-Salt loading (SL) and water deprivation (WD) are experimental challenges that are often used to study the osmotic circuitry of the brain. Central to this circuit is the supraoptic nucleus (SON) of the hypothalamus, which is responsible for the biosynthesis of the hormones, arginine vasopressin (AVP) and oxytocin (OXT), and their transport to terminals that reside in the posterior lobe of the pituitary. On osmotic challenge evoked by a change in blood volume or osmolality, the SON undergoes a functionrelated plasticity that creates an environment that allows for an appropriate hormone response. Here, we have described the impact of SL and WD compared with euhydrated (EU) controls in terms of drinking and eating behavior, body weight, and recorded physiological data including circulating hormone data and plasma and urine osmolality. We have also used microarrays to profile the transcriptome of the SON following SL and remined data from the SON that describes the transcriptome response to WD. From a list of 2,783 commonly regulated transcripts, we selected 20 genes for validation by qPCR. All of the 9 genes that have already been described as expressed or regulated in the SON by osmotic stimuli were confirmed in our models. Of the 11 novel genes, 5 were successfully validated while 6 were false discoveries. transcriptome; supraoptic nucleus; water restriction; salt load; neuroendocrine TERRESTRIAL LIFE requires that the osmolality of the extracellular fluid (ECF) is strictly controlled. Increased ECF osmolality results in water leaving the cell, reducing intracellular fluid (ICF) volume, while increasing ICF osmolality, which will compromise the metabolic processes necessary for life. Chronic increases in ECF osmolality can be brought about experimentally by a high intake of salt (salt loading, SL) or by water deprivation (WD) (5). In the absence of drinking fluid (WD), extracellular and intracellular fluid volumes decrease, as water and sodium are inevitably lost in sweat and urine leading to hypovolemia and, as a consequence of dehydration-induced natriuresis, sodium depletion (14,35). This depletion of sodium means that WD animals also display enhanced salt appetite (14). In contrast, SL increases body sodium content, causing an increase in ECF volume, but a decrease in the volume of the ICF (35).Angiotensin II (ANG II), atrial natriuretic peptide (ANP), arginine vasopressin (AVP), and oxytocin (OXT) are the main hormones involved in the control of hydromineral homeostasis in mammals (5). ANP is synthesized and secreted into the bloodstream in response to stretching of the right atrial muscle cells by increased blood volume. Once in the bloodstream, ANP has a potent natriuretic effect, acting on the distal convoluted tubule of the nephron to inhibit sodium reabsorption (13,44). ANP is an important indicator of blood volume. AVP and OXT release are stimulated by hypovolemia, hypertonicity, and hypernatremia, among other stimuli (36). Circulating levels of AVP correlate with plasma osmolality (4) and thirst perce...

TheNa-K-2Clcotransporter2(NKCC2)wasthoughttobekidneyspecific.Hereweshowexpressioninthebrainhypothalamo-neurohypophyseal system (HNS), wherein upregulation follows osmotic stress. The HNS controls osmotic stability through the synthesis and release of the neuropeptide hormone, arginine vasopressin (AVP). AVP travels through the bloodstream to the kidney, where it promotes water conservation. Knockdown of HNS NKCC2 elicited profound effects on fluid balance following ingestion of a high-salt solution-rats produced significantly more urine, concomitant with increases in fluid intake and plasma osmolality. Since NKCC2 is the molecular target of the loop diuretics bumetanide and furosemide, we asked about their effects on HNS function following disturbed water balance. Dehydration-evoked GABAmediated excitation of AVP neurons was reversed by bumetanide, and furosemide blocked AVP release, both in vivo and in hypothalamic explants. Thus, NKCC2-dependent brain mechanisms that regulate osmotic stability are disrupted by loop diuretics in rats.

