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.     

CRF receptor type 1 mediates continual hypoxia-induced CRF peptide and CRF mRNA expression increase in hypothalamic PVN of rats

We demonstrated previously that hypoxia activated CRF and CRF mRNA in PVN, and CRF receptor 1 (CRFR1) mRNA in rat pituitary. The aim of the study is to test whether the hypoxia-activated CRF and CRF mRNA is associated with triggering CRFR1. Rats were exposed to hypobaric hypoxia at altitude of 2 and 5 km. CRF and CRF mRNA were assayed by immunostaining and in situ hybridization. CRFR1 mRNA was assayed by RT-PCR. Results showed that 5 km continual hypoxia increased CRF and CRF mRNA in PVN, CRFR1 mRNA in pituitary, and plasma corticosterone. The hypoxia-increased CRF, CRF mRNA, CRFR1 mRNA, and corticosterone were blocked by CRFR1 antagonist (CP-154,526), suggesting that CRFR1 in PVN and pituitary are responsible for the hypoxia-increased CRF and CRF mRNA in PVN.     

Differential contribution of hypothalamic MAPK activity to anxiety-like behaviour in virgin and lactating rats

The c-Raf - MEK1/2 - ERK1/2 mitogen-activated protein kinase (MAPK) intracellular signalling cascade in neurons plays important roles in the control of a variety of behaviours, including social behaviours and anxiety. These roles partially overlap with those described for oxytocin (OXT), and it has been shown that OXT activates the MAPK pathway in the hypothalamus (of male), and hippocampus (of female) rats. Here, by combining behavioural (light/dark box) and biochemical analyses (western blotting), we tested two hypotheses: (i) that OXT is anxiolytic within the hypothalamus of females, and (ii) that this effect, as well as that of lactation-associated anxiolysis, depends on the recruitment of the MAPK pathway. We found that, when injected bilaterally into the hypothalamic paraventricular nucleus (PVN), OXT decreased anxiety-like behaviour in virgins, and that this effect depended on phosphorylation of MEK1/2. MAPK pathway activation in lactation was evident by high phosphorylated (p) MEK1/2 levels, and nuclear translocation of ERK1. The high pMEK1/2 levels were necessary for the anxiolytic phenotype typically observed during lactation. Interestingly, exogenous OXT in lactating rats reduced pMEK1/2 levels without a concomitant effect on anxiety, indicating that OXT receptor activation can lead to recruitment of additional intracellular pathways to modulate MEK activity. Still other pathways could include MEK, but without subsequent activation of ERK, as we did not observe any increase in OXT-induced ERK phosphorylation. Together the results demonstrate that the MAPK pathway, especially MEK1/2, is critically involved in the regulation of anxiety-like behaviour in female rats.     

Physiological changes in rat hypothalamic CRF: Circadian,stress and steroid suppression

Hypothalamic CRF-like immunoreactivity was measured in the a.m. and p.m., after systemic dexamethasone administration or after either stress in adult male rats. Measurement of plasma corticosterone levels revealed the expected circadian rhythmicity, suppression after dexamethasone administration and increase after ether stress. The hypothalamic content of CRF-like immunoreactivity was significantly decreased in the p.m. and after dexamethasone administration. However, no change in hypothalamic CRF-like immunoreactivity was observed after ether stress. The results are consistent with an increased release in the p.m. and decreased synthesis of hypothalamic CRF after systemic dexamethasone administration. The observation that there is no change in content of hypothalamic CRF-like immunoreactivity after ether stress could be due to the fact that the animals were stressed by handling. The results show that this immunoreactivity present in the hypothalamus is altered by changes in the hypothalamic-pituitaryadrenal axis and thus suggest that this peptide is a physiologically significant CRF in the rat.     

