低氧暴露条件下高原鼠兔和大鼠HPA轴活动的比较

采用人工模拟低气压低氧的方法比较研究了不同程度（模拟海拔5 km和7 km)和不同时间（24d和5d）低氧暴露,对大鼠和高原鼠兔（Ochotona curzoniae）下丘脑-垂体-肾上腺皮质 (hypothalamo-pituitary-adrenalcortex,HPA)轴活动的影响。结果如下：7 km低氧暴露24 h,大鼠下丘脑的促肾上腺皮质激素释放激素（corticotropin-releasing actor,CRF）和肾上腺皮质激素皮质酮分泌显著增加,大鼠HPA低氧暴露对大鼠HPA 轴活动无显著差异。低氧暴露5天后,大鼠7 km、5 km组的HPA轴活动与对照相比无明显差异。低氧暴露对高原鼠兔的HPA轴无明显影响。上述结果表明：低氧暴露的时间和程度与大鼠HPA的活动密切相关;从HPA的活动来看,高原鼠兔表现出较强的低氧耐受性。     

睡眠中间断低氧对大鼠下丘脑-垂体-肾上腺轴和生长激素的影响

目的:探讨睡眠中间断低氧对大鼠下丘脑-垂体-肾上腺轴和生长激素水平的影响.方法:大鼠分别给予吸入空气,持续低氧和间断低氧气体,在1 d,3 d,7 d和30 d后测定下丘脑促肾上腺皮质激素释放激素(CRH)和生长激素释放激素(GHRH)mRNA水平,并测定30d后血浆CRH,GHRH,促肾上腺皮质激素(ACTH)和皮质酮水平,分析其间的变化关系.结果:与对照组比较,在低氧后1 d,3 d,7 d后大鼠下丘脑CRH mRNA升高,GHRH mRNA降低,在30 d后,间断低氧组下丘脑CRH mRNA升高,GHRH mRNA降低,而持续低氧组则接近正常.间断低氧30 d后,血浆CRH、ACTH,皮质酮均升高,GHRH降低,而生长激素没有明显变化.结论:大鼠睡眠中慢性间断低氧可以引起下丘脑-垂体-肾上腺轴激素水平升高,反馈调节紊乱,可引起GHRH分泌抑制.     

新生大鼠下丘脑CRF和AVP神经元对急性低氧的应答

目的:观察肾上腺摘除新生大鼠下丘脑促肾上腺皮质激素释放激素(CRF)和精氨酸加压素(AVP)神经元对急性低氧的应答.方法:在低压氧舱中模拟高海拔低氧,用放免法测定AVP和CRP含量.结果:新生大鼠暴露于急性低氧环境下(模拟5 000 m和7 000 m海拔高度,24 h),其下丘脑CRP在3 d和7 d龄大鼠中无明显变化,但14d、21 d和28 d时低于对照;下丘脑AVP在3 d大鼠中亦无变化,但14 d时低于对照,7 d、21 d及28 d时高于对照.两者对低氧的应答模式随日龄而变化.摘除肾上腺后,14 d、21 d及28 d大鼠下丘脑CRF和AVP含量均显著低于同龄完整大鼠,此时暴露于急性低氧环境下,CRF和AVP无进一步的变化.结论:摘除肾上腺抑制下丘脑CRF和AVP的发育,影响它们对低氧应激的正常应答.     

自主神经系统参与低氧下的免疫调节作用

目的：探讨低氧条件下自主祖辈 经系统对大鼠脾淋巴细胞转化的调节作用。方法：检测减压低氧下外周血中神经递质与脾淋巴细胞转化。结果：大鼠5km低氧暴露24h,脾淋巴细胞对丝裂原反应性下降,外周交感神经损毁后则可阻断低氧对此的抑制作用;小鼠于真空瓶中0.07MPa缺氧10min血浆中去甲肾上腺素（NE）与肾上腺素（E）均明显升高;大鼠5km低氧24h,血浆中乙酰胆碱水平下降;体外培养的大鼠脾淋邓细胞中加入不同浓度的乙酰胆碱,胸腺嘧啶核苷掺入作用呈浓度依赖性增加。结论：以上结果提示自主神经系统参与低氧下的免疫调节,交感神经系统有免疫抑制作用,副交感神经起免疫增强作用。     

