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Neurochemical and electrophysiological diagnosis of reversible neurotoxicity in earthworms exposed to sublethal concentrations of CL-20.

Gong P, Basu N, Scheuhammer AM, Perkins EJ - Environ Sci Pollut Res Int (2009)

Bottom Line: Our results show that sublethal concentrations of CL-20 significantly reduced mAChR levels in a concentration- and duration-dependent manner, which was accompanied with significant decreases in the conduction velocity of the medial and lateral giant nerve fibers.Our findings support the idea that CL-20 induced neurotoxic effects are reversible, and suggest that CL-20 neurotoxicity may be mediated through the cholinergic system.Ion channels in the nerve membrane should be examined to further define the precise mechanisms underlying CL-20 neurotoxicity.

View Article: PubMed Central - PubMed

Affiliation: SpecPro Inc., 3909 Halls Ferry Road, Vicksburg, MS 39180, USA. ping.gong@us.army.mil

ABSTRACT

Background, aim, and scope: Hexanitrohexaazaisowurtzitane (CL-20) is a relatively new energetic compound sharing some degree of structural similarity with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a known neurotoxic compound. Previously, we demonstrated using a noninvasive electrophysiological technique that CL-20 was a more potent neurotoxicant than RDX to the earthworm Eisenia fetida. In the present study, we investigated the effect of CL-20 exposure and subsequent recovery on muscarinic acetylcholine receptors (mAChRs) to further define the mechanism of reversible neurotoxicity of CL-20 in E. fetida.

Materials and methods: We used a noninvasive electrophysiological technique to evaluate neurotoxicity in CL-20-treated worms, and then measured how such exposures altered levels of whole-body mAChR in the same animals.

Results and discussion: A good correlation exists between these two types of endpoints. Effect on mAChR levels was most prominent at day 6 of exposure. After 7 days of recovery, both conduction velocity and mAChR were significantly restored. Our results show that sublethal concentrations of CL-20 significantly reduced mAChR levels in a concentration- and duration-dependent manner, which was accompanied with significant decreases in the conduction velocity of the medial and lateral giant nerve fibers. After 7-day post exposure recovery, worms restored both neurochemical (mAChR) and neurophysiological (conduction velocity) endpoints that were reduced during 6-day exposures to CL-20 concentrations from 0.02 to 0.22 microg/cm(2).

Conclusions and perspectives: Our findings support the idea that CL-20 induced neurotoxic effects are reversible, and suggest that CL-20 neurotoxicity may be mediated through the cholinergic system. Future studies will investigate other neurotransmission systems such as GABA, glutamate, and monoamine. Ion channels in the nerve membrane should be examined to further define the precise mechanisms underlying CL-20 neurotoxicity.

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Reversible effects of sublethal CL-20 concentrations on muscarinic acetylcholine receptor (mAChR) and conduction velocity of medial (MGF) and lateral (LGF) giant fiber. Data are presented as mean (bar) and standard error (error bar) with n = 10. Statistical significance is indicated by an asterisk ‘*’ at α = 0.05. Endpoints were determined in worms exposed with or without recovery for 1 (a and b), 3 (c and d), 6 (e and f), and 13 days (g and h) in four separate experiments. MGF and LGF were measured repeated but only the last measurement results (a, c, e, and g) are shown in parallel with mAChR results (b, d, f, and h). See “Materials and methods” for details on statistical data analysis
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Fig1: Reversible effects of sublethal CL-20 concentrations on muscarinic acetylcholine receptor (mAChR) and conduction velocity of medial (MGF) and lateral (LGF) giant fiber. Data are presented as mean (bar) and standard error (error bar) with n = 10. Statistical significance is indicated by an asterisk ‘*’ at α = 0.05. Endpoints were determined in worms exposed with or without recovery for 1 (a and b), 3 (c and d), 6 (e and f), and 13 days (g and h) in four separate experiments. MGF and LGF were measured repeated but only the last measurement results (a, c, e, and g) are shown in parallel with mAChR results (b, d, f, and h). See “Materials and methods” for details on statistical data analysis

Mentions: CL-20 exposure reduced both conduction velocity and whole-body mAChR levels in a concentration- and duration-dependent manner (Fig. 1). Although conduction velocity was recorded repeatedly, only results from the final measurement were shown to facilitate comparison with mAChR data obtained from single-time determinations (see Fig. 1). A good correlation exists between these two types of endpoints. Effect on mAChR levels was most prominent at day 6 of exposure (see Fig. 1(f)). After a 7-day recovery, both conduction velocity and mAChR were significantly restored (see Fig. 1(g,h)). However, it should be noted that relative conduction velocity is a more sensitive endpoint than mAChR, and this can be partly attributed to different statistical methods used. One-way ANOVA used for mAChR has less statistical power than the paired t test for conduction velocity because ANOVA does not require pairing of collected data.Fig. 1


Neurochemical and electrophysiological diagnosis of reversible neurotoxicity in earthworms exposed to sublethal concentrations of CL-20.