Early patterned stimulation leads to changes in adult behavior and gene expression in C. elegans

Across phylogeny, early experience plays a critical role in nervous system development. In these experiments, we investigated the long-term effects that specific patterns of sensory experience during development had on the biology and function of the Caenorhabditis elegans nervous system. The delivery of a specific pattern of mechanosensory stimulation in the first larval stage (L1) produced significant enhancement in the tap withdrawal behavioral response, expression patterns of an ionotropic glutamate receptor (iGluR) subunit and mRNA levels for that receptor in 3-day-old adult worms and a depression of these same three measures in 5-day-old adult worms. A critical period for the 3-day enhanced behavior and GLR distribution was observed in L1, whereas there was no critical period for the depressed effects observed in 5-day-old worms. The spaced pattern of stimulation was essential for expression of this effect: Various forms of massed training produced neither the enhancement at 3 days nor the depression at 5 days. The 5-day depressed behavioral response had many features in common with long-term memory, including sensitivity to disruption following retrieval. The different behavioral and molecular effects that early patterned mechanosensory stimulation produced in 3 and 5-day-old worms led us to hypothesize that separate cellular phenomena produced the enhanced 3-day and depressed 5-day behaviors and molecular effects.     

Electroacupuncture suppresses expression of gastric ghrelin and hypothalamic NPY in chronic food restricted rats

Electroacupuncture (EA) has been reported to reduce body weight in overweight subjects in clinical practice, as well as in rats and mice with diet-induced obesity. In the present study, this effect of EA was tested in lean rats subjected to long-term food restriction (FR, food was offered only 1 h/day). Two hertz EA administered once every other day produced a further reduction in body weight in FR rats. Exploration of the mechanism involved revealed significant downregulation of the orexigenic peptides: ghrelin in the stomach, and neuropeptide Y (NPY) but not Agouti-related peptide (AgRP) in the hypothalamus, which was in line with the reduction in food intake in rats receiving EA stimulation as compared with those receiving restraint only. Uncoupling protein 3 (UCP3), involved in accelerating energy expenditure, was not significantly altered. These results suggest that the EA-induced body weight reduction was due mainly to a decrease in food intake rather than an increase in energy expenditure. A reduction in the orexigenic peptides ghrelin and NPY may be involved in the underlying mechanism.     

Cisplatin treatment leads to changes in nuclear protein and microRNA expression

Using a proteomic approach, we have previously shown that exposure to different concentrations of cisplatin during a 12-h period can lead to changes in nuclear protein expression and alternative splicing in HeLa cells. To further shed light on the DNA damage response (DDR) induced by cisplatin, we examined the nuclear proteome profiles of HeLa cells treated with 5μM cisplatin for different times (2, 12, and 24h). Two-dimensional electrophoresis (2-DE) identified 98 differentially expressed proteins in cisplatin-treated cells as compared to control cells. Among them, 54 spots (55%) were down-regulated and 44 spots (45%) were up-regulated. 51 spots were subjected to Matrix-assisted-laser-desorption-ionization Time-of-flight/time-of-flight Mass spectrometry (MALDI-TOF/TOF MS) identification, and 40 spots were identified. Among these, 22 proteins were located in nucleus. These proteins were involved in stress response, cell cycle and division, apoptosis, mRNA processing, transport, splicing and microRNA (miRNA) maturation. The changed expression of Annexin A1 and Lamin B1 were confirmed by Western blot. The role of Annexin A1 in the response to cisplatin-induced DNA damage was further analyzed, and it was shown that after Annexin A1 knockdown, cisplatin-induced DNA damage was significantly increased. In addition, the changed expression of several miRNAs was also observed by quantitative real-time PCR (qRT-PCR). Taken together, these data indicate that cisplatin-induced DDR is a complex process, and that those proteins identified by proteomics can lead to new directions for a better understanding of this process.     

模拟高原低氧对不同性别新生大鼠下丘脑 CRF和AVP水平的影响

目的:探讨高原低氧对雌雄新生大鼠下丘脑-腺垂体-肾上腺皮质轴中枢部位肽能神经元发育的影响.方法:在低压氧舱中模拟高海拔低氧,用放免法测定精氨酸加压素(AVP)和下丘脑促肾上腺皮质激素释放激素(CRF)含量.结果:无论是在2 300 m对照海拔,还是在5 000 m模拟海拔,雌雄生后大鼠具相同的发育模式.低氧下发育至21 d时,CRF水平显著低于对照;相反,21 d及28 d时,低氧组AVP水平高于对照.结论:下丘脑CRF和AVP神经元间不同的发育模式可能与它们的功能及发育阶段特性相异有关.     

