Counter effects of higenamine and coryneine, components of aconite root, on acetylcholine release from motor nerve terminal in mice

The counter effects of higenamine and coryneine, components of aconite root, on acetylcholine (ACh) release from motor nerve terminals in the mouse phrenic nerve-diaphragm muscle preparation were studied by a radioisotope method. Both nerve-evoked release and spontaneous release of [³H]-ACh from the preparation preloaded with [³H]-choline were measured. The change in the tetanic tension of muscle was simultaneously recorded in the same preparation. Higenamine (10 μM) augmented both the nerve-evoked and spontaneous ACh releases, and the muscle tension. The effects were inhibited by pretreatment with propranolol (10 μM), a β-adrenoceptor antagonist. Coryneine reduced the nerve-evoked release of ACh, accelerated the decay of tetanic tension (tetanic fade) at 30 μM, and it depressed the peak amplitude of tetanic tension at a higher concentration of 100 μM. These results suggest that of the two components contained in aconite root, higenamine increases ACh release via activation of β-adrenoceptor, and conversely coryneine depresses ACh release by preferentially acting at motor nerve terminal.     

The inhibitory effect of cadmium on neuromuscular transmission in the rat.

Cadmium (0.125-1 mM) was found to inhibit the isometric response of the isolated rat hemidiaphragm during indirect stimulation, but not during direct stimulation. This effect of cadmium (1 mM) was completely reversed by ethyleneglycol bis-(aminoethyl)-N,N,N',N'-tetra-acetic acid (2 mM) or by L-cysteine (2 mM) but only partially by increased calcium. Cadmium (10 micronM) significantly reduced the quantal release of transmitter in the isolated phrenic diaphragm and a concentration of 0.1 mM frequently caused a complete failure of the endplate response after 30 min. The effect of cadmium on neuromuscular transmission could not be readily reversed by washing with cadmium-free solution. Miniature endplate potential frequency and amplitude were not significantly affected by cadmium (0.1 or 0.5 mM). The results suggest that the effect of cadmium on the isolated phrenic nerve-diaphragm is due largely to inhibition of calcium function at presynaptic nerve terminals.     

附子对小鼠超氧化物岐化酶活性和丙二醛、NO含量的影响

目的:研究附子不同的临床使用剂量对小鼠心脏超氧化物歧化酶(SOD)活性、丙二醛(MDA)、一氧化氮(NO)含量的影响,探讨其对心脏的毒性机制.方法:制备附子及与甘草配伍的水煎液,将小鼠随机分为9组,分别以附子15,45,75,105g的临床使用剂量按等效换算系数换算成小鼠给药剂量,给小鼠灌胃20 d,测其心脏组织SOD活性及MDA、NO含量.结果:与对照组比较,单附子临床剂量45,75,105 g组小鼠心脏SOD活性明显增加,MDA含量显著降低(P＜0.05).甘草配伍后的各组与对照组比较,SOD含量有增加的趋势,但仅105 g组有明显差异(P＜0.05);除15 g组外,其余各组MDA含量均显著降低(P＜0.05);NO含量均呈下降趋势,但差异无统计学意义(P＞0.05).结论:大剂量使用附子对心脏的SOD活力、MDA和NO含量没有负面影响,相反能减轻小鼠心脏组织氧化反应.     

Acetylcholine content of and release from isolated pelviureteral tract

Summary Measurements were taken for the acetylcholine content of animal and human pelviureteral muscle and for the release of acetylcholine at rest and during field stimulation of the isolated renal pelvis and ureter. Release was frequency-dependent, with the maximum output obtained at 10 Hz. The release of acetylcholine from reserpine-pretreated and piperoxan-treated tissues remained unchanged, but tetrodotoxin (1.10^–6 g/ml) and noradrenaline (2.10^–6 g/ml) significantly reduced the output.With the technical assistance of B. STACCHINI     

Effects of the facilitatory compounds catechol,guanidine, noradrenaline and phencyclidine on presynaptic currents of mouse motor nerve terminals

