The long-term goal of this program is to advance understanding of neural mechanisms of chronic pelvic pain in females. Current studies focus on endometriosis, a disorder defined by extrauteral growths of endometrial tissue. Symptoms include subfertility and severe chronic pains, including dyspareunia (vaginal hyperalgesia), dysmenorrhea (menstrual pain) and other pelvic and abdominal visceral and muscle pains. These pains are notoriously difficult to alleviate. A major factor impeding development of better treatments is that mechanisms underlying the relationship between the ectopic growths and pain are poorly understood. A rat model of endometriosis exists (ENDO) that involves autotransplantion on abdominal arteries of pieces of uterus. The transplants form cysts with characteristics similar to the ectopic growths in women. Like women, the rats are subfertile and exhibit vaginal and abdominal muscle hyperalgesia. The proposed studies will use this rat model to test hypotheses concerning mechanisms underlying ENDO-induced vaginal hyperalgesia. The recent discovery that the ectopic growths attract a nerve supply, via spanchnic and vagus nerves in the rat model, provides a new direction to study the elusive association between the ectopic growths and pain. Three studies in Aim #1 will test the hypothesis that development of ENDO-induced vaginal hyperalge- sia results from central neural effects produced by activity in the cysts'developing nerve supply. Studies 1-2 will compare developmental time courses of: (i) the cysts'nerve supply (visualized by immunostaining with neuronal markers), (ii) activity in the nerve supply (assessed by protein extravasation), (iii) changes in spinal and brainstem processing of vaginal information (assessed by neuronal expression of c-Fos and phosphory- lated N-methyl-D-aspartic acid receptor NR1 [pNR1] proteins), and (iv) peritoneal content of cytokines (using protein arrays). By assessing vaginal nociception behaviorally, Study 3 will test the prediction that, if the hy- pothesis is correct, removing cysts before nerve activity develops should prevent the development of ENDO- induced hyperalgesia. Three studies in Aim #2 will test the hypothesis that maintenance of ENDO-induced vaginal hyperalgesia requires maintenance by the cysts'nerve supply of spinal, brainstem, intersegmental and/or supraspinal effects. With behavioral methods, Study 1 will test the prediction from this hypothesis that denervating fully-grown cysts should reduce the hyperalgesia. Study 2 will test the hypothesis differently, by assessing how denervations of fully-grown cysts affect vaginal-stimulation induced c-Fos and pNR1 express- ion in spinal and brainstem neurons. Study 3 will test hypotheses concerning intersegmental and supraspinal effects by assessing how spinal transections affect vaginal-stimulation-induced c-Fos and pNR1 expression in spinal and brainstem neurons. Results of the studies have the potential for improving understanding of mechanisms that contribute to the pains of endometriosis, thereby leading to new treatment strategies.
Endometriosis is common disorder suffered by women of childbearing age in whom abnormal growths of uterine tissue found outside the uterus are associated with severe pains that greatly reduce quality of life. In part because so little is known about how the abnormal growths give rise to these pains, they are notoriously difficult to alleviate without resorting to hormones or surgery that either produce intolerable side effects or fail to help. Studies proposed in this application will use a validated rodent model to investigate how the newly- discovered nerves that sprout to supply the abnormal growths might influence central nervous system processes to induce the pains, thereby improving knowledge that can lead to improved treatment strategies.
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