脂多糖对仔猪下丘脑-垂体-肾上腺轴内应激基因和NOD信号通路关键基因表达的影响

本试验旨在研究免疫应激对仔猪下丘脑垂体肾上腺(HPA)轴应激基因和核苷酸结合寡聚化结构域(NOD)信号通路关键基因表达的影响。选取12头杜×长×大仔猪,分成2个处理,每个处理6个重复。试验组注射100μg/kg体重的脂多糖(LPS)建立免疫应激模型,对照组注射等量的生理盐水。于注射LPS或生理盐水4 h后屠宰,取下丘脑、垂体和肾上腺。应用实时荧光定量PCR技术测定HPA轴应激基因和NOD信号通路关键基因在HPA轴中的mRNA 表达水平。结果表明:LPS导致下丘脑促肾上腺皮质激素释放激素、垂体黑素皮质激素肽和肾上腺类固醇合成急性调节蛋白mRNA 表达量显著升高(P0.05);LPS导致HPA轴中NOD信号通路关键基因NOD1、NOD2、受体互作蛋白2和肿瘤坏死因子-α mRNA 表达量显著升高(P0.05)。综上所述,LPS促进了HPA轴应激基因和NOD信号通路关键基因的表达。     

新城疫病毒对雏鸵鸟下丘脑-垂体-肾上腺皮质轴的形态及γ-氨基丁酸表达的影响

新城疫(ND)是影响鸵鸟养殖业最主要的传染病之一,新城疫病毒(NDV)作为应激原,进入机体后可引起一系列病理变化,使机体下丘脑-垂体-肾上腺皮质轴(HPA)处于过度激活或失活状态,进一步加重内环境紊乱,引起病情加重.鉴于此,本研究以45 d雏鸵鸟为试验动物,分正常组和攻毒组(皮下注射鸡新城疫标准毒株F4s E9);利用HE染色技术、透射电镜(TEM)技术和免疫组化技术定位表达(SABC)技术,研究NDV对雏鸵鸟HPA轴的形态及γ-氨基丁酸(GABA)表达的影响;结果表明:(1)雏鸵鸟HPA轴对鸡源NDV高度敏感,可引起HPA轴发生明显的病理组织学变化,肾上腺病变严重,下丘脑次之,垂体病变较轻,其病变程度反映了HPA轴功能受损的程度;(2)人工感染鸡源NDV,雏鸵鸟HPA轴内GABA表达均下降,其在肾上腺内的消长规律提示GABA可能参与了ND病理应激下的HPA轴应激反应过程;其表达数量和表达强弱与机体的病理性应激反应进程有关.     

脂多糖刺激对仔猪下丘脑-垂体-肾上腺轴Toll样受体4信号通路关键基因表达的影响

本试验旨在研究脂多糖(LPS)刺激对仔猪下丘脑-垂体-肾上腺(HPA)轴Toll样受体4(TLR4)信号通路关键基因表达的影响。选取12头断奶仔猪,分成2个组,每个组6个重复。试验组注射100μg/kg体重的LPS,对照组注射等量的生理盐水。注射LPS或生理盐水4 h后采血,测定血浆中与应激相关激素的含量;采血后屠宰仔猪,取下丘脑、垂体、肾上腺,测定TLR4信号通路关键基因的mRNA表达水平,包括TLR4、髓样分化因子88(My D88)、白细胞介素-1受体相关激酶1(IRAK1)、肿瘤坏死因子受体相关因子6(TRAF6)和核转录因子-κB(NF-κB)mRNA表达水平。结果表明:与对照组相比,1)LPS刺激导致血浆肿瘤坏死因子-α、皮质醇和促肾上腺皮质激素含量显著上升(P<0.05)。2)LPS刺激导致TLR4信号通路关键基因TLR4在下丘脑、垂体、肾上腺中mRNA表达水平显著升高(P<0.05);My D88在垂体、肾上腺中mRNA表达水平显著升高(P<0.05),在下丘脑中mRNA表达水平有升高的趋势(P<0.10);IRAK1在垂体、肾上腺中mRNA表达水平有升高的趋势(P<0.10);TRAF6在下丘脑、垂体、肾上腺中mRNA表达水平显著升高(P<0.05);NF-κB在垂体中mRNA表达水平显著升高(P<0.05)。试验结果表明LPS刺激激活了HPA轴,诱导了HPA轴的TLR4信号通路关键基因的表达。     

