四肽FMRFa对大鼠心室肌Na+/Ca2+交换的抑制

目的　研究四肽FMRFa对大鼠单个心室肌细胞Na⁺/Ca²⁺交换的作用。方法　用膜片钳全细胞记录法测定成年大鼠心室肌细胞Na⁺/Ca²⁺交换电流(I_Na⁺/Ca²⁺)和其他离子通道电流。结果　FMRFa对大鼠心室肌细胞I_Na⁺/Ca²⁺呈浓度依赖性抑制,100μmol·L^-1浓度时抑制内向和外向I_Na⁺/Ca²⁺密度分别达60.1%和56.5%,对内向电流及外向电流的IC₅₀分别为20μmol·L^-1和34μmol·L^-1。FMRFa5μmol·L^-1抑制I_Na⁺/Ca²⁺内向和外向电流密度分别为38.7%和34.9%,但FMRFa5μmol·L^-1及20μmol·L^-1对L型钙电流、钠电流、瞬时外向电流和内向整流钾电流均无显著抑制作用。结论　FMRFa对大鼠心室肌细胞是一个特异性Na⁺/Ca²⁺交换抑制剂。     

(-)-S·R-蝙蝠葛苏林碱对谷氨酸引起的大鼠大脑皮质神经元损伤的保护作用

用细胞培养方法,在原代培养的大鼠皮质神经细胞上,观察了(-)-S·R-蝙蝠葛苏林碱对谷氨酸引起的神经元损伤的保护作用。以Fura-2/AM为Ca²⁺的荧光指示剂,用AR-CM-MIC阳离子测定系统观察(-)-S·R-蝙蝠葛苏林碱对谷氨酸诱发大鼠脑皮质神经细胞内Ca²⁺升高的影响。结果表明(-)-S·R-蝙蝠葛苏林碱能剂量依赖性地抑制谷氨酸的神经毒作用,对谷氨酸诱发的神经细胞内游离Ca²⁺升高有明显的抑制作用。提示蝙蝠葛苏林碱对缺血性脑损伤有保护作用。     

环维黄杨星D对分离大鼠心室肌细胞内Ca2+和L型钙电流的影响

目的研究环维黄杨星D（CD）对大鼠心室肌细胞内Ca²⁺动员和L型钙电流(I_{Ca-L/sub>)的影响。方法采用全细胞膜片钳和激光扫描共聚焦显微术研究CD对心肌细胞ICa-L/sub>以及氯化钾、咖啡因诱发心肌细胞内Ca²⁺动员的影响。结果CD浓度依赖性抑制ICa-L/sub>。指令电压为10 mV时，1和10 μmol·L^-1 CD分别使ICa-L/sub>电流密度从（-9.9±1.8）pA/pF降至（-6.4±1.4）pA/pF和（-4.2±0.6）pA/pF。共聚焦实验显示1和10 μmol·L^-1 CD不影响静息心肌细胞［Ca²⁺］i?/sub>，对氯化钾诱发［Ca²⁺］i?/sub>升高水平无明显抑制作用；咖啡因引起的细胞内Ca²⁺动员可被CD进一步增强。结论CD浓度依赖性抑制大鼠心室肌细胞ICa-L/sub>，并有促进咖啡因诱发心肌细胞内Ca²⁺释放的作用。}     

锰对神经肌肉接头传递的作用

用大鼠隔神经隔肌、小鸡颈二腹肌和蟾蜍腹直肌标本研究了硫酸锰对神经肌肉传递的作用。结果表明，锰对间接或直接刺激引起的肌肉收缩均产生可逆性、浓度依赖性的抑制作用。对间接刺激的ＩＣ５０为０．２８ｍｍｏｌ／Ｌ，对直接刺激的ＩＣ５０。为１０ｍｍｏｌ／Ｌ；对间接刺激肌收缩抑制５０％的时间是４．３±１．０ｍｉｎ。高钙溶液能部分拮抗锰的抑制作用。锰使小鸡颈二腹肌标本对ＡＣｈ的敏感性降低，使ＡＣｈ对蟾蜍腹直肌收缩的量效曲线非平行右移，ｐＤ２＇为２、６２。提示锰不仅作用于突触前膜，对突触后膜亦有抑制作用。     

