman-induced performance decrements, even though they are effective in protecting lives after much higher doses. The soman doses used produce only small, transient performance decrements; animals so exposed can, thus, be used repeatedly in such studies.
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Affiliation(s)
- D W Blick
- Systems Research Laboratories Division of Arvin/Calspan, Brooks AFB, Texas 78235-5000
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Blick DW, Miller SA, Brown GC, Murphy MR. Behavioral toxicity of anticholinesterases in primates: chronic physostigmine and soman interactions. Pharmacol Biochem Behav 1993; 45:677-83. [PMID: 8332626 DOI: 10.1016/0091-3057(93)90524-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Dose rates for continuous infusion of physostigmine salicylate required to inhibit 30 and 60% of normal serum cholinesterase activity in rhesus monkeys were determined. The effects of continuous physostigmine infusion at these dose rates on the behavioral toxicity of daily repeated low-dose soman were determined not to be deleterious; in fact, they were slightly (and variably) protective.
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Affiliation(s)
- D W Blick
- Systems Research Laboratories Division of Arvin/Calspan, USAF Armstrong Laboratory, Brooks AFB, TX 78235-5000
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Abstract
1. Available information describing the behavioural changes induced by anticholinesterases in humans and animals is reviewed. 2. Very little confidence can be placed in existing descriptions of the behavioural effects of anticholinesterases in humans. 3. Although data from animal experimental studies is reliable, the information obtained is relatively superficial. 4. It is concluded therefore, although much information is available, surprisingly little is known of the behavioural changes induced by anticholinesterases.
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Affiliation(s)
- G D D'Mello
- Chemical and Biological Defence Establishment, Salisbury, Wiltshire, UK
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Abstract
In human volunteers, studies to assess the adverse effects of the carbamate anticholinesterase physostigmine showed that the intramuscular dose observed to induce emesis in 50% of subjects tested (ED50) was 28.1 (23.5-120.7) micrograms/kg. This dose reduced whole blood cholinesterase (ChE) activity to 60% of control values. Studies in marmosets to assess the behavioural toxicology of physostigmine showed that the corresponding ED50 and ChE activity values were 34.3 (21.5-55.8) micrograms/kg and 66% respectively. Sarin was also shown to induce emesis in marmosets, but only at doses that reduced erythrocyte ChE activity to 12% of control values. These data seem also to correspond with reports of organophosphate poisoning in humans. It is concluded that the marmoset may be a very good model of both carbamate and organophosphate-induced emesis in humans.
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Affiliation(s)
- G D D'Mello
- Biology Division Chemical Defence Establishment, Salisbury, Wiltshire, UK
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Blick DW, Kerenyi SZ, Miller S, Murphy MR, Brown GC, Hartgraves SL. Behavioral toxicity of anticholinesterases in primates: chronic pyridostigmine and soman interactions. Pharmacol Biochem Behav 1991; 38:527-32. [PMID: 2068189 DOI: 10.1016/0091-3057(91)90008-p] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Dose rates for continuous infusion of pyridostigmine bromide required to inhibit 30% and 60% of normal serum cholinesterase activity in rhesus monkeys were determined. The effects of continuous pyridostigmine infusion at these dose-rates on the behavioral toxicity of 5 daily repeated low-dose exposures to a toxic organophosphate (soman) were determined not be deleterious; in fact, they were slightly (and variably) protective. Relative to controls (5-day soman ED50 = 0.89 micrograms/kg/day), pyridostigmine infusions producing 30% and 60% inhibition produced 5-day ED50s of 1.25 and 1.11 micrograms/kg/day, respectively. Variability in response to the pyridostigmine-soman combinations appeared to be greater than in response to daily soman exposure without pyridostigmine infusion.
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Affiliation(s)
- D W Blick
- Systems Research Laboratories Division of Arvin/Calspan, Brooks AFB, TX
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Nieminen SA, Lecklin A, Heikkinen O, Ylitalo P. Acute behavioural effects of the organophosphates sarin and soman in rats. PHARMACOLOGY & TOXICOLOGY 1990; 67:36-40. [PMID: 2395814 DOI: 10.1111/j.1600-0773.1990.tb00778.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The effects on behaviour of single subtoxic doses of two potent organophosphorous compounds, sarin (isopropyl methylphosphonofluoridate, 12.5 and 50 micrograms/kg, intraperitoneally) and soman (pinacolyl methylphosphonofluoridate, 4 and 20 micrograms/kg, intraperitoneally) were studied in male Wistar rats. In the open field test, soman dose-dependently decreased rearing and ambulation and increased non-mobile exploration. The higher dose of sarin changed only the rearing and grooming behaviour. Sarin and soman decreased locomotor activity on the Animex for at least one hour at the beginning of the monitoring period. In the doses used, both organophosphates inhibited acetylcholinesterase (AChE) activity significantly in the blood. The results suggest that small doses of sarin and soman have inactivating effects on the behaviour of rats. Although the findings cannot be extrapolated directly to behavioural changes in man, they indicate that subtle behavioural dysfunctions could also occur in humans at exposures which do not cause acute toxicity.
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Affiliation(s)
- S A Nieminen
- Department of Pharmacology and Toxicology, University of Kuopio, Finland
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Gause EM, Hartmann RJ, Leal BZ, Geller I. Neurobehavioral effects of repeated sublethal soman in primates. Pharmacol Biochem Behav 1985; 23:1003-12. [PMID: 4080770 DOI: 10.1016/0091-3057(85)90107-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Juvenile male baboons were trained to perform a match-to-sample discrimination task; effects of repeated sublethal exposure to the organophosphate nerve gas, soman, upon task performance were then explored. Both acute and subchronic exposure schedules were employed, and soman potency was verified by assay of soman-induced inhibition of acetylcholinesterase activity in whole blood, plasma, and erythrocytes. A characteristic profile of behavioral effects encompassing immediate, persistent, and delayed effects was observed. Immediate dose-related effects of soman included: increases in mean session response time, increases in errors, and decreases in extra responses. Seizures were also observed at the highest dose of soman employed (5 micrograms/kg). The increase in mean session response time was due to intermittent lapses in responding to stimuli (attentional deficits). Both the attentional deficits and intermittent generalized seizures were also persistent effects, with both occurring randomly after acute exposure to 5 micrograms/kg soman. Preliminary evidence suggests that occurrence of attentional deficits was associated with the occurrence of generalized and/or focal seizures; and that these effects may reflect irreversible lesions which become more threatening to the animal with increasing time. An additional, delayed effect was a sudden marked increase in the incidence of extra inconsequential responses which occurred several weeks after cessation of soman exposures.
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