Pharmacological characterization of the calcium influx pathways involved in nitric oxide production by endothelial cells.

Objective: To characterize the calcium influx pathways implicated in the sustained elevation of endothelial intracellular calcium concentration, required for the synthesis and release of relaxing factors.

Methods: We evaluated the effect of the newly synthesized pyrazole derivatives, described as selective inhibitors for ORAI (BTP2/Pyr2 and Pyr6) and TRPC3 (Pyr3 and Pyr10) channels, upon endothelium- and extracellular calcium-dependent relaxations stimulated by acetylcholine and thapsigargin, in pre-constricted rat thoracic aortic rings.

Results: Acetylcholine and thapsigargin responses were completely reverted by Pyr2 and Pyr6 (1 to 3μM).

Long-lasting endothelium-dependent relaxation of isolated arteries caused by an extract from the bark of Combretum leprosum.

Objective: To describe and to characterize the relaxing effect of an extract of the bark of Combretum leprosum on isolated arterial rings from different animals.

Methods: Rings (3 to 4mm) from rabbit, rat, or porcine arteries rings were suspended in an organ bath (Krebs, 37°C, 95%O2/5%CO2) to record isometric contractions. After the stabilization period (2 to 3 hours) contractions were induced by the addition of phenylephrine (0.

Nitric oxide metabolites in the lumbosacral spinal cord interstice and cerebrospinal fluid in female rats with acute cyclophosphamide-induced cystitis. An in vivo microdialysis study.

Objective: To determine the concentration of nitrate/nitrite in the cerebrospinal fluid and in the dorsal horn interstice of the L6-S1 spinal cord boundary in rats with or without cystitis induced by cyclophosphamide.

Methods: All experiments were conducted using Wistar female rats. A microdialysis probe was implanted in the subarachnoid space or in the spinal cord tissue at the L6-S1 segments (confirmed histologically).

Activation of neural cholecystokinin-1 receptors induces relaxation of the isolated rat duodenum which is reduced by nitric oxide synthase inhibitors.

Cholecystokinin (CCK) influences gastrointestinal motility, by acting on central and peripheral receptors. The aim of the present study was to determine whether CCK has any effect on isolated duodenum longitudinal muscle activity and to characterize the mechanisms involved. Isolated segments of the rat proximal duodenum were mounted for the recording of isometric contractions of longitudinal muscle in the presence of atropine and guanethidine.

Enhanced TGFalpha-EGFR expression and P53 gene alterations contributes to gastric tumors aggressiveness.

We determined whether alterations in the expression of p53, p16(INK4) and p21(WAF1/CIP1) influence the invasiveness of a subset of gastric adenocarcinomas co-expressing TGFalpha and EGFR. Immunopositivity for TGFalpha-EGFR (26%) was observed in both early and advanced adenocarcinomas, and 88% of these showed immunoreactivity for p53. SSCP analysis revealed that in 81% of these tumors the p53 gene was mutated in exons 5-8.

Role of spinal nitric oxide synthase-dependent processes in the initiation of the micturition hyperreflexia associated with cyclophosphamide-induced cystitis.

The aim of this study was to examine the participation of nitrergic neurotransmission in the initiation of micturition hyperreflexia associated to cyclophosphamide (CP)-induced cystitis in rats. Micturition threshold volume was significantly reduced 4 h after CP administration (100 mg/kg, i.p.

SR141716A-sensitive enhancement of ET-1 hypotensive effect by chronic NOS inhibition.

The present study evaluated the potential mechanism involved in the hypotensive effect induced by ET-1 in rats treated with the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) in the drinking water during 7 days. Hypertension developed in the L-NAME-treated rats (164+/-3 versus 112+/-1 mm Hg in untreated control rats), and the hypotensive effect of ET-1 (100 pmol/kg IV) was significantly enhanced compared with control rats (32+/-2% versus 20+/-1% fall in mean arterial pressure). The enhanced ET-1 hypotensive effect in L-NAME-treated rats was abolished by the ETB receptor antagonist BQ-788 but was unaltered by the cyclooxygenase inhibitor diclofenac, the cytochrome P450 inhibitor fluconazole, or the potassium channel blockers apamin, glibenclamide, tetraethylammonium, and 4-aminopyridine.

Pregnancy-associated increase in rat systemic arteries endothelial nitric oxide production diminishes vasoconstrictor but does not enhance vasodilator responses.

Late pregnancy in rats is characterized by a decrease in arterial pressure and in isolated arterial vessels response to vasoconstrictors. In uterine arteries the pregnancy-associated attenuation of the response to vasoconstrictors has been attributed to an increase in basal and agonist-induced endothelial NO production. However, the role of NO in pregnancy-associated changes of systemic arteries reactivity to vasoactive agents remains to be fully elucidated.