海马内NA能神经损毁对抗急性低氧诱发皮质酮分泌

本工作观察了６羟多巴胺（６ｈｙｄｒｏｘｙｄｏｐａｍｉｎｅ,６ＯＨＤＡ）损毁大鼠腹侧海马去甲肾上腺素能神经对急性低氧诱发皮质酮分泌的影响。结果显示,吸入１０４％Ｏ２３０ｍｉｎ后血浆皮质酮水平显著升高,６ＯＨＤＡ注入腹侧海马致使海马内去甲肾上腺素（ＮＡ）含量降低（－３８５％）;血浆皮质酮水平也较未损毁组为低（－３３２％）。吸入１０４％Ｏ２后,皮质酮对低氧刺激的反应性升高现象消失。结果提示：海马内ＮＡ可能参与急性低氧应激引发血浆皮质酮分泌的调节活动。     

慢性低氧对雄性大鼠血浆皮质酮及睾酮水平的影响

目的:研究低氧对雄性大鼠性腺及相关激素水平的影响。方法:分别检测3km、5km及杭州海拔水平雄性大鼠睾丸和附睾指数、血浆皮质酮和睾酮水平。结果:3km组体重、睾酮含量均显著下降,睾丸指数、血浆皮质酮显著上升;5km组体重、附睾指数和睾酮含量均显著下降,皮质酮含量显著上升。结论:慢性低氧能显著影响雄性成年大鼠性腺及血浆睾酮水平,该结果显示哺乳动物在慢性低氧条件下生殖内分泌功能呈现抑制状态。     

间断性低氧对大鼠淋巴细胞转化的影响

目的: 探讨间断性低氧对机体免疫反应的影响.方法: 以模拟海拔高度间断性低氧(4 h/d)模型观察大鼠脾淋巴细胞对丝裂原(Con A)的反应性.结果: 与对照相比,5 km急性低氧4 h大鼠淋巴细胞的转化率下降25.43%(P<0.05) ,间断性低氧2、5、15 d后淋巴细胞转化率分别为97.03%、104.5%和99.55%,与对照组无明显差异.2 km间断性低氧(4 h/d)1、2、5、15 d,大鼠脾淋巴细胞转化率分别为93.19%、96.43%、99.03%和100.54%,与对照组无明显差异.脾单个核细胞DNA含量显示, 5 km急性低氧4 h DNA含量明显下降(76.22%±7.06%,P<0.05),间断性低氧5 d和15 d后与对照组无显著差异.结论: 急性低氧抑制淋巴细胞的转化,并随低氧的加重而增加,重复间断性低氧暴露其抑制作用减弱,引起大鼠淋巴细胞转化产生适应.推测免疫适应与HPA轴的适应有关.     

低氧暴露对大鼠外周血T淋巴细胞活化的影响

目的：探讨低氧暴露后大鼠外周血T淋巴细胞亚群及活化共刺激分子的变化,为干预措施的研究提供科学依据。方法：采用三色免疫荧光标记流式细胞仪分析法,观察在低氧暴露前和模拟海拔8 000 m低氧暴露8 h、3d6、d和10 d后,大鼠外周血T淋巴细胞亚群和T淋巴细胞活化共刺激分子的变化。结果：模拟海拔8 000 m低氧暴露8 h后,大鼠CD3＋、CD8＋、CD8＋CD28-细胞数较低氧前均显著降低（P均〈0.01）;低氧暴露3 d后,除上述变化外,CD4＋CD28＋细胞数也显著降低（P〈0.01）,CD4＋CD28-细胞数显著增加（P〈0.01）;低氧暴露6 d和10 d后,CD3＋、CD4＋呈现进一步降低趋势,CD8＋CD28＋细胞数显著增加（P〈0.01）。结论：说明模拟海拔8 000 m低氧暴露8 h和3 d后,大鼠外周血CD8＋、CD4＋T淋巴细胞活化水平均显著下降,随着低氧暴露时间的延长,CD8＋T淋巴细胞活化水平由降低变为增加。     

