Title:
Investigating the neurotoxic effects of acute lead exposure on nerve
conduction velocity in the Earthworm Lumbricus terrestris.
Abstract: (Your abstract must use 10pt Arial font and must not be longer than this box)
Extensive use of the heavy metal lead (Pb) throughout history has led to it becoming a major
environmental pollutant, thus lead poisoning remains a global health risk. Lead exposure produces its
most detrimental health effects on the nervous system impairing both motor and cognitive function in
humans (1). Myelin dysfunction is one purported mechanism of lead induced neurotoxicity; morphological
disturbances in myelin sheaths were shown in rats after acute lead exposure (2), however whether this
functionally impacted on nerve conduction velocity (CV) is not known. The aim of this study was to
investigate whether acute lead exposure (1hr) impaired CV of median (MGFs) and lateral giant fibres
(LGFs), both myelinated neurons, in earthworms (Lumbricus terrestris).
Mature earthworms (n=30) were prepared for nerve conduction experiments in accordance with past
study (3) and time 0mins established at the point MGF & LGF threshold responses were obtained. From
0mins to 60mins, earthworms were topically administered either: 10% (v/v) ethanol Ringer’s solution (RSEtOH) (control group, n=10), RS-EtOH containing 16mg/L lead nitrate (n=10), or RS-EtOH containing
160mg/L lead nitrate (n=10). Salt type and concentration chosen on the basis of available literature (2).
Weight and dosing regimen (frequency & volume) were standardised across all groups and CV recorded
at 0mins and 60mins according to previous study (3). The difference in CV (CV), CV at 0mins - CV at
60mins, was calculated for each worm. Intergroup differences in mean CV compared using a one-way
ANOVA, and Tukey’s (HSD) test used for post-hoc multiple comparisons. All values are presented as
mean ±SEM (error bars) and significance defined as *p<0.05 and **p<0.01. Post-hoc power calculations
were performed and a 1-𝛽 error probability (1-𝛽) ≥0.80 considered an adequately powered result.
There was a statistically significant difference in mean CV between groups for both MGFs
(F(2,27)=5.844, p=0.0078) (Fig.1) and LGFs (F(2,27)=3.859, p=0.0336) (Fig. 2). The result for the MGFs
was adequately powered (1-𝛽=0.87), though was not for the LGFs (1-𝛽=0.70). Tukey’s test revealed
differences in mean CV only reached statistical significance at 160mg/L for both MGFs (p=0.0055) &
LGFs (p=0.0258).
-1.1m/s
-5.1m/s
-6.7m/s
-1.6m/s
-8.3m/s
Fig. 1 Effect of 1hr topical lead nitrate exposure on
CV in MGFs.
Numbers in bars represent the mean CV (correct to
1dp) from 0mins to 60mins for that group.
-2.1m/s
Fig. 2 Effect of 1hr topical lead nitrate exposure on
CV in LGFs.
Numbers in bars represent the mean CV (correct to
1dp) from 0mins to 60mins for that group.
In summary, acute lead nitrate intoxication decreased CV in both MGFs and LGFs relative to control,
though statistical significance was only obtained at a concentration of 160mg/L. However, whether
aberrant myelination is responsible for aforementioned decrease cannot be ascertained from this study.
(1) Sanders T et al. (2009). Rev Environ Health 24: 15-45.
(2) Dabrowska-Bouta B et al. (2000). Exp Toxicol Pathol 52: 257-263.
(3) Kladt N et al. (2010). J Undergrad Neurosci Educ 9: A20-A35.
Important notes:
Do NOT enter author and affiliation information on this document. You will be able to enter
this information online when you submit the abstract.
Do NOT write outside the boxes. Any text or images outside the boxes will be deleted.
Do NOT alter the structure of this document. Simply enter your title and abstract in the
boxes. The document will be automatically processed – if you alter its structure your
submission will not be processed correctly.