415 - Long-term Behavioral and Proliferating Neuron of Repetitive Pain in Neonatal Rat Pups

Poster Number: 415
Publication Number: 415.237

Dong Li, Dalian woman and children's medical group, Dalian, Liaoning, China (People's Republic); 婧 许, Dalian Medical University, Dalian, Liaoning, China (People's Republic)

Background: The short-term consequence of pain in neonate intensive care unit has been convinced, and more neonatologist pay more attention to decrease pain procedure in NICU, while the long-term influence for pain stimulus still need explore.

Objective: To explore the effect of repetitive pain in neonatal rats pups on cognitive and memory abilities in adulthood and the expression of hippocampal neurons.

Design/Methods: Neonatal rats pups were randomly divided into two groups(n=24) at postnatal 1 day (P1), the experimental group and the control group. Neonatal rats pups in the experimental group was pricked for 7 consecutive days; pups in the sham group was stroked at the same time. All the rats were weighed weekly. Morris water maze test were carried out from P44 to P49 to detect their cognitive and memory abilities. Rats were killed and the hippocampal tissues were taken in P50. HE stain and electron microscope were used to observed hippocampal neurons. Ki-67 was used to label new neuron and the proliferation was observed by immunohistochemistry.

Results: With the increase of age, the body weight of rats in the experimental group increased slower than that of the control group, and there was a significant difference (P < 0.05) between the two groups at P43 and P49 (P43:F=11.750; P49:F=12.302). The escape latency of the experimental group was significantly higher than that of the control group in the water maze test at P45 and P48 (P45:F=3.830,P < 0.05; P48: F=4.424,P < 0.05), and the number of crossing the platform was lower than that of the control group (t=-2.785,P < 0.05). The HE stain of hippocampal tissue showed that the neurons in the experimental group were disorganized, with irregular morphology, uneven colored, pyknosis and edema. The ultrastructural changes, including heterochromatin aggregation, reduction of mitochondrial volume, decreasing of intercristal space, illegibility of the endoplasmic reticulum and occurring apoptotic body, were observed in hippocampal CA1 pyramidal neurons in the experimental group. In immunohistochemistry experiment, the average optical density values of Ki-67 positive cells in hippocampal subgranular zone in the experimental group were lower than those in the control group(t=4.266,P < 0.05),and the difference was statistically significant.Conclusion(s): Repetitive pain in neonatal rats pups can cause cognitive impairment and memory loss later in life, disruption of hippocampal tissue structure, and diminished neuronal regeneration.