BACKGROUND: Studies have shown that abnormal innervation is an important factor impacting occurrence and development of pathological pain in endometriosis.OBJECTIVE: To observe uterine innervation of adenomyosis mice and to analyze the cause of innervation changes due to nerve growth factor (NGF) expression, inflammation, and vascularization. DESIGN, TIME AND SETTING: This randomized, controlled, animal experiment was performed at the Research Institute of Obstetrics and Gynecology Hospital, and Central Laboratory of Zhongshan Hospital, Fudan University from March to December 2008. MATERIALS: Tamoxifen was provided by Fudan Forward, China. Rabbit anti-mouse NGF was purchased from Santa Cruz Corporation, USA; rabbit anti-protein gene product 9.5 (PGP9.5) and rabbit anti-substance P (SP) were purchased from Chemicon, USA.METHODS: A total of 40 newb ICR mice were randomly assigned to adenomyosis model and control groups, with 20 animals in each group. Mice in the adenomyosis model group were orally administrated 2.7 μmol/kg tamoxifen on days 2-5 after birth, while the controls were not treated. MAIN OUTCOME MEASURES: Both uteri from all mice were harvested at days 135-145 after birth. Expressions of polyclonal PGP9.5 and SP were immunohistochemically detected to demonstrate pan- and sensory nerve fibers. Microvessel density was quantified in the endometrium and myometrium using immunochemical staining for polyclonal rabbit anti-CD31, which stained vessels. Gene expression for NGF, high-affinity tyrosine kinase receptor (trkA), p75 neurotrophin receptor (p75NTR), bradykinin receptor-1 (BKR-1), and 2 (BKR-2), as well as substance P receptor (neurokinin1 receptor, NK1-R), were detected by reverse transcription-polymerase chain reaction. NGF-β protein expression was detected by West blot analysis. RESULTS: More nerve fibers were stained with PGP9.5 in the endometrium and myometrium, and with SP in the endometrium, in adenomyosis mice compared with controls (P < 0.01 and P < 0.05). Microvessel density in the myometrium of adenomyosis mice was significantly greater than the controls (P < 0.01). In the uterus of adenomyosis mice, mRNA expression of NGF and its two receptors (trkA and p75 NTR), BKR-1, and NK1-R, as well as protein expression of NGF-β, were greater than the control mice (P < 0.01 or P < 0.05).CONCLUSION: Uterine innervation in the adenomyosis mice was increased compared with the controls. Moreover, NGF expression, inflammation, and vascularization, which have been shown to be impact factors of innervation, were abnormal in the uteri of adenomyosis mice.