Site-specific regulation of gene expression by estrogen in the hypothalamus of adult female rats

Estrogen plays critical roles in the neuroendocrine system of adult female rats through separate actions, respectively, in the preoptic area (POA) and the ventromedial nucleus of the hypothalamus (VMH). Seven-week-old rats were treated with/without estrogen after they were ovariectomized, and four estrogen-responsive, neuronal system-related genes, encoding alpha4 neuronal nicotinic acetylcholine receptor (Chrna4), GABA_A receptor delta (Gabrd), serotonin receptor 6 (Htr6), and GABA transporter 2 (Slc6a13), were investigated by real-time RT-PCR and Western blot analyses to examine their differential regulation by estrogen between the anterior part containing POA and the posterior part containing VMH. We further examined Bax, Bcl2, and Prkce, the former two genes to be involved in the gene expression network of Chrna4 and the latter gene, that of Gabrd. The regulation of Bax and Bcl2 by estrogen differed between the anterior and posterior parts. The results demonstrated differential regulation of these neuronal system-related genes by estrogen between the anterior and posterior parts of the hypothalamus and suggested the roles of gene expression networks for the respective genes in the neuroendocrine system of adult female rats.     

Inhibition of gastric acid secretion evoked by activation of the hypothalamic paraventricular nucleus

Summary Electrical stimulation of the paraventricular nucleus depressed the gastric acid output of adrenalectomized male rats of which gastric acid output had been induced by insulin hypoglycemia. Electrical stimulation of the pituitary stalk produced a similar secretory response, but the response was abolished by bilateral lesion of the paraventricular nucleus. These findings allow us to speculate that the paraventricular nucleus is capable of modulating gastric acid secretion, and suggest that the nucleus has a neural connection between the neurohypophysis and the system relevant to gastric acid secretion.     

Mechanism of inhibition of gastric acid secretion by vagal denervation in the rat

Acute bilateral subdiaphragmatic vagotomy in the conscious fistula rat greatly reduced gastric acid secretion, stimulated by the combined intravenous infusion of pentagastrin (10 μg/kg/h), histamine dihydrochloride (3 mg/kg/h) and carbachol (50 μg/kg/h). The reduction of acid output was immediate (within 15 min after vagotomy). The greatly reduced acid response to these secretagogues persisted for at least 8 weeks after vagal denervation (longest time studied). The sudden and dramatic effect of vagotomy on acid secretion is not related to a possible deficiency of either acetylcholine or histamine at the respective receptor site since the combined infusion of gastrin, histamine and carbachol did not prevent the suppression of acid secretion. Since the decline in acid output following vagal denervation was immediate, it probably reflects a sudden inaccessibility rather than loss of muscarinic or H₂-receptors. The acid output obviously depends upon intramural “transducer” systems that respond to and transmit the vagal input. It is likely that the intramural ganglia represent such “transducer” systems. In the absence of a vagal drive these neuronal “transducers” cease to fire and as a result the parietal cells become almost unresponsive to stimuli.     

下丘脑外侧区对大鼠胃缺血-再灌注损伤调控的神经机制

目的:观察电刺激下丘脑外侧区(LHA)对胃缺血-再灌注损伤(GI-RI)的影响,并初步分析其可能的神经机制。方法:用电和化学刺激、电损毁神经核团及切断外周神经等方法,观察LHA对大鼠胃缺血30min,再灌注60min所致损伤的影响并分析背侧迷走复合体(DVC)、迷走神经和交感神经在这一效应中的作用。结果:①电刺激LHA或LHA内注射L-谷氨酸(L-Glu),GI-RI均显著加重;②电损毁双侧LHA则减轻GI-RI;③损毁双侧DVC能取消电刺激LHA对GI-RI的加重;④分别切断膈下迷走神经和切除腹腔交感神经节后再电刺激LHA,GI-RI则减轻。结论:LHA是对GI-RI具有加重作用的特异性中枢部位,DVC以及迷走神经、交感神经均参与了LHA对GI-RI的调控作用。     

