INFLUENCE OF LONG-TERM EXPOSURE TO STATIC, HIGH VOLTAGE ELECTRIC
FIELD ON BEHAVIOURAL REACTIONS IN RATS
Grzegorz Cieslar(1), Janina Mrowiec(1), Pawel Sowa(2), Slawomir Kasperczyk(3), Aleksander Sieron(1)
(1)
Chair and Clinic of Internal Diseases, Angiology and Physical Medicine, Silesian Medical University, Batorego St.
15, PL-41902 Bytom, Poland, e-mail: cieslar@mediclub.pl
(2)
(3)
Institute of Power System and Control, Silesian University of Technology, Bolesława Krzywoustego St. 2, PL41100 Gliwice, Poland, e-mail: pawel.sowa@polsl.pl
Chair and Department of Biochemistry, Silesian Medical University, Jordana St. 19, PL-41808 Zabrze, Poland, email: kaslav@mediclub.pl
ABSTRACT
In this study the influence of long-term, whole-body exposure to strong static electric field generated usually near high
voltage direct current transmission lines on such behavioural reactions as locomotor activity, exploratory activity, space
memory and irritability in rats was estimated. Experimental material consisted of 24 male Wistar albino rats aged 8
weeks, weighting 180-200 g. During the whole experiment all animals were placed in identical environmental under a
12 h light-dark cycle with free access to standard laboratory pellet food and tap water. All animals were randomly
divided into 3 groups (8 animals each). The rats from two experimental groups were exposed for 56 consecutive days (8
hours daily) to static electric field with electric field intensity values of 16 kV/m and 35 kV/m respectively, in a
specially designed experimental system. The control animals were subjected to a sham-exposure in the same
experimental system, during which no electric field was generated between electrodes. Rats from control group were
sham-exposed in the same experimental system, with no electric field generated between electrodes during exposure.
The evaluation of behaviour was made at 24 hours before first exposure, at 24 hours after first exposure, at 7th, 14th, 21st,
28th, 42nd and 56th day of exposure cycle and at 28th day after the end of a cycle of exposures. A locomotor activity was
determined in the open field test by recording a number of episodes of crossings, peepings, rearings, washing and
defecation per 3 minutes of observation. An exploratory activity was examined in the hole test by recording a number of
head dips into a board hole per 3 minutes. Space memory was determined by means of water maze test on the basis of
measurement of time recquired for crossing of a specially constructed water maze. An irritability was investigated by
means of Nakamura and Thoenen’s score test. As a result of repeated exposures in first group of electric field - exposed
rats a significant decrease in the number of episodes of crossings (7th day of exposures), peepings (14th day of
exposures) and washing (21st and 28th day of exposures) was observed as compared to control animals. In second group
of electric field - exposed rats a significant decrease in the number of episodes of crossings (7th day of exposures),
peepings (14th day of exposures), washing (7th, 14th and 21st day of exposures) and defecation (42nd and 56th day of
exposures) was observed as compared to control animals. In both groups of electric field – exposed rats no significant
changes in the water maze crossing time, in the number of episodes of rearings and head dips in hole test as well as in
irritability score were observed comparing with control animals. On the basis of obtained results one can conclude that
long-term, whole-body exposure of rats to strong, static electric field with parameters generated nearby high voltage
direct current transmission lines causes only a transcient, significant reduction of locomotor activity in the initial phase
of exposure cycle.
INTRODUCTION
So far there are only sparse data on the effect of 50-60 Hz electric fields generated nearby electric field transmission
lines on the function of central nervous system resulting in behavioral alterations in occupationally exposed humans
[1,2]. The results of experimental studies showed that low frequency high voltage electric fields can change the
behaviour of mice, rats, and nonhuman primates; however, these changes were transitory, appeared to be secondary to
detection of a novel stimulus, and did not suggest acute adverse effects [3-7]. The aim of this study was to estimate in
an experimental model the influence of long-term, whole-body exposure to strong static electric field with parameters
which frequently occur nearby high voltage direct current transmission lines on such behavioural reactions as locomotor
activity, exploratory activity, space memory and irritability in rats.
