Journal of Rafsanjan University of Medical Sciences

The Role of Estrogen Receptors of Paragigantocellularis Lateralis Nucleus in the Formalin-Induced Pain Modulation in Female Rats
 
R[j1] . Khakpay[1], Z. Heidarzadeh[2], F. Khakpai[3]
 
 
 
 
 
Received: 10/06/2017  Sent for Revision: 28/10/2017    Received Revised Manuscript: 01/05/2018              Accepted: 20/06/2018
 
 
 
Background and Objectives: Since intra-paragigantocellularis lateralis (LPGi) injection of 17β-estradiol induces strong analgesia in male rats which might be mediated via estrogen receptors, this study investigated the role of estrogen receptors of LPGi nucleus in the modulation of formalin-induced pain (while being stimulated by 17β-estradiol) during estrus phase in female rats.
Materials and Methods: In this experimental study, 48 female Wistar rats (200-270 gr) were randomly divided into 8 groups including control, sham, normal saline (17β-estradiol solvent), DMSO (ICI182,780 solvent), 17β-estradiol, estrogen receptor antagonist (ICI182,780; 15&50 nmol) and ICI182,780/17β-estradiol. After entrance into the estrus phase, drugs were injected into the LPGi nucleus; 15 minutes later, formalin injection (5%, 50 μl) was done into the left rat's hind paw and formalin-induced paw jerking behavior was recorded for 1 hr. Data were analyzed using one-way ANOVA analysis followed by Tukey multiple comparison test.
Results: The results of this research showed that during estrus phase, the treatment of LPGi nucleus with 17β-estradiol significantly attenuated paw jerking behavior in the both phases of formalin test (p<0.001). Pretreatment of the LPGi nucleus with ICI182,780 prevented the 17β-estradiol-induced antinociception (p<0.001).
Conclusion: Based on these results, it can be suggested that intra-LPGi injection of 17β-estradiol induces robust analgesia during the estrus phase in female rats; and this effect may be mediated via estrogen receptors.
Key words: 17β-Estradiol, Estrus phase, ICI182,780, Pain modulation, Paragigantocellularis lateralis nucleus, Female rat
 
 
Funding: This research was funded by University of Tabriz.
Conflict of interest: None declared.
Ethical approval: The Ethics Committee of University of Tabriz approved the study (303/52).
 
 
How to cite this article: Khakpay R, Heidarzadeh Z, Khakpai F. The Role of Estrogen Receptors of Paragigantocellularis Lateralis Nucleus in the Formalin-Induced Pain Modulation in Female Rats. J Rafsanjan Univ Med Sci 2018; 17 (7): 597-610. [Farsi]