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Objective To explore the impact of early repetitive painful procedures on subsequent pain behaviors and physiological indicators in full-term infants.Methods Sixty-two full-term neonates were enrolled (male 36 cases,female 26 cases) from the medical center of neonatal care at Nanjing Children's Hospital Affiliated to Nanjing Medical University from March to May in 2009.The data of all painful procedures were performed on those neonates and their responses to them were collected by using digital video recording were collected.The Neonatal Facial Coding System C(NFCS) and Neonatal Infant Pain Scale(NIPS) were used prospectively to evaluate the pain response to painful procedures.Results The average experience of pain caused by operation on newborn at the hospital was 56.5 times (12-249 times),and the daily average was 5.9 times (4-26 times).After they were exposed to more than 10 repetitive pain procedures,the full-term neonates showed the declining pain response assessed by NFCS and NIPS during the subsequent painful procedures (NFCS:P10=0.012,P20=0.015,P30=0.041;NIPS:P10=0.006,P20=0.015,P30=0.049),and the temporarily enhanced pain response was observed in the preparation phase of the subsequent painful procedures (NFCS:P2＜0.001,P3＜0.001,P4=0.004,P5=0.009;NIPS:P2＜0.001,P3＜0.001,P4=0.045,P5 =0.031).Bnt there was no difference in preparation phase.There was no alternation in latency and crying time after repetitiing painful procedures,but the proportion of crying neonates in the preparation phase of the painful procedures was increased(P=0.032).Conclusions After exposed to repetitive pain,full-term neonates expressed hypoalgesia during subsequent painful procedures,but the temporary irritation was enhanced during the following phases exposed to stress.
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Objective To evaluate the effects of repetitive noxious stimuli during the neonatal period on the pain sensitivity during adulthood in rats.Methods Twenty pathogen-free male neonatal SpragueDawley rats,weighing 6.2-6.8 g,were randomly divided into 2 groups (n=10 each) using a random number table:control group (group C) and repetitive noxious stimuli group (group RNS).In RNS group,neonatal rats sequentially received needle pricks into the dorsal surface of 4 paws at 6 h intervals with a 28 G needle per day during the first postnatal week.In group C,the animals received non-painful tactile stimuli with cotton tip rub.At the age of 10 weeks,complete Freund' s adjuvant was injected into the plantar surface of the right hind paw to induce inflammatory pain.Before injection,and at 24 h and 7 days after injection (T0-2),the mechanical and thermal thresholds were measured,and alcohol preference test was performed for assessment of the behavior at T2.Results The mechanical threshold of the right paws was significantly lower at T1.2 than that of the left paws in the two groups.Compared to group C,the mechanical threshold of the left and right paws at T0-2 and thermal threshold of the right paws at T1 were significantly decreased,and alcohol intake was increased in group RNS.Conclusion Repetitive noxious stimuli during the neonatal period can lead to increase in the pain sensitivity during adulthood in rats.
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Objective To study the effects of postnatal overfeeding and high-fat diet on blood pressure of rats,and to explore the pathophysiological mechanism underlying hypertension induced by continuous early postnatal overfeeding.Methods Male Sprague-Dawley rats were randomly divided into normal feeding group (10/litter) and overfeeding group (3/litter) on postnatal day 3 with a random number table.After weaning at postnatal week 3,the rats were randomly given standard chow or high-fat (HF) diet until week 16.Hence four groups were analyzed,namely normal feeding group,breastfed overfeeding group,post-weaning overfeeding group,and continuous overfeeding group.Body weight was continuously monitored in each week.Visceral fat pad (retroperitoneal and perigenital),systolic pressure,and heart rate were observed at week 3 and week 16.Thoracic aorta was sampled for measurement of vascular endothelial dilation function.Histological morphology was observed with HE staining,nitric oxide content of thoracic aorta was detected with nitrate reductase method.The mRNA expression of endothelial nitric oxide synthase (eNOS) in thoracic aorta was determined by real-time polymerase chain reaction.The protein expressions of eNOS and phosphorylated eNOS were determined by Western blot.Results At week 3,breastfed overfeeding rats displayed significantly larger body weight [(77.80 ± 0.57) g vs.(62.80 ±0.85) g,t =14.576,P ＜ 0.01] and visceral fat [retroperitoneal:(8.19 ± 0.49) mg/g vs.(4.92 ± 0.31) mg/g,t =5.629,P＜0.01;perigenital:(3.50 ±0.29) mg/g vs.(2.08 ±0.13) mg/g,t =4.552,P ＜0.01] compared with normal feedindg rats,and the protein expression of phosphorylated eNOS in aortic tissues was significantly reduced to week 16 (F =15.215,P ＜0.01);high-fat diet feeding after weaning further increased the body weight and fat mass in breastfed overfeeding rats.At week 16,continuous overfeeding rats showed hypertension [(149 ± 1.94) mmHg (1 mmHg =0.133 kPa),F =22.834,P ＜0.01],impaired vascular endothelial dilation function (F =7.648,P ＜ 0.05),and reduced protein expression of phosphorylated eNOS (F =15.215,P ＜ 0.01),while the post-weaning overfeeding group only had elevated blood pressure.Conclusions Overfeeding in breastfeeding period and high-fat diet after weaning leads to hypertension.The continuous decrease in phosphorylated eNOS in vascular tissues may be an important molecular process participating in the occurrence of vascular endothelial dysfunction in adults induced by postnatal overfeeding.