脂多糖刺激对断奶仔猪下丘脑-垂体-肾上腺轴PPARγ表达的影响

研究脂多糖(LPS)对断奶仔猪下丘脑-垂体-肾上腺(HPA)轴过氧化物酶体增殖物活化受体γ(PPARγ)表达的影响。对照组注射生理盐水,试验组注射LPS。注射后1.5 h和3 h采血,3 h采血后屠宰。结果表明:LPS刺激后1.5 h,中性粒细胞含量及其比例显著下降(P<0.05);LPS刺激后3 h,白细胞、淋巴细胞、中性粒细胞含量显著下降(P<0.05)。LPS刺激后1.5 h,血浆肿瘤坏死因子(TNF)-α、皮质醇和促肾上腺皮质激素释放素激素(CRH)含量显著上升(P<0.05);LPS刺激后3 h,血浆TNF-α、皮质醇和促肾上腺皮质激素(ACTH)含量显著上升(P<0.05);LPS刺激导致下丘脑、腺垂体、肾上腺皮质和髓质中PPARγ阳性细胞百分率显著升高(P<0.05)。这表明LPS导致免疫应激,激活HPA轴,诱导HPA轴PPARγ的表达。     

热休克蛋白90在糖皮质激素受体信号通路中的分子伴侣作用

在应激反应时,下丘脑-垂体-肾上腺轴(HPA)在机体的调节方面起主要作用,而糖皮质激素(GC)是HPA轴中的关键物质,因此在考量急性和慢性应激反应时,GC及其受体(GR)的变化常常是首选的研究内容.而GR正常构象的形成、激活、功能发挥与其分子伴侣-热休克蛋白90 (HSP90)关系密切.综述了HSP90的结构和功能、GC-GR信号通路中GC和GR的作用机制以及HSP90在GR信号通路中的分子伴侣作用.     

哺乳动物下丘脑-垂体-卵巢轴的研究进展

哺乳动物的下丘脑、垂体和卵巢分泌的激素在功能上相互作用,构成一个完整的神经内分泌生殖调节体系,即下丘脑垂体卵巢轴,它在生殖活动中起着主要的调节作用。下丘脑中分布的GnRH神经元可以分泌GnRH,GnRH调节垂体中促性腺激素细胞分泌促性腺激素FSH和LH,促性腺激素作用于卵巢受体,引起雌激素和孕酮分泌并影响生殖活动。从组织学角度上研究,下丘脑垂体卵巢轴中的结构,如GnRH神经元、促性腺激素细胞、卵泡随周期性变化而呈现出不同的形态结构和分泌特点。因此,对以上各种细胞的研究是探讨其所分泌激素的基础,而下丘脑垂体卵巢轴中的各种激素的研究则是了解和控制动物繁殖机能的关键。     

妊娠期小鼠下丘N-垂体-卵巢轴中PrRP和PrRP-R mRNA表达规律的研究

为探讨妊娠期小鼠下丘脑一垂体一卵巢轴中催乳素释放肽(PrRP)及其受体(PrRP-R)mRNA的表达规律,选用妊娠6、12、18 d小鼠(n=6),取下丘脑、垂体、卵巢组织,利用半定量PCR方法测定下丘脑-垂体-卵巢轴中PrRP和PrRP-R mRNA表达水平,另外利用放射免疫法(RIA)测定血浆孕酮(P)、雌二醇(E2)和催乳素(PRL)水平,探究下丘脑-垂体-卵巢轴PrRP和PrRP-R mRNA与血浆P、E2、PRL的相关关系.结果表明:妊娠期小鼠下丘脑、垂体、卵巢中都有PrRP、PrRP-R mRNA的表达,其中卵巢PrRP mRNA表达量较高,而下丘脑PrRP-R mRMA的表达量较高.妊娠期小鼠血浆P水平与垂体PrRP mRNA表达量呈显著负相关,而垂体PrRP mRNA与下丘脑PrRP-R mRNA表达量呈显著正相关,结果提示妊娠期m浆高水平的P可能通过抑制垂体PrRP mRNA的表达,进而作用于下丘脑参与妊娠相关调控.妊娠期小鼠血浆PRL水平与下丘腩、垂体、卵巢PrRP和PrRP-R mRNA的表达晕均无显著相关关系,提示血浆PRL水平可能小受上述组织PrRP的影响.     

