Development Of Hippocampus And The Effects Of Food Water Deprivation On The Expression Of HIF-1α In Hippocampus Of Meriones Meridianus

Meriones meridianus is one of the rodents that live in the desert and semi-desertregion. It has many features of adapting dry environment. The hippocampus is one ofthe central nervous system tissues that occur earlier, is also an important part of thelimbic system. It has functions of learning and memory, regulation of visceral activityand so on. The hippocampus is sensitive to a variety of stress and is a good material inthe research for the development and stress responses of animal central nervoussystem. The research on the hippocampal development of Meriones meridianus has acertain significance to investigate the nervous system development.Hypoxia-inducible factor-1α (HIF-1α) is a transcriptional regulatory factor thatinvolved in the regulation on varied physiological response, especially on theparticipation in environmental oxygen homeostasis. Researches on HIF-1α are moreconcentrated in the areas such as tissues hypoxia, cerebral ischemia and cancer. It hasnot been reported if HIF-1α was involved in physiological regulation during waterrestriction in food and HIF-1α expression during the development of hippocampus atMeriones meridianus. It is valuable to the study on the development of nervoussystem and the mechanism for the physiological regulation associated with tolerabilityof dry environment at Meriones meridianus in this experiment.Wild healthy meriones meridianus was captured in Minqin, Gansu Province.Experiment included two parts, one is related to the development of hippocampus infilial merione meridianus that born7-32days and second is to the changes of HIF-1αexpression in hippocampus effected by food water deprivation. The filial Merionemeridianus was select born7,14,21,32days and n=6each group. The hippocampusboth sides of the brain were separated, after that, the cytological changes anddevelopmental characteristics of hippocampus region at different stages wereobserved at filial Merione meridianus. The changes on the expression of HIF-1α, Baxand Bcl-2were determined by immunohistochemistry. The other part is food waterdeprivation experiment. Merione meridianus were randomly divided into0,3,6,9day group of food water deprivation. n=6each group. The expression changes of HIF-1α, Bax and Bcl-2were detected in hippocampus by immunohistochemistry. Theexpression changes of HIF-1αand AQP4mRNA were determined in hippocampus byPCR.Results1.With increased age of filial merione meridianus, the cells diameter ofHippocampus regions significantly increased. CA7-14d pyramidal cell diameterincreased significantly the most significant (P <0.01). DG14-21d granulosa celldiameter increased significantly the most significant (P <0.01). Increases with ageregional of hippocampal, increasing the volume of each layer, in which the7-14dmost obvious changes (P <0.01), DG change bigger than CA. The amplitude ofvolume change at the molecular layer and polymorphic layer is larger than thepyramidal layers and granular layers. The amplitude of volume change at themolecular layer is the largest in the three-layer structure.2. HIF-1α in developing hippocampus of meriones meridianus were expressedat nucleus and cytoplasm in each layers. With increased age of filial merionemeridianus, the expression of HIF-1α、Bax in each layers of hippocampus reduced,the expression of Bcl-2increased. The change amplitude in7-14days after birth atCA is the largest. The change amplitude in14-21days after birth at DG is the largest.With increased age of filial merione meridianus, the ratio of Bcl-2/Bax reduced,7-14days after birth Bcl-2/Bax ratio decreased most significantly,21-32days after birthBcl-2/Bax stabilized.3The expressions of HIF-1α and Bax were increased (P <0.05) and Bcl-2wasdecreased (P <0.05) in the hippocampus after food water deprivation. The ratio ofpositive cell of HIF-1α was raised from0d less than10%to more than80%at3d.HIF-1α at CA3in the group with3d of food water deprivation showed a significantresponse, while HIF-1α at the CA1responded later than that of CA3region duringfood water deprivation. A positive correlation was found between HIF-1α and Baxexpressed in hippocampus, while an inverse relationship between HIF-1α and Bcl-2.4With Prolonged of food water deprivation, the expression of HIF-1α, AQP4mRNA in hippocampal increased. The change amplitude of HIF-1αat0-3days after food water deprivation is the largest, but in AQP4the biggest increase at3-6days.The expression levels of HIF-1α and AQP4mRNA at6-9days after food waterdeprivation have come down, but9days is still higher than3days.Conclusion1. It is an important period of the hippocampus development born7-21d. Theneuronal cell body and neurite grow rapidly in the hippocampus tissues at that stage.The neurite growth is continuing born21-32d and DG region developed is later thanthe CA part. The expression of HIF-1α, Bax, Bcl-2in hippocampus were moresignificant and apoptotic response is relatively prosperous at that stage. It suggestedthat they might be involved in the regulation of hippocampus development.2. HIF-1α protein and mRNA levels was increased during food water deprivationin hippocampus and AQP4mRNA levels was elevated as well. A positive correlationwas found between HIF-1α and Bax expressed in hippocampus, while an inverserelationship between HIF-1α and Bcl-2. HIF-1α might be partly involved in theregulation of Bax and Bcl-2expression in hippocampus during food waterdeprivation.