Real-time quantitative PCR (qPCR) is the most reliable and accurate technique for analyses of gene expression. Endogenous reference genes are being used to normalize qPCR data even though their expression may vary under different conditions and in different tissues. Nonetheless, verification of expression of reference genes in selected studied tissue is essential in order to accurately assess the level of expression of target genes of interest. Therefore, in this study, we attempted to examine six commonly used reference genes in order to identify the gene being expressed most constantly under the influence of testosterone in the kidneys and hypothalamus. The reference genes include glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin beta (ACTB), beta-2 microglobulin (B2m), hypoxanthine phosphoribosyltransferase 1 (HPRT), peptidylprolylisomerase A (Ppia) and hydroxymethylbilane synthase (Hmbs). The cycle threshold (Ct) value for each gene was determined and data obtained were analyzed using the software programs NormFinder, geNorm, BestKeeper, and rank aggregation. Results showed that Hmbs and Ppia genes were the most stably expressed in the hypothalamus. Meanwhile, in kidneys, Hmbs and GAPDH appeared to be the most constant genes. In conclusion, variations in expression levels of reference genes occur in kidneys and hypothalamus under similar conditions; thus, it is important to verify reference gene levels in these tissues prior to commencing any studies.

INTRODUCTION:Gynura procumbens has been shown to decrease blood pressure via inhibition of the angiotensin‐converting enzyme. However, other mechanisms that may contribute to the hypotensive effect have not been studied.OBJECTIVES:To investigate the cardiovascular effects of a butanolic fraction of Gynura procumbens in rats.METHODS:Anaesthetized rats were given intravenous bolus injections of butanolic fraction at doses of 2.5–20 mg/kg in vivo. The effect of butanolic fraction on vascular reactivity was recorded in isolated rat aortic rings in vitro.RESULTS:Intravenous administrations of butanolic fraction elicited significant (p<0.001) and dose‐dependent decreases in the mean arterial pressure. However, a significant (p<0.05) decrease in the heart rate was observed only at the higher doses (10 and 20 mg/kg). In isolated preparations of rat aortic rings, phenylephrine (1×10‐6 M)‐ or potassium chloride (8×10‐2 M)‐precontracted endothelium‐intact and ‐denuded tissue; butanolic fraction (1×10‐6–1×10‐1 g/ml) induced similar concentration‐dependent relaxation of the vessels. In the presence of 2.5×10‐3 and 5.0×10‐3 g/ml butanolic fraction, the contractions induced by phenylephrine (1×10‐9–3×10‐5 M) and potassium chloride (1×10‐2–8×10‐2 M) were significantly antagonized. The calcium‐induced vasocontractions (1×10‐4–1×10‐2 M) were antagonized by butanolic fraction concentration‐dependently in calcium‐free and high potassium (6×10‐2 M) medium, as well as in calcium‐ and potassium‐free medium containing 1×10‐6 M phenylephrine. However, the contractions induced by noradrenaline (1×10‐6 M) and caffeine (4.5×10‐2 M) were not affected by butanolic fraction.CONCLUSION:Butanolic fraction contains putative hypotensive compounds that appear to inhibit calcium influx via receptor‐operated and/or voltage‐dependent calcium channels to cause vasodilation and a consequent fall in blood pressure.

Objectives: To investigate the hypotensive and angiotensin-converting enzyme (ACE) inhibitory activities of a partially purified fraction (FA-I) of the leaves of Gynura procumbens and to qualitatively analyse the putative compounds present in the fraction. Materials and Methods: The hypotensive effect of FA-I was tested in both spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) by an intravenous administration of 0–10 mg/kg of the FA-I. Administration of captopril (20 µg/kg) served as the control. In vitro 0.0–2.0 mg/ml FA-I was added to a mixture of ACE and hippuryl-L-histidyl-L-leucine and assayed by a modification of the colourimetric method of Hurst and Lovell-Smith. All blood pressure measurements were monitored by the Macintosh MacLab set-up. ACE activity was measured by an in vitro assay in which the enzymatic cleavage of hippuryl-L-histidyl-L-leucine to form histidyl-leucine and hippurate was determined colourimetrically by a cyanuric chloride/dioxane reagent. Results: The FA-I produced a marked dose-dependent reduction in mean arterial pressure (MAP) in SHR and WKY rats, with an ED₅₀ of 1.09 and 1.05 mg/kg, respectively (p < 0.01). Furthermore, FA-I at 10 mg/kg strongly inhibited the angiotensin I-induced rise in MAP (p < 0.01). This response was comparable to that of captopril at 20 µg/kg. In the in vitro assay, ACE activity was inhibited with an IC₅₀ of 0.8 mg/ml. The qualitative phytochemical analysis of FA-I indicated the presence of glycoconjugates and peptides. Conclusion: These results suggest that the hypotensive effect of G. procumbens may be due, in part, to the glycoconjugated or peptidal substances found in FA-I that exhibit an inhibitory effect on ACE.