小檗碱通过激活SIRT1通路减轻脑缺血再灌注大鼠炎症及凋亡

目的研究小檗碱预处理对大鼠脑缺血再灌注(I/R)过程中炎症及凋亡的调节作用及分子机制。方法选择40只SPF级成年雄性SD大鼠,随机分为假手术组(Sham组)、I/R组、小檗碱预处理组(BP组)、BP+SIRT1抑制剂EX527处理组(BP+EX组),BP组在造模前给予小檗碱100 mg/(kg·d)灌胃、连续14天,BP+EX组在造模前给予小檗碱100 mg/(kg·d)灌胃及SIRT1抑制剂EX527 5 mg/(kg·d)腹腔注射、连续14天,而后采用线栓法建立脑I/R模型。采用神经功能缺损评分、TUNEL染色、Nissl染色评价神经功能损伤程度,检测SIRT1通路基因、线粒体途径凋亡基因、炎症因子的表达。结果 I/R组大鼠的神经功能缺损评分、TUNEL阳性率及脑组织中核因子κB (NF-κB)、P53、Bax、Caspase-9、Caspase-3、肿瘤坏死因子α(TNF-α)、白细胞介素1β(IL-1β)、IL-6、细胞间黏附分子1(ICAM-1)的表达水平均明显高于假手术组,Nissl阳性数目及脑组织中SIRT1、Bcl-xL的表达水平均明显低于假手术组(P0.05);BP组大鼠的神经功能缺损评分、TUNEL阳性率及脑组织中NF-κB、P53、Bax、Caspase-9、Caspase-3、TNF-α、IL-1β、IL-6、ICAM-1的表达水平均明显低于I/R组,Nissl阳性数目及脑组织中SIRT1、Bcl-xL的表达水平均明显高于I/R组(P0.05);BP+EX组大鼠脑组织中Bax、Caspase-9、Caspase-3、TNF-α、IL-1β、IL-6、ICAM-1的水平均明显高于BP组,Bcl-xL的表达水平明显低于BP组(P0.05)。结论小檗碱预处理能够通过激活SIRT1通路来减轻大鼠脑缺血再灌注过程中的炎症及凋亡。     

川芎嗪抑制大鼠脑缺血再灌注损伤的机制

目的探讨川芎嗪(TMP)抑制脑缺血再灌注损伤(CIRI)的分子机制。方法选择清洁级健康成年雄性SD大鼠,采用改良的Zea Longa栓线法构建大脑中动脉梗塞(MCAO)模型,并将大鼠随机分为三组(n=20):假手术组、模型组、TMP治疗组。假手术组大鼠不插入线栓,其余操作均同模型组;TMP治疗组大鼠在被拔出线栓再灌注时,腹腔注射TMP 20 mg/kg。再灌注24 h后,各组大鼠进行神经功能评分,然后麻醉处死,取材检测。干湿称重法检测大鼠脑组织含水量;2,3,5-三苯基氮化四氮唑(TTC)染色法检测大鼠脑梗死面积,HE染色观察脑组织形态;荧光定量PCR检测大鼠梗死侧脑皮层中miR-199a-5p、Bax、Bcl-2、肿瘤坏死因子(TNF)-α、白细胞介素(IL)-1β、IL-6 mRNA的表达水平;酶联免疫法检测大鼠血清中炎症介质TNF-α、IL-1β和IL-6的含量;免疫组化法观察大鼠梗死侧脑皮质核转录因子(NF)-κB p65及磷酸化NF-κB p65(NF-κB p-p65)的表达。结果 TMP治疗可显著改善神经缺陷评分(P<0.05),降低脑组织含水量(P<0.05),减少梗死体积(P<0.01),减轻脑组织破坏。模型组miR-199a-5p、Bax、TNF-α、IL-1β和IL-6 mRNA的表达明显升高(P<0.05),而Bcl-2 mRNA表达水平显著降低(P<0.05)。而TMP治疗可显著降低miR-199a-5p、Bax、TNF-α、IL-1β和IL-6 mRNA的表达水平(P<0.05),增加Bcl-2 mRNA的表达(P<0.05)。与模型组比较,TMP治疗组大鼠脑皮质和血清中TNF-α、IL-1β和IL-6炎症因子含量均显著降低(P<0.05)。IHC结果显示,TMP治疗组中NF-κB p-p65阳性细胞数明显减少(P<0.05)。结论 TMP可减轻CIRI,其机制可能为抑制miR-199a-5p的表达,减少凋亡,降低炎症反应,且可降低NF-κB的活化。     

