前胡丙素对高血压大鼠血压及犬血管阻力的影响

目的　观察前胡丙素(pra C)的降压及对外周血管阻力的影响。方法　在肾型高血压大鼠模型与正常血压大鼠用尾容积法测血压。用RDB III型输液泵连接于麻醉杂种犬,以控制血流量与压力法直接测定锥动脉、冠脉左旋支、股动脉的阻力。结果　pra-C 20 mg·kg^-1·d^-1 ig给药3 0d对肾性高血压大鼠(RHR)降压峰值时间为6h ,从(213±10 )mmHg降至(144.0±1.5)mmHg,降低原水平30% ,持续至20h。pra-C分别以100 μg·kg^-1 及20 μg·kg^-1与pra-E 20 μg·kg^-1iv可降低上述血管的阻力,减慢心率,降低阻力呈剂量相关。结论　pra-C有降压作用,降低犬外周动脉阻力,增加小鼠耐缺氧时间。     

γ-羟基丁酸受体在大鼠局灶性脑缺血再灌注损伤中的作用

研究γ-羟基丁酸(gamma-hydroxybutyric acid，GHB)受体在大鼠局灶性脑缺血再灌注损伤中的作用及其机制。选用GHB受体选择性激动剂NCS-356和特异性拮抗剂NCS-382作为工具药，采用改良的Longa法制备大鼠大脑中动脉栓塞(MCAO)模型。缺血2 h再灌注2 h后，动物进行Longa法行为功能评分；再灌注24 h后，部分动物用TTC染色法测定大鼠脑梗死体积；部分动物应用流式细胞仪测定神经细胞内游离钙离子浓度；分光光度法测定缺血侧大脑皮质中总一氧化氮合酶(tNOS)、诱导型一氧化氮合酶(iNOS)活性和一氧化氮(NO)含量；放射免疫法测定大鼠缺血侧大脑皮层环磷酸鸟苷(cGMP)含量。Isc/R组大鼠行为功能评分、脑梗死体积、神经细胞内游离Ca²⁺浓度、cGMP和NO含量、tNOS及iNOS活性均显著高于假手术组；NCS-356 160 μg·kg^-1(N₁)、NCS-356 320 μg·kg^-1(N₂)、 NCS-356 640 μg·kg^-1(N₃)和尼莫地平600 μg·kg^-1(Nim)组的上述各指标均不同程度地低于Isc/R组，而NCS-382 640 μg·kg^-1+NCS-356 640 μg·kg^-1 (NCS-382+N₃)组则能显著对抗N₃组的作用。激动GHB受体对大鼠局灶性脑缺血再灌注损伤具有一定的保护作用，其作用机制可能与降低神经细胞内游离Ca²⁺浓度，减少NO及cGMP含量有关。     

脑5-HT1A/1B、α2受体及腺苷酸环化酶参与了胍丁胺的抗抑郁作用

为了在单胺受体及受体后腺苷酸环化酶(adenylate cyclase,AC)水平探讨胍丁胺(agmatine,AGM)抗抑郁作用的精细机制,采用小鼠悬尾实验和强迫游泳实验观察AGM抗抑郁行为改变。采用放射免疫方法测定大鼠前额皮层突触膜蛋白AC活性。结果表明,AGM(5～40 mg·kg^-1,ig)在小鼠悬尾实验和强迫游泳实验模型上均有显著抗抑郁活性。同时伍用β受体/5-HT_1A/1B受体阻断剂吲哚洛尔(pindolol, PIN, 20 mg·kg^-1, ip)、 α₂肾上腺素受体拮抗剂育亨宾(yohimbine, YOH, 5～10 mg·kg^-1, ip)或咪唑克生(idazoxan, IDA, 4 mg·kg^-1, ip)对AGM(40 mg·kg^-1, ig)的抗抑郁活性具有显著拮抗效应; 而β受体阻断剂普萘洛尔(propranolol, PRO, 5～20 mg·kg^-1, ip)或5-HT₃受体拮抗剂曲匹西隆(tropisetron, TRO, 5～40 mg·kg^-1, ip)对AGM(40 mg·kg^-1, ig)的抗抑郁活性无显著影响。AGM(0.1～6.4 μmol·L^-1)与大鼠前额皮层提取的突触膜共孵可剂量依赖地激活AC活性, 而PIN(1 μmol·L^-1)或YOH(0.25～1 μmol·L^-1)均显著拮抗AGM(6.4 μmol·L^-1)对AC的激活作用; 慢性给予大鼠AGM(10 mg·kg^-1, ig, bid)或氟西汀(fluoxetine, FLU, 10 mg·kg^-1, ig, bid) 2 w也显著增强大鼠前额皮层基础及Gpp(NH)p 预激活的AC活性。本研究表明, 调节脑内5-HT_1A/1B和α₂等受体功能, 并激活前额皮层AC可能是AGM抗抑郁活性的重要机制之一。     

