Does Exogenous
Melatonin Influence the Free Radicals Metabolism
and Pain Sensation in Rat?
I. PEKÁRKOVÁ1,
S. PARARA1, V. HOLEČEK3,
P. STOPKA2, L. TREFIL3, J.
RACEK3 ,
R. ROKYTA1
1Department of
Normal, Pathological and Clinical Physiology,
Third Faculty of Medicine, Charles University,
Prague, 2Institute of
Inorganic Chemistry, Czech Academy of Sciences,
Řež near Prague, 3Department of
Clinical Biochemistry and Laboratory Diagnostics,
Faculty of Medicine, Charles University, Pilsen,
Czech Republic
Received
October 12, 2000
Accepted February 28, 2001
Summary
Melatonin
has been shown to play a role in antioxidative
defence. We therefore studied its effect on
oxidative damage to the rat cerebral cortex
evoked by painful stimulation and
immobilization-induced stress. Moreover, the
effect of melatonin on chronic pain perception
was examined. Rats were injected with either a
high dose of melatonin (100 mg/kg i.p.) or a
vehicle for five days and were subjected to
painful stimulation or immobilization stress 30
min after the treatment. To determine the degree
of oxidative stress, the levels of free radicals,
thiobarbituric acid reactive substances (TBARS)
as indicators of lipid peroxidation and
glutathione peroxidase (GSHPx) were estimated in
somatosensory cortex. Pain perception was
measured by the tail-flick and plantar test.
Melatonin reduced the level of TBARS previously
increased by painful stimulation. Melatonin also
exhibited a slight analgesic effect in those
animals exposed to painful stimulation but its
role in free radical scavenging did not
contribute to this effect.
Key words
Melatonin
· Oxidative stress · Pain · Stress · Free radicals
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I.
Pekárková, M.D., Department of Neurology,
Rudolf and Stefanie Hospital in Benešov, Máchova
400, 257 01 Benešov, Czech Republic. Fax +420 2
24923827. e-mail: ivanapekarkova@seznam.cz
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