Pavlovian conditioning of the cephalic phase of gastric acid secretion in the rat

In this experiment the potential for the stimulus control of cephalic phase visceral secretions was examined. A Pavlovian conditioning procedure was used to train one set of rats to expect food in a specific test environment. The gastric acid outputs of these animals to this signalled meal were compared to the acid responses of two other groups of rats which served as controls for associative learning effects. The results of this experiment indicated that after only two CS-US pairings cephalic phase acid output of conditioned rats prior to feeding was statistically greater than that of controls. These data reveal that cephalic gastric acid responses can be brought rapidly under stimulus control by conditioning techniques. The implications of these findings to the control of cephalic phase visceral responses and to the role of conditioning in the elaboration or natural development of these responses are discussed.     

Effects of chemical stimulation of the hypothalamus upon gastric secretion

Male rats with a permanently implanted cannula in the feeding area of the hypothalamus were tested for a reliable eating response to adrenergic stimulation of the LHA and a reliable drinking response to cholinergic stimulation. The effects of intrahypothalamic administration of 40 mM norepinephrine and 2, 4 mM carbachol upon the acid output of the constantly perfused stomach of curarized rats were investigated. After the injection of norepinephrine a twofold increase in the acid output was observed and a decrease of an equal amount occurred after an injection of carbachol. The results are consistent with the hypothesis that some regions of the hypothalamus can subserve a sympathic and parasympathic function depending upon how they are chemically stimulated.     

Copulatory behavior and hypothalamic estrogen and progestin receptors in chronically insulin-deficient female rats

The effects of relatively short- or long-term diabetes on sexual receptivity and proceptivity and on hypothalamic estrogen and progestin receptors were examined in rats fed regular chow or high fat diet. Ovariectomized, streptozotocin-induced chronically insulin deficient and normal rats received sequential treatments with 2 μg estradiol benzoate (EB) and 1 mg progesterone (P) 10 days following the induction of diabetes and were tested for lordosis and soliciting behaviors. Nondiabetic rats fed either diet displayed significantly higher lordosis and solicitation behaviors than chow-fed diabetics, and fat-fed diabetic animals displayed behavior levels intermediate to those of nondiabetic and chow-fed rats. Ten days after the induction of diabetes, the levels of hypothalamic estrogen receptors of chow-fed diabetics were significantly lower than nondiabetics with the fat-fed diabetic group showing intermediate levels. However, 70 days after streptozotocin treatment diabetic rats had significantly lower estrogen receptors than nondiabetics regardless of the diet. Treatment of long-term (70 days) diabetic rats with 1–2 U of U-100 Lente insulin for 24 hr or 7 days was ineffective in restoring the hypothalamic estrogen receptor concentrations to those of nondiabetics. Three weeks following induction of diabetes, induction of cytoplasmic progestin receptors by EB treatment was significantly impaired in diabetic animals fed either chow or high fat diet. Although the reproductive dysfunctions present in short-term diabetic female rats may be due in part to chronic fuel deprivation, it appears that the long-term maintenance of cytosol estrogen receptor level is dependent on other actions of insulin. Furthermore, restoration of hypothalamic estrogen receptors in long-term diabetic rats may require either longer than 7 days of insulin therapy or another mode of treatment (e.g., sex hormones). The behavioral improvement of diabetic animals on HF diet could be accounted for by mechanisms other than enhancement of EB-induced cytoplasmic progestin receptors.     

A new method for the collection of gastric secretion in conscious rats

Summary A new method has been devised for the collection of gastric secretion in conscious rats. A stainless steel wire loop was placed around the pylorus. Seven to 10 days later when the rat had recovered from the operation and was showing significant weight gains and food intake, it was starved for 48 h and collection of gastric juice was begun by tightening the wire loop. This effectively occluded the pylorus, and had the advantage that the animal remained conscious during the procedure. The rat was sacrificed after a certain period of time, and the gastric content was collected. After centrifugation, the total acidity of the supernatant was determined by titration with 0.01 N NaOH. With the present method, the total acid output as well as the rate of gastric secretion were significantly higher than those of similarly operated rats under restraint and those which were investigated using the Shay method. The gastric mucosa of each rat was examined and it was found that the incidence of gastric lesions in the control group using the present method was significantly lower than that in the other operated groups.This method is regarded as less unphysiological than the widely used Shay technique, in which pyloric ligation is performed in the unconscious rat immediately before the collection of gastric juice.     

