Effect of 5-HT1A receptors in the hippocampal DG on active avoidance learning in rats / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To investigate the effects of serotonin (5-HTIA) receptors in the hippocampal dentate gyrus (DG) on active avoidance learning in rats.</p><p><b>METHODS</b>Totally 36 SD rats were randomly divided into control group, antagonist group and agonist group(n = 12). Active avoidance learning ability of rats was assessed by the shuttle box. The extracellular concentrations of 5-HT in the DG during active avoidance conditioned reflex were measured by microdialysis and high performance liquid chromatography (HPLC) techniques. Then the antagonist (WAY-100635) or agonist (8-OH-DPAT) of the 5-HT1A receptors were microinjected into the DG region, and the active avoidance learning was measured.</p><p><b>RESULTS</b>(1) During the active avoidance learning, the concentration of 5-HT in the hippocampal DG was significantly increased in the extinction but not establishment in the conditioned reflex, which reached 164.90% ± 26.07% (P <0.05) of basal level. (2) The microinjection of WAY-100635 (an antagonist of 5-HT1A receptor) into the DG did not significantly affect the active avoidance learning. (3) The microinjection of 8-OH-DPAT(an agonist of 5-HT1A receptor) into the DG significantly facilitated the establishment process and inhibited the extinction process during active avoidance conditioned reflex.</p><p><b>CONCLUSION</b>The data suggest that activation of 5-HT1A receptors in hipocampal DG may facilitate active avoidance learning and memory in rats.</p>

Altered Regulation of Aquaporin-2 Water Channels in the Kidney Following Acute Blood Volume Depletion in Rats / 대한신장학회잡지

BACKGROUND: The present study was aimed to examine the regulation of aquaporin (AQP)-2 water channels in the kidney following blood volume depletion. METHODS: Male Sprague-Dawley rats were acutely blood volume-depleted by withdrawal of arterial blood up to 2% of body weight. The expression of AQP2 mRNA and protein was determined by reverse transcription - polymerase chain reaction and Western blot analysis, respectively, in the inner medulla of the kidney 1 and 3 hours after the hemorrhage. RESULTS: The mRNA expression of AQP2 was significantly increased 1 hour after the bleeding. However, neither the shuttling nor the total abundance of AQP2 proteins was significantly altered. On the contrary, 3 hours after the bleeding, the expression of AQP2 proteins as well as that of AQP2 mRNA was significantly increased. The shuttling of AQP2 proteins was also increased. CONCLUSION: These results suggest that an increased expression of AQP2 channels in the kidney may confer one of compensatory mechanisms restoring the circulating volume in an acute hypovolemic state.

Decreased Expression of Aquaporin-2 Water Channels in the Kidney in Rats Treated with Chlorpropamide / 대한신장학회잡지

BACKGROUND: Whether blood glucose levels may change the regulation of aquaporin(AQP) water channels in the kidney was investigated. METHODS: Male Sprague-Dawley rats were treated with chlorpropamide(40 mg/100 g body weight per day, per oral, for 7 days), and their expression of AQP1-3 and type VI adenylyl cyclase proteins was determined in the kidney. RESULTS: Following the treatment with chlorpropamide, the blood glucose level was significantly decreased compared with that in the control(64+/-8 vs 106+/-7 mg/dL, n=6 each, p < 0.01). Accordingly, the expression of AQP2 proteins was decreased in the cortex, outer medulla, and inner medulla. The AQP2 targeting was not significantly altered, as evidenced by parallel decreases of its expression in the membrane and the cytoplasmic fractions. No significant changes were observed in the expression of either AQP1 or of AQP3. The protein expression of type VI adenylyl cyclase was not significantly altered. CONCLUSION: These results suggest that hypoglycemia attenuates the expression of AQP2 water channels in the kidney.

Differential Regulation of Atrial Natriuretic Peptide in Clipped and Contralateral Kidneys in Two-Kidney, One Clip Hypertension / 대한신장학회잡지

BACKGROUND: The present study was aimed to determine the pathophysiological implications of local atrial natriuretic peptide (ANP) system in the kidney in two- kidney, one clip (2K1C) hypertension. METHODS: Rats were made 2K1C hypertensive, and their mRNA expressions of ANP and natriuretic peptide receptors (NPR) were determined in the clipped and contralateral kidneys by reverse transcription-polymerase chain reaction. RESULTS: The expression of ANP was decreased in the clipped kidney and increased in the contralateral kidney. Similarly, the expression of both NPR-A and NPR-C was decreased in the clipped kidney and increased in the contralateral kidney. CONCLUSION: These findings indicate a differentially-altered ANP system in the clipped and the contralateral kidneys in 2K1C hypertension.

Influence of Nitric Oxide Synthesis Inhibition on Endothelin-1 and Its Receptor Expression in Rat Kidney / 대한신장학회잡지

BACKGROUND: The present study was aimed to evaluate the influence of nitric oxide(NO) synthesis inhibition on endothelin(ET) expression in rat kidney. METHODS: Male Sprague-Dawley rats were treated with N(G)-nitro-L-arginine methyl ester(L-NAME, 100 mg/L drinking water) for 4 weeks to inhibit the endogenous synthesis of NO. The tissue expression of ET-1, ET(A) receptor, and ET(B) receptor mRNA in the kidney was determined by reverse transcription-polymerase chain reaction. RESULTS: Tissue levels of NO metabolites were significantly decreased in the plasma and the kidney, along with the increased blood pressure. The expression of ET-1 mRNA was increased in the cortex, but not in the medulla. The expression of ET(A) and ET(B) receptor mRNA was not significantly altered either in the cortex or in the medulla. The plasma level of ET-1 peptide was significantly increased, along with the increased blood pressure, when L-NAME(200 microgram/kg per min, iv) was administered in an acute preparation of animals. Accordingly, the expression of ET-1 mRNA was increased in the cortex, whereas that of ET(A) and ET(B) receptor mRNA was not altered. CONCLUSION: These results suggest that enhanced activity of ET system induced by NO synthesis inhibition may be associated with hypertension although direct association between two factors is not confirmed.