MATERIAL AND METHODS
Experimental material consisted of 24 male Wistar albino rats aged 8 weeks, weighting 180-200 g. During the whole
experiment all animals were placed in identical environmental conditions (constant temperature 22 ± 1oC and humidity
of air) under a 12 h light-dark cycle with free access to standard laboratory pellet food and tap water. All animals were
randomly divided into 3 groups (8 animals each) with no significant differences in body weight.
The animals from 2 experimental groups were exposed for 56 consecutive days (8 hours daily) to static electric field in
a specially designed experimental system consisting of autotransformer, high voltage transformer 220V/60000V,
cascade rectifier, water rheostat, 2 electrodes with round shape and specially profiled edges placed in a distance of 50
cm from each other, plastic cage placed between both electrodes containing 8 animals at a same time and magnetostatic
kilo-voltmeter C196 type. Rats from first experimental group were exposed to static electric field with intensity of 16
kV/m. Rats from second experimental group were exposed to static electric field with intensity of 35 kV/m. The control
animals were subjected to sham-exposure in the same experimental system, during which no electric field was
generated between electrodes.
The evaluation of behaviour was made at 24 hours before first exposure, at 24 hours after first exposure, at 7th, 14th, 21st,
28th, 42nd and 56th day of exposure cycle and at 28th day after the end of a cycle of exposures. A locomotor activity was
determined in the open field test by recording a number of episodes of crossings, peepings, rearings, washing and
defecation per 3 minutes of observation [8]. An exploratory activity was examined in the hole test by recording a
number of head dips into a board hole per 3 minutes [9]. Space memory was determined by means of water maze test on
the basis of measurement of time required for crossing of a specially constructed water maze [10,11]. An irritability was
investigated by means of Nakamura and Thoenen’s score test [12]. The results of particular tests were presented as
percentage change in relation to initial values before a beginning of exposure cycle. Statistical analysis was performed
by means of ANOVA and post-hoc Mann-Whitney’s U test.
RESULTS
Percentage change in the number of episodes of
crossings per 3 minutes in relation to initial values [%]
As a result of repeated exposures in first experimental group of rats exposed to static electric field with intensity of 16
kV/m a significant decrease in the number of episodes of crossings (7th day of exposures) (Fig. 1), peepings (14th day of
exposures) (Fig. 2) and washing (21st and 28th day of exposures) (Fig. 3) in “open field” test was observed as compared
to control animals.
120
* p<0,05
comparison
to control
100
80
60
40
*
*
20
0
before
exposure
1 day of
7 day of
14 day of 21 day of 28 day of 42 day of 56 day of
exposures exposures exposures exposures exposures exposures exposures
control
16 kV/m
28 day
after
exposures
35 kV/m
Fig. 1 Percentage change in the number of crossings in „open field” test in relation to initial values before the beginning
of exposure cycle in both groups of electric field-exposed rats in particular days of exposure cycle and at 28 day after
the end of exposure cycle with statistical comparison to control group.
Percentage change in the number of episodes of
peepings per 3 minutes in relation to initial values [%]
120
* p<0,05
** p<0,01
comparison to
control
100
80
60
*
**
40
20
0
before
exposure
1 day of
7 day of
14 day of 21 day of 28 day of 42 day of 56 day of
exposures exposures exposures exposures exposures exposures exposures
control
16 kV/m
28 day
after
exposures
35 kV/m
Fig. 2 Percentage change in the number of peepings in „open field” test in relation to initial values before the beginning
of exposure cycle in both groups of electric field-exposed rats in particular days of exposure cycle and at 28 day after
the end of exposure cycle with statistical comparison to control group.
Percentage change in the number of episodes of
washing per 3 minutes in relation to initial values [%]
In second experimental group of rats exposed to static electric field with intensity of 35 kV/m a significant decrease in
the number of episodes of crossings (7th day of exposures) (Fig. 1), peepings (14th day of exposures) (Fig. 2), washing
(7th, 14th and 21st day of exposures) (Fig. 3) and defecation (42nd and 56th day of exposures) (Fig. 4) in “open field” test
was observed as compared to control animals. In either group of electric field – exposed rats no significant changes in
the water maze crossing time, in the number of episodes of rearings in “open field” test and head dips in “hole” test as
well as in irritability score were observed comparing with control animals.