阿托伐他汀对Livin、NF-κB与IL-1β在脑缺血再灌注大鼠脑组织中表达的影响

目的 检测脑缺血再灌注大鼠脑组织Livin、NF-κB和白介素(IL)-1β表达及观察阿托伐他汀对其表达的影响,探讨阿托伐他汀对脑缺血再灌注后的脑保护作用机制.方法 大脑中动脉线栓方法制作大鼠脑缺血再灌注模型;实验大鼠随机分为假手术组(S组)、模型组(M组)及阿托伐他汀治疗组(MT组);免疫印迹法和RT-PCR检测大鼠脑组织Livin、NF-κB和IL-1β的表达,TTC染色法测量脑梗死体积.结果 梗死灶体积MT组较M组显著降低(P<0.05), 较S组显著增高(P<0.01);MT组NF-κB和IL-1β表达较M组降低(P<0.05),MT组Livin表达较M组增高(P<0.05);MT组Livin、NF-κB和IL-1β表达较S组增高(P<0.05);M组Livin、NF-κB和IL-1β表达较S组显著增高(P<0.01).结论 阿托伐他汀可以通过降低脑缺血再灌注大鼠脑组织NF-κB和IL-1β、增强Livin表达抑制细胞凋亡和脑内炎症发挥脑保护作用.     

SIRT1/TLR4/NF-κB在丹参素治疗大鼠心肌梗死的保护作用

目的 探讨SIRT1/TLR4/NF-κB在丹参素治疗大鼠心肌梗死的保护作用。方法 构建SD大鼠心肌缺血再灌注损伤模型,随机分为:对照组,模型组、丹参素组(2 mg/kg)三组,每组15只。HE染色法观察心肌组织病理学改变;TTC双染法测定心肌梗死面积;免疫组织化学法检测SIRT1表达;采用Western blot法检测SIRT1、TLR4、NF-κB、Bcl-2、Caspase3蛋白的表达;ELISA法检测心肌组织IL-6和TNF-α表达。结果 丹参素组大鼠心肌凋亡数量、心肌梗死面积比模型组显著降低(P0.05)。丹参素组SIRT1表达平均光密度显著升高(P0.05)。丹参素组TLR4、NF-κB、Caspase3蛋白表达明显下降,SIRT1、Bcl-2蛋白含量表达比模型组显著上升(P0.05);丹参素组心肌组织IL-6和TNF-α表达显著下降(P0.05)。结论 丹参素可通过促进SIRT1表达,抑制TLR4/NF-κB信号通路来改善大鼠心肌梗死,对心肌起到营养和保护的作用。     

左旋卡尼汀联合CrkL降低缺氧复氧诱导的心肌细胞损伤

目的研究左旋卡尼汀联合CT10激酶调节子样蛋白(CrkL)降低缺氧复氧(H/R)诱导的心肌细胞损伤的作用。方法利用H/R损伤心肌细胞H9c2,使用左旋卡尼汀处理。细胞计数试剂盒8(CCK-8)、流式细胞术、Western blot分别检测细胞的增殖、凋亡和细胞核相关抗原Ki-67(Ki-67)、增殖细胞核抗原(PCNA)、B细胞淋巴瘤/白血病2(Bcl-2)、Bcl-2相关X蛋白(Bax)、肿瘤坏死因子α(TNF-α)、白细胞介素1β(IL-1β)、核因子κB(NF-κB)、CrkL水平。在细胞H9c2中转染pcDNA-CrkL,使用H/R处理或H/R+左旋卡尼汀处理。采用上述方法检测细胞增殖、凋亡等。结果与对照组比较,H/R组H9c2细胞的活力、Ki-67、PCNA、Bcl-2、CrkL蛋白表达量明显降低,细胞凋亡率、Bax蛋白水平及炎症因子TNF-α、IL-1β、NF-κB的蛋白水平显著升高(P0.05)。与H/R组比较,左旋卡尼汀明显增加H/R诱导的H9c2细胞活力及Ki-67、PCNA、Bcl-2、CrkL蛋白表达量,显著降低细胞凋亡率、Bax蛋白水平及TNF-α、IL-1β、NF-κB蛋白水平(P0.05)。CrkL过表达明显提高H/R诱导的H9c2细胞活力和Ki-67、PCNA、Bcl-2蛋白表达量,显著降低细胞凋亡率、Bax蛋白水平及TNF-α、IL-1β、NF-κB蛋白水平(P0.05)。与单独使用左旋卡尼汀或CrkL过表达比较,左旋卡尼汀联合CrkL过表达明显提高H9c2细胞的活力和Ki-67、PCNA、Bcl-2蛋白表达量,显著降低细胞凋亡率、Bax蛋白水平及TNF-α、IL-1β、NF-κB蛋白水平(P0.05)。结论左旋卡尼汀联合CrkL可以促进缺氧复氧诱导的心肌细胞增殖,降低细胞凋亡和炎症反应,从而保护心肌细胞。     

