Author/Authors :
-، - نويسنده 1 Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran
Pharmaceutical Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Mobasher, Mohammad Ali , -، - نويسنده Department of Physiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran Sajedianfard, Javad , -، - نويسنده Pharmaceutical Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Jamshidzadeh, Akram , -، - نويسنده Department of Physiology and Pharmacology, Institute Pasture of Iran, Tehran, Iran Naghdi, Naser , -، - نويسنده Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran
Pharmaceutical Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran Namvaran, Mohammad Mehdi
Abstract :
Objective(s):The relationship between tramadol, as an antinociceptive drug, and locus coeruleus (LC), the main noradrenergic nucleus of the brain that affects regulation and modulation of pain through descending noradrenergic pathways was investigated. Materials and Methods: Male Sprague-Dawley rats were divided into four groups of 10 rats. The rats were fixed in stereotaxic instrument and then a probe was inserted into LC. Pain was induced by subcutaneous injection of 50 μl of 2.5% formalin 40 minutes after initiation of microdialysisin right hind paw, and nociceptivepain scores were calculated every 5 minutes. Subsequently noradrenaline (NA) and its metabolite, 3-methoxy-4-hydroxyphenylglycol (MHPG), were collected and measured by microdialysis of locus coeruleus in freely moving rats every 15 minutes during formalin injection. Results: Nociceptive pain scores observed in formalin test had the highest nociceptive sensation 5 minutes after injection. Significant rises in concentrations of NA and MHPG, in samples taken between 30 and 45 min after initiation of the locus coeruleusmicrodialysis, coincided with the peak of the pain after injection of formalin. Conclusion: According toconcurrency of the highest nociceptive sensation and peak of NE and MHPG concentrations, tramadol can indirectly affect the LC by blocking the pain signals from different parts of the brain such as periaqueductal gray mater, central nucleus of amygdale or the spinal cord.
