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NEUROENDOCRINOLOGY LETTERS
including Psychoneuroimmunology, Neuropsychopharmacology,
Reproductive Medicine, Chronobiology
and Human Ethology, ISSN 0172–780X

NEL Vol.24 Nos.3/4, Jun-Aug 2003

ORIGINAL ARTICLE

Effects of central and peripheral administration of leptin on pain threshold in rats and mice

2003; 24:193196
pii: NEL243403A07
PMID: 14523356

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Effects of central and peripheral administration of leptin on pain threshold in rats and mice

Selim Kutlu, Sinan Canpolat, Suleyman Sandal, Mete Ozcan, Mustafa Sarsilmaz & Haluk Kelestimur

Firat University, The Institute of Health Science, Department of Neuroendocrinology, Elazig, TURKEY.

Submitted: July 27, 2002
Accepted: September 19, 2002

Key words:
leptin, pain threshold

 

Abstract

OBJECTIVE: This study was planned to investigate the effects of exogenous leptin on the pain threshold.

METHODS: Adult male Wistar rats weighing 250–300 g and mice weighing 25–30 g were used in this study. Leptin was intracerebroventricularly (i. c. v.) injected in a dose of 3.5 g/rat. Mice were intraperitoneally (i. p.) injected with leptin in a dose of 25 g/mouse. Control animals were injected with the respective vehicle. The pain threshold test was performed using hot plate analgesia meter. The experiments were performed during the day and at night. The data were statistically analysed by Mann-Whitney U test. Level of significance was set at p<0.05.

RESULTS: During the day, there were no significant changes in hot plate latencies half an hour after i.c.v. injection of vehicle or leptin in the control and leptin-treated rats, respectively. At night, like during the day, i.c.v. injection of neither vehicle nor leptin caused any significant change in pain sensitivity. In mice, i.p. injection of leptin decreased latencies significantly (p<0.05) during the day and at night. Thus, leptin caused an increase in pain sensitivity during the day and at night.

CONCLUSION: These results clearly demonstrated that leptin has a decreasing-effect on pain threshold if it is peripherally administered in mice.

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