速激肽受体拮抗剂对白三烯C4引起的豚鼠心血管反应的抑制作用

iv白三烯C₄(LTC₄)0.8nmol·kg^-1引起麻醉豚鼠血压降低和心脏微血管依文思蓝渗出增加。速激肽NK-1受体拮抗剂CP-96345 (2.06μmol·kg^-1,iv)和NK-2受体拮抗剂SR-48968(1.66μmol·kg^-1,iv)部分抑制心房微血管渗漏(分别为46.6%和37.5%);两药合用可明显抑制LTC₄引起的低血压和心房、心室微血管渗漏(分别为58.1%和54.1%),其作用与白三烯特异性拮抗剂ONO-1078(0.06μmol·kg^-1,iv)相似。结果表明速激肽NK-1和NK-2受体可能参与白三烯引起的低血压和心脏炎症反应。     

去甲肾上腺素能系统对埃必定镇痛作用的影响

在大鼠电刺激甩尾测痛模型上,sc或icv埃必定(ipalbidine,Ipa)均具有剂量依赖性的镇痛作用,而脊髓蛛网膜下腔注射Ipa人产生镇痛作用;预先给予利血平可以取消scIpa的镇痛作用,这一作用可被icv补充NE所翻转;电解损毁大鼠叹侧蓝斑,ip二乙基二硫代氨基甲酸钠200mg·kg^-1,酚妥拉明ip10mg·kg^-1或icv150μg和sc哌唑嗪5mg·kg^-1均能使Ipa的镇痛作用明显减弱或消失,而sc育亨宾5mg·kg^-1和ip普萘洛尔10mg·kg^-1对Ipa的镇痛作用无明显影响。上述结果提示Ipa在中枢有镇痛作用,其部位主要在脊髓以上的神经结构,Ipa的镇痛作用可能与去甲肾上腺素能系统的a₁受体有关,而与a₂和β受体无明显关系。     

M3受体与大鼠缺血性心肌细胞凋亡关系的研究M3受体与大鼠缺血性心肌细胞凋亡关系的研究

目的观察M₃受体对大鼠缺血性心肌细胞凋亡的作用及其机制。方法结扎大鼠左冠状动脉前降支建立急性心肌缺血模型,给予M₃受体激动剂胆碱或阻断剂4DAMP进行干预,观察M₃受体对其的影响。结果缺血前15 min iv胆碱10 mg·kg^-1可提高血清超氧化物歧化酶(SOD)活力,降低丙二醛(MDA)含量,减少凋亡细胞的数量(P<0.01),并可增加Bcl-2表达,减少Fas表达。预先5 min iv 4DAMP 0.12 mg·kg^-1阻断心肌M₃受体可逆转胆碱的作用。结论激动M₃受体对结扎大鼠冠状动脉诱导的心肌损伤有保护作用,其机制可能与调节Bcl-2和Fas表达从而抑制心肌细胞凋亡有关。     

关附甲素对实验性心律失常和心肌收缩性的影响

关附甲素(GFA)浓度为20～3oμg·ml^-1时,可以降低无K⁺高Ca²⁺液灌流离体大鼠心脏诱发VT和VF的发生率。清醒大鼠ivGFA2.5～10mg·kg^-1,可依剂量性显著增加北草乌头碱引起室性早搏的用量。清醒犬ivGFA10mg·kg^-1,可逆转哇巴因引起VT,并对麻醉犬(10～20mg·kg^-1),由ACh诱发房颤有明显的抑制作用。GFA10mg·kg^-1iv可明显减慢麻醉犬或清醒犬心率,对心肌收缩性(V_max和V_pm)只有轻度而短暂的抑制,但对左室收缩压,心搏量和心输出量无明显影响。     