Summary Catechol, guanidine, noradrenaline, and phencyclidine can increase acetylcholine release at neuromuscular junctions. To determine if they act by affecting nerve terminal action potentials, the electrical activity of the terminal regions of motor nerves was recorded with an extracellular electrode inserted in the perineural sheaths of nerves in the mouse triangularis sterni preparation. Catechol (from 10 M) and guanidine (from 1 mM) produced a selective reduction in the component of the perineural waveform associated with voltage-dependent K⁺ currents, without significant effects on Na⁺, Ca⁺, or Ca²⁺-activated K⁺ currents. A selective block of K⁺ channels in nerve terminals would cause a prolonged depolarization and hence a large influx of Ca²⁺ to trigger acetylcholine release; this could explain the facilitatory effects of guanidine and catechol. Noradrenaline produced a slight increase in the amplitude of the. perineural waveform. This is consistent with hyperpolarization of the resting membrane potential of the nerve, which could lead to facilitation of acetylcholine release. Phencyclidine blocked Na⁺- and K⁺-related portions of the signal. Send offprint requests to A. L. Harvey at the above address     

Controlled Release of Lidocaine from Injectable Gels and Efficacy in Rat Sciatic Nerve Block

Purpose. Methods of delaying the action of local anesthetics are important, since short duration of action limits their use in the treatment of postoperative and chronic pain. The present study evaluated the use of low-viscosity gels in prolonging the release of lidocaine. Methods. Release of lidocaine from 2% lidocaine-HC1 containing methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), sodiumcarboxymethyl cellulose (CMC), and poloxamer 407 (PO) gels was studied in phosphate buffer, pH 7.4, at 37°C. Commercial metylcellulose gel (MC_com) served as control. The in vivo efficacy of the respective gel formulations were evaluated in rats. The gel was injected into the vicinity of the sciatic nerve and nociception and motor function were tested. Results. The cumulative amount of lidocaine released during 8 hr was slowest from the PO gel, followed by the CMC, HPMC and MC gels. The antinociceptive effect was not prevented by the motor block and lasted longest with the PO gel. Good linear and rank order correlation was obtained between in vitro and in vivoresults. The microscopic examination of the tissue samples revealed only mild or no irritation of the skeletal muscle tissue by the PO, HPMC, and CMC gels. Conclusions. Based on these results poloxamer gel proved to be the most promising carrier for lidocaine.     

附子对两种不同慢性肾病小鼠乳酸代谢的影响

目的：观察附子对两种不同慢性肾病模型小鼠乳酸代谢的影响,探讨附子的温阳、肾脏保护作用及与乳酸酸中毒的关系。方法：将雄性ICR小鼠随机分为7组：正常对照组、关木通模型组、关木通＋附子低剂量组、关木通＋附子高剂量组、腺嘌呤模型组、腺嘌呤＋附子低剂量组和腺嘌呤＋附子高剂量组。正常对照组灌胃等体积饮用水;关木通模型组灌胃给予7g·kg^-1·d^-1的关木通水煎剂,给药4天后停药3天,持续5周;腺嘌呤模型组先以250mg·kg^-1腺嘌呤隔天灌胃1次,持续1周,再以130mg·kg^-1腺嘌呤隔天灌胃1次,持续3周;关木通（腺嘌呤）模型＋附子低剂量组、关木通（腺嘌呤）模型＋附子高剂量组在造模的同时分别给予3、10g·kg^-1·d^-1的附子水煎剂。实验结束时,测定各组血清肌酐和尿素氮、乳酸含量及乳酸脱氢酶活性,以及肝、肾、睾丸的蛋白、乳酸含量和乳酸脱氢酶活性,并记录左肾、左睾系数及附睾精子数。结果：附子能显著降低两种肾病模型小鼠的血清尿素氮、乳酸含量、乳酸脱氢酶活性及左肾系数,显著提高精子数及肾脏蛋白含量;显著降低关木通模型小鼠的肝脏乳酸含量、肾脏的乳酸含量和乳酸脱氢酶活性,显著增加肾脏蛋白含量;显著增加腺嘌呤模型小鼠肾脏、皋丸的乳酸含量,提高肝脏、皋丸乳酸脱氢酶活性,降低肾脏乳酸脱氢酶活性及睾丸蛋白含量。附子剂量与药效呈一定的正相关性。结论：两种肾病模型均存在不同程度的乳酸酸中毒。附子对关木通致慢性马兜铃酸肾病的肾脏酸中毒的纠正情况最明显;而腺嘌呤致慢性肾衰模型虽血清乳酸含量显著升高,但肝、肾、睾丸中均未出现乳酸蓄积,相反,肾脏、睾丸中乳酸含量有所降低,附子也能使该模型小鼠的肝、肾乳酸含量和乳酸脱氢酶活性趋于正常值,提示附子的温阳、肾脏保护作用与调节乳酸代谢有关。     

