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1.
本研究旨在探讨围产期窒息时内皮素( ET)和一氧化氮 ( NO)的变化与急性胃黏膜损伤的关系及 NO的前体 L-精氨酸 ( L-Arg)和NO合成酶抑制剂 L-硝基 -精氨酸甲酯 ( L-NAME)在胃黏膜损伤中的作用。结果显示窒息组血浆 ET和胃壁 NO水平显著高于正常对照组 ( p<0 .0 1 ) ,胃黏膜损伤明显 ;L -Arg组血浆ET水平较窒息组显著下降 ( p <0 .0 1 ) ,血浆和胃壁 NO含量则显著升高 ( p <0 .0 1 ) ,胃黏膜损伤减轻 ;L-NAME组血浆 ET水平和 L I显著高于正常对照组和 L -Arg组 ( p <0 .0 1 ) ,血浆和胃壁 NO含量较 L-Arg组显著下降 ( p <0 .0 1 ) ,表明围产期窒息时 NO和 ET的变化与胃黏膜损伤的程度密切相关。NO在围产期窒息时有保护胃黏膜的作用 ,而 ET则作用相反。L -Arg的保护作用和 L -NAME的损伤作用均是通过 NO的变化来实现的。 相似文献
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为了研究内毒素(LPS)和NO酶抑制剂(NOSI)[氨基胍(AG)、左旋硝基精氨酸(L-NNA)、NG-硝基-L-精氨酸甲酯(L-NAME)]对肝细胞增殖的影响,试验通过体外培养山羊肝细胞,应用LPS结合NO酶抑制剂对细胞进行处理观察细胞增殖的变化。结果表明:当LPS1μg/m L时抑制体外肝细胞的增殖,且随着剂量的增加差异显著(P0.05),说明大剂量的LPS能抑制肝细胞的增殖。应用NOSI(AG,L-NNA,L-NAME)结合1μg/m L LPS处理肝细胞,则发现AG(1 mmol/L)+LPS试验组与LPS对照组肝细胞的增殖差异显著(P0.05);LPS+L-NAME(1 mmol/L)处理的d组显著高于LPS对照组,差异显著(P0.05),使吸光度达到最高水平;LPS+L-NNA(1 mmol/L)处理的γ组、δ组与LPS对照组相比差异显著(P0.05)。说明随着NOSI(AG,L-NNA,L-NAME)浓度的增加,NOSI可以颉颃LPS对肝细胞增殖的抑制,使肝细胞的增殖水平在一定程度上恢复到正常。 相似文献
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腺相关病毒(AAV),尤其是从轴突末端转移到神经元的AAV9型,是研究神经环路和解析大脑功能的有力工具。利用囊泡型谷氨酸神经元(VGlut2)基因敲入小鼠联合脑立体定向注射,通过将AAV9-DIO-ChR2-EGFP病毒注射于VGlut2转基因小鼠的蓝斑核(LC),探究不同注射剂量对病毒侵染范围和小鼠体重的影响。结果表明,与高注射量(1μL)相比,低注射量(0.5μL)可将AAV9-DIO-ChR2-EGFP限定至蓝斑核(LC)。在AAV9-DIO-ChR2-EGFP注射3周后,侵染范围由LC延伸至初级运动皮质(primary motor cortex, M1)、下丘脑、中缝苍白核(araphe pallidus nucleus, Rpa)和颈髓(cervical spinal cord, CSC)。随后检测了低注射量的AAV9(0.5μL)是否影响小鼠体重,统计结果表明,0.5μL AAV9注射对小鼠体重无影响(P=0.979 5)。结果表明,低注射量(0.5μL)可以在一定程度上限制AAV的表达范围,并且脑内注射AAV9不会改变小鼠体重。 相似文献
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研究了疑核内胆碱能神经元、去甲肾上腺素能神经元、脑啡肽能神经元对机体细胞免疫机能的影响 ,并对疑核内 3种神经元之间的相互关系进行了探讨。实验用麻醉家兔 ,分 6组进行 ,分别在疑核处通过微量注射器注入氯化乙酰胆碱 ( Ach)、密胆碱 -3( HC-3)、酒石酸去甲肾上腺素 ( NA)、6-羟基多巴胺 ( 6-OHDA)、盐酸吗啡 ( MP)、盐酸纳络酮 ( NX) ,并分别于注射前和注射后不同时间取外周血 ,测定 T细胞百分率及PHA诱导的有丝分裂原反应。结果 :Ach组上述免疫指标比注射前明显升高 ;HC-3组上述免疫指标比注射前明显降低 ;NA组上述免疫指标在注射后 30、60 min时明显低于注射前 ;6-OHDA组上述免疫指标在注射后 1 0～ 1 2 0 min时明显升高 ;MP组上述免疫指标在注射后 60、1 2 0 min时明显降低 ;NX组上述免疫指标注射前、后无明显变化。提示 :疑核增强机体细胞免疫的作用可能是通过胆碱能神经元实现的 ;疑核内的去甲肾上腺素能神经元与胆碱能神经元的作用相拮抗 ;而疑核内的脑啡肽能神经元可能对前两者的活动起一种调整作用 相似文献
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本试验旨在研究L-精氨酸(L-Arg)对猪胎儿皮肤成纤维细胞(PFSF)免疫应激参数和β防御素基因mRNA表达的影响。采用培养至4～5代的PFSF,通过脂多糖诱导建立免疫应激模型,在DMEM/F12培养液中添加不同浓度(0、35、70、140、280和560μg/mL)的L-Arg,培养24 h后,检测培养液一氧化氮(NO)含量及乳酸脱氢酶(LDH)、一氧化氮合酶(NOS)和溶菌酶(LSZ)活性;采用实时定量PCR法检测PFSFβ防御素1(pBD-1)、β防御素2(pBD-2)和β防御素3(pBD-3)基因mRNA表达量。结果表明:1)L-Arg能够降低培养液LDH活性,正常细胞和应激细胞分别在L-Arg浓度为70和140μg/mL时达到最低;2)L-Arg能够极显著提高培养液NO含量(P<0.01),正常细胞和应激细胞均在L-Arg浓度为140μg/mL达到最高;3)L-Arg能够显著或极显著增加正常细胞培养液NOS活性(P<0.05或P<0.01),而对应激细胞无显著影响(P>0.05),L-Arg浓度为35和70μg/mL时,应激细胞显著或极显著高于正常细胞(P<0.05或P<0.01);4)560μg/mL L-Arg可显著提高培养液LSZ活性(P<0.05);5)70μg/mLL-Arg可极显著提高正常细胞和应激细胞pBD-1和pBD-2基因mRNA表达量(P<0.01),140μg/mL L-Arg可极显著提高正常细胞和应激细胞pBD-3基因mRNA表达量(P<0.01)。结果提示,适宜浓度的L-Arg能够降低培养液LDH活性,提高NO含量以及NOS和LSZ活性,上调应激细胞和正常细胞β防御素基因mRNA表达;本试验条件下,L-Arg的适宜添加浓度为70～140μg/mL。 相似文献
