100cm by 100cm Poster Template

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Static magnetic field exposure suppresses
mechanical allodynia in experimental model of
neuropathy in mice János László1 and Miklós
Antal2 1 Hungarian Academy of Sciences, Section
of Mathematics, Budapest, Hungary
(laszlo.janos_at_office.mta.hu) 2 University of
Debrecen, Department of Anatomy, Histology and
Embriology, Debrecen, Hungary (antal_at_chondron.anat
.dote.hu)
Table 1 Mechanical withdrawal threshold values
for the right hind paws measured before surgery
(day 0) and on postoperative days 1, 4, 6, 8, 11,
13, 15, 18, 20, 22, 25, 27, 29, 36 and 40. The
responsiveness of the right hind paw to
mechanical stimulation was similar in all animals
in all experimental groups throughout the entire
length of the experiment. Thus, here we
calculated the average values and S.E.M. of data
obtained from all experimental animals (5
experimental group, 6 animal in each group, 5
measurements in each animal).
Figure 5 Histogram showing the mechanical
withdrawal threshold of two groups of animals
with partial nerve ligation of the left sciatic
nerve (Groups 3 and 5). Animals in Group 5 were
exposed to magnetic field once a day on
postoperative days 15 to 28. Threshold values are
represented as means the vertical bars at
measurement points represent S.E.M. Asterisks
along the histogram curve of Group 5 label
measurement points that are significantly
different (p lt 0.05) from corresponding values
obtained from Group 3 animals. Open circles along
the histogram curve of Group 5 mark measurement
points that are not significantly different (p gt
0.05) from corresponding values obtained from
control (Group 1) animals. Lines guide the eye
only.
The effect of sham operation on the mechanical
withdrawal threshold MWT in the untreated control
animals (Group 1) varied randomly from 4.61
0.14 g to 4.91 0.04 g during the experiment
(Fig. 3). The sham operation (Group 2) caused
a transient but significant drop in MWT. On
postoperative day 1, the MWT of sham operated
animals decreased to the value of 3.99 0.29 g
(Fig. 3). After this, however, the animals showed
a rapid spontaneous recovery. MWT figures
continuously increased day by day and reached the
control values on postoperative day 11 (4.660.15
g Fig.3).
Figure 3 Histogram showing the mechanical
withdrawal threshold of control (Group 1), sham
operated (Group 2) and operated animals with
partial nerve ligation of the left sciatic nerve
(Group 3). None of the animals in Groups 1, 2 and
3 were exposed to magnetic field. Threshold
values are represented as means the vertical
bars at measurement points represent S.E.M.
Asterisks along the histogram curves of Groups 2
and 3 label measurement points that are
significantly different (p lt 0.05) from
corresponding control values. Lines guide the eye
only.
Table 2 Statistical differences between
experimental groups computed by using Dunnetts
post hoc test for the comparison between pairs of
data series. Equal numbers of mechanical
withdrawal threshold values for the right hind
paws measured before surgery (day 0) and on
postoperative days 1, 4, 6, 8, 11, 13, 15, 18,
20, 22, 25, 27, 29, 36 and 40 were compared.
Probabilities (p) of less than 0.05 were
considered to be statistically significant and
marked with asterisks in the table.
The effect of partial nerve ligation on the
mechanical withdrawal threshold The partial
ligation of the sciatic nerve resulted in a
sudden and dramatic drop in MWT. On postoperative
day 1, MWT values decreased to 2.43 0.18 g,
2.63 0.17 g 2.49 0.24 g in animals within
Groups 3, 4 and 5, respectively (Figs. 3-5).
Without any iSMF exposure this condition did not
really improved within the 40 days long
experimental period. Although MWT value showed a
slight elevation with time, it was still at the
level of 3.07 0.31 g at postoperative day 40 in
Group 3 animals (Fig. 3).
Animals and surgical procedure Experiments were
carried out on thirty adult male mice (Balb/c,
2025 g). Animals were divided into five
experimental groups with six animals in each
group. Animals in the different experimental
groups went through the following surgical
procedures Group 1 No surgical procedure was
carried out on these animals. Group 2 The
animals were deeply anesthetized by sodium
pentobarbital (3.5 mg/100 g body weight i.p.).