Gong P, Basu N, Scheuhammer AM, Perkins EJ - Environ Sci Pollut Res Int (2009)

Reversible effects of sublethal CL-20 concentrations on muscarinic acetylcholine receptor (mAChR) and conduction velocity of medial (MGF) and lateral (LGF) giant fiber. Data are presented as mean (bar) and standard error (error bar) with n = 10. Statistical significance is indicated by an asterisk ‘*’ at α = 0.05. Endpoints were determined in worms exposed with or without recovery for 1 (a and b), 3 (c and d), 6 (e and f), and 13 days (g and h) in four separate experiments. MGF and LGF were measured repeated but only the last measurement results (a, c, e, and g) are shown in parallel with mAChR results (b, d, f, and h). See “Materials and methods” for details on statistical data analysis
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2801850&req=5

Fig1: Reversible effects of sublethal CL-20 concentrations on muscarinic acetylcholine receptor (mAChR) and conduction velocity of medial (MGF) and lateral (LGF) giant fiber. Data are presented as mean (bar) and standard error (error bar) with n = 10. Statistical significance is indicated by an asterisk ‘*’ at α = 0.05. Endpoints were determined in worms exposed with or without recovery for 1 (a and b), 3 (c and d), 6 (e and f), and 13 days (g and h) in four separate experiments. MGF and LGF were measured repeated but only the last measurement results (a, c, e, and g) are shown in parallel with mAChR results (b, d, f, and h). See “Materials and methods” for details on statistical data analysis
Mentions: CL-20 exposure reduced both conduction velocity and whole-body mAChR levels in a concentration- and duration-dependent manner (Fig. 1). Although conduction velocity was recorded repeatedly, only results from the final measurement were shown to facilitate comparison with mAChR data obtained from single-time determinations (see Fig. 1). A good correlation exists between these two types of endpoints. Effect on mAChR levels was most prominent at day 6 of exposure (see Fig. 1(f)). After a 7-day recovery, both conduction velocity and mAChR were significantly restored (see Fig. 1(g,h)). However, it should be noted that relative conduction velocity is a more sensitive endpoint than mAChR, and this can be partly attributed to different statistical methods used. One-way ANOVA used for mAChR has less statistical power than the paired t test for conduction velocity because ANOVA does not require pairing of collected data.Fig. 1

Bottom Line: Our results show that sublethal concentrations of CL-20 significantly reduced mAChR levels in a concentration- and duration-dependent manner, which was accompanied with significant decreases in the conduction velocity of the medial and lateral giant nerve fibers.Our findings support the idea that CL-20 induced neurotoxic effects are reversible, and suggest that CL-20 neurotoxicity may be mediated through the cholinergic system.Ion channels in the nerve membrane should be examined to further define the precise mechanisms underlying CL-20 neurotoxicity.

View Article: PubMed Central - PubMed

Affiliation: SpecPro Inc., 3909 Halls Ferry Road, Vicksburg, MS 39180, USA. ping.gong@us.army.mil

ABSTRACT

Background, aim, and scope: Hexanitrohexaazaisowurtzitane (CL-20) is a relatively new energetic compound sharing some degree of structural similarity with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a known neurotoxic compound. Previously, we demonstrated using a noninvasive electrophysiological technique that CL-20 was a more potent neurotoxicant than RDX to the earthworm Eisenia fetida. In the present study, we investigated the effect of CL-20 exposure and subsequent recovery on muscarinic acetylcholine receptors (mAChRs) to further define the mechanism of reversible neurotoxicity of CL-20 in E. fetida.

Materials and methods: We used a noninvasive electrophysiological technique to evaluate neurotoxicity in CL-20-treated worms, and then measured how such exposures altered levels of whole-body mAChR in the same animals.

Results and discussion: A good correlation exists between these two types of endpoints. Effect on mAChR levels was most prominent at day 6 of exposure. After 7 days of recovery, both conduction velocity and mAChR were significantly restored. Our results show that sublethal concentrations of CL-20 significantly reduced mAChR levels in a concentration- and duration-dependent manner, which was accompanied with significant decreases in the conduction velocity of the medial and lateral giant nerve fibers. After 7-day post exposure recovery, worms restored both neurochemical (mAChR) and neurophysiological (conduction velocity) endpoints that were reduced during 6-day exposures to CL-20 concentrations from 0.02 to 0.22 microg/cm(2).

Conclusions and perspectives: Our findings support the idea that CL-20 induced neurotoxic effects are reversible, and suggest that CL-20 neurotoxicity may be mediated through the cholinergic system. Future studies will investigate other neurotransmission systems such as GABA, glutamate, and monoamine. Ion channels in the nerve membrane should be examined to further define the precise mechanisms underlying CL-20 neurotoxicity.

Show MeSH
Related in: MedlinePlus