Pyridostigmine bromide (PB) is an FDA-approved drug for the treatment of myasthenia gravis and a prophylactic
pre-treatment for organophosphate nerve agent poisoning. Current methods for evaluating nerve agent
treatments include enzymatic studies and mammalian models. Rapid whole animal screening tools for assessing
the effects of nerve agent pre-treatment and post-exposure drugs represent an underdeveloped area of research.
We used zebrafish as a model for acute and chronic developmental exposure to PB and two related carbamate
acetylcholinesterase (AChE) inhibitors, neostigmine bromide (NB) and physostigmine (PS). Lethal doses and
gross morphological phenotypes resulting from exposure to sub-lethal doses of these compounds were
determined. Quantitative analyses of motility impairment and AChE enzyme inhibition were used to determine
optimal dosing conditions for evaluation of the effects of carbamate exposures on neuronal development; ~50%
impairment of response to startle stimuli and N50% inhibition of AChE activity were observed at 80 mM PB,
20 mM NB and 0.1 mM PS. PB induced stunted somite length, but no other phenotypic effects were observed.
In contrast, NB and PS induced more severe phenotypic morphological defects than PB as well as neurite outgrowth
mislocalization. Additionally, NB induced mislocalization of nicotinic acetylcholine receptors, resulting
in impaired synapse formation. Taken together, these data suggest that altered patterns of neuronal connectivity
contribute to the developmental neurotoxicity of carbamates and demonstrate the utility of the zebrafish model
for distinguishing subtle structure-based differential effects of AChE inhibitors, which include nerve agents,
pesticides and drugs.
Pyridostigmine bromide (PB) is an FDA-approved drug for the treatment of myasthenia gravis and a prophylacticpre-treatment for organophosphate nerve agent poisoning. Current methods for evaluating nerve agenttreatments include enzymatic studies and mammalian models. Rapid whole animal screening tools for assessingthe effects of nerve agent pre-treatment and post-exposure drugs represent an underdeveloped area of research.We used zebrafish as a model for acute and chronic developmental exposure to PB and two related carbamateacetylcholinesterase (AChE) inhibitors, neostigmine bromide (NB) and physostigmine (PS). Lethal doses andgross morphological phenotypes resulting from exposure to sub-lethal doses of these compounds weredetermined. Quantitative analyses of motility impairment and AChE enzyme inhibition were used to determineoptimal dosing conditions for evaluation of the effects of carbamate exposures on neuronal development; ~50%impairment of response to startle stimuli and N50% inhibition of AChE activity were observed at 80 mM PB,20 mM NB and 0.1 mM PS. PB induced stunted somite length, but no other phenotypic effects were observed.In contrast, NB and PS induced more severe phenotypic morphological defects than PB as well as neurite outgrowthmislocalization. Additionally, NB induced mislocalization of nicotinic acetylcholine receptors, resultingin impaired synapse formation. Taken together, these data suggest that altered patterns of neuronal connectivitycontribute to the developmental neurotoxicity of carbamates and demonstrate the utility of the zebrafish model
for distinguishing subtle structure-based differential effects of AChE inhibitors, which include nerve agents,
pesticides and drugs.
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