牵拉左心房和夹闭颈总动脉对猫下丘脑前部和后部单位放电的影响

在40只氯醛糖和乌拉坦麻醉的猫,观察了牵拉左心房肺静脉入口处(atrial stretch,AS)和关闭一侧颈总动脉(carotid occlusion,CO)对下丘脑前部(AH)和下丘脑后部(PH)单位放电的影响。共记录了185个自发放电单位。对 AS 有反应的 AH 和 PH 单位分别为46.3%和23.3%,其中均以出现抑制反应者居多。有少数单位仅在 AS 开始和停止时出现短暂的兴奋反应。在上述185个神经元中观察了85个对 AS 和 CO 两种刺激的反应,有15个(17.6%)对两种刺激均反应,其中被 AS 所抑制而为 CO 所兴奋的有11个,占73.3%(11/15)。这些结果表明:(1)AS 可对 AH 神经元活动起抑制作用;(2)AS 也可影响 PH 神经元活动;(3)动脉压力感受性和心房容量感受性刺激可会聚于同一下丘脑神经元。     

呼吸中枢发育的基因调控研究进展

脑干呼吸中枢组成一个复杂的网络系统,产生和调控节律性呼吸。近年来,人们利用分子生物学技术研究发现,小鼠某些基因突变可影响呼吸中枢特定神经元的发育,并由此导致特殊的呼吸表型。最近,在人类某些中枢性呼吸疾病中,也发现了相应的基因突变。因此,基因水平的研究为深入认识节律性呼吸活动的产生和调控机制提供了新的研究途径。本文就目前研究较多、相对较深入的一些呼吸中枢发育调节基因的研究进展作一综述。     

兔脑内Orexin B免疫阳性神经元的分布定位

采用免疫组织化学方法研究了10只青紫蓝兔脑内Orexin B免疫阳性神经元的分布定位。结果显示,Orexin B免疫阳性神经元分布于下丘脑的室旁核、背内侧核、穹隆周核、外侧区和后区以及底丘脑的未定带。以下丘脑背内侧核、穹隆周核和外侧区的阳性神经元数量较多,下丘脑室旁核、后区和未定带较少。表明了兔脑内Orexin B免疫阳性神经元的分布与Orexin A免疫阳性神经元的分布存在一些差异,提示两种Orexin的产生部位和生理功能可能也存在差异。     

海马参与自主神经系统调控的研究进展

海马在解剖结构上属于边缘前脑皮质结构,它与下丘脑、杏仁核、脑干有着极其复杂的相互联系。研究发现,刺激海马对自主神经活动产生影响,可引起心率、呼吸、血压等变化;而刺激外周自主神经也影响海马的结构和功能。进一步研究发现,海马可能是通过下丘脑和脑干的核团（如下丘脑室旁核、孤束核等）、内分泌系统和神经递质等参与自主神经系统的调控。     

小脑间位核和顶核对下丘脑外侧区神经元电活动的影响

电刺激猫小脑问位核和顶核可以影响下丘脑外侧区神经元的电活动,其中有一些神经元是葡萄糖敏感神经元.这一结果揭示小脑不仅具有经典的躯体运动调节功能,同时也可以通过小脑-下丘脑通路参与机体非躯体活动的调节.     

孤束核参与刺激下丘脑室旁核的镇痛作用

本实验用电刺激鼠尾-嘶叫法测痛,观察电刺激下丘脑室旁核的镇痛效应,并采用核团损毁和核团内微量注射药物等方法分析其镇痛通路。实验结果如下:(1)电刺激下丘脑室旁核能产生明显的镇痛效应。同时,放射免疫测定发现脑干加压素含量升高。(2)损毁孤束核能取消刺激下丘脑室旁核的镇痛效应,但对基础痛阈无影响。(3)孤束核内微量注射加压素拮抗剂[d(CH_2)_5 TYr(Me)-AVP]60ng/0.6μl 和加压素抗血清0.6μl 都可明显对抗刺激下丘脑室旁核的镇痛效应。(4)直接在孤束核内微量注射加压素60ng/0.6μl,能模拟刺激下丘脑室旁核的镇痛效应。实验结果表明:电刺激下丘脑室旁核能产生镇痛效应,其机理之一可能是兴奋了下丘脑室旁核中加压素能神经元胞体,后者通过下行投射纤维在孤束核中释放加压素,影响孤束核神经元的活动,从而产生镇痛。     