120
* p<0,05
** p<0,01
comparison to
control
100
80
60
40
*
20
*
**
*
**
0
before
exposure
1 day of
exposures
7 day of
exposures
14 day of
exposures
control
21 day of
exposures
28 day of
exposures
16 kV/m
42 day of
exposures
56 day of 28 day after
exposures exposures
35 kV/m
Fig. 3 Percentage change in the number of washing in „open field” test in relation to initial values before the beginning
of exposure cycle in both groups of electric field-exposed rats in particular days of exposure cycle and at 28 day after
the end of exposure cycle with statistical comparison to control group.
Percentage change in the number of episodes of
defecation per 3 minutes in relation to initial values [%]
300
*
**
p<0,05
p<0,01
comparison to
control
250
200
150
100
50
*
**
0
before
1 day of
7 day of 14 day of 21 day of 28 day of 42 day of 56 day of
exposure exposures exposures exposures exposures exposures exposures exposures
control
16 kV/m
35 kV/m
28 day
after
exposures
Fig. 4 Percentage change in the number of defecation in „open field test” in relation to initial values before the
beginning of exposure cycle in both groups of electric field-exposed rats in particular days of exposure cycle and in 28
day after the end of exposure cycle with statistical comparison to control group.
CONCLUSION
Long-term, whole-body exposure of rats to strong, static electric field generated usually near high voltage direct current
transmission lines causes only a transcient, significant reduction of locomotor activity in the initial phase of exposure
cycle.
REFERENCES
[1] F.F. Fole, “The HVS effect in electric power substations, ”Med. Segur. Trab., vol. 23, pp. 15-18, 1973.
[2] R. Hauf, and J. Wiesinger, “Biological effects of technical, electric, and electromagnetic VLF fields,” Int. J.
Biometeorol., vol. 17, pp. 213-215, 1973.
[3] A.M. Coelho Jr., S.P. Easley and W.R. Rogers, “Effects of exposure to 30 kV/m, 60 Hz electric fields on the social
behavior of baboons,” Bioelectromagnetics, vol. 12, pp. 117-135, 1991.
[4] S.P. Easley, A.M. Coelho Jr. and W.R. Rogers, “Effects of a 30 kV/m, 60 Hz electric field on the social behavior of
baboons: a crossover experiment,” Bioelectromagnetics, vol. 13, pp. 395-400, 1992.
[5] D.L. Hjeresen, W.T. Kaune, J.R. Decker and R.D. Phillips, “Effects of 60 Hz electric fields on avoidance behavior
and activity of rats,” Bioelectromagnetics, vol. 1, pp. 299-312, 1980.
[6] D.L. Hjeresen, M.C. Miller, W.T. Kaune and R.D. Phillips, “A behavioral response of swine to a 60 Hz electric
field,” Bioelectromagnetics, vol. 3, pp. 443-452, 1982.
[7] R.S. Rosenberg, P.H. Duffy and G.A. Sacher, “Effects of intermittent 60 Hz high voltage electric fields on
metabolism, activity, and temperature in mice,” Bioelectromagnetics, vol. 2, pp. 291-303, 1981.
[8] P.A. Janssen., A.H. Jageneau and K.H. Schellekens, “Chemistry and pharmacology of compounds related to 4-(4hydroxy-4-phenyl-piperidino)-butyrophenone. IV. Influence of haloperidol (R 1625) and of chlorpromazine on the
behaviour of rats in an unfamiliar “open field” situation,” Psychopharmacologia, vol. 1, pp. 389-392, 1960
[9] S.E. File, “Effects of chlorpromazine on exploration and habituation in the rat,” Brit. J. Pharmacol., vol. 49, pp.
303-310, 1973.
[10] R. Morris, “Development of a water maze procedure for studying spatial learning in the rat,” J. Neurosci. Methods,
vol. 11, pp. 47-60, 1984.
[11] A. Plech, T. Klimkiewicz and H. Jakrzewska, “Neurotoxic effect of copper salts in rats,” Pol. J. Environ. Stud.,
vol. 9, pp. 301-304, 2000.
[12] K. Nakamura and H. Thoenen, “Increased irritability: a permanent behaviour change induced in the rat by
intraventricular administration of 6-hydroxydopamine,” Psychopharmacologia, vol. 24, pp. 359-372, 1972.