间硝苯地平在Beagle犬体内的药代动力学

目的用反相高效液相色谱法研究间硝苯地平(m-nifedipine，m-Nif)在Beagle犬体内的药代动力学特征。方法正交设计优化色谱分离条件，Beagle犬分别iv给予m-Nif 0.288 mg·kg^-1和ig m-Nif 1.152，3.456，10.370 mg·kg^-1。用反相高效液相色谱法分析血浆中原型药物浓度，血浆药物浓度-时间数据用3P97药代动力学软件分析。结果Beagle犬iv m-Nif，其体内过程符合二室模型，T_1/2β为116.8 min；ig给予m-Nif 后在Beagle犬体内的代谢符合一室模型，其中低剂量(1.152 mg·kg^-1)组C_max为20 μg·L^-1， T_1/2(k_e)为147 min；中剂量(3.456 mg·kg^-1)组C_max为36 μg·L^-1，T_1/2(k_e) 为122 min；高剂量(10.37 mg·kg^-1)组C_max为69 μg·L^-1，T_1/2(k_e)为144 min。结论Beagle犬ig和iv m-Nif 后，血浆中药物消除迅速，口服绝对生物利用度较低。     

内吗啡肽-1对麻醉大鼠左心室功能的影响

目的：观察内吗啡肽-1（endomorphin-1,EM-1）静脉注射和侧脑室注射对麻醉大鼠左心室功能的影响,并初步探讨其可能的作用机理。方法：Wistar大鼠麻醉后,静脉注射或侧脑室注射EM-1,经右颈总动脉左心室插管测定左心室功能,并测定血清和心肌组织NO和T-NoS含量。结果：静脉注射、侧脑室注射EM-1均剂量依赖性地降低麻醉大鼠左心室功能,预先给予阿片受体阻断剂纳洛酮或特异性肚受体阻断剂cyprodime可阻断EM-1引起的心功能降低反应;预先给予胆碱能M受体阻断剂阿托品可减弱EM-1引起的心功能降低反应。静脉注射EM-1血清中NO和T-NOS比对照组有所增加,而心肌组织的NO和T-NOS无明显变化;侧脑室注射EM-1的血清和心肌组织的NO和T-NOS均无明显变化。结论：静脉注射、侧脑室注射EM-1可引起麻醉大鼠在体左心室功能下降,此效应由阿片受体介导,可能有胆碱能M受体参加。     

β-榄香烯经大鼠呼吸道排泄研究

目的研究β-榄香烯自大鼠呼吸道排泄规律。方法采用自制的呼吸道药物收集装置，大鼠iv或ip β-榄香烯75 mg·kg^-1后，于不同时间点收集呼出气体，用气相色谱法测定药物浓度。结果大鼠iv或ip β-榄香烯75 mg·kg^-1 6 h后的累积排出量分别为给药剂量的1.41%和0.51%。结论原形药可经呼吸道排出，但不是β-榄香烯在大鼠体内消除的主要方式。     

Gastric blood flow responses to autonomic nerve stimulation and related pharmacological studies in rats

The effects of autonomic nerve stimulation on rat gastric blood flow (GBF) were studied using a cross thermocouple method. Stimulation of the periarterial nerve bundles along the left gastric artery produced a decrease in GBF which was antagonized by phenoxybenzamine (0.05 mg kg-1 i.v.), but not by propranolol (1 mg kg-1 i.v.). Stimulation of the vagus nerves elicited an increase in GBF, within a latency of 20 s, which was not apparently affected by atropine (0.15 and 1.5 mg kg-1 i.v.) but was completely blocked by hexamethonium (10 mg kg-1 i.v.). The GBF increase due to acetylcholine (0.25 micrograms rat-1 i.a.), was markedly blocked by atropine (0.15 mg kg-1 i.v.). Vagal stimulation also produced both the cholinergic excitation and non-cholinergic inhibition of gastric motility. The vagally induced GBF increase was little affected by any pretreatment with phentolamine, propranolol, indomethacin or aprotinin. These results suggest that sympathetic nerve stimulation creases GBF through alpha-adrenoceptors and parasympathetic nerve stimulation increases GBF through a non-cholinergic mechanism in rats and that the GBF increase may result from a primary dilator effect of vagal stimulation on the blood vessels because of the immediate initiation of the response.     

Restoration of blood pressure by choline treatment in rats made hypotensive by haemorrhage.