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精氨酸对左旋硝基精氨酸甲酯诱导猪宫内生长受限的缓解作用 总被引：1，自引：1，他引：0
本研究旨在探讨L-精氨酸(L-Arg)对左旋硝基精氨酸甲酯(L-NAME)诱导的猪宫内生长受限的缓解作用.试验选取40头预产期相近、2～4胎次的长白×大约克夏妊娠母猪,随机分为4个处理:处理Ⅰ(正对照)、处理Ⅱ(负对照,注射L-NAME)、处理Ⅲ(L-NAME+1.0%L-Arg)和处理Ⅳ(1.0%L-Arg),每个处理10个重复,每个重复1头母猪.孕85～105 d,处理Ⅱ、Ⅲ世猪连续21 d于颈背部皮下多点注射2.5 mL的L-NAME溶液以诱导宫内生长受限(IUGR),剂量为15.0 mg/kg BW.处理Ⅰ和Ⅳ母猪则以相同方式注射等体积的生理盐水.于妊娠第85天、第105天耳静脉采血,分娩时取胎盘血液以测定一氧化氮(NO)、总一氧化氮合酶(TNOS)含量.记录窝产仔数、窝活仔数、窝仔重、窝活仔重、仔猪初生重及活仔初生重,计算IUGR发生率.结果表明:1)在妊娠后期母猪饲粮中添加1.0%精氨酸,窝产活仔数由11.20头显著提高到12.60头(P<0.05),窝活仔重由16.21 kg提高至18.26 kg(P<0.05),仔猪IUGR发生率由17.49%降低至6.35%(P<0.05);2)注射L-NAME的母猪窝产活仔数降低了19.64%(P<0.05),窝活仔重降低了27.14%(P<0.01),而仔猪IUGR发生率则显著提高至34.49%(P<0.01).但在注射L-NAME的同时给母猪补充1.0%精氨酸后,窝产活仔数、窝活仔重达正常水平,仔猪IU-GR发生率与正对照组差异不显著(P>0.05);3)给妊娠母猪注射L-NAME,胎盘血清NO、TNOS合成量显著降低(P<0.01),但饲粮中补充1.0%精氨酸后,胎盘血清NO、TNOS合成量恢复至正常水平.由此可知,给妊娠期母猪饲粮中添加1.0%精氨酸后抵消或逆转了由L-NAME诱导的胎盘血清TNOS、NO合成最降低及胎猪生长受限作用,促进了胎猪在宫内的生长发育,并有效地预防了IUGR的发生. 相似文献
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法氏囊提取物提高仔猪体液免疫力的初步研究 总被引：7，自引：0，他引：7
将法氏囊提取物 (相对分子质量 1 0 0 0以下 )以不同剂量梯度 (1、 2 5、 5、 2 5mg/头 )配合伪狂犬病毒 (PRV)灭活苗给断乳仔猪同时同部位注射 ,记录个体在试验期间的伪狂犬病毒抗体水平 (ELISA、VN)、血清中IgG含量变化。结果①注射了 1、 2 5mg提取物 /头剂量的试验个体的PRV中和抗体水平显著高于对照组及注射了 5、 2 5mg提取物 /头剂量的试验个体 ;而注射了 5、 2 5mg提取物 /头剂量的试验个体的PRV中和抗体水平则低于对照组。②在一免后 1 4d、二免后 0～ 7d ,注射了 1、 2 5mg提取物 /头剂量的试验个体的PRVELISA抗体水平显著高于对照组及注射了 5、 2 5mg提取物 /头剂量的试验个体。③试验组与对照组血清中的IgG差异不显著 (P >0 0 5) ;只是在一免的第 2 1天 ,剂量为 5mg/头组显著低于其他组。研究表明 ;相对分子质量为 1 0 0 0以下的法氏囊提取物对仔猪体液免疫力的影响是呈剂量相关的 相似文献
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《黑龙江畜牧兽医》2016,(3)
为了探索应用高效液相色谱法(HPLC)测定母猪血清的多巴胺(DA)、五羟色胺(5-HT)的条件,并试图快速准确测定妊娠母猪血清内DA、5-HT的含量,试验以12头妊娠母猪为试验群体,于妊娠期第103天耳静脉采血并进行HPLC测定。试验色谱条件:色谱柱CAPCELL PAK C18(4.6 mm×250 mm,5μm),柱温35℃,流动相为甲醇和0.1 mol/L磷酸二氢钾(15∶85),p H值为4.6,激发波长为254 nm,发射波长为338 nm,流速为1.5 m L/min。结果表明:母猪血清DA平均含量为(37.84±6.45)μg/m L、血清5-HT含量为(48.00±22.82)ng/m L。 相似文献
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The effect of nitric oxide synthase (NOS) inhibition during exercise on lactate production was investigated in five Thoroughbred horses. A standard exercise test (SET), consisting of three canters (approximately 55 per cent VO2max), with walking and trotting between each canter, was performed twice (control and test, in random order) by each horse. Nphi-nitro-L-arginine methyl ester (L-NAME; 20 mg