This study evaluated whether α-adrenergic activation contributes to collateral circuit vascular resistance in the hindlimb following acute unilateral occlusion of the femoral artery in rats. Blood pressures (BPs) were measured above (caudal artery) and below (distal femoral artery) the collateral circuit. Arterial BPs were reduced (15-35 mmHg) with individual (prazosin, rauwolscine) or combined (phentolamine) α-receptor inhibition. Blood flows (BFs) were measured using microspheres before and after α inhibition during the same treadmill speed. α 1 inhibition increased blood flow by ∼40% to active muscles that were not affected by femoral occlusion, whereas collateral-dependent BFs to the calf muscles were reduced by 29 ± 8.4% (P < 0.05), due to a decrease in muscle conductance with no change in collateral circuit conductance. α 2 inhibition decreased both collateral circuit (39 ± 6.0%; P < 0.05) and calf muscle conductance (36 ± 7.3%; P < 0.05), probably due to residual α 1 activation, since renal BF was markedly reduced with rauwolscine. Most importantly, inhibiting α 2 receptors in the presence of α 1 inhibition increased (43 ± 12%; P < 0.05) collateral circuit conductance. Similarly, non-selective α inhibition with phentolamine increased collateral conductance (242 ± 59%; P < 0.05). We interpret these findings to indicate that both α 1 -and α 2 -receptor activation can influence collateral circuit resistance in vivo during the high flow demands caused by exercise. Furthermore, we observed a reduced maximal conductances of active muscles that were ischaemic. Our findings imply that in the presence of excessive sympathetic activation, which can occur in the condition of intermittent claudication during exertion, an exaggerated vasoconstriction of the existing collateral circuit and active muscle will occur.

Heterocyclic diradicaloids with atom‐precise control over open‐shell nature are promising materials for organic electronics and spintronics. Herein, we disclose quinoidal π‐extension of a B/N‐heterocycle for generating B/N‐type organic diradicaloids. Two quinoidal π‐extended B/N‐doped polycyclic hydrocarbons that feature fusion of the B/N‐heterocycle motif with the antiaromatic s‐indacene or dicyclopenta[b,g]naphthalene core were synthesized. This quinoidal π‐extension and B/N‐heterocycle leads to their open‐shell electronic nature, which stands in contrast to the multiple‐resonance effect of conventional B/N‐type emitters. These B/N‐type diradicaloids have modulated (anti)aromaticity and enhanced diradical characters comparing with the all‐carbon analogues, as well as intriguing properties, such as magnetic activities, narrow energy gaps and highly red‐shifted absorptions. This study thus opens the new space for both of B/N‐doped polycyclic π‐systems and heterocyclic diradicaloids.

Exercise training is known to be an effective means of improving functional capacity and quality of life in patients with peripheral arterial insufficiency (PAI). However, the specific training-induced physiological adaptations occurring within collateral vessels remain to be clearly defined. The purpose of this study was to determine the effect of exercise training on vasomotor properties of isolated peripheral collateral arteries. We hypothesized that daily treadmill exercise would improve the poor vasodilatory capacity of collateral arteries isolated from rats exposed to surgical occlusion of the femoral artery. G -nitro-l-arginine methyl ester (l-NAME; 300 μm) eliminated this AChor flow-induced vasodilatation. The depressed vasodilatory response to SNP caused by vascular occlusion was reversed with training. These data indicate that exercise training improves endothelium-mediated vasodilatory capacity of hindlimb collateral arteries, apparently by enhanced production of the putative endothelium-derived hyperpolarizing factor(s). If these findings were applicable to patients with PAI, they could contribute to an improved collateral vessel function and enhance exercise tolerance during routine physical activity.

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Aims: To evaluate whether low level left vagus nerve stimulation (LLVNS) in early stage of myocardial infarction (MI) could effectively prevent ventricular arrhythmias (VAs) and protect cardiac function, and explore the underlying mechanisms.Methods and Results: After undergoing implantable cardioverter defibrillators (ICD) and left cervical vagal stimulators implantation and MI creation, 16 dogs were randomly divided into three groups: the MI (n = 6), MI+LLVNS (n = 5), and sham operation (n = 5) groups. LLVNS was performed for 3 weeks. VAs, the left ventricular function, the density of the nerve fibers in the infarction area and gene expression profiles were analyzed. Compared with the MI group, dogs in the MI+LLVNS group had a lower VAs incidence (p &lt; 0.05) and better left ventricular function. LLVNS significantly inhibited excessive sympathetic nerve sprouting with the evidences of decreased density of TH, GAP43 and NF positive nerves (p &lt; 0.05). The gene expression profiling found a total of 206 genes differentially expressed between MI+LLVNS and MI dogs, mainly involved in cardiac tissue remodeling, cardiac neural remodeling, immune response and apoptosis. These genes, including 55 up-regulated genes and 151 down-regulated genes, showed more protective expressions under LLVNS.Conclusions: This study suggests that LLVNS was delivered without altering heart rate, contributing to reduced incidences of VAs and improved left ventricular function. The potential mechanisms included suppressing cardiac neuronal sprouting, inhibiting excessive sympathetic nerve sprouting and subduing pro-inflammatory responses by regulating gene expressions from a canine experimental study.