1. Intracerebroventricular (i.c.v.) injection of choline (25-150 micrograms) increased blood pressure in rats made acutely hypotensive by haemorrhage. Intraperitoneal administration of choline (60 mg kg-1) also increased blood pressure, but to a lesser extent. Following i.c.v. injection of 25 micrograms or 50 micrograms of choline, heart rate did not change, while 100 micrograms or 150 micrograms i.c.v. choline produced a slight and short lasting bradycardia. Choline (150 micrograms) failed to alter the circulating residual volume of blood in haemorrhaged rats. 2. The pressor response to i.c.v. choline (50 micrograms) in haemorrhaged rats was abolished by pretreatment with mecamylamine (50 micrograms, i.c.v.) but not atropine (10 micrograms, i.c.v.). The pressor response to choline was blocked by pretreatment with hemicholinium-3 (20 micrograms, i.c.v.). 3. The pressor response to i.c.v. choline (150 micrograms) was associated with a several fold increase in plasma levels of vasopressin and adrenaline but not of noradrenaline and plasma renin. 4. The pressor response to i.c.v. choline (150 micrograms) was not altered by bilateral adrenalectomy, but was attenuated by systemic administration of either phentolamine (10 mg kg-1) or the vasopressin antagonist [beta-mercapto-beta,beta-cyclopenta-methylenepropionyl1, O-Me-Tyr2,Arg8]-vasopressin (10 micrograms kg-1). 5. It is concluded that the precursor of acetylcholine, choline, can increase and restore blood pressure in acutely haemorrhaged rats by increasing central cholinergic neurotransmission. Nicotinic receptor activation and an increase in plasma vasopressin and adrenaline level appear to be involved in this effect of choline.     

Possible dependence of pressor and heart rate effects of NG-nitro-L-arginine on autonomic nerve activity.

1. The effects of NG-nitro-L-arginine (L-NNA) on mean arterial pressure (MAP) and heart rate (HR) were investigated in conscious rats. 2. Intravenous bolus cumulative doses of L-NNA (1-32 mg kg-1) dose-dependently increased MAP. Both mecamylamine and phentolamine increased MAP responses to L-NNA, angiotensin II and methoxamine. Propranolol, reserpine, atropine and captopril did not affect MAP response to L-NNA. 3. A significant negative correlation of HR and MAP responses to L-NNA was obtained in control rats but not in rats pretreated with reserpine or mecamylamine. Significant negative correlations also occurred in the presence of atropine, propranolol, phentolamine or captopril. 4. A single i.v. bolus dose of L-NNA (32 mg kg-1) raised MAP to a peak value of 53 +/- 3 mmHg and the effect lasted more than 2 h; the rise and recovery of MAP were accompanied by significant decrease and increase in HR, respectively. While both phentolamine and mecamylamine increased peak MAP response to L-NNA, mecamylamine abolished the biphasic HR response and phentolamine potentiated the bradycardiac component of HR. 5. Blockade of the autonomic nervous and renin-angiotensin systems did not attenuate the pressor effects of L-NNA. However, the biphasic HR response to L-NNA is mediated via modulation of autonomic nerve activities.     

Modulation of non-adrenergic, non-cholinergic neural bronchoconstriction in guinea-pig airways via GABAB-receptors.

1. Evidence suggests that gamma-aminobutyric acid (GABA) and its receptors are present in the peripheral nervous system. We have now investigated the effect of GABA and related substances on non-adrenergic, non-cholinergic (NANC) neurally-evoked bronchoconstriction in the anaesthetised guinea-pig. 2. Bilateral vagal stimulation (5 V, 5 ms, 3 or 5 Hz) for 30 s, after propranolol (1 mg kg-1 i.v.) and atropine (1 mg kg-1 i.v.) evoked a NANC bronchoconstrictor response manifest as a mean tracheal pressure rise of 21.9 +/- 1.04 cmH2O (n = 70). The bronchoconstrictor response was reproducible for any given animal. 3. GABA (10 micrograms-10 mg kg-1 i.v.) did not alter basal tracheal pressure but reduced the NANC bronchoconstrictor response to vagal stimulation in a dose-dependent manner (ED50 = 186 micrograms kg-1 with a maximal inhibition of 74 +/- 3.4% at 10 mg kg-1). Neither the opioid antagonist naloxone (1 mg kg-1 i.v.) nor the alpha-adrenoceptor antagonist phentolamine (2.5 mg kg-1 i.v.) had any significant effect on the inhibitory response produced by GABA (500 micrograms kg-1). 4. GABA-induced inhibition was not antagonised by the GABAA-antagonist bicuculline (2 mg kg-1 i.v.). 5. The GABAB-agonist baclofen (10 micrograms-3 mg kg-1 i.v.) caused a dose-dependent inhibition of the NANC response (ED50 = 100 micrograms kg-1 with a maximal inhibition of 35.5 +/- 2.8% at 3 mg kg-1). The GABAA-agonist, 4,5,6,7-tetrahydroisoxazolo[5,4-C] pyridin-3-ol (THIP), also inhibited the NANC bronchoconstrictor response.(ABSTRACT TRUNCATED AT 250 WORDS)     