参芎注射液对脑缺血再灌注大鼠炎症因子变化的影响

目的观察脑缺血再灌注(I/R)大鼠脑组织核因子-κB(NF-κB)、肿瘤坏死因子-α(TNF-α)、细胞间粘附分子-1(ICAM-1)表达及血清白细胞介素(IL)-1β、IL-6、IL-10质量浓度的变化,并探讨参芎注射液对其影响。方法2006年4月至7月间于苏州大学附属第二医院将54只健康雄性大鼠随机分为生理盐水对照组、川芎嗪组和参芎组。采用线栓法制作大脑中动脉I/R模型,缺血1h时回抽栓线实现再灌注,造模成功后,于再灌注6h、12h及24h3个时间点断头取脑及采血;采用免疫组化法标记脑组织NF-κB、TNF-α及ICAM-1表达;用酶联免疫吸附试验(ELISA)法检测血清IL-1β、IL-6及IL-10质量浓度。结果各组脑组织TNF-α、ICAM-1均随再灌注时间延长而表达增强,但NF-κB于再灌注12h达高峰;与对照组相比,参芎组NF-κB、TNF-α及ICAM-1表达明显减弱(P均<0.05);参芎可降低IL-1β的质量浓度,促使IL-6的峰值提前,提高IL-10的质量浓度(P<0.05或P<0.01)。结论参芎注射液抑制脑I/R炎症损伤的作用优于川芎嗪。     

牛蒡子苷元抑制HMGB1/TLR4/NF-κB信号通路对肺炎链球菌脑膜炎大鼠神经元凋亡的影响北大核心CSCD

目的探讨牛蒡子苷元(ATG)抑制HMGB1/TLR4/NF-κB信号通路对肺炎链球菌脑膜炎大鼠神经元凋亡的影响。方法通过脑内注射Ⅲ型肺炎链球菌建立脑膜炎大鼠模型,并随机分为模型组、ATG低(ATG-L)、中(ATG-M)、高(ATG-H)剂量组以及ATG-H+重组高迁移率组蛋白B1(rHMGB1)组,另取正常大鼠为对照组,10只/组。治疗结束后,对各组大鼠进行神经系统评分;分离大鼠脑组织,检测其病理变化、含水量、IL-1β、IL-6、TNF-α水平以及神经元细胞凋亡,同时检测HMGB1/TLR4/NF-κB信号通路蛋白表达水平。结果与对照组比较,模型组大鼠神经系统评分显著下降(P<0.05),脑组织含水量、IL-1β、IL-6、TNF-α、HMGB1、TLR4、p-NF-κB p65/NF-κB p65水平及TUNEL荧光染色阳性细胞数量均显著增加(均P<0.05);ATG-L组、ATG-M组、ATG-H组小鼠神经系统评分均较模型组显著增加(均P<0.05),脑组织含水量、IL-1β、IL-6、TNF-α水平、TUNEL荧光染色阳性细胞数量、HMGB1、TLR4、p-NF-κB p65/NF-κB p65均较对照组显著下降(均P<0.05);ATG-H+rHMGB1组较ATG-H组神经系统评分显著下降(P<0.05),脑组织含水量、IL-1β、IL-6、TNF-α、HMGB1、TLR4、p-NF-κB p65/NF-κB p65水平及TUNEL荧光染色阳性细胞数量均显著增加(均P<0.05)。结论ATG可抑制肺炎链球菌脑膜炎大鼠神经元凋亡,减轻炎症反应,其机制可能与抑制HMGB1/TLR4/NF-κB信号通路有关。     