人参根和茎叶皂苷对孤独饲养小鼠自发运动及攻击行为的影响

目的探讨乌贼墨提取物对氧化性损伤小鼠心、脑组织的保护作用以及在不同剂量条件下的作用效果。方法40只昆明系健康小鼠随机分为空白对照组、模型组、低、高剂量组。模型组腹腔注射环磷酰胺造氧化性损伤模型。检测各组小鼠心肌和脑组织中SOD(超氧化物歧化酶),MDA(丙二醛),CAT(过氧化氢酶),GSH-Px(谷胱甘肽过氧化物酶)变化,血液中SOD,MDA变化。结果环磷酰胺均能不同程度的影响上述指标的变化(P<0.01或P<0.05),说明造模成功。与模型组比较,不同剂量的乌贼墨提取物均能不同程度的抑制由环磷酰胺所致的上述指标的变化(P<0.01或P<0.05),但部分数据表明,较高浓度的提取物的抑制作用有所减弱,有的甚至不起作用。结论适当浓度的乌贼墨提取物对氧化性损伤小鼠心肌和脑组织具有一定的保护作用。     

环丙沙星聚乳酸微球的制备、性状和体外释药性能的研究

目的采用乳化-溶剂蒸发法制备环丙沙星聚乳酸微球,并对其性状进行考察.方法通过正交设计试验筛选其最佳制备工艺, 用电子显微镜观察微球表面形态, 差示扫描热分析确证含药微球的形成, 并对微球的平均粒径、载药量、包封率、体外释药性能进行了研究.结果环丙沙星聚乳酸微球的形态圆整, 且药物确已被包裹在微球中, 微球的平均粒径为280.80±0.15 μm, 粒径在250-390 μm之间的占总数的90%以上. 包封率为68.5%±0.58, 载药量为34.1%±0.51,环丙沙星微球的体外释药情况为53.2小时的累积释药量为84.0%,T1/2为31.9 h, Higuchi方程为Q=-0.004 3 0.003 9 t1/2,r=0.994 1.结论本研究获得了较满意的制备环丙沙星聚乳酸微球的工艺, 且微球的体外释药性能具有明显的缓释效果.     

Effects of (+)-tubocurarine on [3H]acetylcholine release from the rat phrenic nerve at different stimulation frequencies and train lengths

Summary The effect of (+)-tubocurarine (TC) on the release of [³H]acetylcholine from the rat phrenic nerve-hemidiaphragm preincubated with [3H]choline was investigated at different stimulation frequencies and train lengths.At 0.5 Hz (100 pulses) TC failed to modulate the evoked acetylcholine release. A slight (30%) inhibition was observed at 1 Hz (100 pulses). Release of acetylcholine evoked at 5, 25 and 50 Hz (100 pulses) or 100 Hz (200 pulses) was markedly reduced by TC. The degree of inhibition (60%) was similar between 5 Hz and 100 Hz. A concentration of 1 mol/l TC was a maximal effective concentration at 5 Hz whilst at all higher stimulation frequencies a 10-fold higher concentration was necessary for the maximal effect. When 300 pulses were continuously applied at 5 Hz or 50 Hz TC caused only a slight inhibition (20%). Additionally, the phrenic nerve was stimulated intermittently. Trains of 15 pulses were repeated 10 times with an interval of 3 s between each train. Under this latter stimulation condition TC failed to reduce acetylcholine release.It is concluded that nicotinic autofacilitation of acetylcholine release from the motor nerve operates at frequencies and stimulation conditions similar to the pattern of nerve activity under in vivo conditions. At least more than 15 pulses are required before the nicotinic autofacilitation becomes apparent. It appears unlikely that the TC induced fading of end-organ responses can only be attributed to a blockade of the presynaptic nicotine receptors. Send offprint requests to I. Wessler at the above address     

Neurotensin: contractile activity, specific binding, and lack of effect on cyclic nucleotides in intestinal smooth muscle.