Involvement of beta2-adrenergic and mu-opioid receptors in antinociception produced by intracerebroventricular administration of alpha,beta-methylene-ATP

The present study examined what kind of receptors are involved in the antinociception produced by intracerebroventricular (i.c.v.) administration of a,beta-methylene-ATP using antagonists at adrenergic, serotonin or opioid receptors. Antinociceptive effect of alpha,beta-methylene-ATP (10 nmol/rat) was significantly attenuated by subcutaneous pretreatment with propranolol and naloxone, but not phentolamine or methysergide, at a dose of 10 mg/kg. I.c.v. pretreatment with propranolol (100 nmol/rat), butoxamine (100 nmol/rat), ICI-I 18,551 (100 nmol/rat) and naloxone (30 nmol/rat) significantly attenuated the antinociceptive effect of alpha,beta-methylene-ATP. However, i.c.v. pretreatment with atenolol (100 nmol/rat), naltrindole (30 nmol/rat) or nor-binaltorphimine (30 nmol/rat) did not show any significant effects. These results suggest that supraspinal beta2-adrenergic and mu-opioid receptors are involved in the antinociceptive effect of i.c.v. administered alpha,beta-methylene-ATP.     

Clonidine mydriasis in the rat.

Pupillary responses to clonidine (3--100 micrograms/kg, i.v.) and epinephrine (1--30 micrograms/kg, i.v.) were observed in anesthetized rats. Clonidine caused a dose-dependent mydriasis which was effectively antagonized by pretreatment with yohimbine (1.5 mg/kg, i.v.). Pretreatment with phentolamine (5 mg/kg, i.v.) was less effective in antagonizing this clonidine-induced mydriasis. Phenoxybenzamine (2 mg/kg, i.v.) was almost without effect. In contrast, both phentolamine and phenoxybenzamine blocked the pupillary dilation produced by epinephrine while yohimbine pretreatment resulted in no antagonism of epinephrine-induced mydriasis. These results suggest that clonidine-induced mydriasis in the rat is mediated by a central adrenergic inhibitory mechanism.     

The involvement of endothelium-derived relaxing factor in the regulation of renal cortical blood flow in the rat.

1. In the present study the role of endogenous nitric oxide (NO) was investigated, in the regulation of renal cortical blood flow (RCBF) in vivo in anaesthetized rats under conditions in which prostacyclin involvement had been eliminated. 2. Infusions of the NO synthesis inhibitor NG-monomethyl-L-arginine (MeArg) at 1 or 3 mg kg-1 min-1, i.v., produced significant decreases in RCBF of 29 +/- 7% and 35 +/- 5%, respectively. These effects were reversed by co-infusion of a 3 fold excess of L-arginine (L-Arg). 3. Similarly, intravenous infusion of N omega-nitro-L-arginine methyl ester (NO2Arg) at 30 or 300 micrograms kg-1 min-1 attenuated RCBF by 21 +/- 4% or 53 +/- 4%, respectively, and these effects were reversed by L-Arg (3 or 10 mg kg-1 min-1, i.v.). Most importantly, a low dose of NO2Arg (30 micrograms kg-1 min-1, i.v.), while having no pressor effect, considerably reduced RCBF, indicating that basal release of NO is important for the maintenance of renal cortical blood flow. 4. MeArg (3 mg kg-1 min-1, i.v.) or NO2Arg (300 micrograms kg-1 min-1, i.v.) inhibited endothelium-dependent acetylcholine (ACh, 10 micrograms kg-1 min-1, i.v. for 3 min) increases in RCBF in an L-Arg reversible manner, but did not affect endothelium-independent (dopamine 10 micrograms kg-1 min-1, i.v., for 3 min) increases.(ABSTRACT TRUNCATED AT 250 WORDS)     

