Volume 50, Issue 6:

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

Reprint requests
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

 

PHYSIOLOGICAL RESEARCH
© 2001 by the Institute of Physiology,
Czech Academy of Sciences

ISSN 0862 - 8408

Issue 6