Phosphorylation of spinal signaling-regulated kinases by acute uterine cervical distension in rats
Accepted 2 April 2009. published online 30 November 2009.
Abstract
Background
Spinal extracellular signaling-regulated kinase 1 and 2 (ERK 1/2) have been found to contribute to nociceptive processing, but the role of spinal ERK 1/2 in visceral pain related to the uterine cervix, the source of pain during the first stage of labor, is unknown. The aim of this study was to investigate ERK activation (phosphorylation) in spinal dorsal horn neurons after acute uterine cervical distension.
Methods
Under intraperitoneal anesthesia using chloral hydrate 300mg/kg, female Sprague-Dawley rats were exposed to a 10-s uterine cervical distension of 25, 50, 75, and 100g or no distension (sham). The electromyographic response in the rectus abdominis muscle and mean arterial blood pressure and heart rate changes to uterine cervical distension were determined. The numbers of phosphorylated-ERK 1/2- immunoreactive (pERK 1/2-IR) dorsal horn neurons in cervical (C5-8), thoracic (T5-8), thoracolumbar (T12-L2) and lumbosacral (L6-S1) segments were counted using immunohistochemistry.
Results
Compared with the non-distended sham rats, uterine cervical distension resulted in a stimulus-dependent increase in electromyographic activity and the number of pERK-IR neurons that selectively located to the thoracolumbar segment, mostly in the deep dorsal and the central canal regions. The time course study demonstrated that spinal ERK activation peaked at 60min with a slow decline for 120min after uterine cervical distension stimulation.
Conclusion
This study suggests that activation of spinal ERK might be involved in acute visceral pain arising from the uterine cervix.
ABSTRACT