A life of pelvic pain

Pelvic pain associated with menstruation, i.e., dysmenorrhea, is a chronic pelvic pain that not only interferes with a woman's wellbeing for a large part of her life but also often co-occurs with other chronic painful conditions such as interstitial cystitis and irritable bowel syndrome and others. Little has been known about mechanisms underlying these chronic pelvic pains. This paper reviews 37 years of research in my laboratory at Florida State University on such mechanisms. Our research, mostly on rats, has contributed to the following findings: (1) Female reproductive organs are innervated in a topographic fashion by afferents in the pelvic (vagina/cervix) and hypogastric (cervix/uterine horn) nerves. (2) The input contributes to uterine and vaginal perceptions (nociception) that are modified by reproductive status. (3) Throughout the CNS, neurons responsive to stimulation of the reproductive tract also respond to stimulation of skin and other internal organs, in a manner modifiable by reproductive status and peripheral pathophysiology. (4) This dynamic physiological convergence may reflect extensive anatomical divergence of and interconnections between pathways entering the CNS via gateways through the spinal cord, dorsal column nuclei, and solitary nucleus. (5) The convergence also indicates the existence of extensive cross-system, viscero-visceral interactions within the CNS, that, while organized for coherent bodily functioning, serves as a substrate by which pathophysiology in one organ can influence physiology and responses to pathophysiology in other organs. (6) Some cross-system effects observed so far include: (a) Bladder inflammation reduces the rate of uterine contractions and the effects of drugs on the uterus. (b) Colon inflammation produces signs of inflammation in the otherwise healthy bladder and uterus. (c) A surgical model of endometriosis produces vaginal hyperalgesia, exacerbates pain behaviors induced by a ureteral stone, and reduces volume voiding thresholds if the bladder. These cross-system effects, which likely involve CNS mechanisms, likely also underlie co-occurrence of painful clinical conditions. Research continues on details of these mechanisms and their relevance for clinical diagnosis and therapy. None of this work could have been done without collegial support of colleagues and technical staff at Florida State University.