Ultrastructural localization of neuronal nitric oxide synthase in the laterodorsal tegmental nucleus of wild-type and knockout mice

We have previously reported significant increases in neuronal nitric oxide synthase (NOS) immunostaining in renal arterioles of angiotensin type 1A receptor (AT1A) knockout mice, and in arterioles and macula densa cells of AT1A/AT1B knockout mice. The contribution of nitric oxide derived from endothelial and macula densa cells in the maintenance of afferent arteriolar tone and acetylcholine-induced vasodilation was functionally determined in kidneys of wild-type, AT1A, and AT1A/AT1B knockout mice. Acetylcholine-induced changes in arteriolar diameters of in vitro blood-perfused juxtamedullary nephrons were measured during control conditions, in the presence of the nonspecific NOS inhibitor, Nω-nitro-l-arginine methyl ester (NLA), or the highly selective neuronal NOS inhibitor, N5-(1-imino-3-butenyl)-l-ornithine (VNIO). Acetylcholine (0.1 mM) produced a significant vasoconstriction in afferent arterioles of AT1A/AT1B mice (−10.9 ± 5.1%) and no changes in afferent arteriolar diameters of AT1A knockout mice. NLA (0.01–1 mM) or VNIO (0.01–1 μM) induced significant dose-dependent vasoconstrictions (−19.8 ± 4.0% 1 mM NLA; −7.8 ± 3.5% 1 μM VNIO) in afferent arterioles of kidneys of wild-type mice. VNIO had no effect on afferent arteriole diameters of AT1A knockout or AT1A/AT1B knockout mice, suggesting nonfunctional neuronal nitric oxide synthase. These data indicate that acetylcholine produces a significant renal afferent arteriole vasodilation independently of nitric oxide synthases in wild-type mice. AT1A receptors are essential for the manifestation of renal afferent arteriole responses to neuronal nitric oxide synthase-mediated nitric oxide release.

Download Full-text

Effects of Targeted Neuronal Nitric Oxide Synthase Gene Disruption and Nitro sup G -L-Arginine Methylester on the Threshold for Isoflurane Anesthesia

Anesthesiology ◽

10.1097/00000542-199507000-00013 ◽

1995 ◽

Vol 83 (1) ◽

pp. 101-108. ◽

Cited By ~ 61

Author(s):

Fumito Ichinose ◽

Paul L. Huang ◽

Warren M. Zapol

Keyword(s):

Nitric Oxide ◽

Nitric Oxide Synthase ◽

Knockout Mice ◽

Minimum Alveolar Concentration ◽

Neuronal Nitric Oxide Synthase ◽

Separate Experiment ◽

Wild Type ◽

Isoflurane Anesthesia ◽

Congenital Deficiency ◽

Oxide Synthase

Background Considerable evidence suggests that nitric oxide plays a role in synaptic transmission in the central and peripheral nervous system. Nonselective inhibition of nitric oxide synthase by nitroG-L-arginine methylester (L-NAME) reduces the minimum alveolar concentration of halothane anesthesia. The effects of selective neuronal nitric oxide synthase inhibition on the anesthetic requirements in mice congenitally deficient in neuronal nitric oxide synthase (knockout mice) were examined. Methods Isoflurane minimum alveolar concentration and righting reflex ED50 (RRED50) were determined in knockout and wild-type mice. Subsequently, the effects of intraperitoneal L-NAME on minimum alveolar concentration and RRED50 of knockout and wild-type mice were examined. In a separate experiment, the effects of week-long administration of L-NAME were examined in wild-type mice. Isoflurane minimum alveolar concentration and RRED50 were measured on the 8th day and were repeated after an acute intraperitoneal dose of L-NAME. Results Targeted disruption of the neuronal nitric oxide synthase gene did not modify isoflurane minimum alveolar concentration and RRED50 of knockout mice. Acute intraperitoneal L-NAME decreased the minimum alveolar concentration and RRED50 of wild-type but did not alter those values in knockout mice. The wild-type mice, when given L-NAME for a week, showed a minimum alveolar concentration and RRED50 identical to that of untreated wild-type mice. Conclusions Although acute nonselective inhibition of nitric oxide synthase reduces the anesthetic requirements of wild-type mice, a chronic congenital deficiency of neuronal nitric oxide synthase or a week of L-NAME treatment of wild-type mice does not produce a state of greater sensitivity to the effects of isoflurane anesthesia.

Download Full-text

Defective fluid and HCO3 − absorption in proximal tubule of neuronal nitric oxide synthase-knockout mice

AJP Renal Physiology ◽

10.1152/ajprenal.2000.279.3.f518 ◽

2000 ◽

Vol 279 (3) ◽

pp. F518-F524 ◽

Cited By ~ 40

Author(s):

Tong Wang ◽

Fiona M. Inglis ◽

Robert G. Kalb

Keyword(s):

Nitric Oxide ◽

Blood Pressure ◽

Metabolic Acidosis ◽

Nitric Oxide Synthase ◽

Proximal Tubule ◽

Knockout Mice ◽

Neuronal Nitric Oxide Synthase ◽

Fluid Absorption ◽

Wild Type ◽

Oxide Synthase

Using renal clearance techniques and in situ microperfusion of proximal tubules, we examined the effects of N G-monomethyl-l-arginine methyl ester (l-NAME) on fluid and HCO3 −transport in wild-type mice and also investigated proximal tubule transport in neuronal nitric oxide synthase (nNOS)-knockout mice. In wild-type mice, administration of l-NAME (3 mg/kg bolus iv) significantly increased mean blood pressure, urine volume, and urinary Na+ excretion. l-NAME, given by intravenous bolus and added to the luminal perfusion solution, decreased absorption of fluid (60%) and HCO3 − (49%) in the proximal tubule. In nNOS-knockout mice, the urinary excretion of HCO3 − was significantly higher than in the wild-type mice (3.12 ± 0.52 vs. 1.40 ± 0.33 mM) and the rates of HCO3 − and fluid absorption were 62 and 72% lower, respectively. Both arterial blood HCO3 − concentration (20.7 vs. 25.7 mM) and blood pH (7.27 vs. 7.34) were lower, indicating a significant metabolic acidosis in nNOS-knockout mice. Blood pressure was lower in nNOS-knockout mice (76.2 ± 4.6 mmHg) than in wild-type control animals (102.9 ± 8.4 mmHg); however, it increased in response to l-NAME (125.5 ± 5.07 mmHg). Plasma Na+ and K+ were not significantly different from control values. Our data show that a large component of HCO3 − and fluid absorption in the proximal tubule is controlled by nNOS. Mice without this isozyme are defective in absorption of fluid and HCO3 − in the proximal tubule and develop metabolic acidosis, suggesting that nNOS plays an important role in the regulation of acid-base balance.

Download Full-text