Ghrelin-GHSR通路在急性低氧暴露大鼠胃炎症反应中的调节作用

由胃合成分泌的食欲刺激激素（ghrelin）可通过结合并激活生长激素促分泌激素受体,（growth hormone secretagogue receptor,GHSR）在调节胃功能方面发挥重要作用。急性低氧暴露导致的消化系统营养吸收障碍和胃肠道炎症反应是否通过Ghrelin-GHSR通路调控尚无研究。本研究采用Wistar大鼠为研究对象,随机分为4组：低氧暴露0 h组、12 h组、24 h组和48 h组,低氧干预在10.2%氧浓度的低氧房中进行。干预前后记录体重;通过分子生物学检测指标评价胃组织炎症因子含量、食欲刺激激素和下丘脑GHSR mRNA相对含量和蛋白质表达水平。本研究证实,随着低氧暴露时间的延长,大鼠体重减少量逐渐增加（12 h：3.73±3.08 g、24 h：8.77±5.04 g、48 h：12.53±6.16 g）;胃组织炎症因子IL-2、IL-4、IL-10、TNFα和MCP-1蛋白含量在低氧12 h后增加（4816.9±983.7 / 9074.5±1107.8 / 18895.1±2967.5 / 37.1±9.8 / 143.5±12.5 pg/mL vs. 166.1±34.6 / 38.3±4.2 / 1429.6±123.9 / 1.7±0.3 / 13.5±2.1 pg/mL）,随着低氧时间延长,炎症因子水平逐渐下降至正常水平（24 h：846.4±94.8 / 1269.8±167.9 / 5769.7±892.6 / 7.5±2.1 / 39.3±8.5 pg/mL;48 h：546.5±97.3 / 374.9±84.9 / 1889.7±982.3 / 2.1±0.8 / 24.6±6.4 pg/mL）;低氧12 h后胃组织食欲刺激激素 mRNA水平较0 h组下降（0.49±0.06 vs. 1, P < 0.05）,48 h后上升（3.79±0.54 vs. 1, P < 0.01）,胃组织的食欲刺激激素蛋白含量在低氧24 h和48 h后均出现上升（1.23±0.15 / 1.16±0.12 vs. 1, P < 0.05）;下丘脑GHSR mRNA在低氧48 h后上升（1.99±0.29 vs. 1, P < 0.01）,蛋白质水平在低氧24 h和48 h后均出现下降（0.35±0.06 / 0.48±0.04 vs. 1, P < 0.05）。表明急性低氧暴露会导致Ghrelin-GHSR通路下调,进而促进胃组织炎症反应,而随着低氧暴露时长的延续,Ghrelin-GHSR通路可通过下调胃中炎症因子水平而避免消化系统的进一步损伤。     

低氧调节大鼠前额叶皮层IGFs家族基因的表达

目的：探讨急性和慢性低氧对胰岛素样生长因子（IGFs）家族中IGF-I,IGF一Ⅱ,IGF-1R和IGFBPlmRNA表达变化的调节。方法：我们利用低压低氧舱模拟5km低氧环境,研究大鼠暴露于急性和慢性低氧后的前额叶皮层IGF家族基因的表达变化。结果：急性和慢性连续低氧暴露后,大鼠前额叶皮层中IGF-I,IGF-II,IGF-1R和IGFBPlmRNA对低氧应激表现出明显不同的变化模式。急性低氧时,IGF-I和IGFBPlmRNA表达显著升高。而在慢性连续低氧暴露5～15d后,IGF-I和IGFBPlmRNA表达量逐渐回复到对照水平。但IGF-1R的表达仍然保持较高水平。结论：急性低氧上调IGF基因表达可能参与皮层神经元的保护,而慢性低氧升高的IGF-1R基因表达可能参与慢性低氧损伤的适应过程。     

Effects of hypothalamus destruction on the level of plasma corticosterone after blast injury and its relation to interleukin-6 in rats