Following an incision at the level of the mid
thigh, the left sciatic nerve was exposed by
blunt dissection. Without making any further
surgical intervention the incision was sutured
and the animals were allowed to recover. Groups
3-5 Following anesthesia, an incision at the
level of the mid-thigh was made, the left sciatic
nerve was exposed by blunt dissection. A suture
was then passed through the dorsal third of the
nerve and tied tightly according to Seltzer et
al. 1990. The incision on the skin was then
sutured and the animals were allowed to
recover. Exposure to magnetic field Animals in
Groups 4 and 5 were exposed to iSMF, whereas
animals in Groups 1, 2 and 3 received no magnetic
exposure. Animals in Group 4 were treated once a
day on postoperative days 1 to 14, whereas
animals in Group 5 were exposed also daily to
the magnetic field on postoperative days 15 to
28. For iSMF exposure, animals were put into the
plastic cage one at a time, then the cage with
the animal was inserted into the magnetic device
for 30 min. The magnetic exposure did not cause
any change in the normal locomotor activity of
the animals. The behavioral test on the days of
iSMF treatment was performed within 20 minutes
after the magnetic exposure. Behavioral test All
mice were tested for withdrawal responses to
noxious mechanical stimuli using a dynamic
plantar aesthesiometer. Animals were placed upon
a network platform and covered with a Perspex
enclosure that rendered the animal unrestrained
for the duration of the experiment. The hind paw
of the animal was positioned above a von
Frey-type filament with a tip diameter of about 1
mm. The filament exerted an increasing
pressure to the plantar surface until the animal
removed its paw. At this point the
measurement was terminated and the actual force
at which paw withdrawal occurred was
recorded. The measurement was repeated 5 times in
each case. The mechanical withdrawal threshold
(MWT) for both hind paws was determined before
surgery (day 0) and the test was repeated on
postoperative days 1, 4, 6, 8, 11, 13, 15, 18,
20, 22, 25, 27, 29, 36 and 40. The magnetic
exposure and the following mechanical withdrawal
tests were always carried out in the morning in a
defined sequential order, starting with animals
in Group 1 and finishing with animals in Group 5.
Figure 4 Histogram showing the mechanical
withdrawal threshold of two groups of animals
with partial nerve ligation of the left sciatic
nerve (Groups 3 and 4). Animals in Group 4 were
exposed to magnetic field once a day on
postoperative days 1 to 14. Threshold values are
represented as means the vertical bars at
measurement points represent S.E.M. Asterisks
along the histogram curve of Group 4 label
measurement points that are significantly
different (p lt 0.05) from corresponding values
obtained from Group 3 animals. Lines guide the
eye only.
The effect of magnetic exposure on the mechanical
withdrawal threshold in animals with partial
nerve ligation The daily exposure to iSMF during
the first postoperative week did not inhibit the
decrease of MWT values in animals with partial
nerve ligation. By postoperative day 8, the MWT
value of animals in Group 4 elevated to 3.05
0.21 g, whereas it was 3.07 0.25 g and 2.93
0.17 g for animals in Groups 3 and 5,
respectively that did not receive magnetic
treatment (Figs. 4, 5). However, by the end of
the two week long magnetic treatment, the MWT
values of animals that were and were not exposed
to the iSMF showed a modest but significant
difference (Table 2). On postoperative day 13,
the MWT values were 3.40 0.16 g for animals in
Group 4 and 2.88 0.28 g and 2.91 0.52 g for
animals in Groups 3 and 5, respectively (Figs. 4,
5). In addition, with transient drops during the
third and fourth weeks, MWT kept rising even
after the termination of the magnetic treatment
and reached the value of 3.95 0.16 g by
postoperative day 40, whereas the MWT of
nerve-ligated animals without magnetic exposure
(Group 3) was only 3.07 0.31 g at this time
(Fig. 4). The effectiveness of exposure to iSMF
was much more prominent when it was applied
between postoperative days 15 and 28. MWT was
noticeably elevated right after the first
treatment (Fig. 5). On postoperative day 15,
animals in Group 5 showed an elevated MWT (3.31
0.11 g) that was significantly higher than the
MWT value of animals in Group 3 (2.84 0.15 g
Table 2). During the two week long treatment, the
MWT value showed a remarkable continuous increase,
and by the end of the two week long exposure
period it reached the control value (Fig. 5). On
postoperative day 29, MWT value for animals in
Group 5 was 4.80 0.11 g. On top of this, this
value was maintained even after the termination
of the treatment as far as postoperative day 40
(the end of the experiment), when the MWT value
was 4.82 0.05 g for these animals (Fig. 5).
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