用Fura-2测定突触体内游离Ca2+浓度及Ca2+通道激动剂和阻断剂的影响

用Fura-2测定大鼠突触体内游离Ca²⁺浓度,探讨Ca²⁺通道激动剂和阻断剂对突触体内钙浓度的影响。测得突触体内Ca²⁺浓度为200～400 nmol/L。观察了不同浓度KCl,CaCl₂,NMDA和谷氨酸对突触体内Ca²⁺增加的影响以及维拉帕米及MgCl₂对KCl和NMDA引起钙内流的阻断作用。本实验提供一个研究突触体内Ca²⁺变化的准确而稳定的方法,并对测定中几个影响因素加以讨论。     

可乐定镇痛与中枢Ca2+的关系

用大鼠甩尾法和放射配基结合实验,探讨了可乐定镇痛与中枢Ca²⁺的关系。CaCl₂(1μmol/rat,icv)和EGTA(0.2μmol/rat,icv)分别拮抗和增强可乐定(1mg/kg,sc)的镇痛。戊脉安(0.1μmol/rat,icy)对可乐定(1 mg/kg,sc)镇痛无明显影响,但可部分翻转CaCl₂对可乐定镇痛的拮抗。CaCl₂(1×10^-3mol)对[³H]-可乐定结合无明显抑制。结果表明可乐定镇痛与脑室周围组织中Ca²⁺浓度变化密切相关,Ca²⁺至少部分需经对戊脉安敏感的钙通道进入细胞内方可拮抗可乐定镇痛。推沦:可乐定镇痛与神经元内Ca²⁺有关。     

蚓激酶的心肌保护作用及机制

目的研究蚓激酶对心肌缺血的保护作用，并进一步探讨其可能机制。方法采用结扎大鼠左冠状动脉前降支制备急性心肌缺血模型，观察蚓激酶对心肌缺血的保护作用；应用全细胞膜片钳和激光扫描共聚焦技术，研究蚓激酶对L-型钙电流(I_Ca-L)和细胞内游离钙离子浓度的影响。结果蚓激酶80，40和20 mg·kg^-1剂量组均可缩小心肌梗死面积。膜片钳研究结果表明，当刺激电压为+10 mV时，10和50 μmol·L^-1蚓激酶使I_Ca-L降低共聚焦结果显示，在静息状态下，10 μmol·L^-1蚓激酶对［Ca²⁺］_i无明显影响；但10 μmol·L^-1蚓激酶对60 mmol·L^-1 KCl诱导的［Ca²⁺］_i升高却有明显抑制作用，并且在整个实验过程中(240 s)并未出现明显的峰值。结论蚓激酶对大鼠心肌缺血具有保护作用，其机制可能与抑制I_Ca-L及下调［Ca²⁺］_i有关。     

赛庚啶对离体犬心肌肌质网Ca2+,Mg2+—ATP酶活性和45Ca2+摄取功能的影响

当赛庚啶浓度在8×10^-6mol/L～2×10^-4mol/L之间时,该药对正常犬心肌肌质网Ca²⁺,Mg²⁺—ATP酶活性几乎没有影响,仅在10^-3mol/L时对该酶活性才有一定的抑制作用(抑制率为39.85%,P<0.01)。正常犬心肌肌质网的⁴⁵Ca²⁺摄取过程有明显的时间依赖性,至第30 min,其⁴⁵Ca²⁺摄取量可达312.79±22.25 nmol/mg protein.赛庚啶对心肌肌质网的~(45)Ca²⁺摄取有一定的抑制作用,其IC₅₀为1.94×10^-4mol/L。     

D-半乳糖衰老模型观察的新指标

目的　观察D-半乳糖衰老模型与正常小鼠之间衰老指标的差别。方法　采用D 半乳糖sc造成衰老小鼠模型,测定脑组织Ca²⁺含量、Ca²⁺-ATP酶(钙泵)、Na⁺-ATP酶(钠泵)、NO和AngII胰岛素(ISN)活性。结果　D-半乳糖衰老模型小鼠与对照组比较脑组织Ca²⁺含量(P<0.01)、NO水平(P<0.05)明显增加;Ca²⁺-ATP酶、Na⁺-ATP酶活性下降(P<0.01) ,胰岛素、AngII水平明显下降(P<0.01) ,Zn²⁺/Cu²⁺比值有显著性差异。结论　D-半乳糖衰老模型小鼠与正常小鼠之间在组织Ca²⁺含量、Ca²⁺-ATP酶(钙泵)、Na⁺-ATP酶(钠泵)、NO、AngII和胰岛素活性有显著性差异,Zn²⁺/Cu²⁺比值下降,可作为抗衰老药物研究的模型。     