Pharmacological profile of nitrergic nerve-, nitric oxide-, nitrosoglutathione- and hydroxylamine-induced relaxations of the rat duodenum.

Activation of inhibitory nonadrenergic noncholinergic (NANC) nerves in the rat duodenum cause relaxations, which are reduced by nitric oxide synthase (NOS) inhibitors indicating that this response involves a nitrergic neurotransmission. The precise nature of the nitrergic neurotransmitter is still controversial since nitric oxide (NO) scavengers and superoxide generators, even in the presence of superoxide dismutase inhibitors, failed to inhibit nitrergic neurotransmission mediated relaxations. In order to understand the role of NOS in nitrergic neurotransmission and considering that N-OH-arginine (OH-L-Arg), L-citrulline, NO, S-nitrosoglutathione (GSNO) and hydroxylamine (NH2OH) can be formed in cells during the N(G)-oxidation of L-arginine catalyzed by NOS we explored whether any of these products could exhibit biological properties comparable to those of the nitrergic neurotransmitter.

Cardiac sympathetic overactivity and decreased baroreflex sensitivity in L-NAME hypertensive rats.

The present study evaluated the possible changes in the autonomic control of heart rate in the hypertensive model induced by the inhibition of nitric oxide synthase. Rats were treated with N(G)-nitro-L-arginine methyl ester (L-NAME group) in the drinking water during 7 days, whereas control groups were treated with tap water (control group) or with the N(G)-nitro-D-arginine methyl ester (D-NAME group), an inactive isomer of the L-NAME molecule. The L-NAME group developed hypertension and tachycardia.

Effect of hydroquinone, hydroxocobalamin and carboxy-PTIO on non-adrenergic non-cholinergic nerve mediated relaxations of the rat duodenum.

Relaxation induced by NANC-nerve stimulation is reduced by nitric oxide synthase (NOS) inhibitors but not by superoxide generators or NO scavengers, casting doubts on the precise nature of the neurotransmitter being released by these nerves. The lack of effect of superoxide anion generators to inhibit nitrergic nerve-mediated relaxations has been attributed to the protective action of high tissue levels of superoxide dismutase (SOD). The effects of hydroquinone, hydroxocobalamin and carboxy-PTIO, three NO inactivators which do not depend on superoxide anion generation, upon nitrergic nerve-mediated relaxations of the rat proximal duodenum were determined in order to elucidate whether they are mediated by free NO.

Power spectra of arterial pressure and heart rate in streptozotocin-induced diabetes in rats.

Background: Chronic diabetes is associated with alterations in autonomic modulation of the cardiovascular system. Although the rat has been used extensively in studies of experimental diabetes, there have been no reports on the changes in autonomic modulation of the cardiovascular function in chronic diabetic rats.

Objective: To examine chronic diabetic rats to determine the autonomic modulation of arterial pressure and heart rate variabilities in the time and frequency domain.

Isolation and characterization of an arginine ester hydrolase from Bothrops jararacussu venom which induces contractions of the isolated rat uterus.

The isolation and partial characterization of a serine protease with arginine ester hydrolase activity from Bothrops jararacussu snake venom are described. The purification procedure consisted of a gel filtration of the crude venom on Sephadex G-75 followed by an ion-exchange chromatography of the active fraction on DEAE-cellulose and a rechromatography on Bio-Rex 70 resin. The esterase fraction (DI-III), M(r) = 25,000 by SDS-PAGE, showed proteolytic activity on fibrinogen and casein.

Role of non-nitric oxide non-prostaglandin endothelium-derived relaxing factor(s) in bradykinin vasodilation.

The most conspicuous effect of bradykinin following its administration into the systemic circulation is a transient hypotension due to vasodilation. In the present study most of the available evidence regarding the mechanisms involved in bradykinin-induced arterial vasodilation is reviewed. It has become firmly established that in most species vasodilation in response to bradykinin is mediated by the release of endothelial relaxing factors following the activation of B2-receptors.

Mechanism of neuromuscular blockade induced by phenthonium, a quaternary derivative of (-)-hyoscyamine, in skeletal muscles.

1. The mechanisms underlying the postjunctional blockade induced by phenthonium [N-(4-phenyl) phenacyl 1-hyoscyamine] were investigated in mammalian and amphibian muscles. This muscarinic antagonist was previously shown to enhance specifically the spontaneous acetylcholine (ACh) release at concentrations that blocked neuromuscular transmission.

In vitro and in vivo effects of nitric oxide synthase inhibitors and nitric oxide inactivators on the South American opossum ileocolonic junction.

The potential role of nitrergic nerves in the regulation of the South American (SA) opossum ileocolonic junction (ICJ) function was investigated. In vitro, the effects of nitric oxide (NO) synthase inhibitors and NO inactivators on the non-adrenergic non-cholinergic (NANC) nerve-mediated relaxations of the circular muscle of the SA opossum ICJ were determined by employing isolated strips. Electrical field stimulation (0.