下丘脑hypocretin神经元协调睡眠-觉醒功能

哺乳动物的生活实际上是由睡眠与觉醒、休息与活动、镇静与警戒组成的。上世纪早期的研究预示了在下丘脑后部有一促觉醒区 ,目前神经科学家已证实了上述预测。下丘脑的hypocretin(也称为orexin)神经元对于觉醒系统的调节起着决定性作用 ,该神经元的活动能使睡意减少 ,同时提高觉醒和警戒。Hypocretin神经元分泌兴奋性神经递质hypocretin 1和hypocretin 2 ,投射到参与睡眠 觉醒机制的脑干 ,脑干的这些结构各有自己主要的神经递质 (如缝核的 5 羟色胺、蓝斑的去甲肾上腺素、背侧被盖的乙酰胆碱、乳头结节核的组胺、内侧隔核与斜角带核的γ …     

Orexin神经元调节应激反应的研究进展

orexin是下丘脑的一种重要神经肽,在摄食、睡眠和药物成瘾等生理心理过程中起着重要作用.近年来发现下丘脑Orexin能神经纤维密集地投向参与应激调控的脑区;orexin基因敲除的老鼠表现为防御反应迟钝;另外,侧脑室微量注射orexin可导致血浆中ACTH水平的上升并诱导出应激样呼吸-心血管反应和行为反应;因此,下丘脑及中枢orexin系统对应激的调控可能起关键作用.其可能机制为强烈刺激能活化下丘脑orexin神经元,诱导中枢神经系统orexin的释放,从而激活CRF通路及蓝斑-交感-肾上腺髓质系统,提高血浆皮质酮与去甲肾上腺素的水平,诱导应激反应,维持机体的稳定.     

下丘脑下行通路及其功能

长期以来认为下丘脑室旁核和视上核神经元是通过垂体后叶分泌催产素和加压素对生殖和泌尿等功能进行调节的;但在雄性动物催产素有何生理意义,很长时间曾是个谜。近年来发现,室旁核等下丘脑结构还与脑干和脊髓有直接纤维联系,并以催产素和加压素为递质或调制物,完成对内脏活动的调节作用。这是一种神经调节,与内分泌调节并存。     

中枢注射抗Orexin抗体对禁食大鼠摄食的抑制作用

目的:探讨中枢注射抗Orexin抗体对禁食大鼠摄食的抑制作用。方法:采用免疫组织化学法和蛋白质免疫印迹分析法,对Orexin抗体的特异性进行了检测,分析Orexin阳性神经元和阳性神经纤维在大脑中的分布。给予24 h禁食大鼠中枢注射抗Orexin抗体,计算其对大鼠食物摄入量的影响。结果:蛋白质免疫印迹分析显示,Orexin抗体能够检测到合成的Orexin-A。免疫组织化学分析显示,Orexin阳性神经元存在于外侧下丘脑区域和穹窿周核,Orexin阳性神经纤维大量投射至弓状核、下丘脑室周核和下丘脑室旁核、菱形丘脑核、丘脑室旁核、缰内侧核和纹质丘脑、中脑的中央灰质区、蓝斑核和中缝核、脑桥和髓质的网状结构、对疑核和迷走神经复合体。与注射羊血清相比,给予45μg/10μL抗Orexin抗体侧脑室注射则抑制了大鼠的食物摄入量(P0.05)。高剂量抗Orexin抗体能显著地抑制大鼠摄食,并且呈剂量依赖关系(P0.05)。结论:中枢注射抗Orexin抗体对禁食大鼠摄食具有抑制作用,并呈剂量依赖关系。     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

Scurvy in capybaras bred in captivity in Argentine

In order to determine if the absence of vitamin C in the diet of capybaras (Hydrochoerus hydrochaeris) causes scurvy, a group of seven young individuals were fed food pellets without ascorbic acid, while another group of eight individuals received the same food with 1 g of ascorbic acid per animal per day. Animals in the first group developed signs of scurvy-like gingivitis, breaking of the incisors and death of one animal. Clinical signs appeared between 25 and 104 days from the beginning of the trial in all individuals. Growth rates of individuals deprived of vitamin C was considerably less than those observed in the control group. Deficiency of ascorbic acid had a severe effect on reproduction of another population of captive capybaras. We found that the decrease in ascorbic acid content in the diet affected pregnancy, especially during the first stages. The results obtained suggest that it is necessary to supply a suitable quantity of vitamin C in the diet of this species in captivity.     

Changes in lactate dehydrogenase activity in chicken tissues in hyperthyreosis in ontogenesis

The lactate dehydrogenase activity in reactions of lactate oxidation and synthesis was studied in subfractions of the chicken brain, heart and liver at the embryonal, early postembryonal and adult stages of development after thyroxine administration. It has been shown that during embryogenesis thyroxine predominantly enhanced the rate of lactate oxidation in the mitochondrial tissues. A marked increase in the lactate synthesis was found in cytoplasm of the adult chicken tissues. Specificity of enzyme activity alterations was detected in the chicken brain during ontogenesis after thyroxine administration.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.