Search results for "Quinoxaline"

Relaxant effect of sildenafil in the rabbit basilar artery

2005

We hypothesized that sildenafil, inhibitor of phosphodiesterase-5 (PDE-5), interacts with the nitric oxide (NO)-cGMP pathway in the cerebral arteries and shows vasoactive effects. To prove it in the isolated rabbit basilar artery, we compared the effects of sildenafil with other PDE-5 inhibitors, assessed the endothelial dependence of the vasoactive responses, and used modulators of the cGMP and cAMP signaling processes. Sildenafil (10 nM-0.1 mM) induced concentration-dependent relaxations of endothelin-1 (10 nM)-precontracted basilar artery, which were partially inhibited both in endothelium-denuded arteries and in arteries precontracted by depolarization with KCl (50 mM). Endothelin-1 (1 …

Phosphodiesterase inhibitors suppress alpha2-adrenoceptor-mediated 5-hydroxytryptamine release from tracheae of newborn rabbits.

1998

The outflow of 5-hydroxytryptamine (5-HT) from isolated tracheae of newborn rabbits was determined by high pressure liquid chromatography with electrochemical detection. This 5-HT outflow reflects release from neuroendocrine epithelial cells of the airway mucosa, as previously shown. Phenylephrine, via alpha2B-adrenoceptors, caused a transient increase in 5-HT outflow, maximally by about 250%, an effect mediated by liberation of intracellular Ca2+, as previously shown. The non-selective phosphodiesterase inhibitor 2-isobutyl-1-methylxanthine (IBMX) concentration-dependently inhibited phenylephrine-induced 5-HT release (completely at 100 microM, IC50: 1.3 microM). Likewise, benzafentrine (in…

Evidence for a role of inducible nitric oxide synthase in gastric relaxation of mdx mice

2006

Alterations of gastric mechanical activity have been reported in mdx mouse, animal model for Duchenne muscular dystrophy. This study examined if alterations in the vasoactive intestinal polypeptide (VIP) system are present in mdx stomach. Gastric mechanical activity was recorded in vitro as changes of endoluminal pressure and neurally or pharmacologically evoked relaxations were analysed in mdxvs normal stomach. Reverse-transcription polymerase chain reaction was used to detect inducible nitric oxide synthase (iNOS) expression. Relaxations to sodium nitroprusside in mdx stomach showed no difference in comparison with normal preparations. In normal stomach, VIP produced relaxation, which was…

Analytical method for simultaneous determination of pesticide and veterinary drug residues in milk by CE-MS

2009

10 páginas, 2 figuras, 4 tablas.

Evidence for an involvement of NMDA and non-NMDA receptors in synaptic excitation of phrenic motoneurons in the rabbit

1991

Abstract The action of endogenous excitatory amino acids on phrenic motoneurons was studied in anesthetized, vagotomized, paralyzed and artificially ventilated rabbits. The NMDA receptor antagonists APV and ketamine, as well as the non-NMDA receptor antagonists GAMS and DNQX were administered by microinjection into the ventral horn of the spinal segments C3-C5. Injection of each antagonist resulted in a reversible reduction of the phrenic nerve activity. Results suggest an important function of endogenous excitatory amino acids in the excitation of phrenic motneurons. NMDA as well as non-NMDA receptors are involved. The functional role of both receptor types in bulbospinal neurotransmission…

Isoindolo[2,1-a]quinoxaline derivatives, novel potent antitumor agents with dual inhibition of tubulin polymerization and topoisomerase I.

2008

Isoindoloquinoxalines 4 and 5 were obtained by refluxing 2-(2'-aminoaryl)-1-cyanoisoindoles 3a- e in acetic or formic acid. All derivatives were screened by the National Cancer Institute (Bethesda, MD) for the in vitro one dose primary anticancer assay against a 3-cell line panel. Compounds 4a- e, screened against a panel of about 60 human tumor cell lines, showed remarkable antineoplastic activity; they had GI 50 values in the low micromolar or submicromolar range and reached, in the case of 4c, nanomolar concentrations on 88% of the 59 tested cell lines. Flow cytometric analysis of cell cycle after treatment with 4c demonstrated an arrest of the cell cycle in G2/M phase. This effect was a…

Spectroscopic and theoretical study of the molecular and electronic structures of a terthiophene-based quinodimethane.

2004

The UV/Vis, infrared absorption, and Raman scattering spectra of 3',4'-dibutyl-5,5"-bis(dicyanomethylene)-5,5"-dihydro-2,2':5',2"-terthiophene have been analyzed with the aid of density functional theory calculations. The compound exhibits a quinoid structure in its ground electronic state and presents an intramolecular charge transfer from the terthiophene moiety to the C(CN)2 groups. The molecular system therefore consists of an electron-deficient terthiophene backbone end-capped with electron-rich C(CN)2 groups. The molecule is characterized by a strong absorption in the red, due to the HOMO-->LUMO pi-pi* electronic transition of the terthiophene backbone that shifts hypsochromically on …

Reduced presynaptic efficiency of excitatory synaptic transmission impairs LTP in the visual cortex of BDNF-heterozygous mice

2006

The neurotrophin brain-derived neurotrophic factor (BDNF) plays an important role in neuronal survival, axonal and dendritic growth and synapse formation. BDNF has also been reported to mediate visual cortex plasticity. Here we studied the cellular mechanisms of BDNF-mediated changes in synaptic plasticity, excitatory synaptic transmission and long-term potentiation (LTP) in the visual cortex of heterozygous BDNF-knockout mice (BDNF(+/-)). Patch-clamp recordings in slices showed an approximately 50% reduction in the frequency of miniature excitatory postsynaptic currents (mEPSCs) compared to wild-type animals, in the absence of changes in mEPSC amplitudes. A presynaptic impairment of excita…

Synthesis of Pyrrolo-Condensed Derivatives with Potential Antiviral Activity

2014

Experimental and theoretical studies into the structural perturbations between neutral, oxidised and reduced forms of 1,4-dithiinoquinoxaline derivat…

2000

The syntheses and electrochemistry of thieno[3',4'r5,6][1,4]dithiino[2,3-b]quinoxaline (9), 2,3-bis(methylsulfanyl)[1,4]dithiino[2,3-b]quinoxaline (16) and 2,3-ethylenedisulfanyl[1,4]dithiino[2,3-b]quinoxaline (17) are reported, together with the X-ray crystal structures of 9, 16 and the charge-transfer complex 9.TCNQ. In the thieno derivative 9, the molecular structure undergoes a significant change from a boat conformer to a planar system, upon oxidation with TCNQ. Theoretical calculations show that oxidation leads to planarisation of the molecular structure due to the aromatisation of the dithiine moiety. The study of the oxidised/reduced species helps to rationalise the electrochemical …