下丘脑-垂体-性腺轴系统在动物疾病中的作用

下丘脑-垂体-性腺轴系统作为人体内三大内分泌系统之一,通过对生殖激素的分泌调节,在动物机体的生育繁殖过程中具有极其重要的作用。但是随着人们对各种疾病发生机制的了解,发现下丘脑-垂体-性腺轴系统对生殖激素调节异常也会导致许多非生殖方面疾病的发生。相应的一些其他疾病也会通过影响下丘脑-垂体-性腺轴系统,导致生殖激素分泌异常,造成生殖方面的障碍。因此对于下丘脑-垂体-性腺轴系统的研究越来越显得重要。     

HPA轴应激应答反应产生的中枢调节机制

目前普遍接受的关于应激的定义是:应激反应是机体受到强烈刺激或有害刺激以后产生的非特异性适应反应,其主要特征为机体下丘脑-垂体-肾上腺轴(hypothalamic pituitary adrenocortical axis, HPA轴)及交感肾上腺髓质系统活动增强[1].关于HPA轴功能的中枢调节研究尽管是老话题,但最近有很多新进展,本文主要就国内外近年来在这方面开展的研究作一综述.     

新型厌食神经肽nesfatin-1的分布和生物学功能

nesfatin-1是新近发现的一种厌食神经肽,在中枢主要位于下丘脑和脑干,在外周主要分布于胃、肠、胰岛和性腺,其表达受到营养、生理、病理和其他摄食激素的调节。nesfatin-1在中枢神经元和外周细胞中与多种激素协同参与摄食和血糖稳衡等能量代谢过程,并激活下丘脑-垂体-肾上腺轴(HPA)参与应激反应,还能作用于HPA影响发育期的启动。本文重点对nesfatin-1在中枢和外周的分布、影响其表达的因素以及生物学功能进行了综述。     

Hypothalamic-pituitary-adrenal axis responsiveness to insulin-induced hypoglycaemia is modified by trypanosome infection in Boran (Bos indicus) cattle.

Ten Boran (Bos indicus) cattle were used to study the stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis during trypanosome infection. Five cattle were infected with Trypanosoma congolense IL 1180 by tsetse challenge and five cattle served as controls. All infected animals developed acute trypanosomiasis. Insulin-induced hypoglycaemia (50 per cent of pre-insulin glucose concentration) was used as a stress factor. Acute hypoglycaemia was observed in three infected and three control animals after insulin challenge. Two animals from each group either did not respond or responded slowly. Hypoglycaemia in infected animals completely failed to induce an HPA axis response, while in control animals an HPA axis response was indicated by a significant increase in plasma adrenocorticotrophic hormone (ACTH) and cortisol concentrations (P less than 0.01). The results show that trypanosomiasis in Boran cattle can cause a decrease in the stress responsiveness of the HPA axis as indicated by a blunted ACTH/cortisol response to insulin-induced hypoglycaemia.     

Association study of molecular polymorphisms in candidate genes related to stress responses with production and meat quality traits in pigs

The hypothalamic-pituitary-adrenal (HPA) axis exerts a large range of effects on metabolism, the immune system, inflammatory processes, and brain functions. Together with the sympathetic nervous system, it is also the most important stress-responsive neuroendocrine system. Both systems influence production traits, carcass composition, and meat quality. The HPA axis may be a critical target for genetic selection of more robust animals. Indeed, numerous studies in various species have demonstrated the importance of genetic factors in shaping the individual HPA axis phenotype, and genetic polymorphism can be found at each level of the axis, including hormone production by the adrenal cortices under stimulation by adrenocorticotropic hormone (ACTH), hormone bioavailability, or receptor and postreceptor mechanisms. The aim of the present experiment was to extend these findings to the brain neurochemical systems involved in stress responses. To this end, a number of candidate genes were sequenced for molecular polymorphisms and their association was studied with stress neuroendocrine and production traits in a genetically diverse population consisting of 100 female pigs from an advanced intercross (F10-F12) between 2 highly divergent breeds, Large White (LW) and Meishan (MS). The LW breed has a high production potential for lean meat and a low HPA axis activity, and the MS breed has low growth rate, fat carcasses—but large litters of highly viable piglets—and a high HPA axis activity. Candidate genes were chosen in the catecholaminergic and serotonergic pathways, in the pituitary control of cortisol production, among genes previously demonstrated to be differentially expressed in ACTH-stimulated adrenal glands from LW and MS pigs, and in cortisol receptors. Sixty new polymorphisms were found. The association study with carcass and meat quality traits and with endocrine traits showed a number of significant results, such as monoamine oxidase (MAOA) polymorphisms with growth rate (P = 0.01); lean content and intramuscular fat (P < 0.01), which are the most important traits for carcass value; dopamine receptor D3 (DRD3) with carcass composition (P < 0.05); and vasopressin receptor 1B (AVPR1B) with meat quality traits (P ≤ 0.05). The effect of these polymorphisms on neuroendocrine parameters (eg DRD3 and HPA axis or AVPR1B and catecholamines) indicates information regarding their biological mechanism of action.     