Comparison in male and female rats of ACTH content and response to corticotrophin-releasing factor (CRF) of cultured adenohypophyseal cells and in vivo hypothalamic CRF content.

Although mean ACTH concentration was significantly higher in cultured adenohypophyseal cells from female than from male rats, there was no significant sex difference in the ACTH secretory response of these cells to hypothalamic extract containing CRF. Hypothalamic CRF content in the “basal” state $\text{in}$$\text{vivo}$ was slightly higher in female than $\text{in}$ male rats.     

Human apoA-I expression in CETP transgenic rats leads to lower levels of apoC-I in HDL and to magnification of CETP-mediated lipoprotein changes

Plasma cholesteryl ester transfer protein (CETP) has a profound effect on neutral lipid transfers between HDLs and apolipoprotein B (apoB)-containing lipoproteins when it is expressed in combination with human apoA-I in HuAI/CETP transgenic (Tg) rodents. In the present study, human apoA-I-mediated lipoprotein changes in HuAI/CETPTg rats are characterized by 3- to 5-fold increments in the apoB-containing lipoprotein-to-HDL cholesterol ratio, and in the cholesteryl ester-to-triglyceride ratio in apoB-containing lipoproteins. These changes occur despite no change in plasma CETP concentration in HuAI/CETPTg rats, as compared with CETPTg rats. A number of HDL apolipoproteins, including rat apoA-I and rat apoC-I are removed from the HDL surface as a result of human apoA-I overexpression. Rat apoC-I, which is known to constitute a potent inhibitor of CETP, accounts for approximately two-thirds of CETP inhibitory activity in HDL from wild-type rats, and the remainder is carried by other HDL-bound apolipoprotein inhibitors. It is concluded that human apoA-I overexpression modifies HDL particles in a way that suppresses their ability to inhibit CETP. An apoC-I decrease in HDL of HuAI/CETPTg rats contributes chiefly to the loss of the CETP-inhibitory potential that is normally associated with wild-type HDL.     

Long-term ovariectomy and hormone-induced sexual behavior, progestin receptors, and hypothalamic morphology in female rats

Long-term ovariectomy reduces the ability of estradiol and progesterone treatment to induce sexual receptivity in female rats. Previous researchers suggested that this effect may be due to a decreased induction of neural progestin receptors by estradiol in the long-term ovariectomized rats. The present study was designed to replicate and extend this finding, and to search for neuroanatomical correlates by measuring the volume of the ventromedial nucleus (VMN) of the hypothalamus, a putative site of action of estradiol and progesterone for the induction of female sexual behavior. Long-term ovariectomy (5 to 6 weeks) as compared to short-term ovariectomy (1 week) reduced the ability of estradiol-17 beta and progesterone treatment to induce sexually receptive and proceptive behaviors. Consistent with previous reports, our data show that the reduced levels of cytosol progestin receptors after long-term ovariectomy and estradiol treatment are related to a reduced ability of estradiol to induce the receptors. Long-term ovariectomy did not affect the concentration of cytosol progestin receptors in the preoptic area, suggesting a neuroanatomical specificity to this effect. Contrary to our predictions, long-term ovariectomy did not affect the volume of the VMN. In fact, estradiol treatment, while blocking the effect of long-term ovariectomy on sexual behavior, decreased the volume of the VMN. Therefore, the measurement of the volume of the VMN is not a good predictor of the responsiveness to steroid hormone induction of sexual behavior.     

