Estrogen receptor‐α expression in nociceptive‐responsive neurons in the medullary dorsal horn of the female rat

Abstract

Estrogens exert a substantial influence on the transmission of nociceptive stimuli and the susceptibility to pain disorders as made evident by studies in both animals and human subjects. The estrogen receptor (ER) seems to be of crucial importance to the cellular mechanisms underlying such an influence. However, it has not been clarified whether nociceptive neurons activated by pain express ERs. In this study, a noxious injection of formalin was given into the lower lip of female rats, thereby activating nociceptive neurons in the trigeminal subnucleus caudalis as demonstrated by immunohistochemical labeling of Fos. Using a dual-label immunohistochemistry protocol ERalpha-containing cells were visualized in the same sections. In the superficial layers of the medullary dorsal horn, 12% of ERalpha-labeled cells, mainly located in lamina II, also expressed noxious-induced Fos. These findings show that nociceptive-responsive neurons in the medullary dorsal horn express ERalpha, thus providing a possible morphological basis for the hypothesis that estrogens directly regulate pain transmission at this level.

Influence of Estrogen Levels on Thermal Perception, Pain Thresholds, and Pain Tolerance: Studies on Women Undergoing in Vitro Fertilization

“…[1][2][3][4]6,9,29 Nevertheless, the underlying networks are complex and the results of studies on hormonal pain modulation in humans, particularly those using laboratory induced pain, 14 remain notoriously diverse. 5,19,20,24,25,34,39,41 The clinical studies performed are generally based on a hormonal replacement therapy regimen.…”

“…40 In the present study, we have examined all major thin fiber sensory modalities at the very extremes of estradiol levels, thereby optimizing the possibility to discern significant effects of estradiol. Even so, no measurable changes in pain perception that could be (2,32) 5.26 (1,32) 4.46 (2,32) (2,32) 9.69 (1,32) 0.30 (2,32) (2,32) 1.07 (1,32) 0.05 (2,32) (2,32) 0.10 (1,32) 0.34 (2,32) 0.005 0.75…”

“…Heat pain tolerance, VAS (mm) Group Session Group x Session 10.7 (2,32) 0.09 (1,32) 0.12 (2,32) 0.000 0.77…”

“…Session Group x Session 0.30 (2,32) 0.24 (1,32) 0.79 (2,32) (2,32) 0.81 (1,32) 0.19 (2,32) 0.98 0.37…”

Bioelectric Activity of Interneurones of Spinal Cord in the Experimental Menopause in Femal Rats

“…Також показано, що в задніх рогах спинного мозку тварин ERα бере участь у модуляції больової Aδ-і C-афферентної передачі [12]. Ці дані створюють основу для висунення гіпотези, що естроген, через активацію ERα, безпосе-редньо може регулювати передачу болю на центральному рівні [13].…”