The immediate effects of weaning stress on the hypothalamus‐pituitary‐adrenal alteration of newly weaned piglets

This study was conducted to examine the effects of weaning stress on gene expression of specific markers in hypothalamus‐pituitary‐adrenal (HPA) axis and neuronal activity in the newly weaned piglets. Twelve 28‐days‐old, newly weaned crossbred (Landrace × Yorkshire × Duroc) male piglets from 6 l (2 piglets/l) were randomly categorized into two groups: (a) weaning stress: piglets were separated from their dams, relocated and mixed with the unacquainted domestic piglets for 2 hr (stress, n = 6); (b) no‐stress: piglets stayed with their dams in the farrowing house (NS; n = 6). After weaning stress, all piglets were electrically euthanized and the blood samples/HPA tissues were collected for subsequent analysis, including plasma cortisol and mRNA expression of c‐fos, c‐jun, corticotropin‐releasing hormone (CRH), CRH receptor 1 (CRHR‐1) and adrenocorticotropin hormone receptor (MC2R). Results: Weaning stress significantly (p < 0.05) increased the plasma cortisol level and suppressed the expression of c‐fos and CRH in hypothalamus. In addition, weaning stress enhanced the mRNA abundance of c‐jun and CRHR‐1 in the pituitary gland. No significant differences in the gene expression of MC2R and CRHR‐1 were observed in the adrenal gland between treatment groups. Taken together, HPA involved in weaning stress and CRHR‐1 and c‐jun could be potential markers to evaluate the activation of HPA axis.     

NDV对雏鸵鸟HPA轴的影响

以45日龄雏鸵鸟为试验动物,分正常组和攻毒组,利用RIA技术和TUNEL技术,探讨新城疫病毒（NDV）对雏鸵鸟HPA轴的影响。结果表明,雏鸵鸟感染NDV,HPA轴内细胞凋亡数量在病毒感染期间明显高于对照组,提示NDV能诱导雏鸵鸟HPA轴系统发生细胞凋亡;在病毒接种后1d,肾上腺内可检测到大量凋亡细胞,接种5d后凋亡数量显著增加（P〈0.05）,之后凋亡呈下降趋势,肾上腺内细胞凋亡的动态变化反映了雏鸵鸟HPA轴对ND病变的适应和调节。雏鸵鸟感染NDV,血清ACTH水平于NDV接种后1d开始上升,至5d达到峰值（P〈0.01）,之后有所下降,渐趋于正常;血清Cor水平于病毒接种后1d开始下降,至7d有所回升,9d渐趋于正常水平,表明NDV接种后雏鸵鸟血清ACTH和Cor水平的变化与其HPA轴功能的损伤及恢复密切相关。     

Comparison of the hypothalamic–pituitary–adrenal axis in MDR1-1Δ and MDR1 wildtype dogs