Hypothalamus-pituitary-adrenal (HPA) axis is involved in the modulation of the innate immune response. The purpose of this study was to evaluate the dynamic relationship between plasma corticosterone and interleukin-6 in the hypothalamus-destroyed rats after blast injury. A total of 105 Sprague-Dawley rats were divided randomly into normal control (normal), sham operated (sham), blast injury plus sham operated (blast injury) and blast injury plus hypothalamus destruction groups. Symmetric electrolytic bilateral destruction of the hypothalamus was performed for the deeply anesthetic rats under sterile conditions. Seven days after the destruction of the hypothalamus, the animals were succumbed to moderate blast injury using a BST-I bioimpact machine. Plasma corticosterone and IL-6 levels were determined by radioimmunoassay and enzyme-linked immunosorbent assay, respectively. After blast injury, the corticosterone level in the hypothalamus-destroyed rats was significantly lower than that in the rats without destruction of hypothalamus at 3h (P<0.01) or from 5 to 8h (P<0.05). Reduction of corticosterone may be intrinsically correlated with the severe tissue injury and increased mortality (4/15 vs. 0/15, P<0.05). Circulating IL-6 level was markedly elevated in response to blast injury and hypothalamus destruction further increased IL-6 secretion (P<0.05). We concluded that elevation of pro-inflammatory IL-6 secretion might compensate the impaired HPA axis function after the trauma occurred in the hypothalamus-destroyed rats. These results also suggested that release of hypothalamus hormones is necessary to maintain certain magnitude of innate immunity after trauma.     

Repeated stress alters the ability of nicotine to activate the hypothalamic-pituitary-adrenal axis

Acute nicotine administration has been shown to activate the hypothalamic-pituitary-adrenal (HPA) axis and stimulate secretion of adrenocorticotrophic hormone (ACTH), corticosterone/cortisol and beta-endorphin (beta-END) in both rodents and humans, raising the possibility that activation of the HPA axis by nicotine may mediate some of the effects of nicotine. Since stress can increase the risk of drug use and abuse, we hypothesized that repeated stress would increase the ability of nicotine to stimulate the secretion of HPA hormones. To test our hypothesis, mice were exposed to repeated stress (swimming in 15 degrees C water for 3 min/day for 5 days) and killed 15 min after injection of saline or nicotine (0.1 mg/kg, s.c.). Repeated exposure to stress increased the ability of nicotine to stimulate plasma ACTH (p<0.05) and beta-END (p<0.05), but not corticosterone secretion. In contrast, repeated exposure to stress increased the post-saline injection levels of corticosterone (p<0.05), but not ACTH and beta-END. The present results suggest that chronic stress leads to an enhanced sensitivity of some components of the HPA axis to a subsequent nicotine challenge.     

CRF-dependent and CRF-independent mechanisms involved in hypophysial-adrenal system activation by bacterial endotoxin.

The immune system and the hypothalamic-pituitary-adrenal (HPA) axis play important role in the overall inflammatory response. The mechanism through which lipopolysaccharide (LPS, endotoxin) stimulates the HPA axis is not well understood. In order to clarify the role of hypophysiotropic peptides of paraventricular origin in the effect of LPS on ACTH and corticosterone secretion, the effect of LPS was studied on rats with lesions of hypothalamic paraventricular nucleus (PVN). It was shown that 90 min after 2 mg/kg LPS i.p. the ACTH, but not the corticosterone response was effectively blunted in PVN-lesioned rats, as compared to sham operated animals. However, in PVN-lesioned rats 240 min after treatment with LPS a significantly higher plasma ACTH and corticosterone level was monitored. It is, therefore, suggested that in response to LPS activation of HPA both CRF(s)-dependent and CRF(s)-independent mechanisms are involved, even a direct effect of the adrenal cortex should be taken into account.     

Effect of cyclooxygenase inhibitors on the vasopressin induced ACTH and corticosterone response during crowding stress.