积雪草酸通过SIRT3/β-catenin/PPARγ信号通路影响急性心肌梗死模型大鼠血管新生及心室重构

目的基于急性心肌梗死(AMI)发生发展过程中沉默信息调节因子3(SIRT3)/β-连环蛋白(β-catenin)/过氧化物酶体增殖物激活受体γ(PPARγ)信号通路的变化,探讨积雪草酸(AA)对AMI模型大鼠血管新生及心室重构的影响及作用机制。方法将72只SD大鼠按照体重均衡的原则随机分组,其中12只为空白对照组,剩余的大鼠制备AMI模型。造模成功后将大鼠采用随机数字表法分为5组:模型组、阳性对照组、AA高剂量组、AA中剂量组和AA低剂量组,每组12只。空白对照组和模型组给予生理盐水,阳性对照组给予阿司匹林肠溶片,药物干预组给予不同剂量的AA。28天后采用多普勒超声仪检测各组大鼠的血管新生和心室重构情况。采用逆转录-聚合酶链反应检测大鼠心肌SIRT3、β-catenin和PPARγmRNA表达。采用酶联免疫吸附法检测各组大鼠白细胞介素6(IL-6)、肿瘤坏死因子α(TNF-α)、核因子κB(NF-κB)等炎症因子水平。结果与空白对照组相比,模型组大鼠的心脏功能变差,微血管密度(MVD)增加,心肌SIRT3、β-catenin、PPARγmRNA表达和血清IL-6、TNF-α、NF-κB水平均升高(P0.05);与模型组相比,各给药组大鼠的心脏功能明显改善,MVD增加,心肌SIRT3、β-catenin、PPARγmRNA表达均增加,血清IL-6、TNF-α、NF-κB水平降低(P0.05);与阳性对照组相比,AA高、中、低剂量组大鼠的心脏功能改善,MVD增加,心肌SIRT3、β-catenin、PPARγmRNA表达均升高,血清IL-6、TNF-α、NF-κB水平降低(P0.05)。结论积雪草酸抑制大鼠梗死心肌SIRT3/β-catenin/PPARγ信号通路,对AMI大鼠心肌组织具有一定的保护作用。     

有氧运动对自发性高血压大鼠心脏炎症的影响及机制的探讨

目的 探讨有氧运动对自发性高血压大鼠（SHR）心脏炎症的调节及其机制。方法 8周龄雄性SHR大鼠和正常血压对照WKY大鼠各16只,将SHR大鼠随机分为SHR安静组和SHR运动组;将WKY大鼠随机分为WKY安静组和WKY运动组,每组8只。其中运动组大鼠进行8周无负重游泳运动。采用超声心动仪检测心脏功能,用ELISA试剂盒检测心脏炎症因子TNF-α和IL-1β的含量,Western blot法检测心脏叉头框蛋白1（FoxO1）、p65 NF-κB、磷酸化Akt（p-Akt）和总Akt（t-Akt）的表达。结果 与WKY安静组大鼠相比,SHR安静组大鼠左心室p65 NF-κB的表达以及炎症因子TNF-α、IL-1β的含量及FoxO1表达明显升高（P<0.05,P<0.01）,p-Akt的水平下降（P<0.05）;与SHR安静组相比,8周有氧运动能够增强SHR大鼠心脏功能,降低p65 NF-κB的表达以及炎症因子TNF-α和IL-1β的含量（P<0.05）,同时降低FoxO1表达（P<0.05）,提高p-Akt的水平（P<0.05）。8周有氧运动同样能够降低WKY大鼠心脏FoxO1表达（P<0.05）,提高p-Akt的水平（P<0.05）。结论 8周无负重游泳运动能够降低SHR大鼠心脏炎症因子TNF-α和IL-1β的含量,其可能与加强Akt磷酸化水平和下调FoxO1表达有关,确切机制有待进一步研究。     

人参二醇组皂苷对内毒素休克大鼠脑皮质损伤的保护作用

目的探讨内毒素休克时大脑皮质损伤状况及人参二醇组皂苷对大鼠脑保护作用机制。方法将28只Wistar成年大鼠随机分为实验对照(control)组,内毒素休克(LPS)组,地塞米松(LPS+DEX)组和人参二醇组皂苷(LPS+PDS)组。大鼠静脉注射内毒素制作内毒素休克大鼠模型。生物化学法检测脑组织中超氧化物歧化酶(SOD)活力和丙二醛(MDA)含量。蛋白印迹检测大鼠核转录因子(NF)-κB蛋白P65亚基表达含量的变化。ELISA法检测脑组织内白细胞介素(IL-1β),肿瘤坏死因子(TNF-α)和IL-6水平。结果与LPS组比较,LPS+DEX组和LPS+PDS组大鼠脑组织MDA含量降低,SOD活性上调,NF-κB蛋白表达降低,IL-1β,TNF-α和IL-6水平显著降低(P<0.05)。结论 PDS能够下调内毒素休克脑组织中NF-κB蛋白表达,改善自由基和炎症因子对脑组织的损伤作用,对中枢神经系统具有保护作用。     

