A Qualitative and Quantitative Study of the Innervation of the Human Non Pregnant Uterus

Human female reproductive system is closely dependent by hormonal stimulation. Anyway it is now commonly stated that autonomic innervation system regulates, along with hormonal stimulation, the uterine physiology. Cholinergic and adrenergic innervations have a critical role in mediating input to the uterus, but other neurotransmitters and neuropeptides exist that influence uterine physiology, as well. In the present investigation, we analyzed the uterine distribution of a large set of neurotransmitters, focusing on adrenergic, noradredenergic, acetylcholine (AChE) positive, dopaminergic, serotoninergic and peptidergic neurofibers; among these latter, we focused on those releasing prolattine, enkephalines (ENKs), Vasoactive Intestinal Polypeptide (VIP), substance P (SP) and oxytocine. Authors demonstrate the differential localization of these neurofibers in non pregnant uterine fundus, corpus and cervix, sampling myometrial assays of 31 patients submitted to hysterectomy. In fundus uteri, we observed a prevalence of prolactinergic (32.1 ± 1.4 Conventional Unit, C.U.) and adrenergic (36.4 ± 4.5 C.U.) neurofibers; in uterine body VIP positive neurofibers (32.6 ± 4.8 C.U.) and prolactinergic neurofibers (30.3 ± 1.2 C.U.) were the most represented. In uterine cervix, we detected the highest concentration of all the neurofibers analysed, with enkephalinergic neurofibers (94 ± 1.7 C.U.), oxitocinergic neurofibers (72.1 ± 5.1 C.U.), SP positive neurofibers (66.1 ± 4.4 C.U.), acetylcholine positive neurofibers (64.5± 3.6 C.U.), serotoninergic neurofibers (56.4 ± 3.9 C.U.) and VIP positive neurofibers (58.3 ± 5.2 C.U.) being the most expressed. This study demonstrates that uterine cervix harbors a higher concentration of almost all neurotransmitters, compared to the other two uterine anatomic sites. The uterine cervix is largely involved during pregnancy and labor, and the rich neurotransmitters density could contribute to confer to the cervix a proper potential plasticity, necessary for pregnancy and labour.