Paper Information

Title: 

CHANGES IN GENE EXPRESSION OF THE ENZYMES INVOLVED IN BIOSYNTHESIS AND DEGRADATION OF CATECHOLAMINES FOLLOWING CHRONIC ADMINISTRATION OF MORPHINE AND PAIN IN RATS

Type: POSTER
Author(s): SATARIAN L.*,JAVAN MOHAMMAD,MOTAMEDI F.
 
 *DEPARTMENT OF PHYSIOLOGY, SCHOOL OF MEDICAL SCIENCES, TARBIAT MODARES UNIVERSITY, TEHRAN, IRAN
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2009Volume 19
 
 
Abstract: 

Stress inhibits the development of tolerance to morphine analgesia via activating Hypothalamic-Pituitary-Adrenal (HPA) axis. Catecholamine systems have been reported to be involved following morphine tolerance development. We tried to evaluate changes in the gene expression levels for MAO-A, MAOB, COMT and TyH enzymes following chronic pain, development of morphine tolerance and their combined administration. Analgesic tolerance was induced by intrapritoneal injections of morphine 20 mg/kg twice a day for 4 days. To study the effect of pain on morphine tolerance, 50 μl of formalin 5% was injected into the animal paws prior to morphine injections. RT-PCR was used toevaluate the gene expression level in lumbar spinal cord on day 5. Three separate control groups received saline, morphine injections and pain induction. Chronic administration of morphine increased the expression level of MAO-B,decreased the expression of TyH and did not change the expression of COMT and MAO-A. Pain increased the expression of MAO-A, but did not change the expression of MAO-B, COMT and TyH. The combination of morphine treatment and pain induction for 4 days partially reversed the reduced expression of TyH and did not change the expression of MAO-A, MAO-B and COMT. Our results showed that in the context of morphine tolerance, gene expression was changed toward decreased biosynthesis and increased elimination of catecholamines. It seems that chronic administration of morphine caused lower level of catecholamines in spinal neurons and help development of morphine tolerance. Also, chronic pain partially produced compensational changes in gene expression. This may explain its anti-tolerance effect.

 
Keyword(s): CATECHOLAMINES, MORPHINE, PAIN, RAT
 
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