Analgesic mechanism in descending pain modulation system : Involvement of sex difference and emotion

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 13671592
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Anesthesiology/Resuscitation studies
• Research Institution: Saga University (2004); 佐賀医科大学 (2001-2003)
• Principal Investigator: HIRAKAWA Naomi Saga University, Faculty of Medicine, Associate Professor, 医学部, 助教授 (20173221)
• Co-Investigator(Kenkyū-buntansha): MORIMOTO Masatoshi Saga University, Anlalytical Research and Experimental Center, Associate Professor, 総合分析実験センター, 助教授 (90136482) ; TAKASAKI Mitsuhiro Saga University, Faculty of Medicine, Associate Professor, 医学部, 助教授 (70236206) ; OGAWA Ikuyo Saga University, Faculty of Medicine, Research Associate, 医学部, 助手 (90304914) ; TOTOKI Tadahide Saga University, Trustee, 理事 (20038722)
• Project Period (FY): 2001 – 2004
• Keywords: descending pain modulation system / opioid receptor / cannabinoid / conditioned place preference / immunohistochemistry / sex difference / RVM

Research Abstract

Distributions of opioid receptors, enkephalin, SP, and CGRP were immunohistochemically investigated in normal rats and rats after administration of opioid agonists. There were no obvious sex differences in the spinal cord, PAG, or RVM.
μ Opioid receptor-positive nerve fibers were most dense in the 1st and 2nd layers of the spinal cord posterior horn. However, in RVM,μ,k, and δ opioid-positive fibers were very scarce, and no positive cells were present, showing no sex difference. The fibers were abundant in the nucleus accumbens and amygdala. These findings suggested the association of pain reactions and the intracranial reward system.
Regarding conditioned place preference(CPP), administration of DAMGO and endomorphin 1 induced preference in both male and female rats. DAMGO also induced preference in the neuropathic pain model