kg-1), a competitive inhibitor of NOS, induced a significant increase (P < 0.05) in plasma lactate [5.7 (2.9) vs 11.8 (3.8) mmol L-1], which continued to increase despite administration of L-arginine, the substrate for NOS. There were no differences in cardiac output (Q) or the total body oxygen consumption (VO) between each SET. The results show that non-specific inhibition of NOS isoforms during exercise in the horse increases plasma lactate concentration, although the mechanism/s remain uncertain. 相似文献
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《中国畜牧杂志》2017,(3)
本试验旨在研究约氏乳杆菌对大鼠生长性能、血液指标及脏器指数的影响。试验选取SD大鼠80只,雌雄各半。大鼠按照体重相近的原则随机分为4个剂量组,即阴性对照组、试验Ⅰ(5 000 mg/kg体重)、试验Ⅱ(1 000 mg/kg体重)和试验Ⅲ组(200 mg/kg体重)。试验期为30 d。结果表明:试验剂量为200~1 000 mg/kg体重时,约氏乳杆菌对大鼠体增重、总采食量、饲料转化率、血液学指标和病理学指标的影响无显著性差异(P>0.05);试验剂量为5 000 mg/kg体重时,谷草转氨酶、血糖、总胆固醇差异不显著(P>0.05);与其他剂量组相比,大鼠的体增重和总采食量显著降低(P<0.05),但饲料转化率无显著差异(P>0.05);谷丙转氨酶水平显著降低(P<0.05),白蛋白和总蛋白显著增高(P<0.05);雌性大鼠尿素氮和雄性大鼠肌酐显著增高(P<0.05)。综合分析,约氏乳杆菌剂量低于1 000 mg/kg体重时,对大鼠平均日增重、血液指标及脏器指数无影响;约氏乳杆菌剂量高于5 000 mg/kg体重时,对大鼠脏器指数有影响。 相似文献
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D. M. Vaughn D. M. Lindley N. R. Cox S. T. Simpson W. L. Whitmer 《Veterinary research communications》1989,13(3):173-181
Twenty retinas from 10 cats were evaluted for dopamine (DA) and its metabolites dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT) and homovanillic acid (HVA) by high pressure liquid chromatography and electrochemical detection. Dopamine was present in all 20 retinas at a mean concentration of 3.00±0.54 ng/mg protein. Dihydroxyphenylacetic acid, 3-MT and HVA were detected in 16, 14 and 9 retinas respectively.In retinas in which these metabolites were detectable, they were present in the following mean concentrations: DOPAC, 1.07±0.21 ng/mg protein; 3-MT, 3.44±0.97 ng/mg protein and HVA, 4.54±1.05 ng/mg protein. Significantly higher concentrations of 3-MT (p=0.0108, paired t test) and HVA (p=0.0166, paired t test) than DOPAC were present in cat retina. Linear correlation analysis between DA and its metabolites indicated that the 3-MT and DOPAC concentrations correlated well with each other and with the amount of DA in cat retina. The concentrations of the end product metabolite, HVA, had poor correlations with the concentrations of 3-MT, DOPAC or DA. These data indicated that once DA is released in cat retina it can be metabolized to 3-MT, DOPAC and HVA. 相似文献
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Sagar P Prasad JK Prasad S Gupta HP Das A 《Tropical animal health and production》2012,44(7):1697-1702