The aim of the present study was to compare the effect of social stress on the corticotropin releasing hormone (CRH) and arginine vasopressin (AVP)-induced pituitary-adrenocortical activity. Also the significance of prostaglandins (PG) generated by constitutive and inducible cyclooxygenase (COX-1 and COX-2) in the stimulation of hypothalamic-pituitary-adrenal (HPA) axis by AVP under basal and crowding stress conditions was investigated. The control rats were housed 7 in a standard cage and stressed rats were crowded 24 in a cage of the same size during 7 days. The activity of HPA axis was determined by measuring plasma ACTH and serum corticosterone levels 1 h after i.p. AVP administration. Indomethacin (2.0 mg/kg i.p.), a non-selective COX inhibitor, piroxicam (0.2, 2.0, and 5.0 mg/kg), a more potent COX-1 than COX-2 inhibitor, and compound NS-398 (0.2 and 2.0 mg/kg) a selective COX-2 inhibitor, were administered i.p. 15 min prior to AVP (5.0 microg/kg i.p.) to control or crowded rats. The obtained results indicate that social stress for 7 days considerably inhibits the stimulatory action of AVP on ACTH secretion, while it intensifies the CRH-induced ACTH secretion. Indomethacin, piroxicam and NS-398 significantly diminished the AVP-elicited ACTH and corticosterone secretion in non-stressed rats. None of these COX antagonist induced any significant inhibition of the AVP-induced ACTH and corticosterone secretion in stressed rats. Therefore, PG generated by COX-1 or COX-2 do not participate to a significant extent in the HPA stimulation by AVP during crowding stress. These results suggest that social crowding stress desensitizes the PG stimulatory mechanism which considerably mediates the AVP-induced HPA stimulation under basal conditions. The results contrast with a lack of any involvement of PG in the CRH-induced stimulation of HPA response under basal or crowding stress conditions.     

Effects of acute and repeated exposure to stress on the hypothalamo-pituitary-adrenocortical activity in mice during postnatal development

Hypothalamo-pituitary-adrenocortical (HPA) response to a mild stressful procedure was investigated in mice at Days 8, 10, 12, and 14 of postnatal development. Pups that were removed from the dam and exposed to a novel odor (clean bedding) for 15 min showed higher plasma corticosterone levels than pups whose mother was removed from the cage for 15 min or unhandled pups at all ages, although statistically significant differences were only evident at Days 12 and 14. Lower HPA axis responding in younger mice was not due to immaturity since 8-day-old mice showed a significant and larger increase of plasma corticosterone levels when separated from the mother and isolated from littermates in the absence of bedding. Mice daily exposed to clean bedding (15 min) for the first 13 days of life did not show reduced plasma corticosterone response when reexposed to the stressor at 14 days of age. Conversely, increased plasma corticosterone levels in dams in response to removal of pups was not detectable after repeated exposure to this manipulation (14 days) regardless of the procedure their pups were submitted to, thus ruling out a role of maternal corticosterone passing through the milk on which the pups were fed. These results demonstrate that 15 min exposure to clean bedding is a noninvasive procedure able to elicit HPA axis response in developing mice over a wide age range without producing habituation.     

Effect of constitutive- and inducible-cyclooxygenase in the carbachol-induced pituitary-adrenocortical response during social stress.

Acetylcholine potently stimulates the hypothalamic-pituitary-adrenal (HPA) axis. Cholinergic receptor agonist carbachol, given intraperitoneally (i.p.) or into the lateral cerebral ventricle (i.c.v.) to non-anesthetized rats acts via multiple pathways to stimulate the HPA axis. The present study sought to determine 1) the functional selectivity of carbachol for cholinergic muscarinic and/or nicotinic receptors involved in the stimulation of HPA axis; 2) the involvement of prostaglandins (PGs) generated by constitutive and inducible cyclooxygenase (COX-1 and COX-2) in the carbachol-induced ACTH and corticosterone secretion in non-stressed rats and animals exposed to social crowding stress for 7 days (24 per a cage for 6). Carbachol was given i.c.v. or i.p. and cholinergic receptor antagonists or cyclooxygenase isoenzyme antagonists were given by the same routes 15 min earlier. One hour after the last injection trunk blood was taken for ACTH and corticosterone determinations. Atropine (0.1 microg i.c.v.), a cholinergic receptor antagonist, totally abolished the carbachol (2 microg i.c.v.)-induced ACTH and corticosterone secretion and mecamylamine (20 microg i.c.v.), a selective nicotinic receptor antagonist, did not affect this secretion. This finding indicates that carbachol functions as a selective central cholinergic muscarinic receptor agonist for the HPA axis stimulation. Crowding stress significantly diminished the carbachol (0.2 mg/kg i.p.)-induced plasma ACTH and corticosterone levels measured 1 hr after administration. Pretreatment with indomethacin (2 mg/kg i.p.), a non-selective cyclooxygenase inhibitor, significantly diminished the ACTH and corticosterone responses to carbachol (0.2 mg/kg i.p.) in control rats and moderately decreased these responses in stressed rats. Piroxicam (0.2 and 2.0 mg/kg i.p.), a COX-1 inhibitor, considerably impaired the carbachol-induced ACTH and corticosterone responses in control rats and markedly diminished these responses in stressed rats. A selective COX-2 blocker, compound NS-398 (0.2 and 2.0 mg/kg i.p.), substantially decreased the carbachol-induced hormones secretion in control rats but did not markedly alter this secretion in stressed rats. These results indicate that in the carbachol-induced HPA axis activation PGs generated by COX-1 are considerably and to a much greater extent involved than PGs generated by COX-2. Social stress markedly diminishes the mediation of PGs generated by COX-1 but PGs synthesized by COX-2 do not substantially participate in the carbachol-induced HPA response.     