Shock predictability and gastric secretion in the chronic gastric fistula rat

In Experiment 1 rats exposed to unpredictable grid shock demonstrated a significant decrease in gastric secretion and total acid output as compared to rats exposed to predictable shock and rats exposed only to the tone stimulus. In Experiment 2 rats were immobilized in restraint cages. Restraint plus predictable shock and restraint plus unpredictable shock resulted in a significant decrease in stomach acid output as compared to restrained no-shock controls. These results do not support a gastric hypersecretion hypothesis for studies which have reported the development of stomach ulcers by using unpredictable shock stress.     

Effect of vagotomy and glucose administration on gastric acid secretion in the Atlantic cod,Gadus morhua

Cods were prepared for measurement of gastric acid secretion. Cannulae were implanted for drainage of the stomach and for separate perfusion of the stomach and intestine. Fishes, intestinally perfused with diluted sea-water (33% SW) exhibited high rates of acid secretion. This “basal” secretion was abolished (96% inhibition) by bilateral vagotomy. Perfusion of the stomach with isosmotic glucose (5.5%) diminished the amount of titratable acid in the gastric effluence, and induced oral ingestion of water. Only part of the decrease could be explained by neutralization by ingested sea-water. Perfusion of the intestine with 5.5% glucose, containing sea-water to raise the osmolality to that of 50% SW, depressed gastric acid secretion compared to 50% SW-perfused controls, without significantly affecting oral intake of water. I.m. administration of glucose, increasing plasma glucose to the same level as intraluminal administration, did not affect acid secretion or oral water ingestion. The study demonstrates the existence of a potential intestinal mechanism for inhibition of gastric acid secretion, and indicates that vagal activity is independent of the blood glucose level in the cod.     

去卵巢大鼠骨质疏松对下丘脑雌激素α受体的影响

目的 观察去卵巢雌性大鼠骨质疏松对下丘脑雌激素α受体(estrogen receptor alpha,ERa)及基基因表达的影响。方法 将45只SD大鼠随机分为对照组、假手术对照组和去卵巢组,用免疫组织化学方法和原位杂交方法检测下丘脑ERa及其mRNA表达。结果 去卵巢组ERa受体及其mRNA阳性细胞与对照组比较显著减少(P<0.01)。结论 下丘脑ERa受体及其mRNA阳性细胞的减少可能在绝经后骨质疏松发生起重要作用。     

Shock-stress,gastric secretion and habituation in the chronic gastric fistula rat

Unrestrained rats exposed to shock-stress showed an abrupt reduction in both the volume and acidity of gastric secretions, followed by a rapid poststress recovery. The gastric response pattern did not distinguish between rats receiving avoidable or unavoidable shock. Marked habituation of the acid inhibition response occurred within 4 stress sessions.     

雌激素α、β受体在雌性大鼠眼葡萄膜组织中的表达

目的 探讨雌激素α、β受体（ERα、ERβ）在雌性大鼠眼葡萄膜组织的表达。方法 选择青春期SD雌性大鼠22只,采用颈椎脱臼处死大鼠, 取眼球作常规石蜡包埋,连续切片, SP免疫组织化学方法显示ERα、ERβ在葡萄膜组织的表达;采用Tanaka记分法对ERα、ERβ进行定量分析,并设正常大鼠子宫作阳性对照;PBS代替一抗作阴性对照。同时采用放射免疫分析方法检测大鼠血清雌二醇的浓度。结果 ERβ在虹膜基质细胞、虹膜前后两层色素上皮细胞、睫状体非色素上皮和色素上皮、脉络膜各层血管内皮的表达水平主要呈中表达或高表达;ERα则表达不明显。ERβ阳性表达率明显高于ERα,经统计学分析两者间有显著性差异（P＜0.05）。ERα、ERβ免疫阳性反应物呈颗粒状,定位在细胞质或细胞核。正常大鼠血清雌二醇水平经检测含量为(22.13±3.54)ng/L。结论 大鼠葡萄膜组织以ERβ表达为主,雌激素主要通过ERβ信号转导途径对这些组织的功能起调控作用。     