The present study was undertaken to evaluate the effect of L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor on serum nitric oxide, progesterone, estradiol profiles and estrous cycle length in buffaloes. Murrah buffaloes (n?=?16) exhibiting regular estrous cycles were randomly allocated to two groups of eight animals. In the treatment group, buffaloes were administered 400?mg/h?L-NAME over 2?h (total dose?=?800?mg) via the coccygeal artery and the aorta abdominalis on day 15 of the estrous cycle. In the control group, normal saline was infused on the same day of the cycle by the same route. Blood samples were collected every 4?h on days 15 and 16, and once daily from days 17 to 21 of the estrous cycle for the assay of progesterone, estradiol and nitric oxide. L-NAME treatment significantly (p?相似文献
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Rakestraw PC Snyder JR Sanders KM Shuttleworth WC 《American journal of veterinary research》2000,61(4):362-368
OBJECTIVE: To evaluate electrical activity of jejunal circular muscle in horses and characterize electrical responses to stimulation by intrinsic inhibitory neurons. SAMPLE POPULATION: Portions of jejunum obtained from horses euthanatized for reasons other than gastrointestinal tract disease. PROCEDURE: Isolated circular muscle preparations were perfused with oxygenated modified Krebs solution. Glass microelectrodes were used for intracellular recording of membrane potentials from single smooth muscle cells. Electrical activity and responses to electrical field stimulation (EFS) of intrinsic neurons in the presence of guanethidine and atropine were recorded. Mediators of responses to nerve stimulation were also evaluated, using N-nitro-L-arginine methyl ester (L-NAME) and apamin. RESULTS: Mean resting membrane potential (RMP) was 41.5+/-1.8 mV. Small membrane potential oscillations were observed in muscle cells. Single or multiple action potentials were often superimposed on the peaks of these oscillations. Spontaneous oscillations and action potentials were blocked by nifedipine. Transient hyperpolarizations of smooth muscle cell membrane potentials (inhibitory junction potentials [IJP]) were observed in response to electrical field stimulation. The IJP evoked by stimulus trains consisted of an initial fast component followed by a slow component. The L-NAME did not have a significant effect on RMP and did not significantly affect the fast component of IJP at any stimulus frequency tested. In contrast, L-NAME abolished the slow component of IJP observed after trains of pulses. In the continued presence of L-NAME, apamin had no significant effect on RMP but effectively reduced the fast component of IJP. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggest that inhibitory neurotransmitters supplying equine jejunum act through different ionic mechanisms. Understanding these mechanisms may suggest new therapeutic targets for treatment of motility disorders. 相似文献
