Expression of certain proteins in the subfornical organ and cerebrospinal fluid of spontaneously hypertensive rats.

The objective of this study was to analyze the proteins in the cerebrospinal fluid of spontaneously hypertensive rats and to study their possible role in the relationship between hydrocephalus, arterial hypertension and variations in the subfornical organ. Brains and cerebrospinal fluid from control Wistar-Kyoto rats and spontaneously hypertensive rats sacrificed with chloral hydrate were used. Cerebrospinal fluid and extract of subfornical organ were processed by protein electrophoresis. Antisera against protein bands of 141, 117 and 48 kDa and Concanavalin A were used for immunohistochemical and western blot study of the subfornical organ, adjacent circumventricular structures and cerebrospinal fluid. Ventricular dilation in the spontaneously hypertensive rats and the presence of quite a lot of protein bands in the cerebrospinal fluid of the hypertensive rats, which were either not observed or scarcely present in the cerebrospinal fluid of the Wistar-Kyoto rats, were confirmed. The subfornical organ, third ventricle ependyma and choroideus plexus showed immunoreactive material for antibodies against 141kDa, 117 and 48 kDa proteins band (anti-B1, anti-B2 and anti-B3). The larger amount of the immunoreactive material was found in the subfornical organ of the spontaneously hypertensive rat. Our results and the alterations observed by other authors in the subfornical organ in hydrocephalic and hypertensive rats support the possibility that this circumventricular organ, some proteins of the cerebrospinal fluid and ventricular dilation could be connected with the physiopathology of this type of hypertension.

Postnatal development of the secretory activity of the goat subcommissural organ. A Reissner's fibre and angiotensin II immunohistochemical study.

Subcommissural organ (SCO) secretory activity of the goat (variations of Capra hircus, that live in arid conditions) was examined during the postnatal development, using specific antibodies against the Reissner's fibre (AFRU) and angiotensin II (AAGII). The SCO was strongly stained with the anti-glycoproteins that form the Reissner's fibre and lightly marked with the anti-angiotensin II. The AFRU-immunoreactivity (ir) was found in the ependymal and hypendymal cells and in the ventricular and peripheral secretory routes of the goat SCO. The amount AFRU increases at 6 months and decreases at adult age. In contrast, the anti-angiotensin II-ir was mainly found in the adult age, not being practically observed at one postnatal month. The AAGII-ir was mainly found in ependymal cells in which AFRU-ir was downregulated. In addition, we detected the presence of double immunostained for AFRU and AAGII in ependymocytes of the pre-commissural and subcommissural parts. In conclusion the present results may suggest a functional interrelation between AAGII and the secretory activity of the SCO of this kind of goat.

Effect of the arterial hypertension and captopril treatment on the angiotensin II content in the subfornical organ. A study in SHR rats.

We studied the effects of spontaneous high blood pressure and the captopril treatment on the subfornical organ (SFO) of rats. The brains of control Wistar-Kyoto rats (WKY), WKY rats treated with captopril (WKY-T), spontaneously hypertensive rats (SHR) and SHR rats treated with captopril (SHR-T) were processed immunohistochemically using anti-angiotensin II as primary antibody. Immunorective material (IRM) for angiotensin II was observed in a group of neurons and some cells of the ependymal layer of the SFO in WKY rats. The angiotensin II immunoreactive (AGII-ir) in the SHR rats was decreased, showing positive reaction only in a few neurons, while captopril treatment induced an increase in immunoreactive material in hypertensive rats, but contrarily, the expression of AGII-ir in the WKY-T group was scarce. The variations of the angiotensin II observed in the SFO could be owing to an interaction between the hypertension and its captopril treatment.

Reelin receptors in developing laminated brain structures of mouse and human.

Reelin is an extracellular matrix protein secreted by a variety of cell types throughout the developing brain. The target cells for reelin express the cytoplasmic adapter protein Dab1, which binds to the reelin receptors VLDLR and ApoER2. In the present work, we have studied the localization of both receptors in developing mouse and human cortex, olfactory bulb and cerebellum. In mouse, some Cajal-Retzius cells express reelin and VLDLR; in humans, all the components of the signalling pathway (Reelin, Dab1, VLDLR and ApoER2) are present in subsets of Cajal-Retzius cells. In the mouse cortical plate, VLDLR and ApoER2 are present from E15 to postnatal stages; in human cortical plate they are most prominent at approximately 20 gestational weeks. In mice, cerebellar Purkinje cells only express VLDLR whereas in humans they express both VLDLR and ApoER2. Mitral cells of the mouse olfactory bulb are ApoER2-positive and VLDLR-negative. In sum, the receptor expression patterns are similar in the human and mouse cortical plate but differ in Cajal-Retzius and Purkinje cells, which in humans express additional components of the reelin-Dab1 pathway.

Reelin-immunoreactive neurons in the adult vertebrate pallium.

Reelin, an extracellular matrix protein, plays a crucial role in cortical development. By using Reelin-immunohistochemistry in different vertebrates (fish, amphibians, reptiles, and mammals : insectivores, odontocetes, rodents, carnivores and man) we show here that Reelin is also expressed by a variety of neurons in the adult pallium. In the everted telencephalon of the zebrafish, Reelin-positive neurons are widely distributed over the dorsal pallium. In land vertebrates, the most consistent and evolutionary conserved location of Reelin-expressing neurons is in the cell-sparse molecular layer associated with laminated cortical organization. We describe an additional heterogeneous population of Reelin-positive neurons outside the molecular layer, the location and distribution of which are more variable, and which may reflect major evolutionary changes in cortical architecture. In squamate reptiles, the Reelin-negative main cell layer is flanked by a superficial and a deep plexiform layer which both contain Reelin-expressing neurons. In mammals, Reelin-positive interneurons are dispersed throughout layers II--VI; the human neocortex is particularly poor in Reelin-positive interneurons. Reelin is also expressed by large stellate and modified pyramidal neurons in layer II of the mammalian entorhinal cortex, and in the superficial lateral cortex of lizards. Examination of this cell population (layer II Pre-alpha) in human brains of different age groups points to a decrease in Reelin-expression in the course of adult life.