1.Localization Of AQP4 In The Brain 2.Changes Of AQP4 Expression In Ischemic Brain Edema

Aims: The study was to define the localization of AQP4 in the brain, especially, in the periventricular organs, such as ependyma,choroid,area postrema(AP) and neurohypophysis ,and telencephalon as well as two kinds of endocrine gland: pineal gland and adenohypophysis, so as to provid morphological bases for water transport and balance, the secretion and regulation mechanisms of endocrine gland in the brain.Methods: Heathy wistar rats (n=10) were used in the study. The rats were deeply anesthetized with iso-pentobarbital, and perfused through the ascending aorta. The telencephalon,area postrema,hypophysis and pineal gland were removed ,fixed,dehydrated and then cut into sections(15μm) on a cryostat microtome. The sections were incubated with AQP4 antibody and reacted with LAB-SA- BCIP/NBT or staining with HE. The slices were examined with a light microscope after they were protected with a coverlip.Results: AQP4 was most abundantly expressed in the tissues directly contacting with CSF, including the cerebral pia mater,ependyma,the central duct of spinal cord and choroid plexes.Heavy express of AQP4 was also found in the perivascular glial processes of the brain tissue and AP. In addition, AQP4 was also distributed in the pyramidal cell layer of hippocampus,granular cell layer and polymorphic cell layer of dentate gyrus ,adenohypophysis and pineal gland cells. The basophilic cells,acidophilic cells and chromophilic cells were observed in the adenohypophysis with HE staining. Some AQP4-positive cell were also present in the whole brain tissue with an ellipse ,small, rounded cell body and light-coloured plasma.Conclusions: The study demonstrates that AQP4 is distributed in the cortical pia mater ,the perivascular glial processes of the brain tissue, ependyma lining of ventricules and the aqueductal system as well as the periventricular organs. The localization of AQP4 indicates that AQP4 may regulate the recycle of CSF.The distribution of AQP4 in the brain tissue,the pyramidal cell layer of hippocampus,granular cell layer and polymorphic cell layer of dentate gyrus reveals that AQP4 is involved in the regulation of water and electrolyte balance between extra- and intra-neurocyte. The analysis combing ICC with HE implys AQP4-positive cells in the adenohypophysis might be basophilic cells,acidophilic cells,chromophilic cells or intential cell(stellate cells).The presence of AQP4 in the intential and gland cell of hypophysis and pineal body suggests that AQP4 might be associated with the regulation of secretion of the endocrine gland. It is the first to find the expression and distribution of AQP4 in the perivascular organs and endocrine gland in the brain.