Clinical Neuroscience

[FINE STRUCTURE OF THE AREA SUBPOSTREMA IN RAT. OPEN GATE FOR THE MEDULLARY AUTONOMIC CENTERS]

FODOR Mariann, PALKOVITS Miklós, GALLATZ Katalin

MARCH 20, 2007

Clinical Neuroscience - 2007;60(03-04)

[The area subpostrema (ASP) is a V-shaped area, ventral and ventrolateral to the area postrema. It constitutes the upper border zone of the commissural portion of the nucleus of the solitary tract. The ASP is considered as a morphological and functional key area for the medullary autonomic center. The capillaries here, in contrast to the capillaries of the area postrema are not fenestrated but establish a specific staining for acetylcholinaestherase (AChE). The ASP contains a high density of fibers and terminals of several neuropeptides which are known to affect on NTS activity. Receptors of different neuropeptids and cathecholamines and a dense network of GFAP positive glial processes are found also here. The neurons and the glial cells of the ASP are connected with the AP and a bidirectional connection exists between the ASP and NTS.]

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[Even tough the central nervous system (CNS) of gastropods has long been used as a model for studying different neuronal networks underlying behaviors, there is only little information on the molecular components of the extracellular matrix (ECM) of the nervous tissue. Therefore, the aim of the present study was to identify some of the ECM molecules by acid-base histochemistry. Staining with alcian blue at strong acidic pH, and with acridine orange at different pH and salt concentrations was carried out on cryostat sections taken from CNS preparations of adult specimens of the terrestrial snail, Helix pomatia, and the aquatic species, Lymnaea stagnalis, in order to visualize mild (carboxyl) and strong (sulphate) acidic groups, which are characteristic for different glucosaminoglycans. According to our findings, sulphated proteoglycans were abundant in the periganglionic sheath of both species, and they also occurred in the neuropil of Helix, whereas they were absent in Lymnaea. The interperikaryonal space contained mainly carboxyl residues, which might refer to the presence of hyaluronic acid. It is concluded that the ECM of the snail CNS, similarly to that in vertebrates, is partly composed of polymer macromolecules of different chemical properties. It is suggested that adaptation to environmental conditions and/or altered neuronal plasticity are responsible for the differences found in chemical characters of the ECM molecules between the two snail species.]

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[SALSOLINOL AND THE PERIPHERAL SYMPATHETIC ACTIVITY: THE EFFECTS OF HYPOPHYSECTOMY, ADRENALECTOMY AND ADRENAL MEDULLECTOMY]

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[The endogenous isoquinoline salsolinol (SALS) is a recently identified prolactin (PRL) releasing factor, a selective and potent stimulator of PRL secretion both in vivo and in vitro. SALS decreased the peripheral tissue dopamine (DA) level dose dependently, consequently increased the NE/DA ratio, indicating reduced release of newly formed norepinephrine (NE) from sympathetic terminals. The aim of our study was to investigate the effect of adrenal medullectomy (MEDX), adrenalectomy (ADX) and hypophysectomy (HYPOX) on the action of SALS on the PRL secretion, and on the catecholamine concentration of the selected sympathetically innervated peripheral tissues (atrium, spleen, etc). The experiments were done in male rats of 200-300 g body weight kept in air conditioned room with regular lighting. We used high-pressure liquid chromatography with electrochemical detection (HPLC-EC) for measurement of NE and DA concentrations, and radioimmunoassay for prolactin measurement. In MEDX as well as in ADX rats, SALS (25 mg/kg i.p.) was able to reduce DA level and increase the NE/DA ratio. The changes of prolactin secretion (increase by SALS) were not affected either by ADX or MEDX. Therefore the presence of the adrenal gland is not required for the changes of prolactin secretion, nor for the reduction of peripheral sympathetic activity induced by SALS. Investigating the possible effect of pituitary hormones on the peripheral sympathetic system, the action of SALS has been tested in HYPOX rats. We have found that the effect of SALS on peripheral sympathetic terminals is not affected by HYPOX, consequently the role of pituitary hormones in the effect of SALS on the peripheral catecholamine metabolism may be excluded.]

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[To test the effect of dehydration on brain atrial natriuretic peptide (ANP) concentrations in areas important to salt appetite, water balance and cardiovascular regulation, we subjected rats to dehydration and rehydration and measured ANP concentration in 18 brain areas, as well as all relevant peripheral parameters. Water deprivation decreased body weight, blood pressure, urine volume, and plasma ANP, while it increased urine and plasma osmolality, angiotensin II, and vasopressin. ANP greatly increased in 17 and 18 brain areas (all cut cerebral cortex) by 24 h. Rehydration for 12 h corrected all changes evoked by dehydration, including elevated ANP levels in brain. We conclude that chronic dehydration results in increased ANP in brain areas important to salt appetite and water balance. These results support a role for ANP as a neuroregulatory substance that participates in salt and water balance.]

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