Nuerotensin contracted the isolated longitudinal smooth muscle strip of the guinea-pig intestine. It induced a biphasic response (relaxation followed by contraction) when the muscle was contracted by histamine. Tetrodotoxin blocked the contraction and the contraction phase of the biphasic response. Dose responses of the relaxing effect of neurotensin and its analogs D-Arg8-neurotensin and D-Arg 9-neurotensin on tetrodotoxin-treated muscle gave EC50 values of 5 nM, 5.5 nM and 110 nM for the three peptides, respectively. [3H]Neurotensin bound specifically to membranes prepared from isolated longitudinal muscle strips of the guinea-pig intestine. In binding studies using [3H]neurotensin and unlabelled peptides, the KDs of neurotensin, D-Arg 8-neurotensin and D-Arg9 neurotensin were 4 nM, 2 nM and 300 nM, respectively, values which are in close agreement with the EC50 of the three peptides. Neurotensin had no effect on the cAMP and cGMP contents in longitudinal intestinal muscle strips of the guinea pig, an observation which suggests that cyclic nucleotides are not involved in the mechanism of action of neurotensin in this muscle preparation.     

Release of acetylcholine and its dopaminergic control in slices from striatal grafts in the ibotenic acid-lesioned rat striatum

Summary Tritium accumulation during incubation with ³-H-choline, and the efflux as well as the electrically evoked overflow of tritium during subsequent superfusion, were investigated in slices from unilateral striatal suspension grafts 16 to 20 weeks after implantation into the previously ibotenic acid-lesioned rat striatum. Slices from non-operated animals, from striata contralateral to grafts, and from animals with acute ibotenic acid lesions of the striatum were studied in parallel. The accumulation of tritium and the overflow of tritium in response to electrical stimulation (2 min, 3 Hz) were markedly impaired in acutely lesioned striata. In graft slices, tritium accumulation and the subsequent electrically evoked overflow were greater than in slices obtained after acute lesions, but were still smaller than in non-operated animals or in the contralateral striata. The dopamine D₂-receptor agonist quinpirole inhibited the electrically evoked overflow of tritium in grafts, but only to a small extent. The D₂-receptor antagonist sulpiride increased, whereas the dopamine uptake inhibitor nomifensine and the dopamine releasing drug amphetamine decreased the evoked overflow in slices from non-operated rats and from striata contralateral to grafts, but had no significant effect in grafts. As in graft slices, the release of acetylcholine in striata from animals in which the mesostriatal dopamine pathway had been lesioned by 6-hydroxy-dopamine was not changed by sulpiride and amphetamine, and was only minimally decreased by nomifensine. Our data show that striato-striatal grafts can partly restore the impaired choline accumulation and acetylcholine release in excitotoxinlesioned striata. Functional D₂-receptors are present on graft cholinergic cells, but are not activated by endogenous dopamine under the present in vitro conditions. Send offprint requests to T. Wichmann at the above address     

Effects of Membrane Type and Liquid/Liquid Phase Boundary on In Vitro Release of Ketoprofen from Gel Formulations

The aim of this study was to test the hypothesis that the most appropriate model for studying the diffusional release of an active from a topical formulation is one in which the membrane offers minimal resistance to release and involves a receptor phase that presents the least possible interfacial discontinuity. Using ketoprofen as the active, a series of simple gels were prepared consisting of PEG400 thickened with Cabosil M5. Using Franz-type diffusion cells, three different types of membrane (two porous and one non-porous) were compared, as were receptor phases of PEG400 (component of formulation) and PBS. Of the membranes tested only 0.2 μm nylon provided consistent first order kinetics for a range of gel consistencies, indicating negligible influence of the membrane. The non-porous silicone membrane did not show first order kinetic profile confirming the diffusional nature of such a membrane. From the non-thickened formulations, diffusional release into a receptor phase of PEG400 was some 3× that into PBS, whereas from the formulation thickened with 5% Cabosil_® M5, diffusional release into a receptor phase of PEG400 was 6× lower than that into PBS. Diffusional release into PBS did not follow first order kinetics while diffusion into PEG400 did, suggesting that the existence of a discontinuity affected the release process. Although the importance of zero-resistance membranes is of perhaps obvious importance, it is often not stated in the literature. The existence of phase/hydrodynamic boundaries in release studies can be a source of significant inaccuracy.     