重组人脑钠肽及米力农对麻醉犬血流动力学及肾功能的影响

目的观察重组人脑钠肽(rhBNP)对麻醉犬血流动力学和肾功能的作用。方法给麻醉开胸犬恒速输注rhBNP(采用累积给药方式),或iv米力农后,进行血流动力学测定,并测定尿量、尿钠和血钠含量。结果rhBNP可使MAP,LVSP,LVdP/d_t,PAP,LVEDP,TPR及RVR呈剂量依赖性下降,CO有增加趋势,尿量和尿钠排出量呈剂量依赖性增加。米力农则明显降低MAP,PAP,LVEDP,TPR,RBF及RVR,升高LVSP,LVdP/d_t和CO,加快心率,对尿量、尿钠排出量和血钠无明显影响。结论rhBNP能明显降低心脏前后负荷,改善心脏功能;可舒张肾动脉,有扩张血管和利尿排钠作用。米力农则有正性肌力和频率作用,无利尿利钠作用。     

5-Carboxamidotryptamine is a selective agonist at 5-hydroxytryptamine receptors mediating vasodilatation and tachycardia in anaesthetized cats.

We have attempted to characterize the 5-hydroxytryptamine (5-HT) receptors mediating bronchoconstriction, vasodilatation, vasodepression and tachycardia in anaesthetized cats following bilateral vagosympathectomy and beta-adrenoceptor blockade with propranolol. 5-HT (1-100 micrograms/kg-1 i.v.) caused dose-related bronchoconstriction and tachycardia but variable and complex effects on diastolic blood pressure and carotid arterial vascular resistance. In contrast, 5-carboxamidotryptamine (5-CT; 0.01-1 micrograms kg-1 i.v.) caused consistent, dose-related decreases in diastolic blood pressure and carotid arterial vascular resistance and increases in heart rate. 5-CT did not cause bronchoconstriction. The 5-HT-induced bronchoconstriction was dose-dependently antagonized by methiothepin, methysergide and ketanserin (10-100 micrograms kg-1 i.v.). The highest doses used of these antagonists did not antagonize bronchoconstriction induced by prostaglandin F2 alpha. The high potency of all three antagonists indicate a 5-HT2-receptor mediated effect. The 5-HT- and 5-CT-induced tachycardia as well as the 5-CT-induced vasodepressor and carotid arterial vasodilator responses were dose-dependently antagonized by low doses of methiothepin (10-100 micrograms kg-1 i.v.) and by high doses of methysergide (100-1000 micrograms kg-1 i.v.) but were little affected by ketanserin in doses up to 1000 micrograms kg-1 i.v. These selective effects of 5-CT appear to be mediated by '5-HT1-like' receptors.     

Airways hyperreactivity and bronchoconstriction induced by vanadate in the guinea-pig.

1 The characteristics of vanadate-induced bronchoconstriction and airways hyperreactivity were observed in spontaneously breathing anaesthetized guinea-pigs by measurement of airways resistance (Raw) and dynamic lung compliance (Cdyn). Vanadate (0.3-3 mg kg-1 i.v. over 25 min) increased Raw and decreased Cdyn in a reversible, dose-related manner. This action (1 mg kg-1 vanadate) was not inhibited by atropine (1 mg kg-1 i.v.), propranolol (1 mg kg-1 i.v.) or bilateral vagotomy, suggesting a direct effect on the airways smooth muscle. 2 An aerosol of vanadate (10% w/v in H2O) for 3 min decreased Cdyn by 19.5% (P less than 0.05, n = 6) but caused no change in Raw. 3 Histamine (3 micrograms kg-1 i.v.) caused a bronchoconstriction which was enhanced by vanadate in a dose-related manner. This hyperreactivity (after 1 mg kg-1 i.v. vanadate) was unchanged after propranolol or bilateral vagotomy, but was partly blocked by atropine (enhancement by vanadate of the Cdyn change to histamine was diminished, P less than 0.02, n = 3). 4 Bronchoconstrictor responses to acetylcholine (6 micrograms kg-1 i.v.) and 5-hydroxytryptamine (6 micrograms kg-1 i.v.) were also enhanced by vanadate (1 mg kg-1 i.v.) Hyperreactivity after vanadate to the three bronchoconstrictors tested continued during vanadate infusion and was reversed 45 min after cessation of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)