An Experimental Study on Spinal Cord µ-Opioid and α2-Adrenergic Receptors MRNA Expression Following Stress-Induced Hyperalgesia in Male Rats

Overview

Journal Iran J Med Sci

Publisher Shiraz University of Medical Sciences

Specialty General Medicine

Date 2019 Oct 5

PMID 31582864

Citations 1

Authors

Asef Hormozi

Asadollah Zarifkar

Bahar Rostami

Fakhraddin Naghibalhossaini

Affiliations

Soon will be listed here.

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<0.05 was considered statistically significant.

Results: There was a significant (P=0.0014) decrease in tail-flick latency in the stress group compared to the control group. Nociceptive behavioral responses to formalin-induced pain in the stress group were significantly increased in the acute (P=0.007) and chronic (P=0.001) phases of the formalin test compared to the control group. A significant reduction was also observed in MOR mRNA level of the stress group compared to the control group (P=0.003). There was no significant difference in α2-AR mRNA level between the stress and control group.

Conclusion: The results indicate that chronic stress can affect nociception and lead to hyperalgesia. The data suggest that decreased expression of spinal cord MOR causes hyperalgesia.

Citing Articles

Effects of Stress Exposure to Pain Perception in Pre-Clinical Studies: Focus on the Nociceptin/Orphanin FQ-NOP Receptor System.

Pola P, Frezza A, Gavioli E, Calo G, Ruzza C Brain Sci. 2024; 14(9).

PMID: 39335430 PMC: 11431041. DOI: 10.3390/brainsci14090936.

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