Objective: To evaluate the hypothalamic–pituitary–adrenal (HPA) axis in MDR1‐1Δ (dogs with the MDR1 mutation associated with ivermectin sensitivity) and MDR1 wildtype dogs. Design: Prospective study. Setting: Institutional vivarium. Animals: Seven healthy Collie dogs. Measurements: MDR1 genotyping was used for allocation of dogs to 1 of 2 groups: dogs homozygous for the wildtype MDR1 allele (MDR1 wildtype) and those homozygous for the MDR1‐1Δ mutation (MDR1 mutant). Blood samples were obtained for determination of cortisol and adrenocorticotropin hormone (ACTH) concentrations under basal conditions, before and after ACTH administration, and before and after dexamethasone administration. Main results: Significant differences were identified between the MDR1 mutant and MDR1 wildtype groups. Basal plasma cortisol concentrations and cortisol concentrations after ACTH administration were significantly lower in MDR1 mutant dogs as compared with MDR1 wildtype dogs. Plasma ACTH concentrations after dexamethasone administration were significantly lower in MDR1 mutant dogs as compared with MDR1 wildtype dogs. Conclusions: Results suggest that P‐glycoprotein (P‐gp) plays a role in regulation of the HPA axis. Furthermore, it appears that the HPA axis in MDR1 mutant dogs that lack P‐gp is suppressed compared with MDR1 wildtype dogs. This finding may explain some clinical observations in breeds known to harbor the MDR1 mutation including Collies, Shelties, Australian Shepherds, and others. There is a clinical impression that many of these dogs have worse outcomes in response to stress and, at times, respond poorly to appropriate therapy. HPA axis suppression, secondary to the MDR1 mutation, could result in a relative adrenal insufficiency (RAI) state during times of stress or illness. Further studies are required to determine the relationship between the MDR1 genotype and RAI.     

慢性冷热应激对放牧西门塔尔牛抗氧化功能及HPA轴、SAM轴激素分泌的影响

为研究慢性冷热应激对放牧条件下西门塔尔牛生理指标、抗氧化功能及下丘脑-垂体-肾上腺皮质轴(HPA)、交感-肾上腺-髓质轴(SAM)激素分泌的影响,选取内蒙古锡林郭勒盟苏尼特左旗某家庭牧场体质量相近、体况健康的西门塔尔牛20头,试验期间测定试验牛生理指标,于试验期最后一天清晨进行颈静脉采血并制备血清,采用ELISA方法检测血清中超氧化物歧化酶(SOD)、丙二醛(MDA)、总抗氧化能力(T-AOC)、谷胱甘肽过氧化物酶(GSH-Px)、促肾上腺皮质激素(ACTH)、糖皮质激素(GC)、肾上腺素(EPI)及去甲肾上腺素(NE)的含量。结果表明,冷热应激对西门塔尔牛产生了一定的应激:冷应激状态下(冬季)西门塔尔牛血清中ACTH、GC含量显著高于热应激状态(夏季)和非应激状态(春季)(P<0.05),夏季和冬季西门塔尔牛血清中NE、EPI含量均显著高于春季(P<0.05);夏季和冬季西门塔尔牛血清中MDA含量显著高于春季(P<0.05),春季和夏季T-AOC含量显著高于冬季(P<0.05),GSH-Px含量在3个季节之间差异不显著(P>0.05)。综上所述,冷热应激降低了西门塔尔牛的抗氧化能力,可能对西门塔尔牛机体造成了一定的损伤;冷热应激激活了西门塔尔牛的HPA轴和SAM轴,进而提高机体对冷热应激的适应能力。     

Hypothalamic-Pituitary-Adrenal Axis Dysfunction in Hospitalized Neonatal Foals

Background: Transient hypothalamic-pituitary-adrenal (HPA) axis dysfunction occurs frequently in critically ill humans and impacts survival. The prevalence and impact of HPA axis dysfunction in critically ill neonatal foals are not well characterized.
Hypotheses: (1) HPA axis dysfunction occurs in hospitalized neonatal foals, and is characterized by inappropriately low basal serum cortisol concentration or inadequate cortisol response to exogenous adrenocorticotropic hormone (ACTH); (2) hospitalized foals with HPA axis dysfunction have more severe disease and are less likely to survive than hospitalized foals with normal HPA axis function.
Animals: Seventy-two hospitalized foals and 23 healthy age-matched foals.
Methods: Basal ACTH and cortisol concentrations were measured and a paired low-dose (10 μg)/high-dose (100 μg) cosyntropin stimulation test was performed at admission in hospitalized foals. HPA axis dysfunction was defined as (1) an inappropriately low basal cortisol concentration or (2) an inadequate increase in cortisol concentration (delta cortisol) after administration of cosyntropin, with cut-off values for appropriate basal and delta cortisol concentrations determined from results obtained in healthy age-matched foals.
Results: Forty-six percent of hospitalized foals had an inappropriately low basal cortisol concentration and 52% had an inadequate delta cortisol concentration after administration of the 100 μg dose of cosyntropin. An inadequate delta cortisol response to the high (100 μg) dose of cosyntropin was significantly correlated with shock and multiple organ dysfunction syndrome in hospitalized foals, and with decreased survival in a subgroup of septic foals.
Conclusions and Clinical Importance: HPA axis dysfunction occurs frequently in hospitalized neonatal foals, and negatively impacts disease severity and survival.     