Three layer functional model and energy exchange concept of aging process

Relying on a certain degree of abstraction, we can propose that no particular distinction exists between animate or living matter and inanimate matter. While focusing attention on some specifics, the dividing line between the two can be drawn. The most apparent distinction is in the level of structural and functional organization with the dissimilar streams of ‘energy flow’ between the observed entity and the surrounding environment. In essence, living matter is created from inanimate matter which is organized to contain internal intense energy processes and maintain lower intensity energy exchange processes with the environment. Taking internal and external energy processes into account, we contend in this paper that living matter can be referred to as matter of dissipative structure, with this structure assumed to be a common quality of all living creatures and living matter in general. Interruption of internal energy conversion processes and terminating the controlled energy exchange with the environment leads to degeneration of dissipative structure and reduction of the same to inanimate matter, (gas, liquid and/or solid inanimate substances), and ultimately what can be called ‘death.’ This concept of what we call dissipative nature can be extended from living organisms to social groups of animals, to mankind. An analogy based on the organization of matter provides a basis for a functional model of living entities. The models relies on the parallels among the three central structures of any cell (nucleus, cytoplasm and outer membrane) and the human body (central organs, body fluids along with the connective tissues, and external skin integument). This three-part structural organization may be observed almost universally in nature. It can be observed from the atomic structure to the planetary and intergalactic organizations. This similarity is corroborated by the membrane theory applied to living organisms. According to the energy nature of living matter and the proposed functional model, the decreased integrity of a human body's external envelope membrane is a first cause of the structural degradation and aging of the entire organism. The aging process than progresses externally to internally, as in single cell organisms, suggesting that much of the efforts towards the restoration and maintenance of the mechanisms responsible for structural development should be focused accordingly, on the membrane, i.e., the skin. Numerous reports indicate that all parts of the human body, like: bones, blood with blood vessels, muscles, skin, and so on, have some ability for restoration. Therefore, actual revival of not only aging tissue of the human body's membrane, but the entire human body enclosed within, with all internal organs, might be expected. We assess several aging theories within the context of our model and provide suggestions on how to activate the body's own anti-aging mechanisms and increase longevity. This paper presents some analogies and some distinctions that exist between the living dissipative structure matter and inanimate matter, discusses the aging process and proposes certain aging reversal solutions.     

Unusual responses of nocturnal pineal melatonin synthesis and secretion to swimming: Attempts to define mechanisms

Abstract: The effect of swimming at night on rat pineal melatonin synthesis was compared with that of light exposure at night. Rats were forced to swim at 0030 hr (lights out at 2000 hr) and sacrificed by decapitation 15 and 30 min later, immediately after swimming. Other groups of animals were exposed to white light (650μW/cm²) for 15 and 30 min at same time. Swimming caused a rapid and highly significant drop in the melatonin content in the pineal gland; however, the activity of N-acetyltransferase (NAT), the supposed rate limiting enzyme in the melatonin production, was not changed. Despite the drop in pineal melatonin levels, serum concentrations of the indole remained elevated in the rats that swam. In contrast, melatonin levels in the pineal and serum of light exposed rats fell precipitously, accompanied by a significant suppression of NAT activity. Since we anticipated that the strenuous exercise associated with swimming may induce release of artrial natriuretic peptide (ANP) from the heart, which in turn could cause the release of pineal melatonin, in a second study we injected physiological saline intravenously to stretch the cardiac muscle and release ANP. Three milliliters of normal saline was injected during the day into the jugular vein of anesthetized rats that were pretreated with isoproterenol to stimulate pineal melatonin production. Animals were killed 15 min after the saline injection, and pineal NAT activity and pineal melatonin levels were measured. The saline injections caused no alteration in the elevated levels of either NAT or melatonin. These data suggest that the disparity in pineal NAT activity (which was high) and pineal melatonin (which was low), in animals swum at night, may not be caused by ANP which is released during strenuous exercise such as swimming.     

Melatonin and photoperiodic time measurement: Seasonal breeding in the sheep

Abstract: Well-established circadian physiology supports the view that photoperiodic time measurement utilizes the coincidence between the presence of light and a photosensitive phase of a 'biological clock' to alter reproductive status—the so-called external coincidence model of seasonal breeding. In this review, we examine the mechanism whereby photoperiod interacts with presumed suprachiasmatic nuclei activity to allow endogenous melatonin to normally synchronize reproductive activity to the optimal time of year. The Romney Marsh sheep is particularly explored as an experimental model. It is suggested that the on/off activity of seasonal reproduction may be a robust mechanism able to be predictably manipulated by the judicious use of the light/dark cycle and exogenous melatonin, but firmly based on circadian principles.     