nNOS抑制剂亚胺基烯丁基-L-鸟氨酸对心肌缺血再灌注损伤的影响及机制

目的 探讨nNOS选择性抑制剂亚胺基烯丁基-L-鸟氨酸（L-VNIO）对心肌缺血再灌注（I/R）损伤的影响及机制。方法 构建SD大鼠离体心脏I/R模型和H9c2细胞缺氧/复氧（H/R）模型；nNOS抑制剂L-VNIO（10 μmol·L^-1）持续给药整个再灌注或复氧过程。TTC染色测定心肌梗死面积；流式细胞术检测H9c2细胞凋亡率；Fluo-3/AM Ca²⁺荧光探针通过流式细胞仪检测H9c2细胞内Ca²⁺浓度；试剂盒法测定离体心脏灌流液乳酸脱氢酶（LDH）、丙二醛（MDA）水平以及H9c2细胞MDA水平和超氧化物歧化酶（SOD）活性；离体心脏提取肌浆网，试剂盒法检测肌浆网Ca²⁺-ATP酶（SERCA）活性，Western blotting检测肌浆网SERCA蛋白表达；Western blotting检测离体心脏中受磷蛋白（PLB）和兰尼碱受体2（RyR2）蛋白表达水平和磷酸化水平。结果 与I/R或H/R模型组相比，L-VNIO显著降低细胞凋亡率，减少心肌梗死面积，降低LDH、MDA水平，提高SOD活性，差异均有统计学意义（P<0.05）；此外，与I/R或H/R模型组相比，L-VNIO组明显降低细胞内Ca²⁺超载，增高PLB磷酸化水平，降低RyR2磷酸化水平，增强SERCA活性（P<0.05）。结论 nNOS抑制剂L-VNIO可以减轻I/R损伤，机制与调节Ca²⁺转运相关蛋白而降低I/R引起的Ca²⁺超载相关。     

The actions of aminopyridines on avian muscle

Summary The effects of 2-, 3-, and 4-aminopyridines were investigated on the isolated chick biventer cervicis nerve-muscle preparation and on nerve-free cell cultures of embryonic chick skeletal muscle. All 3 compounds reversed tubocurarine blockade and augmented twitch height in indirectly stimulated biventer cervicis preparations. 4-Aminopyridine was approximately 10 times more potent than 2-, or 3-aminopyridine. Twitch augmentation was also seen in directly stimulated preparations but to a much lesser extent. The compounds did not have significant anticholinesterase activity, nor did they have any depolarizing activity when tested on nerve-free cultured muscle fibres. At high concentrations the aminopyridines produced a maintained contracture in the biventer preparations which was enhanced by neostigmine and inhibited by tubocurarine. It is suggested that the aminopyridines facilitate neuromuscular transmission by increasing acetylcholine release in response to nerve stimulation, and that the compounds can also increase spontaneous transmitter release.     

Pharmacological studies on the bungarotoxins: an analysis of the site of action of nicotinic agonists

The possibility that nicotinin agonists may exert an indirect action by releasing endogenous acetylcholine from nerve terminals has been examined by the use of nerve-free cultured muscle, and by the use of the specifically prejunctionally active β-type bungarotoxins.In cultured muscle the depolarizations produced by acetylcholine and carbachol were not greatly affected by treatment of the cultures with β-type bungarotoxins for 60 min.In the chick biventer cervicis nerve-muscle preparations dose-response curves to acetylcholine, carbachol, dimethylphenylpiperazinium and nicotine were not affected even after abolition of responses to nerve stimulation by the β-types toxins.As the responses to nicotinic agonists were obtainable in nerve-free muscle and were unimpaired in the chick biventer after elimination of nerve function by β-type bungarotoxins, we conclude that such agonists exert a direct action on the postjunctional acetylcholine receptors.     

