Expression Changes Of Fos And NNos In Medullary Visceral Zone Induced By Varied Distention Of Uterine Cervix

Background:Labor pain is clinically one of the severe visceral pains. It can cause a series of negative effects on parturient, such as circulatory overloading, respiratory acid-base disorder, in-coordinated uterine contraction and prolonged labor, and finally endanger the lives of parturient and fetal. Uterine cervical distension(UCD) is the main cause of labor pain especially in the first stage of labor but there is no clear understanding about the detailed mechanism and no ideal and effective labor analgesia clinically. Some research shows that medullary visceral zone (MVZ) is involved in the causing and conducting of visceral pains, but there have been no further reports by now on whether the causing and conducting of labor pain is also related to MVZ. This paper tries to establish the model of UCD in rats, and then studies the expression changes of such neurons as c-fos nNOS of rats’ MVZ. when rats experiencing different UCD and discusses the mechanism of c-fos、nNOS’s effects on the pain of UCD.Objection:1. Establishing the uterine cervical distension model in non-pregnant rats.2. The research aimed at investigating the expression changes of nNOS and c-fos in the rat medullary visceral zone with different UCD,of which the transferring mechanismin the medulla oblongata is still unclear.Materials and Method:Thirty-six adult female Sprague-Dawley rats weighing 250g-280g were randomly divided into the control group (UCD Og group),50g tension group (UCD 50g group) and 100 g tension group (UCD 100 g group), were anesthetized with isofiurane inhalation.The right carotid artery was catheterized for continuous monitoring of arterial blood pressure and heart rate. Incise the abdomen from the midline to expose the cervix and two metal crooks were used to pass through both sides of the cervix. Establish the UCD model through distension forces generated by hanging different standard weights (50g、100g) at the end of metal crooks, while the Control group without UCD stimulation.UCD was performed for 30min.The distribution of nNOS, c-fos and c-fos/nNOS positive neurons was observed 2 hours after UCD by NADPH-d immunohistochemistry and Fos immunohistochemical staining. The protein expression of nNOS and c-fos in the medulla oblongata was detected by western blotting. The mRNA expression of nNOS and c-fos in the medulla oblongata was detected by RT-PCR.Results:1. C-fos immunoreactive neurons in nucleus of brown were round or oval, while the cytoplasm was unstained. The cell bodies and processes of nNOS positive neurons were blue, and the nuclei were not stained in the form of a bubble. c-fos/nNOS double labeled cell bodies and dendrites of neurons stained blue, and nucleus showed brown yellow. These neurons were mainly distributed in the nucleus of the solitary tract nucleus (NTS) and the lateral reticular nucleus (LRN).2. Compared with UCD 0 g group, the number of nNOS, c-fos and c-fos/nNOS positive neurons in the NTS and LRN of UCD 50 g group and UCD 100 g group were significantly increased, and the dyeing significantly deepened. The protein and mRNA levels of c-fos, nNOS in UCD 100 g group was higher than that of UCD 50 g group (p<0.05). And both of the two groups were significantly elevated (p<0.01) compared with UCD 0 g group.Conclusion:1. Our experiment explained that uterine cervical distension results in a similar pattern of the medulla oblongata c-fos protein expression as seen with other noxious visceral stimuli and c-fos expression increased with the increased distension force. Thus, the model contributes to exploring the uterine cervical distension pain.2. Acute uterine cervical distension in rats can lead to increased expression of c-fos and nNOS in NTS and LRN of the medulla oblongata, nNOS positive neurons in NTS and LRN may be involved in the conduction of the uterine cervical distension pain in the medulla oblongata.