The effect of acute bilateral adrenalectomy on serotonin-induced inhibition of gastric acid secretion and acute gastric mucosal injury in rats

Serotonin (5-hydroxytryptamine, 5-HT) produces many changes in gastric functional parameters, including the inhibition of gastric acid secretion and changes in mucosal blood flow. Exogenous 5-HT has also been shown to induce gastric erosion. The influence of adrenalectomy on experimental lesions in the rat gastric mucosa remains controversial. The aim of this study was to see the effects of adrenalectomy on pentagastrin stimulated gastric acid secretion in anaesthetized male Wistar rats. Gastric acid was collected via cannulae placed in the stomach. 5-HT (3.5 μmol/kg, i.v.) inhibited pentagastrin stimulated acid output by 54% and produced haemorrhagic gastric lesions with a mean ulcer index of 2±0.3. Adrenalectomy prevented both 5-HT induced inhibition of gastric acid secretion and mucosal injury. The results suggest that the effects of 5-HT require an intact adrenal gland.     

Mechanism of inhibition of gastric acid secretion by hypertonic solutions and vasopressin

Summary An experiment was performed in female rats in order to assess the influence and mechanism underlying the effects of hyperglycemia, hypertonic saline and vasopressin upon the gastric acid secretion and mucosal blood flow (MBF). Infusion of isotonic saline did not alter acid output and gastric clearance of plasma aminopyrine whereas hypertonic solutions (20% glucose or 3% NACl) significantly increased plasma osmolality and decreased the acid secretion within 30 min and recovered to normal levels after 2 h. Vasopressin also effectively inhibited acid secretion. Both hypertonic solutions and vasopressin decreased the mucosal blood flow. However, the ratio (R) of MBF to gastric secretory rate which is a helpful guide to the mechanism of secretory inhibition did not significantly change in either case. We concluded that all three agents probably had a direct action on secretion rather than decreasing MBF. The mechanism of inhibition of acid secretion and its relationship to MBF was suggested and discussed.     

Intracerebroventricular pentagastrin fails to affect feeding and acid secretion in the rat

The recent finding of immunoreactive gastrin in the pituitary and hypothalamus of the pig, cow and rat suggests that this peptide may have a physiologic function in the central nervous system. Because gastrin is an important regulator of gastric acid secretion, and may also affect food intake, we tested the hypothesis that direct intracerebroventricular injection of pentagastrin may also affect these variables. The results fail to support the hypothesis.     

侧脑室注射nesfatin-1抑制大鼠胃酸分泌

 目的 观察侧脑室注射nesfatin-1对大鼠胃黏膜泌酸功能的影响,并探讨其可能作用机制。方法 雄性SD大鼠,侧脑室置管后,分别给以侧脑室注射1、5和50pmol/rat的nesfatin-1及等体积的灭菌水（5μL/rat）,于20min及1、2、4和6h处死大鼠,收集胃液,测定其胃酸的变化。并用RT-PCR、Western blot检测胃黏膜中组胺酸脱羧酶（HDC）mRNA及蛋白的表达,ELISA法检测胃体黏膜中组胺的含量。其后选择最强作用浓度进一步检测nesfatin-1在不同作用时间点对大鼠胃酸分泌的影响。结果 注射浓度为5和50pmol/rat的nesfatin-1后2h,大鼠胃酸分泌减少,其中50pmol/rat作用最强（均P <0.05）。同时大鼠胃黏膜中 HDC mRNA及蛋白的表达受到抑制（P <0.05）。注射50pmol/rat的nesfatin-1在1,2h能够抑制胃体黏膜中组胺的表达,2h抑制更明显（P<0.05）。结论 侧脑室注射nesfatin-1可呈剂量和时间依赖性的抑制大鼠胃酸的分泌,组胺信号通路可能参与了上述过程。     