Effects of 2.5 s mouse nerve growth factor on regeneration of injured sciatic nerves in mice and rats

目的：证实ＮＧＦ促进坐骨神经再生的作用．方法：夹断小鼠和大鼠坐骨神经轴索，测再生轴索计数及分类，在比目鱼肌远（Ｄｉｓ）、近（Ｐｒｏ）端测神经肌肉电潜伏期（ＮＭＥＰＬ）．结果：小鼠ＮＧＦｉｍ０５－１ｋＢＵ·ｋｇ－１２０ｄ增加轴索再生率，２－４ｋＢＵ·ｋｇ－１减轻比目鱼肌萎缩．大鼠ＮＧＦｉｍ１（４０ｄ），２（３０和４０ｄ），４（２０，３０，４０ｄ）ｋＢＵ·ｋｇ－１均显著增加损伤神经的轴索再生率；高、中剂量增加粗轴索计数；各剂量均缩短ＤｉｓＮＭＥＰＬ（２０ｄ，３０ｄ）和ＰｒｏＮＭＥＰＬ（４０ｄ）；高剂量在各时点使两者均缩短．结论：ＮＧＦｉｍ明显促进大鼠和小鼠坐骨神经损伤后再生并减轻骨骼肌萎缩．     

Effects of Cholinergic Drugs and Imidazole on Ca Release and Cyclic AMP Formation in Microsomal Fractions from Rabbit Colon

Abstract Following the addition of carbachol or acetylcholine to microsomal fractions isolated from rabbit colon which were preloaded with Ca, the ions were rapidly released. In the 35-45% fraction Ca was completely released within 10 min., but in the 35 % fraction only 30 % was released. Carbachol reduced the adenylate cyclase activity of the 35-45 % fraction. Both these effects were blocked by atropine. Exogenous cyclic AMP completely inhibited the Ca-releasing action of carbachol in the 35 % fraction and markedly reduced it in the 35-45 % fraction. Imidazole released Ca from the 35-45 % fraction and stimulated its phosphodiesterase activity. It is suggested that the microsomal fractions are parts of a Ca-sequestering system in smooth muscle which are able to bind Ca and which on the addition of some contracting drugs release the ions and thereby activate the contractile system. The release of Ca may partly at least be due to a reduction of the adenylate cyclase activity, although other mechanisms must also be considered.     

Effects of the Method of Preparation on the Compression,Mechanical, and Release Properties of Khaya Gum Matrices

A study has been made of the compression properties of khaya gum matrices and the effects of drug concentration and method of preparation of the material on the compression, mechanical and the drug release characteristics of the matrices. Khaya gum matrix tablets were prepared by direct compression and wet granulation methods. The compression properties of the formulations were assessed using the equations of Heckel and Kawakita. The mechanical properties of the tablets were evaluated using crushing strength and friability of the tablets, whereas the release properties of the tablets were evaluated by using the disintegration and dissolution times. The results obtained show that khaya gum deformed mainly by plastic deformation. The compression properties of the formulations were affected by the concentration of the drug and the method of preparation of the materials for compression. Tablets prepared by wet granulation showed faster onset and higher amount of plastic deformation during compression than those prepared by direct compression. Tablets containing dicalcium phosphate showed higher mechanical strength and disintegration and dissolution times. Wet granulation also increased the mechanical strength of the tablet without significantly affecting the drug release characteristics from the matrix tablets. Thus, the wet granulation method could be useful in the preparation of khaya gum matrix tablet with acceptable mechanical properties and drug release properties.     

