cyclic-gmp and 6-7-dihydroxyflavone

We recently reported that intraperitoneal injection of 7,8-dihydroxyflavone (7,8-DHF), a brain-derived neurotrophic factor-mimicking small compound, could attenuate alcohol-related behaviors in a two-bottle choice ethanol consumption procedure (IA2BC) in rats via tropomyosin receptor kinase B in the ventral tegmental area (VTA), which is closely related to alcohol use disorder. However, the detailed mechanisms underlying the regulation of 7,8-DHF on alcohol drinking behavior remain elusive. In this study, we determined the role of nitric oxide (NO), a pleiotropic signaling molecule, in the VTA in the action of 7,8-DHF upon alcohol drinking behavior. Intermittent alcohol exposure led to the overexpression of NO in the VTA, especially 72 h after withdrawal from four weeks of ethanol exposure in IA2BC rats. A higher amount of alcohol intake was also found at the same time point, consistent with the overexpression of NO in the VTA. Microinjection of NG-Nitro-l-Arginine Methyl Ester, (NO synthase inhibitor) or 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (NO scavenger) into the VTA inhibited alcohol intake, whereas application of S-Nitroso-N-acetyl-DL-penicillamine (SNAP, the NO donor) in the VTA further enhanced alcohol consumption in IA2BC rats. Interestingly, either 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (a sGC inhibitor) or KT5823 [a selective protein kinase G (PKG) inhibitor] blocked NO's enhancing effect on ethanol intake. Intraperitoneal injection of 7,8-DHF reduced the overexpression of NO; SNAP microinjected into the VTA reversed the inhibitory effects of 7,8-DHF on alcohol consumption. Our findings suggest that NO-cGMP-PKG might be involved in regulation of 7,8-DHF on alcohol consumption in IA2BC rats.

Topics: Alcohol Drinking; Animals; Cyclic GMP; Flavones; Male; Nitric Oxide; Rats; Rats, Sprague-Dawley; Signal Transduction; Ventral Tegmental Area

Although 7,8-dihydroxyflavone (7,8-DHF) has been demonstrated to be potently neuroprotective, its effect on vascular function remains unknown.. The effect of 7,8-DHF on phenylephrine (PE)-induced preconstriction was examined with aortic rings isolated from normal rats. Its effective mechanisms were studied with blockers, Western blotting, and primarily cultured vascular smooth myocytes. The blood pressure (BP) of rats was measured with a tail cuff method.. 7,8-DHF dose-dependently dilated the PE-preconstricted, endothelia-intact aortic rings with concentration for 50% of maximal effect (EC50) of approximately 24 µM. Both Nω-nitro-L-arginine methyl ester hydrochloride, a nitric oxide synthase inhibitor, and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, a soluble guanylyl cyclase blocker, significantly reduced the vasorelaxing effect of 7,8-DHF. Western blotting showed that 7,8-DHF increased the aortic endothelial nitric oxide synthase protein expression and phosphorylation. With endothelia removed, 7,8-DHF also dilated the PE-preconstricted rings but with EC50 of approximately 104 µM. Ca(2+) imaging experiments detected that 7,8-DHF probably blocked both intracellular Ca(2+) release and extracellular Ca(2+) influx. Therefore, the mechanisms of 7,8-DHF dilating effect might be stimulating the nitric oxide/cGMP production and blocking the Ca(2+) signaling pathway instead of tropomyosin receptor kinase B receptors because ANA-12, its specific antagonist, did not show any effect against 7,8-DHF. When administered intravenously, 7,8-DHF significantly reduced the BP of the spontaneously hypertensive rats. However, when used orally, there was only a slight but significant reduction in the diastolic pressure.. The results suggest that neuro-protective 7,8-DHF is also a vasorelaxing and antihypertensive substance in rats.

Topics: Administration, Oral; Animals; Antihypertensive Agents; Aorta, Thoracic; Calcium Signaling; Cells, Cultured; Cyclic GMP; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelium, Vascular; Flavones; Hypertension; Injections, Intravenous; Nitric Oxide; Nitric Oxide Synthase Type III; Phosphorylation; Rats, Inbred SHR; Vasodilation; Vasodilator Agents