Stress and its influence on reproduction in pigs: a review

The manifestations of stress, defined as a biological response to an event that the individual perceives as a threat to its homeostasis, are commonly linked to enhanced activity of the hypothalamo-pituitary-adrenal (HPA) axis and the activation of the sympathetic adreno-medullary (SA) system. Activation of the HPA system results in the secretion of peptides from the hypothalamus, principally corticotropin releasing hormone (CRH), which stimulates the release of adrenocorticotropic hormone (ACTH) and beta-endorphin. ACTH induces the secretion of corticosteroids from the adrenal cortex, which can be seen in pigs exposed to acute physical and/or psychological stressors. The present paper is a review of studies on the influence of stressors on reproduction in pigs. The effects of stress on reproduction depend on the critical timing of stress, the genetic predisposition to stress, and the type of stress. The effect of stress on reproduction is also influenced by the duration of the responses induced by various stressors. Prolonged or chronic stress usually results in inhibition of reproduction, while the effects of transient or acute stress in certain cases is stimulatory (e.g. anoestrus), but in most cases is of impairment for reproduction. Most sensitive of the reproductive process are ovulation, expression of sexual behaviour and implantation of the embryo, since they are directly controlled by the neuroendocrine system.     

Effects of dermal dexamethasone application on ACTH and both basal and ACTH-stimulated cortisol concentration in normal horses

There are no data available regarding the systemic (adverse) effects which might be induced by topical/dermal glucocorticoids (GCs) application in the horse. Besides their widespread use for the treatment of a variety of peripheral inflammatory disorders such as atopic dermatitis, eczemas or arthritis in the horse, their surreptitious application has become a concern in doping cases in competition/performance horses. Assessing both basal and ACTH‐stimulated plasma cortisol as well as basal ACTH concentrations following application of dexamethsone‐containing dermal ointment is necessary to determine influences on hypothalamus‐pituitary‐adrenal (HPA) axis. Ten clinically healthy adult standardbred horses (6 mares, 4 geldings) were rubbed twice daily each with 50 g dexamethasone‐containing ointment on a defined skin area (30 × 50 cm) for 10 days. RIA and chemiluminescent enzyme immuno‐metric assay were used to determine resting and ACTH‐stimulated plasma cortisol and basal ACTH concentrations, respectively. HPA feedback sensitivity and adrenal function were measured by a standard ACTH stimulation test. Dermal dexamethasone suppressed significantly the resting plasma cortisol level (to 75–98%) below baseline (P < 0.001) within the first 2 days and decreased further until day 10. ACTH stimulation test showed a markedly reduced rise in plasma cortisol concentrations (P < 0.001 vs. baseline). Plasma ACTH level decreased also during topical dexamethasone application. The number of total lymphocytes and eosinophil granulocytes was reduced, whereas the number of neutrophils increased. No significant change of serum biochemical parameters was noted. Dermal dexamethasone application has the potential to cause an almost complete and transient HPA axis suppression and altered leukocyte distribution in normal horses. The effects on HPA axis function should be considered in relation to the inability of animals to resist stress situations. The data further implicate that percutaneously absorbed dexamethasone (GCs) may cause systemic effects relevant to ‘doping’.     

Ontogeny of the hypothalamo-pituitary-adrenocortical axis in the chicken embryo: a review

The embryo of the domestic fowl (Gallus domesticus) tenders one distinctive advantage over general mammalian models for investigating the development of the hypothalamo–pituitary–adrenocortical (HPA) axis. This is the relative simplicity with which the embryonic endocrine environment can be influenced without confounding maternal influences. The ease of direct manipulation of the embryonic endocrine system has facilitated analysis of the development and function of the HPA axis in the chick embryo. As the chick embryo develops, functional activation of the adrenal gland is regulated at three different levels: the adrenal gland itself, the anterior pituitary, and the hypothalamus. The adrenal gland appears capable of independent secretion of glucocorticoids from day 8 until shortly after day 14 of embryonic development, at which point the pituitary influences adrenocortical activity. Around the same age, the hypothalamic level of control also begins. The information covered in this review will describe the major steps in the development of the HPA axis in the chicken embryo and show that the chicken has an emblematic HPA neuroendocrine axis.