氨酚氯雷伪麻缓释片的制备及其体外释放度的研究

目的研制亲水凝胶骨架型氨酚氯雷伪麻缓释片,并考察其体外释放度。方法采用湿法制粒工艺,以羟丙基甲基纤维素(HPMC)为缓释骨架材料,制备了氨酚氯雷伪麻缓释片。以对乙酰氨基酚的体外释放度为考察指标,通过正交试验筛选出最佳处方,并考察了原料药粒径、HPMC和碳酸氢钙的用量、颗粒水分和制片压力对缓释片中对乙酰氨基酚体外释放速率的影响。结果原料药粒径、HPMC用量、颗粒水分和制片压力对氨酚氯雷伪麻缓释片体外释放速率有明显的影响;碳酸钙用量对释放速率基本无影响。结论按优化处方制备的氨酚氯雷伪麻缓释片缓释效果明显,符合相关规定,可应用于工业化大生产。     

Comparison of potency of substance P and related peptides on [3H]-acetylcholine release,and contractile actions,in the guinea-pig ileum

Summary A range of tachykinins including substance P were studied for their ability to contract the guinea-pig ileum longitudinal muscle preparation on brief exposure (20 s) to the peptides, and their ability to evoke the release of [³H]-acetylcholine (ACh) from previously labelled stores within the myenteric plexus. With respect to their immediate spasmogenic activity, none of the peptides differed greatly in potency from substance P. Atropine did not modify the response to the tachykinins suggesting that the release of ACh does not contribute to the contraction resulting from brief exposure to the peptides. In the release studies, all tachykinins used produced a dose-related, calcium-dependent release of [³H]-ACh but the differences in potency were much greater. Eledoisin was the most potent and its evoked release of ACh was unaffected by hyoscine, hexamethonium, guanethidine and naloxone suggesting the release is not mediated via, or modulated by, opiate or autonomic neuronal influences. The two orders of tachykinin potency found suggest that the two processes, initial contraction and ACh release, may be principally mediated via two distinct subclasses of substance P receptor designated SP-P and SP-E respectively.     

Influence of Plasticization Time,Curing Conditions,Storage Time,and Core Properties on the Drug Release from Aquacoat-Coated Pellets

Theophylline or chlorpheniramine maleate pellets were coated with an aqueous ethylcellulose dispersion, Aquacoat. The influence of the plasticization time, curing conditions, storage time, and core properties on the drug release were investigated. The plasticization time (time between plasticizer addition to the polymer dispersion and the spraying process) did not affect the drug release, when the water-soluble plasticizer, triethyl citrate, was used because of its rapid uptake by the colloidal polymer particles. In contrast, with the water-insoluble plasticizer, acetyltributyl citrate (ATBC), plasticization time (1/2 h vs 24 h) influenced the drug release, the longer plasticization time resulted in a slower drug release because of a more complete plasticizer uptake prior to the coating step. However, a thermal aftertreatment of the coated pellets at elevated temperatures (curing step) reduced/eliminated the effect of the plasticization time with ATBC. In general, curing reduced the drug release and resulted in stable drug release profiles. The time period between the coating and the curing step was not critical when the pellets were cured for a longer time. The structure of the pellet core (high dose matrix vs low dose layered pellet) strongly affected the drug release. A slow, zero-order drug release was obtained with high dose theophylline pellets, while a more rapid, first-order release pattern was obtained with low dose theophylline-layered nonpareil pellets.     

Effects of cromakalim on acetylcholine release and smooth muscle contraction in guinea-pig small intestine

Summary The effects of the potassium channel opener cromakalim on smooth muscle contraction and ³H-acetylcholine release were studied simultaneously in guinea-pig longitudinal muscle myenteric plexus preparations which had been preincubated with ³H-choline. Cromakalim (10 mol/1) inhibited more markedly the smooth muscle contractions caused by the release of endogenous acetylcholine (via electrical stimulation or via activation of nicotine- and 5-HT₃-receptors) than contractions induced by pilocarpine. Cromakalim (10 ~mol/1) did not affect the release of ³Hacetylcholine evoked by electrical stimulation or by stimulation of nicotine- and 5-HT₃-receptors. In contrast, the release of ³H-acetylcholine caused by stimulation of M₁-receptors was concentration-dependently reduced by cromakalim (1–100 gmol/1). The results suggest that the relaxant effect of cromakalim on smooth muscle contraction is not caused by a reduction of acetylcholine release from myenteric neurones. An opening of cromakalim-sensitive potassium channels may be involved in the inhibition of the M₁-receptor mediated acetylcholine release.This work was supported by the Deutsche Forschungsgemeinschaft (Ki 210/6-3). Send offprint requests to H. Schwörer at the above address