Modulation of neuropeptide FF (NPFF) receptors influences the expression of amphetamine-induced conditioned place preference and amphetamine withdrawal anxiety-like behavior in rats

Many data indicate that endogenous opioid system is involved in amphetamine-induced behavior. Neuropeptide FF (NPFF) possesses opioid-modulating properties. The aim of the present study was to determine whether pharmacological modulation of NPFF receptors modify the expression of amphetamine-induced conditioned place preference (CPP) and amphetamine withdrawal anxiety-like behavior, both processes relevant to drug addiction/abuse. Intracerebroventricular (i.c.v.) injection of NPFF (5, 10, and 20 nmol) inhibited the expression of amphetamine CPP at the doses of 10 and 20 nmol. RF9, the NPFF receptors antagonist, reversed inhibitory effect of NPFF (20 nmol, i.c.v.) at the doses of 10 and 20 nmol and did not show any effect in amphetamine- and saline conditioned rats. Anxiety-like effect of amphetamine withdrawal was measured 24h after the last (14 days) amphetamine (2.5mg/kg, i.p.) treatment in the elevated plus-maze test. Amphetamine withdrawal decreased the percent of time spent by rats in the open arms and the percent of open arms entries. RF9 (5, 10, and 20 nmol, i.c.v.) significantly reversed these anxiety-like effects of amphetamine withdrawal and elevated the percent of time spent by rats in open arms at doses of 5 and 10 nmol, and the percent of open arms entries in all doses used. NPFF (20 nmol) pretreatment inhibited the effect of RF9 (10 nmol). Our results indicated that stimulation or inhibition of NPFF receptors decrease the expression of amphetamine CPP and amphetamine withdrawal anxiety, respectively. These findings may have implications for a better understanding of the processes involved in amphetamine dependence.     

Intrahippocampal administration of an androgen receptor antagonist, flutamide, can increase anxiety-like behavior in intact and DHT-replaced male rats

Testosterone (T) and its 5alpha-reduced metabolite, dihydrotestosterone (DHT), can decrease anxiety-like behavior; however, the mechanisms underlying these effects have not been established. First, we hypothesized that if T reduces anxiety-like behavior through actions of its 5alpha-reduced metabolite, DHT, then gonadectomy (GDX) would increase anxiety-like behavior, an effect which would be reversed by systemic administration of DHT. Second, we hypothesized that if T and DHT reduce anxiety-like behavior in part through actions at intracellular androgen receptors in the hippocampus, then administration of an androgen receptor antagonist, flutamide, directly to the hippocampus should increase anxiety-like behavior of intact and DHT-replaced, but not GDX, male rats. Inserts that were empty or contained flutamide were applied directly to the dorsal hippocampus of intact, GDX, or GDX and DHT-replaced rats 2 h prior to testing in the open field, elevated plus maze, or defensive freezing tasks. GDX rats exhibited significantly more anxiety-like behaviors than intact or DHT-replaced rats. Intact and DHT-replaced rats administered flutamide to the hippocampus showed significantly more anxiety-like behavior than did intact and DHT-replaced controls. However, flutamide alone did not increase anxiety-like behavior of GDX rats. Together, these findings suggest that androgens can decrease anxiety-like behavior of male rats in part through DHT's actions at androgen receptors in the hippocampus.     

Quantitative protein changes in the hypothalamic neurons of pubertal male rats, castrated neonatally.

The effect of neonatal castration of male rats on the sexual differentiation of the hypothalamus at puberty was studied. Male rats were castrated on days 1, 5 and 7 after birth. Their brains were processed for study on days 83-85. The neurons and cell nuclei of the preoptic area, mediobasal and ventromedial nuclei were assessed for changes in cell and nuclear sizes and dry weight (calculated using interferometric methods). Neonatal castration resulted in size as well as dry weight increase in the neurons of the anterior and mediobasal hypothalamus. The dry weight increased by 34% (P less than 0.001) in the medial preoptic area, by 25% (P less than 0.001) in the arcuate neurons and by 22% (P less than 0.001) in the ventromedial nucleus. The cell nuclei exhibited perceptible weight increase too--in the medial preoptic area 68% (P less than 0.001); 55% in the arcuate neurons (P less than 0.001), and 39% in the ventromedial region. The weight and size increases in neonatally castrated males were equal to those of females of the same age. In rats castrated on day 7, the cell sizes and dry weights of the ventromedial nucleus increased but the cell nuclei exhibited only little change. It is assumed that the changes in the dry weight may be the result of increased synthetic processes in these groups of neurons which are connected with the tonic and cyclic release of gonadotropins. These changes also point to the hypothalamic differentiation shifting to the female type in the absence of the inducing effect of androgens.     

