Document Type: Original Article(s)

Authors

1 Department of Physiology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

2 Department of Physiology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran; and Shiraz Neuroscience Research Center, Shiraz University of Medical Sciences, Shiraz, Iran; and Department of Neuroscience, School of Advanced Medical Sciences and Technologies, Shiraz University of Medical Sciences, Shiraz, Iran

3 Department of Biochemistry, Shiraz University of Medical Sciences, School of Medicine, Shiraz, Iran; and Autoimmune Research Center, Shiraz University of Medical Sciences, School of Medicine, Shiraz, Iran

Abstract

Background: Intense stress can change pain perception and induce hyperalgesia; a phenomenon called stress-induced hyperalgesia (SIH). However, the neurobiological mechanism of this effect remains unclear. The present study aimed to investigate the effect of the spinal cord µ-opioid receptors (MOR) and α2-adrenergic receptors (α2-AR) on pain sensation in rats with SIH. Methods: Eighteen Sprague-Dawley male rats, weighing 200-250 g, were randomly divided into two groups (n=9 per group), namely the control and stress group. The stress group was evoked by random 1-hour daily foot-shock stress (0.8 mA for 10 seconds, 1 minute apart) for 3 weeks using a communication box. The tail-flick and formalin tests were performed in both groups on day 22. The real-time RT-PCR technique was used to observe MOR and α2-AR mRNA levels at the L4-L5 lumbar spinal cord. Statistical analysis was performed using the GraphPad Prism 5 software (San Diego, CA, USA). Student’s t test was applied for comparisons between the groups. P

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