碘化二甲基木防己碱对神经肌肉接头传递的作用

碘化二甲基木防己碱(dimethyltrilobine iodide简称DTI)有降压作用,抗心律失常作用和骨骼肌松驰作用。本文采用离体大白鼠膈神经膈肌和小鸡颈二腹肌标本,进一步观察了DTI对神经肌肉系统的作用,并对其作用机制作了初步分析。选体重250～350 g大白鼠,按文献方法制备离体膈神经膈肌标本,固定在含循环Tyrode液的肌槽中,用JSD-731-C型刺激器,超强方波脉冲(波宽0.2ms,频率6/min)刺激膈神经,膈肌收缩用XWT-204型平衡记录仪描记。     

Neuromuscular effects of three phospholipases A2 from the venom of the Australian king brown snake Pseudechis australis

Three single chain phospholipases A2 (Pa-10A, Pa-11 and Pa-13) isolated from Australian king brown snake (Pseudechis australis) venom were tested for effects on neuromuscular transmission and muscle contractility on chick biventer cervicis and mouse diaphragm preparations. At 1 microgram/ml (about 85 nM) and higher, Pa-10A and Pa-11 reduced responses of both preparations to indirect stimulation in a concentration-dependent manner. Responses to direct muscle stimulation were generally reduced more slowly. Pa-11 also decreased membrane potentials of chick biventer muscle fibres and caused damage visible by light microscopy. Pa-13, which is about 50 times less active as a phospholipase A2, was also less potent in its pharmacological effects: 20 micrograms Pa-13 per ml were required to reduce responses of either preparation. The phospholipases A2 also caused a slow contracture. After block of responses to nerve stimulation, responses of the chick preparation to acetylcholine, carbachol and KCl could be obtained, although they were smaller than control and highly variable in different preparations. It is concluded that Pa-10A and Pa-11 produce muscle paralysis by reducing acetylcholine release and by a direct blockade of muscle fibre contractility. Pa-13 has similar, though less pronounced, activities.     

Neuromuscular effects of a toxic phospholipase A2 and its nontoxic homologue from the venom of the sea snake, Laticauda colubrina

A single chain phospholipase A2 (LcPLA-II) and a homologous protein lacking enzymatic activity (LcPLH-I) isolated from the venom of the Solomon Island sea snake (Laticauda colubrina) were tested for effects on neuromuscular transmission and muscle contractility on chick biventer cervicis and mouse hemidiaphragm preparations. LcPLA-II (7.5 nM-1.5 microM) blocked indirectly elicited muscle contractions of both preparations. Low concentrations of LcPLA-II caused little change in sensitivity to acetylcholine, carbachol and KCl. The homologue LcPLH-I (375 nM-1.5 microM) reduced the responses of the biventer cervicis preparation to indirect stimulation and abolished responses to acetylcholine and carbachol, but it did not block KCl responses. These effects were due to minor contamination by a post-junctional neurotoxin. LcPLH-I (375 nM-750 nM) had no effect on indirectly stimulated hemidiaphragm preparations. It is concluded that LcPLA-II blocks neuromuscular transmission by a prejunctional action, and that the homologue lacking phospholipase A2 activity also lacks neuromuscular activity.     

Pharmacological analysis of the neuromuscular properties of diethylcarbamazine citrate in vitro

The actions of diethylcarbamazine citrate (DECC) have been examined on agonist- and electrically-induced contractures and twitches of the isolated chick biventer cervicis and rat phrenic nerve-hemidiaphragm muscle preparations in order to analyse the effects of this commonly-prescribed anthelmintic drug at the neuromuscular junction. DECC (5 x 10(-1)-1.5 mM) produced a concentration-dependent initial augmentation of the indirect electrically-evoked twitches followed by a sustained, longer-lasting secondary depression of the twitches of all the skeletal muscle-nerve preparations examined. The DECC-induced twitch depression was competitively reversed by increasing the bathing fluid calcium ion concentration (Ca2+). DECC (10(-3)-2.5 x 10(-2) M) caused marked augmentation of the contractural responses of innervated chick biventer muscle preparations induced by bath-applied low concentrations of carbachol, acetylcholine or nicotine, and depressed those contractural responses of the muscle elicited by hgh concentrations of the agonists. On their own accord, high concentrations of DECC (10(-1)-2.5 mM) dose-dependently contracted isolated chick biventer cervicis muscle preparations, and demonstrated measurable anticholinesterase activity. It is concluded that DECC has both direct (post-junctional) and indirect (pre-junctional) effects at the neuromuscular junction, and that the neuromuscular blockade produced by this anthelmintic agent is probably post-junctional in origin.     