The immunoneuroendocrine role of melatonin

Abstract: A tight, physiological link between the pineal gland and the immune system is emerging from a series of experimental studies. This link might reflect the evolutionary connection between self-recognition and reproduction. Pinealectomy or other experimental methods which inhibit melatonin synthesis and secretion induce a state of immunodepression which is counteracted by melatonin. In general, melatonin seems to have an immunoenhancing effect that is particularly apparent in immunodepressive states. The negative effect of acute stress or immunosuppressive pharmacological treatments on various immune parameters are counteracted by melatonin. It seems important to note that one of the main targets of melatonin is the thymus, i.e., the central organ of the immune system. The clinical use of melatonin as an immunotherapeutic agent seems promising in primary and secondary immunodeficiencies as well as in cancer immunotherapy. The immunoenhancing action of melatonin seems to be mediated by T-helper cell-derived opioid peptides as well as by lymphokines and, perhaps, by pituitary hormones. Melatonin-induced-immuno-opioids (MHO) and lymphokines imply the presence of specific binding sites or melatonin receptors on cells of the immune system. On the other hand, lymphokines such as -γ-interferon and interleukin-2 as well as thymic hormones can modulate the synthesis of melatonin in the pineal gland. The pineal gland might thus be viewed as the crux of a sophisticated immunoneuroendocrine network which functions as an unconscious, diffuse sensory organ.     

Serological survey of HIV and syphilis in pregnant women in Madagascar

Objectives Peripartal transmission of human immunodeficiency virus (HIV) and Treponema pallidum, the causative agent of syphilis, leads to severe consequences for newborns. Preventive measures require awareness of the maternal infection. Although HIV and syphilis testing in Madagascar could be theoretically carried out within the framework of the national pregnancy follow‐up scheme, the required test kits are rarely available at peripheral health centres. In this study, we screened blood samples of pregnant Madagascan women for HIV and syphilis seroprevalence to estimate the demand for systemic screening in pregnancy. Methods Retrospective anonymous serological analysis for HIV and syphilis was performed in plasma samples from 1232 pregnant women that were taken between May and July 2010 in Ambositra, Ifanadiana, Manakara, Mananjary, Moramanga and Tsiroanomandidy (Madagascar) during pregnancy follow‐up. Screening was based on Treponema pallidum haemagglutination tests for syphilis and rapid tests for HIV, with confirmation of positive screening results on line assays. Results Out of 1232 pregnant women, none were seropositive for HIV and 37 (3%) were seropositive for Treponema pallidum. Conclusions Our findings are in line with previous studies that describe considerable syphilis prevalence in the rural Madagascan population. The results suggest a need for screening to prevent peripartal Treponema pallidum transmission, while HIV is still rare. If they are known, Treponema pallidum infections can be easily, safely and inexpensively treated even in pregnancy to reduce the risk of transmission.     

Response of rat pineal melatonin to calcium, magnesium, and lithium is circadian stage dependent

Abstract: Herein we documented the response of pineal melatonin production to electrolytes known to be effective on pineal function in view of a possible circadian stage dependence. We studied the release of melatonin by perifused rat pineal glands at 2 different circadian stages corresponding to the middle of the light and dark periods, i.e., respectively, 7 and 19 HALO (Hours After Light Onset, L:D = 12:12). The initial efflux rates were, as expected, much higher in the perifusates of glands removed from rats sacrificed during the dark phase than of those removed during the light phase. After 3 hr of perifusion, melatonin release reached similar levels which were found constant up to the 8th hr of perifusion, whatever the circadian stage. Perifusion of the glands with physiological concentrations for the rat of calcium (5.2 mmol/1) and magnesium (1.34 mmol/1) resulted in a stimulatory effect on the pineal glands removed from rats sacrificed in the middle of the dark period (19 HALO), whereas no effects were observed on the pineal glands removed from rats sacrificed during the light (7 HALO). Lithium (0.28 and 0.55 mmol/1) was ineffective on melatonin release in pineal glands removed 7 and 19 HALO. Our results show differences in the initial efflux rates of melatonin and in the response of perifused pineal glands to calcium and magnesium according to the circadian stage.