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试验旨在探讨白肉灵芝水提物（Ganoderma leucocontextum aqueous extracts,GLAE）对脑缺血后海马神经元的保护作用及机制。将50只健康大鼠分为对照组、模型组、GLAE低（0.05 mg/（g·BW））、中（0.1 mg/（g·BW））、高（0.2 mg/（g·BW））剂量组。利用双侧颈总动脉夹闭法建立大鼠脑缺血模型,GLAE组灌胃不同剂量的GLAE干预,对照组和模型组灌胃同体积的生理盐水,连续2周。用跳台试验方法检测记忆获得、记忆巩固和记忆再现障碍大鼠的学习记忆能力,HE染色观察大鼠海马组织的病理形态的变化,比色法检测海马组织一氧化氮合酶（nitric oxide synthase,NOS）活性和一氧化氮（nitric oxide,NO）含量,Western blotting和实时荧光定量PCR法分别检测海马组织生长相关蛋白-43（growth associated protein-43,GAP-43）和脑源性神经生长因子（brain derived neurotrophic factor,BDNF）的水平。结果显示,与对照组相比,模型组大鼠跳台试验的逃避潜伏期显著缩短、电击次数显著增加（P<0.05）;海马神经元细胞出现明显核固缩、排列松散紊乱等退行性改变,细胞数量显著减少（P<0.05）;海马组织NOS活性和NO含量均显著降低（P<0.05）;大鼠海马组织GAP-43蛋白表达量显著升高（P<0.05）;海马组织BDNF mRNA表达量显著下调（P<0.05）。与模型组相比,GLAE干预后,大鼠逃避潜伏期均显著延长、电击次数均显著减少（P<0.05）;GLAE高剂量组大鼠CA1区和齿状回锥体神经元细胞形态明显改善,神经元数量显著增加（P<0.05）;GLAE低剂量组对NOS活性影响不明显（P>0.05）,显著增加NO含量（P<0.05）,GLAE中、高剂量组NOS活性和NO含量均显著升高（P<0.05）;GLAE低、中、高剂量组海马组织GAP-43蛋白表达量均显著增加（P<0.05）;GLAE低、中、高剂量组海马组织BDNF mRNA表达量均显著增加（P<0.05）。以上结果表明,GLAE可通过提高NOS活性和NO水平、促进海马神经发生和功能恢复对脑缺血后海马神经元损伤有一定的保护作用,从而改善大鼠认知功能,0.2 mg/g GLAE效果最好。 相似文献
17.
Takizawa T Kihara T Kamata A Yamamoto M Arishima K 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2000,62(7):707-710
The role of nitric oxide (NO) on the ductus arteriosus (DA) patency was examined in fetal rats at various stages of gestation. N(G)-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg, i.p.), an NO synthase (NOS) inhibitor, or indomethacin (3 mg/kg, p.o.), a cyclooxygenase inhibitor, was administered at 3 hr before cesarean section to pregnant rats ranging from day 17 to day 21 of gestation. Dams were decapitated and the fetuses were obtained by cesarean section. The fetuses were rapidly frozen in an acetone-dry ice mixture. Using rapid-freezing and shaving methods, the calibers of the DA and pulmonary artery were measured. The constrictive effect of L-NAME on the fetal DA caliber was stronger than that of indomethacin in 19-day-old and immature fetuses. In near-term fetuses, the constrictive effects of L-NAME were reduced, while indomethacin caused marked DA constriction. We conclude that endogenous NO may play a major role in regulating the patency of the DA in earlier fetal stages, while dilator prostaglandins may play a greater role in regulating the ductal patency in the near-term fetus. 相似文献
18.
