Skip to main page content
U.S. flag

An official website of the United States government

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2015 Jun;27(6):775-86.
doi: 10.1111/nmo.12549. Epub 2015 Mar 24.

Estradiol modulates visceral hyperalgesia by increasing thoracolumbar spinal GluN2B subunit activity in female rats

Y Ji  1 , G Bai  1 , D-Y Cao  1 , R J Traub  1
Affiliations

Estradiol modulates visceral hyperalgesia by increasing thoracolumbar spinal GluN2B subunit activity in female rats

Y Ji et al. Neurogastroenterol Motil. 2015 Jun.

Abstract

Background: We previously reported estrogen modulates spinal N-methyl-d-aspartate (NMDA) receptor processing of colorectal pain through changes in spinal GluN1 subunit phosphorylation/expression. The purpose of this study was to investigate whether spinal GluN2B containing NMDA receptors are involved in estrogen modulation of visceral pain processing.

Methods: Behavioral, molecular, and immunocytochemical techniques were used to determine spinal GluN2B expression/phosphorylation and function 48 h following subcutaneous injection of estradiol (E2) or vehicle (safflower oil, Saff oil) in ovariectomized rats in the absence or presence of colonic inflammation induced by mustard oil.

Key results: E2 increased the magnitude of the visceromotor response (VMR) to colorectal distention compared to Saff oil in non-inflamed rats. Intrathecal injection of the GluN2B subunit antagonist, Ro 25-6981, had no effect on the VMR in non-inflamed E2 or Saff oil rats. Colonic inflammation induced visceral hyperalgesia in E2, but not Saff oil rats. Visceral hyperalgesia in E2 rats was blocked by intrathecal GluN2B subunit selective antagonists. In inflamed rats, E2 increased GluN2B protein and gene expression in the thoracolumbar (TL), but not lumbosacral (LS), dorsal spinal cord. Immunocytochemical labeling showed a significant increase in GluN2B subunit in the superficial dorsal horn of E2 rats compared to Saff oil rats.

Conclusions & inferences: These data support the hypothesis that estrogen increases spinal processing of colonic inflammation-induced visceral hyperalgesia by increasing NMDA receptor activity. Specifically, an increase in the activity of GluN2B containing NMDA receptors in the TL spinal cord by estrogen underlies visceral hypersensitivity in the presence of colonic inflammation.

Keywords: NMDA receptor; estradiol; gonadal hormones; pain; spinal cord; visceral nociception.

PubMed Disclaimer

Figures

Figure 1
Figure 1
The effect of the GluN2B selective antagonist, Ro 25-6981, on the visceromotor response in rats in the absence of colonic inflammation. A: I.t. Ro 25-6981 had no effect on the VMR in Saff oil rats. B: In E2 rats, Ro 25-6981 did not change the magnitude of the VMR. Distention trials began at the indicated time points. Inset: an example showing the visceromotor response to four 80mmHg colorectal distentions.
Figure 2
Figure 2
The effect of GluN2B selective antagonist, Ro 25-6981, on the visceromotor response in rats with colonic inflammation. A,B. Visceral hyperalgesia was induced in E2 rats that lasted at least 4 hours. In Saff oil rats, colonic administration of mustard oil had no effect on the visceromotor response. Data were normalized to the baseline VMR that was established prior to mustard oil instillation. C,D. In E2 rats, i.t. Ro 25-6981 (80 µg) attenuated the visceral hyperalgesia compared to vehicle. Inset C: there was no visceral hypersensitivity following pretreatment with i.t. Co 101244 (100nmol) compared to baseline (n=4). E,F. In Saff oil rats, i.t. Ro 25-6981 had no effect on the visceromotor response. Dunn’s test following significant ANOVA, *,**,*** p<0.05, 0.01, 0.001 vs. baseline. T-test or ANOVA, #, ## p<0.05, 0.01 vs. vehicle.
Figure 3
Figure 3
Changes of GluN2B phosphorylation and expression in the lumbosacral (LS) and thoracolumbar (TL) spinal cord in the absence of colonic inflammation. A. In the LS spinal cord, 48 hours after E2 injection, there was significantly more immunoprecipated GluN2B protein compared with Saff oil rats (t-test, **p<0.001, n=4–8/group). There was no increase in GluN2B phosphorylation. (B) In the TL spinal cord E2 rats were not different from Saff oil rats in GluN2B protein phosphorylation or expression (t-test, p>0.05; n=4/group).
Figure 4
Figure 4
Colonic inflammation does not affect GluN2B protein and gene expression in the LS spinal cord. A. E2 rats were not different from Saff oil rats in immunoprecipated GluN2B protein phosphorylation or expression in the LS spinal cord (t-test, p>0.05; n=4/group). B. There was no difference in GluN2B gene expression between E2 and Saff oil rats in the LS spinal cord (t-test, p>0.05; n=4/group).
Figure 5
Figure 5
Colonic inflammation alters GluN2B expression in the TL spinal cord. A. Colonic inflammation in E2 rats increased immunoprecipated GluN2B and pGluN2B/GLuN2B level as compared with Saff oil rats (** t-test, p<0.05; n=4/group). B. The increase in GluN2B protein expression in the TL spinal cord was confirmed by western blot of whole protein lysate (* t-test, p<0.05; n=7/group). C. There was a parallel increase in GluN2B gene expression (* t-test, p<0.05; n=4/group).
Figure 6
Figure 6
The distribution of GluN2B immunoreactive neurons in the spinal dorsal horn in the presence of colonic inflammation. A: Representative immunocytochemical staining of LS and TL spinal cord sections with anti-GluN2B antiserum. Scale bar: 100 µm. B: Dorsal horn laminar quantification (I–II and III–V) of GluN2B immunoreactive cells in the LS and TL spinal segments in Saff oil and E2 rats (* t-test, p<0.05; n=4–6/group).
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Chang L, Heitkemper MM. Gender differences in irritable bowel syndrome. Gastroenterology. 2002 Nov;123(5):1686–1701. - PubMed
    1. Vob U, Lewerenz A, Nieber K. Treatment of irritable bowel syndrome: sex and gender specific aspects. Handb Exp Pharmacol. 2012;(214):473–497. - PubMed
    1. Cain KC, Jarrett ME, Burr RL, Rosen S, Hertig VL, Heitkemper MM. Gender differences in gastrointestinal, psychological, and somatic symptoms in irritable bowel syndrome. Dig Dis Sci. 2009 Jul;54(7):1542–1549. - PMC - PubMed
    1. Hungin AP, Chang L, Locke GR, Dennis EH, Barghout V. Irritable bowel syndrome in the United States: prevalence, symptom patterns and impact. Aliment Pharmacol Ther. 2005 Jun 1;21(11):1365–1375. - PubMed
    1. Chang L, Mayer EA, Labus JS, Schmulson M, Lee OY, Olivas TI, et al. Effect of sex on perception of rectosigmoid stimuli in irritable bowel syndrome. Am J Physiol Regul Integr Comp Physiol. 2006 Aug;291(2):R277–R284. - PubMed

Publication types

MeSH terms