Influence of sympathetic blockade on the acute hypertensive response to aortic constriction.

The objective of the present study was to determine the contribution of the sympathetic nervous system to the hypertensive response to acute (45-min) aortic coarctation in conscious intact or sinoaortic-denervated (SAD) rats. Rats were treated chronically (5 wk) with guanethidine (50 mg.kg-1.

Nonadrenergic-noncholinergic relaxations of isolated circular muscle from South American opossum esophagogastric junction: is nitric oxide the inhibitory mediator?

Nonadrenergic-noncholinergic (NANC) inhibitory nerves are responsible for most of the nerve induced relaxations of gastrointestinal muscle. It has recently been proposed that NANC nerves may release nitric oxide (NO) or a related compound derived from L-arginine. We have recently shown that the South American (SA) opossum is another suitable model to elucidate the mechanism involved in these NANC relaxations.

Heart rate variability and baroreceptor function in chronic diabetic rats.

In conscious chronic (12 to 18 weeks) streptozotocin diabetic rats, we examined the changes in basal heart rate, with particular attention to heart rate variability assessed by evaluating the standard deviation (bpm) of the lengths of adjacent pulse pressure. We also investigated in anesthetized rats the ability of the aortic baroreceptors to acutely (30 minutes) reset to hypertensive levels. For this purpose, pressure-nerve activity curves for the baroreceptors were obtained, and gain (slope of the curve) and mean arterial pressure at 50% of maximal baroreceptor activity were calculated.

Nitric oxide blunts sympathetic response of pregnant normotensive and hypertensive rat arteries.

Rat pregnancy is associated with a blunted response to vasocontrictors both in vivo and in vitro as well as a decrease in arterial pressure. We examined the influence of pregnancy on neurally induced vasoconstrictor and vasodilator responses of the isolated mesenteric arterial bed from normotensive Wistar and spontaneously hypertensive nonpregnant and 20-day pregnant rats and determined the possible role of nitric oxide (NO) in modulating these responses. MAP (mm Hg) in pregnant normotensive (98+/-1, n=13) and hypertensive (136+/-5, n=13) rats was lower (P<.

Characterization of nerve-induced relaxation of gastrointestinal sphincteric smooth muscle in a South American opossum (Didelphis albiventris).

The presence of inhibitory nonadrenergic noncholinergic (NANC) intrinsic innervation of the circular muscle of the gastrointestinal sphincters of the South American (SA) opossum was investigated in vitro. Isolated circular muscle strips from the esophagogastric and ileocolonic junctions but not from the gastroduodenal(pylorus)region developed spontaneous tension. Tetrodotoxin (TTX, 1 microM) augmented the spontaneous tension only in the ileocolonic junction strips.

Novel effects of guanidine on the neuromuscular junction.

1. The effects of guanidine on the isolated mouse phrenic nerve diaphragm (MPND) and chick biventer cervicis (CBC) neuromuscular preparations were determined by myographic and electrophysiological methods. 2.

Oxytocin releases atrial natriuretic peptide from rat atria in vitro that exerts negative inotropic and chronotropic action.

Our previous experiments suggested that natriuresis induced by blood volume expansion, was brought about by oxytocin (OT)-stimulated atrial natriuretic peptide (ANP) release from the right atrium. We hypothesized that the ANP released might exert effects on the atrium itself and therefore carried out in vitro experiments to test this hypothesis. Heart rate and isometric tension were recorded from isolated rat atria mounted in an organ bath.

Involvement of nitric oxide in the pathogenesis of cyclophosphamide-induced hemorrhagic cystitis.

The involvement of nitric oxide (NO) and the potential modulation of NO synthase (NOS) activity by platelet-activating factor were investigated in a rat model of cyclophosphamide-induced hemorrhagic cystitis. Male Wistar rats received a single intraperitoneal injection of cyclophosphamide, and cystitis was evaluated 6, 12, 24, 48, and 72 hours later by determining the changes in bladder wet weight and plasma protein extravasation and the macro- and microscopic morphological alterations. In addition, NOS activity and NADPH-diaphorase histochemistry were studied in bladder tissues.

ANP as a neuroendocrine modulator of body fluid homeostasis.

The role played by the central nervous system (CNS) in the control of body fluid homeostasis has been demonstrated by several authors. The AV3V plays a key role in central control of sodium excretion since its cholinergic, adrenergic, angiotensinergic and osmotic stimulation enhances and its destruction blocks sodium excretion in rats and goats. Cholinergic stimulation of the AV3V induced an increase in plasma ANP as well as a marked elevation in content of the peptide in medial basal hypothalamus, neuro and adenohypophysis.