The antinociceptive effects of spinal cyclooxygenase inhibitors on uterine cervical distension.

Pain during labor is common and severe, as is menstrual pain, and this pain originates from the uterine cervix and is transmitted via the hypogastric nerve to the spinal cord. Prostaglandins play an important role in nociceptive transmission in the spinal cord. Pharmacologically, targeting a specific cyclooxygenase (COX) enzyme isoform has as its goal to effectively treat pain while avoiding side effects. Both COX-1 and COX-2 inhibitors have been shown to effectively treat a variety of pain conditions in animals and in humans; however, their efficacy in treatment of acute visceral pain has not been explored. The purpose of this study is to evaluate the pharmacologic effects of specific spinal COX inhibitors on uterine cervical distention induced nociception. The results indicate that intrathecal (i.t.) administration of the COX-2 inhibitor, SC58238, and the nonspecific COX inhibitor, indomethacin, effectively inhibited the electromyographic activity induced by UCD. None of the inhibitors altered hemodynamic response to uterine cervical distension. The study suggests that targeting spinal COX-2 could be useful to treat transient and acute visceral pain from the uterine cervix.