金环蛇(Bungarus fasciatus)蛇毒的分离及其毒性组分的药理研究

金环蛇毒用羧甲基纤维素柱层析分离出17个蛋白组分,其中5个组分是毒性较大的致死成分。在这5个组分中,Ⅺ、Ⅻ、ⅩⅤ是心脏毒,ⅩⅢ、ⅩⅣ是神经毒。心脏毒组分Ⅺ、ⅫⅩⅤ使离体大鼠心脏挛缩,心跳停止于收缩期;使小鸡离体颈二腹肌挛缩,最后致痉挛性麻痹;对兔眼结合膜有局部刺激作用,使结合膜充血水肿。组分ⅩⅤ还具有直接溶血作用。神经毒组分ⅩⅢ阻断大鼠、小鸡、青蛙神经肌肉标本的突触传递,标本对乙酰胆碱的反应消失,对直接刺激以及对高浓度氯化钾的反应无减少,神经末梢乙酰胆碱的释放最无显著改变;使蛙腹直肌乙酰胆碱量效曲线平行右移,新斯的明可以对抗这个作用。组分ⅩⅣ的作用与组分ⅩⅢ相似。实验提示,组分ⅩⅢ、ⅩⅣ是作用于终板后膜的神经毒。     

Actions of 4-methyl-2-aminopyridine on neuromuscular transmission and contractility of skeletal muscle

4-Methyl-2-aminopyridine (4M2AP) increased responses of isolated rat diaphragm and chick biventer cervicis nerve-muscle preparations to nerve stimulation but depressed responses to direct stimulation. Responses to acetylcholine were also increased while responses to carbachol were depressed. When tested after inhibition of acetylcholinesterase activity with neostigmine the effect of 4M2AP on responses to indirect stimulation was greatly reduced and responses to acetylcholine were depressed. It is concluded that, in contrast to other aminopyridines, 4M2AP facilitates neuromuscular transmission by inhibition of cholinesterase rather than augmenting release of acetylcholine and depresses rather than enhances muscles contractility.     

Effects of the venom of the green mamba, Dendroaspis angusticeps on skeletal muscle and neuromuscular transmission.

1 The venom of the green mamba, Dendroaspis angusticeps, was tested for effects on neuromuscular transmission and skeletal muscle contractility in isolated phrenic nerve-hemidiaphragm preparations of the rat and mouse, chick biventer cervicis muscle preparations and in aneural cultures of embryonic chick skeletal muscle. 2 The venom (10 to 40 micrograms/ml) augmented the responses to indirect but not direct stimulation. As the venom did not have anticholinesterase activity and did not increase receptor sensitivity, it is likely that the venom enhanced release of acetylcholine. 3 Higher concentrations of venom (40 to 80 micrograms/ml) inhibited acetylcholine receptor sensitivity. 4 Prolonged exposure to the higher concentrations of venom produced a failure of muscle contractility. Signs of muscle degeneration were seen in skeletal muscle cultures.     

Modulation of acetylcholine release at mouse neuromuscular junctions by interaction of three homologous scorpion toxins with K+ channels.

1. The effects of three scorpion toxins, charybdotoxin (CTX), iberiotoxin (IbTX), and noxiustoxin (NTX) have been studied on acetylcholine release and on K+ channels by means of twitch tension and electrophysiological recording techniques using isolated skeletal muscle preparations and by a radioligand binding assay using 125I-labelled dendrotoxin I (DpI) and rat brain synaptosomal membranes. 2. On chick biventer cervicis preparations, CTX and IbTX (125 nM) augmented the twitch responses to indirect muscle stimulation. Further, the increase (about 70-80% of control twitch height) was fast in onset, reaching a maximum within 25-30 min. NTX at 125 nM produced a slower augmentation of the twitch responses to indirect muscle stimulation, with the maximum response being seen after 40-50 min. 3. On mouse triangularis sterni preparations, CTX (300 nM after 35-40 min) and IbTX (100 nM after 15 min) increased quantal content of the evoked endplate potentials (e.p.p.) by about two fold. However, NTX (300 nM) caused only a small increase in e.p.p. amplitude, which was followed by repetitive e.p.ps in response to single shock nerve stimulation after 40-50 min. 4. Extracellular recording of nerve terminal current waveforms in triangularis sterni preparations revealed that CTX and IbTX (3-100 nM), but not NTX (100 nM), blocked the Ca(2+)-activated K+ current, IK-Ca. However, there was no major change in the portion of the nerve terminal waveform associated with voltage-dependent K+ currents, IKv. 5. In the radioligand binding assay, NTX potently displaced labelled [125I]-DpI, whereas CTX produced only partial displacement.(ABSTRACT TRUNCATED AT 250 WORDS)