Sexual experience changes sex hormones but not hypothalamic steroid hormone receptor expression in young and middle-aged male rats

Testosterone is well known to regulate sexual behavior in males, but this is dependent upon prior sexual experience. Aging is associated with decreased libido and changes in testosterone, but the role of experience in these age-related processes has not been systematically studied. We examined effects of age and sexual experience on serum hormones (total testosterone, free testosterone, estradiol, LH) and on numbers of androgen receptor (AR) and estrogen receptor α (ERα) immunoreactive cells in the hypothalamus. Extensive sexual experience was given to male rats at 4 months of age. Rats were euthanized at either 4 months (young) or 12 months (middle-aged (MA)). Comparable sexually naïve male rats were handled and placed into the testing arena but did not receive any sexual experience. Thus, we had four groups: young-naïve, young-experienced, MA-naïve and MA-experienced. Serum hormone levels were assayed, and numbers of AR and ERα cells were quantified stereologically in the medial preoptic nucleus (MPN) and the anteroventral periventricular nucleus (AVPV). Sexually experienced males had significantly elevated serum testosterone and free testosterone in both age groups. Both total and free testosterone were higher, and estradiol lower, in middle-aged than young rats. Experience did not alter either AR or ERα expression in the preoptic brain regions studied. Aging was associated with increased expression of AR, but no change in ERα. These results show that sexual experience can induce short-term and long-term alterations in serum hormones but these effects are not manifested upon their receptors in the hypothalamus.     

Transgenic expression of Angiopoietin 1 in the liver leads to changes in lymphatic and blood vessel architecture

To investigate the possible role of the Angiopoietins in vessel remodelling, we overexpressed one of the angiopoietins, Angiopoietin-1 (Ang1), in the hepatocytes of mice by means of the conditional binary transgenic system. Animals were examined by Doppler ultrasound, and dissected livers were analyzed by immunohistochemical staining. Double transgenic mice presented with enlarged spleens and kidneys, enlarged, disorganized blood vessels located near the surface of the liver, sprouting, dilation, and disorganization of liver lymphatics, and turbulent flow in about 1/4 of the blood vessels sampled. Most of these characteristics completely resolved within 12 weeks of turning off the expression of the Ang1 transgene, illustrating a dependence on the continual presence of Ang1 for maintenance of the vascular phenotype. Conditional Angiopoietin-1 overexpression in the liver of mice leads to a phenotype highly reminiscent of portal hypertension illustrating that Ang1 can drive both vascular and lymphatic vessel remodelling and may play a role in portal hypertension.     

Hypoxia during pregnancy in rats leads to the changes of the cerebral white matter in adult offspring

The aim of the present study is to evaluate the effect of reduced fetal oxygen supply on cerebral white matter in the adult offspring and further assess its susceptibility to postnatal hypoxia and high-fat diet. Based on a 3 × 2 full factorial design consisting of three factors of maternal hypoxia, postnatal high-fat diet, and postnatal hypoxia, the ultrastructure of myelin, axon and capillaries were observed, and the expression of myelin basic protein (MBP), neurofilament-H+L(NF-H+L), and glial fibrillary acidic protein (GFAP) was analyzed in periventricular white matter of 16-month-old offspring. Demyelination, injured axon and damaged microvasculars were observed in maternal hypoxia offspring. The main effect of maternal hypoxia lead to decreased expression of MBP or NF-H+L, and increased expression of GFAP (all P < 0.05). Moreover, there was positive three-way interaction among maternal hypoxia, high-fat diet and postnatal hypoxia on MBP, NF-H+L or GFAP expression (all P < 0.05). In summary, our results indicated that maternal hypoxia during pregnancy in rats lead to changes of periventricular white matter in adult offspring, including demyelination, damaged axon and proliferated astroglia. This effect was amplified by high-fat diet and postnatal hypoxia.