Effect of cyclooxygenase inhibitors on the CRH-induced pituitary-adrenocortical activity during crowding stress.

The aim of the present study was to determine the effect of social stress and significance of prostaglandins (PG) generated by constitutive and inducible cyclooxygenase (COX-1 and COX-2) in the stimulation of hypothalamic-pituitary-adrenal (HPA) axis by corticotropin releasing hormone (CRH) under basal and social crowding stress conditions. The stressed rats were crowded in groups of 24 to a cage for 3 or 7 days, whereas the control animals were haused in groups of 7 to a cage of the same size. The activity of HPA axis was determined by measuring plasma ACTH and serum corticosterone levels 1 h after i.p. CRH administration. Inhibitors of COX-1, piroxicam (0.2, 2.0, and 5.0 mg/kg), and COX-2, compound NS-398 (0.2 and 2.0 mg/kg), were administered i.p. 15 min prior to CRH (0.1 microg/kg i.p.) to control or crowded rats. The obtained results indicate that social stress for 3 and 7 days markedly intensifies the stimulatory action of CRH on ACTH secretion. Neither piroxicam nor NS-398 induce any significant effect on the CRH-elicited ACTH and corticosterone secretion in non-stressed or crowded rats. Therefore, PG generated by COX-1 or COX-2 do not participate to a significant extent in the stimulation of HPA axis by CRH under either basal conditions or during crowding stress. These results also indicate that the stimulatory action of CRH on ACTH secretion is not only completely resistant to desensitization but is sensitized during social crowding stress. The results contrast with a significant involvement of PG in the vasopressin-induced stimulation of HPA response during crowding stress.     

Repeated handling, restraint, or chronic crowding impair the hypothalamic-pituitary-adrenocortical response to acute restraint stress.

The purpose of the present study was to assess whether, and to what extent prior handling, restraint or social crowding stress during 3-10 days affects the hypothalamic-pituitary-adrenocortical (HPA) response to an acute short-lasting restraint stress. Also the effect of a feedback inhibitory mechanism of corticosterone in the impairment of HPA axis by these stressors was investigated. Male Wistar rats were pretreated with handling 1 min/day for 3-10 days, restraint 2 times daily for 3-7 days and crowding stress for 7 days before exposure to acute restraint stress in metal tubes for 10 min. Some group of rats received exogenous s.c. corticosterone either once 25 mg/kg or 2 times daily 10 mg/kg for 3-10 days before restraint stress. After the last restraint the rats were decapitated and their trunk blood was collected for the measurement of plasma ACTH and serum corticosterone levels. Handling for 3-7 days, restraint for 3-7 days, and crowding for 7 days and a single pretreatment with corticosterone--all significantly and to a similar extent inhibited the restraint stress-induced increase in ACTH and corticosterone secretion. Chronic pretreatment with corticosterone blunted the restraint stress-induced increase in HPA axis activity. These results indicate that repeated short-lasting stress induced by handling, restraint, or crowding potently attenuates the acute restraint stress-induced stimulatory action of the HPA axis. They also indicate adaptive action of moderate stress on the HPA axis response to acute stress. The results also suggest that a short-lasting hypersecretion of corticosterone during psychological stress may induce a prolonged feedback inhibition of the HPA axis activity. The attenuation of HPA axis response by prior handling has also obvious methodological implications.