Piekarzewska AB Rosochacki SJ Sender G 《Journal of veterinary medicine. A, Physiology, pathology, clinical medicine》2000,47(5):257-269
Concentrations of noradrenaline (NA), adrenaline (A), dopamine (DA), 5-hydroxytryptamine (5-HT), the DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and the main 5-HT metabolite 5-hydroxyindole-3-acetic acid (5-HIAA) were measured using HPLC in 16 brain areas of control and immobilized Pietrain pigs. The animals were immobilized for 15, 30 and 60 min in the prone position. Control pigs showed patterns of regional distribution of brain monoamines similar to those described for rats, dogs and Duroc pigs. However, the absolute values of NA and A in the hypothalamus and preoptic area were much higher than those in rats and dogs, but similar to those in Duroc pigs. The concentrations of dopamine and its metabolites DOPAC and HVA were highest in the caudate nucleus, the nucleus accumbens, the olfactory tubercle and the ventral tegmental area. The distributions of serotonin and its metabolite 5-HIAA were similar in all examined structures. DOPAC/DA and HVA/DA ratios were higher in the cornu ammonis, the hippocampus posterior and the raphe nuclei than in other structures, which suggests brain structure-related differences in dopamine turnover. The greatest decreases in NA and A content were observed in the hypothalamus, the preoptic area and the olfactory tuberculum during the first 30 min of immobilization stress. 5-HT turnover was increased in the raphe nuclei, while DA turnover was affected in the raphe nuclei, the septum, the substantia nigra and the olfactory tubercle. We suggest that acute immobilization stress caused differences in regional patterns of brain biogenic amines, thereby maintaining adequate transmitter levels during stress in stress-susceptible pigs. 相似文献
19.
Castro M Muñoz JM Arruebo MP Murillo MD Arnal C Bonafonte JI Plaza MA 《Veterinary journal (London, England : 1997)》2012,192(3):352-358
The objectives of this study were to evaluate the role of nitric oxide (NO) synthase isoforms (nNOS, eNOS, and iNOS) in the regulation of the migrating motor complex (MMC) in sheep using electromyography and their expression in the gastrointestinal (GI) tract by Western blot (WB) and immunohistochemistry. Intravenous administration of L-NAME or the nNOS inhibitor 7-nitroindazole (7-NI) decreased the MMC interval. Myoelectric activity of intestinal phase II was increased, whereas antral activity was reduced. These effects were blocked by L-arginine. Inhibitors of either iNOS (aminoguanidine and S-methylisothiourea) or eNOS (L-NIO) were ineffective. The NO donor sodium nitroprusside decreased GI myoelectric activity, inhibited the MMC pattern, and prevented the effects induced by L-NAME and 7-NI in the intestine. Intracerebroventricular administration of these agents did not modify GI motility. In the rumen, abomasal antrum, duodenum, and jejunum, WB showed three bands at about 155, 145, and 135kDa corresponding to nNOS, and a 140-kDa band (eNOS); however iNOS was not detected. Positive nNOS immunostaining was observed in neurons of the myenteric and submucous plexus of all GI tissues, while eNOS was found in the endothelial cells, ruminal and intestinal epithelium, as well as in some enteric neurons and in endocrine-like cells of the duodenal Brunner's glands. In contrast, only weak iNOS immunoreactivity was found in ruminal epithelium. Taken together, our results suggest that NO, synthesized at a peripheral level by nNOS, is tonically inhibiting the MMC pattern and intestinal motility in sheep. 相似文献
20.
An experiment was conducted to determine if the decrease in circulating concentrations of prolactin in cattle consuming endophyte (Acremonium coenophialum) -infected tall fescue (Festuca arundinacea) was associated with changes in prolactin concentrations in the anterior pituitary and concentrations of dopamine (DA) and its metabolites 3,4-dihydroxyphenyl-acetic acid (DOPAC) and homovanillic acid (HVA) in the stalk median eminence (SME), preoptic area (POA) and hypothalamus (HP). Six crossbred steers that grazed high-endophyte (greater than 90% infected) fescue and four steers that grazed low-endophyte (less than 1% infected) fescue from April to September were slaughtered. Brains and pituitaries were removed and dissected. Extracts from neural tissue were analyzed for DA, DOPAC and HVA using high performance liquid chromatography/electrochemical detection. Pituitary extracts and sera from blood samples taken 5 d prior to slaughter were subjected to prolactin radioimmunoassay. Consumption of high-endophyte fescue was associated with decreased concentrations of prolactin in serum (P less than .01) and in the anterior pituitary (P = .08), decreased (P less than .05) concentrations of DA in the SME and decreased (P less than .01) concentrations of HVA in the POA and HP, but it did not influence levels of DOPAC. These results suggest that endophyte toxins may reduce prolactin synthesis and release and may alter activity of dopaminergic neurons. 相似文献