Immunoelectron microscopic observations of hypothalamic TRH-containing neurons in rats

Summary Immunoreactive TRH-containing neurons and their synaptic associations were studied electron microscopically in the paraventricular nucleus (PVN) and dorsomedial nucleus (DMH) of the rat hypothalamus. In propylthiouracil (PTU)-treated rats, the immunoreactive cell bodies in the PVN appeared to be activated, showing a hypertrophic perikaryon, well developed Golgi bodies and numerous secretory granules. No such alterations were evident in the TRH neurons in the DMH. These findings suggest that the PVN-TRH neurons are involved in the hypothalamic-hypophysial-thyroid axis. Further, it was shown that unlabeled nerve terminals containing small and large clear vesicles make synaptic contacts with the TRH perikarya in the PVN. Thus it is likely that PVN-TRH neurons are regulated both by thyroid hormones and by other neuronal signals. In the DMH, unlabeled nerve terminals containing small and large clear vesicles, and immunoreactive terminals form synapses with TRH neurons. Thus the DMH-TRH neurons may be under dual neuronal control. It was further noted that in the DMH and PVN, TRH nerve terminals make synaptic contacts with other unlabeled neurons. It is evident that TRH acts as a neurotransmitter or neuromodulator, although the origin of TRH terminals should be elucidated.     

Multiple connections of medial hypothalamic neurons in the rat

Summary The responses of 700 single neurons in the hypothalamus to electrical stimulation of the preoptic area, limbic structures, and midbrain were studied to determine the location of neurons with multiple inputs and to identify by antidromic activation the projection areas of those neurons.Converging excitatory inputs, observed in 134 responsive hypothalamic neurons, were principally derived from the preoptic, limbic, and midbrain areas. Inputs from separate nuclei of the amygdala were noted in the response of individual hypothalamic neurons. Two classes of short latency transsynaptic responses to amygdala stimulation were defined, indicating either separate pathways from the amygdala to the medial hypothalamus or two types of fibers conducting at different velocities. Stimulation of single or multiple sites in the preoptic and limbic areas, as well as in the arcuate nucleus and medial forebrain bundle produced inhibition of hypothalamic neuronal activity.Most antidromically identified medial hypothalamic neurons projected to the preoptic area, median eminence (tuberoinfundibular neurons), or midbrain. Evidence is presented for collateral projections of tuberoinfundibular neurons to the preoptic area and reticular formation. Medial hypothalamic neurons received inputs from the preoptic area, lateral septal nucleus, amygdala, ventral hippocampus (subiculum), and fornix. These findings illustrate a pattern of reciprocal connections between the medial hypothalamus and limbic and midbrain structures.It was concluded that the hypothalamus contains a type of neuron that is equipped to perform complex integrations and to coordinate directly the behavior of neurons in a diversity of anatomical regions.Abbreviations ABL basolateral nucleus of the amygdala - ACO cotical nucleus of the amygdala - AHA anterior area of the hypothalamus - ARH arcuate nucleus of the hypothalamus - DMH dorsomedial nucleus of the hypothalamus - FX fornix - HPC ventral hippocampus (subiculum) - LS lateral septal nucleus - ME median eminence - MH medial hypothalamus - MFB medial forebrain bundle - MP posterior mamillary nucleus - PH posterior nucleus of the hypothalamus - PMD dorsal premamillary nucleus - PMV ventral premamillary nucleus - POA preoptic area - PVG periventricular gray - PVH paraventricular nucleus of the hypothalamus - RF reticular formation of the mesencephalon - RT reticular nucleus of the thalamus - SUM supramamillary nucleus - VMH ventromedial nucleus of the hypothalamus Performed with financial support from the National Institutes of Health (Grants NS 09688 and RR 00165)