Clonidine, an α₂-agonist, has been shown to be useful in the treatment of hepatic portal hypertension in cirrhosis. The mechanism has been attributed to a clonidine-induced decrease in sympathetic activity. While clonidine has been shown to stimulate the α₂-adrenoceptors of blood vessels, there is limited knowledge of the effects of clonidine on the circular muscle of the hepatic portal vein which regulates its blood flow. To investigate clonidine-induced contraction of the circular muscle of the hepatic portal vein and to clarify the possible role of the endothelium in the contraction, we examined the effects of clonidine on the isometric contraction of endothelium-intact and -removed ring preparations of the rat hepatic portal vein. In endothelium-intact preparations, clonidine caused a concentration-dependent increase in the amplitude of contractions. Inhibition of NO synthesis with N^ω-nitro-L-arginine (L-NNA) elevated the resting tone, and increased the amplitude of the clonidine-induced contractions. Inhibition of cyclooxygenase by diclofenac did not change the amplitude of the clonidine-induced contractions observed both in the presence and absence of L-NNA. Application of a single concentration of clonidine induced a clear increase in amplitude of both twitch and tonic contractions. Twitch and tonic contractions induced by clonidine were inhibited by yohimbine. When the endothelium was damaged by sodium deoxycholate, tonic contractions induced by clonidine were completely suppressed, whereas the increase in twitch contractions was not influenced by chemical damage of the endothelium. Neither SKF-96365, a nonselective cation channel blocker, nor superoxide dismutase, a free radical scavenger, in the presence of catalase, changed the tonic contraction induced by clonidine. These results indicate that stimulation of α₂-adrenoceptors enhanced twitch contractions and induced tonic contractions in the circular muscle of the rat hepatic portal vein, especially in the absence of NO. The latter, but not the former, occurs through an endothelium-dependent pathway.

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Anthocyanins, which are responsible for a variety of bright colors (including red, blue, and purple) in fruits, vegetables, and flowers, are consumed as dietary polyphenols. Anthocyanin-containing fruits are thought to decrease coronary heart disease and are used in anti-diabetic preparations. Diabetes is associated with a variety of cardiovascular complications that may be mediated by endothelial dysfunction, and so this study was designed mainly to characterize the influence of a synthesized anthocyanidin derivative (HK-008) over acetylcholine (ACh)-induced relaxation in mesenteric arterial beds isolated from rats. In a glucose-tolerance test in intact rats, HK-008 (30 mg/kg) reduced the glucose level as effectively as the same dose of glibenclamide. The aortic relaxation induced by pinacidil (an ATP-sensitive potassium channel opener) was greatly inhibited by glibenclamide (10 μM), and also significantly inhibited by HK-008 (10 μM). Interestingly, the ACh-induced relaxation in the perfused, preconstricted mesenteric arterial bed was significantly enhanced by HK-008 (10 μM), and this enhancement was significantly attenuated by indomethacin (10 μM). The ACh-induced mesenteric relaxation was impaired by an increase in oxidative stress, viz. superoxide-generating treatment [xanthine oxidase (XO; 0.1 U/ml) plus hypoxanthine (HX; 10 μM)]. However, this impairment was strongly suppressed by HK-008 (10 μM). These results suggest that HK-008 increases endothelium-induced relaxation by suppressing oxidative stress or modulating prostanoids signaling. This compound may therefore be useful against certain cardiovascular disorders.

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The goal of the study was to establish if the conductive area size of recording electrodes affects the quality of a multichannel electrogastrogram. In twelve volunteers (9F, 3M, median age 24 years, range 22-28) on three separate days fasted and postprandial four-channel electrogastrograms were registered in randomized order with Red Dot class Ag/AgCl electrodes of a type: `2222' (conductive area/total area: 2.00/10.24 cm<sup>2</sup>, `2271' 2.54/29.64 cm², or `2660' 11.64/11.64 cm² (total surface conductive!), and subsequently analyzed with a dedicated software. In the case of type 2271 and 2660 the between-electrode electrical conductivity improved at the end of the recording relative to the basal measurement, whereas type 2222 yielded a stable between-electrode electrical conductivity throughout the examination. Despite the differences in either the conductive area size or its construction, the analysis of variance on parameters describing quantitatively the multichannel electrogastrogram did not reveal a superiority of any from among the electrodes tested. Type 2271 was, however, rated the less handy among the three electrodes. Multichannel surface electrogastrography seems to be technically feasible with any type of high quality electrodes, therefore small dimensions and easy handling may favor the choice of a particular type for this examination.

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