| Objective: Observe the effect of various neonatal maternal separations (NMS) stimulation on visceral sensibility of pain in developing rats by the method of behavior and electrophysiology research. Explore the best time of the visceral hyperalgesia model in developing rats by NMS. This study can deeply help understanding the future dangers of NMS and providing guidance for prevention and cure in clinic.Method: 50 SD neonatal rats were divided randomly into NMS39,NMS60,NMS78,NMS120 group (n=10) and control group (n=10). Rats in the NMS39 group were separated from the dam for 3h/d (8:00-11:00am) on postnatal days 2~14 for 13 consecutive days, NMS60 group were separated on postnatal days 2~21 for 20 consecutive days;NMS78 group were separated from the dam for 3h/d (8:00-11:00am) and 3h/d (14:00-17:00pm) on postnatal days 2~14 for 13 consecutive days, NMS120 group were separated on postnatal days 2~21 for 20 consecutive days; and the control C group were not treated and remained in the home cage with the dam. Conventionally breeding to the young period (6-week age), observing the score of Abdominal Withdrawal Reflex (AWR),visceral pain threshold and measurement of electrical discharge of external oblique muscle of abdomen (EOMA) under different pressures of colorectal distension irritation (CRD) to evaluate visceral algesthesia in rats. Measure the amount of fecal pellets and the time of glass pellets output in rats to evaluate colon motility. Kill the rats and select descending colon to do pathological examination. SPSS 11.0 software for Windows was used in all statistical tests.α=0.05 was considered significant.Result: The AWR score and the amplitudes of spike of EOMA increased gradually with the rising of the CRD pressure in 5 groups of developing rats. When the CRD pressure were 20mmHg,40mmHg,60mmHg, the AWR score in NMS39 group ,NMS60 group ,NMS78 group and NMS120 group were higher than the control C group. When pressure reached 80mmHg, there were no significant differences of AWR score among five groups. When the CRD pressure were 15mmHg, 30mmHg, 45mmHg, 60mmHg the amplitudes of spike of EOMA score in NMS39 group ,NMS60 group ,NMS78 group and NMS120 group was higher than the control C group. When pressure reached 75mmHg, there were no significant differences of the amplitudes of spike of EOMA score among five groups. The Pain thresholds of the group NMS39, NMS60, NMS78, NMS120 and group C were (15.83±5.05) mmHg, (16.50±8.40) mmHg, (13.50±2.88) mmHg, (16.00±5.28) mmHg, (33.83±4.31) mmHg, but the differences among the group NMS39, NMS60, NMS78 and NMS120 were no statistical significances. There were no significant differences of fecal pellets and the time of glass pellets output among the five groups. There were no obvious histopatholigical changes in descending colon among the five groups.Conclusion: The persistent NMS can result in decreasing of pain threshold in rats, emerging chronic visceral hypersensibility. This hyperalgesia can continue to juvenile stage and there is no altered intestinal motility, no altered bowel function and properties, and no histological change found in colorectal tissues. The visceral hyperalgesia model of developing rat established by maternal separation for 3h/d on postnatal days 2~14 for 13 consecutive days. Objective: Establish the model of visceral hyperalgesia in developing rats by Neonatal maternal separation (NMS). Detect FOS expression in hypothalamus paraventricular nucleus and anterior cingulated cortex of developing rats with visceral hyperalgesia. Explorer the mechanism of visceral hyperalgesia in developing rats, to provide the theoretical basis for prevents and cures the disease of NMS in clinic.Method: According to the factorial design, 32 SD rats were divided into four groups with each 8, Group A1B1 was NMS group and imposed on CRD at 6-week age, yet Group A1B2 was not imposed on CRD as NMS group. Group A2B1 was imposed on CRD at 6-week age while Group A2B2 without treatment both as the control groups. On the 6th week, after the rats of Group A1B1 and A2B1 were imposed on CRD for 2 hours while rats of Group A1B2 and A2B2 not imposed on CRD were sampled hypothalamus paraventricular nucleus and anterior cingulated cortex, the semi-quantity analysis of the cell numbers of Fos-Like Immunoreactivity (FLI) of these sites were made through immunohisrochemical coloration and computer image analyzing system. SPSS 11.0 software for Windows was used in all statistical tests.α=0.05 was considered significant.Result: The number of FLI in PVN in group A1B1,A1B2,A2B1,A2B2 were (50.61±11.68), (31.25±7.28), (43.67±16.03), (18.13±3.41), and (53.48±15.45),(38.42±11.67),(35.02±9.80),(20.13±2.08) in ACC, respectively, NMS and CRD at 6-week age both can make it increase significantly. The main effect of the number of FLI in PVN and ACC caused by NMS were 10.03 and 18.38, while 22.45 and 14.98 by CRD at 6-week age. There was no interaction between NMS and CRD on affecting the number of FLI in PVN and ACC.Conclusion: The persistent stimulation of MS in neonatal period may cause rat's central nervous system abnormalities and sensitization. Accepting detrimental CRD can significantly cause the high expression of FOS in PVN and ACC, and result in emerging visceral hyperalgesia. PVN and ACC were the important domains which transmit the visceral detrimental stimulation and sense signal in developing rats'central nervous system. The activation and hyperalgesia of PVN and ACC play an important role in developing rats'visceral hyperalgesia induced by NMS. |
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