Blood pressure lowering effect of the aqueous extract of the stem of Ipomoea acanthocarpa (convolvulaceae) in spontaneously and salt-loaded hypertensive rats

Spontaneously hypertensive (SHR) and salt-loaded hypertensive rats (SLHR) were submitted to a daily treatment by gavage of 2 mL/100 g body weight of the aqueous extract of the stem of Ipomoea acanthocarpa (30 mg/mL stock solution). A fall in blood pressure of nearly 13% was observed after two successive administrations of the aqueous extract. After 14 days of treatment, the blood pressure fell by more than 30±8%. The hypotensive effect might be due to a direct vascular smooth muscle effect or to its already observed high diuretic effects or might be acting by some other mechanism.     

关附甲素对豚鼠乳头肌动作电位最大除极速度的频率依赖性抑制作用

应用标准微电极技术，研究了关附甲素对豚鼠右心室乳头肌动作电位最大除极速率(V_max)的频率依赖性抑制作用(RDB)，并与美西律，奎尼丁，劳卡尼进行了比较. 在相同刺激间隔(300 ms)，产生50%左右RDB的药物浓度下，美西律的RDB开始最快，其第2个V_max所产生的抑制已占RDB的64%，奎尼丁，劳卡尼和关附甲素的RDB开始速率常数分别为每个动作电位0.165, 0.076和0.136. 美西律，奎尼丁，劳卡尼和关附甲素产生RDB的恢复时间常数分别为1.4, 9.0, 18.2和44.0 s，而且它们的恢复时间常数是不依赖于药物浓度而变化的，结果提示，关附甲素是一个慢动力学钠通道阻滞剂.     

Differences in the temporal dynamics of the visual ON and OFF pathways

The temporal structure of spike trains recorded from optic fibers and single units of the lateral geniculate nucleus (LGN) and primary visual cortex of the cat was studied with a novel method of inter-spike interval analysis. ON type relay cells of the LGN exhibited a multimodal interval distribution preferring a distinct interval (fundamental interval) and its multiples during the sustained light response, whereas most OFF cells showed a broad, unimodal distribution. The general pattern of the interval distribution was relatively independent of stimulus size and contrast and the degree of light adaptation. Simultaneously recorded S-potentials originating from the retinal input generally produced only a single peak at the fundamental interval length. Therefore, the multimodal interval distribution of LGN cells seems to be a result of intra-geniculate inhibition. Cortical cells also showed a weak tendency to fire with spike intervals similar to LGN cells. Therefore, the regular firing pattern observed at peripheral stages of the visual pathway can persist at higher levels and might promote the occurrence of oscillatory activity.     

钙通道阻滞剂在皮肤科的应用

钙通道阻滞剂(CCB)是广泛应用于临床治疗心血管疾病的药物。近年的研究表明，CCB具有稳定肥大细胞膜和阻止脱颗粒，抑制淋巴细胞转化及白介素2产生，降低表皮郎格罕细胞数，扩张血管、抑制血小板聚集、增强红细胞变形能力，抑制细胞的分裂和增殖作用。此外对淋菌的耐药性有逆转作用。用于临床某些过敏性疾病、寒冷性脉管性疾病及银屑病取得了较好的效果，为临床增添了新的治疗手段．给变应性接触性皮炎、耐药性淋病的治疗带来了新的展望。本文对药物的副作用亦有概述。     

粉防己碱舒张离体新西兰白兔阴茎海绵体平滑肌的机制研究

目的观察粉防己碱(tetrandrine,Tet)对阴茎海绵体平滑肌胞内钙释放和胞外钙内流的影响,初步探讨其舒张作用的机制。方法采用离体阴茎海绵体平滑肌肌条张力记录法,观察Tet对去氧肾上腺素(phenylephrine,PE)和氯化钾(KCI)诱导收缩的肌条的影响；采用无Ca~(2 )-复Ca~(2 )实验法,观察Tet对PE诱导的依赖细胞内钙和细胞外钙的肌条收缩反应的影响。结果Tet对PE或kcl诱导的肌条收缩均具有浓度依赖性的抑制作用。100μmol/L Tet可抑制20μmol/L PE引起的依赖细胞内钙和细胞外钙的肌条收缩(P＜0．05)；结论Tet可通过阻滞电压依赖性钙通道、受体依赖性钙通道和抑制细胞内钙库释放,从而介导其对海绵体平滑肌的舒张作用。     

Blockade of the human cardiac K+ channel Kv1.5 by the antibiotic erythromycin

Erythromycin administration has been associated with a prolongation of cardiac repolarization in certain clinical settings. This could be due to blockade of voltage-dependent K⁺ channels in the human heart. For this reason we examined the effects of erythromycin on a rapidly activating delayed rectifier K⁺ channel (Kv1.5) cloned from human heart and stably expressed in human embryonic kidney cells. When examined using the whole-cell patch clamp technique, erythromycin (100 μM) blocked Kv1.5 current in a time-dependent manner but required prolonged exposure to do so. However, when we examined Kv1.5 current using inside-out macropatches, erythromycin applied to the cytoplasmic surface rapidly (within 1-2 min) inhibited Kv1.5 current with an IC₅₀ value of 2.6 x 10^-5M (1.7 - 3.9 x 10^-5M, 95% C.L.). The main effect of erythromycin was to accelerate the rate of Kv1.5 current decay thereby reducing the current at the end of a prolonged voltage-clamp pulse. Erythromycin also blocked Kv1.5 current in both a voltage- and frequency-dependent manner but had little effect on the activation kinetics, deactivation kinetics, or the steady-state inactivation properties of Kv1.5. These data suggest that erythromycin acts as a blocker of an activated state of the Kv1.5 channel and that it may access its binding site from the intracellular face of the channel. This study is the first to examine the effects of erythromycin on a cloned human cardiac K⁺ channel. It is concluded that erythromycin blocks Kv1.5 at clinically relevant concentrations. Blockade of voltage-dependent K⁺ channels in the heart could contribute to the alterations in cardiac repolarization that have been observed with erythromycin. Received: 22 November 1996 / Accepted: 26 February 1997