Dopamine D4 Receptor Transmission in the Prefrontal Cortex Controls the Salience of Emotional Memory via Modulation of Calcium Calmodulin-Dependent Kinase II

Dopamine (DA) signaling in the medial prefrontal cortex (mPFC) plays a critical role in the processing of emotional information and memory encoding. Activation of DA D4 receptors within the prelimbic (PLC) division of the mPFC bidirectionally modulates emotional memory by strongly potentiating the salience of normally nonsalient emotional memories but blocking the acquisition of suprathreshold emotionally salient fear memories. Previous in vitro studies have shown that activation of cortical DA D4 receptors can bidirectionally modulate levels of α-calcium calmodulin-dependent kinase II (α-CaMKII), a molecule essential for learning and memory. Using an olfactory fear conditioning procedure in rats combined with microinfusions into the mPFC, we examined the potential role of D4 receptor-mediated control of emotional memory salience through signaling via CaMKII, cAMP/protein kinase A (PKA), and protein phosphatase-1 (PP1) signaling. We report that CaMKII blockade prevents the ability of intra-mPFC DA D4 receptor activation to potentiate the salience of subthreshold fear memory. In contrast, blockade of either cAMP/PKA or PP1 signaling pathways rescued the blockade of suprathreshold fear memory via intra-mPFC D4 receptor activation. Our results demonstrate that modulation of emotional memory salience via intra-mPFC DA D4 receptor transmission depends upon downstream signaling via CaMKII, cAMP/PKA, and PP1 substrates.     

Signaling elements involved in the metabolic regulation of mTOR by nutrients, incretins, and growth factors in islets

Mammalian target of rapamycin (mTOR) is a protein kinase that integrates signals from mitogens and the nutrients, glucose and amino acids, to regulate cellular growth and proliferation. Previous findings demonstrated that glucose robustly activates mTOR in an amino acid-dependent manner in rodent and human islets. Furthermore, activation of mTOR by glucose significantly increases rodent islet DNA synthesis that is abolished by rapamycin. Glucagon-like peptide-1 (GLP-1) agonists, through the production of cAMP, have been shown to enhance glucose-dependent proinsulin biosynthesis and secretion and to stimulate cellular growth and proliferation. The objective of this study was to determine if the glucose-dependent and cAMP-mediated mechanism by which GLP-1 agonists enhance beta-cell growth and proliferation is mediated, in part, through mTOR. Our studies demonstrated that forskolin-generated cAMP resulted in activation of mTOR at basal glucose concentrations as assessed by phosphorylation of S6K1, a downstream effector of mTOR. Conversely, an adenylyl cyclase inhibitor partially blocked glucose-induced S6K1 phosphorylation. Furthermore, the GLP-1 receptor agonist, Exenatide, dose-dependently enhanced phosphorylation of S6K1 at an intermediate glucose concentration (8 mmol/l) in a rapamycin-sensitive manner. To determine the mechanism responsible for this potentiation of mTOR, the effects of intra- and extracellular Ca2+ were examined. Glyburide, an inhibitor of ATP-sensitive K+ channels (K(ATP) channels), provided partial activation of mTOR at basal glucose concentrations due to the influx of extracellular Ca2+, and diazoxide, an activator of KATP channels, resulted in partial inhibition of S6K1 phosphorylation by 20 mmol/l glucose. Furthermore, Exenatide or forskolin reversed the inhibition by diazoxide, probably through mobilization of intracellular Ca2+ stores by cAMP. BAPTA, a chelator of intracellular Ca2+, resulted in inhibition of glucose-stimulated S6K1 phosphorylation due to a reduction in cytosolic Ca2+ concentrations. Selective blockade of glucose-stimulated Ca2+ influx unmasked a protein kinase A (PKA)-sensitive component involved in the mobilization of intracellular Ca2+ stores, as revealed with the PKA inhibitor H-89. Overall, these studies support our hypothesis that incretin-derived cAMP participates in the metabolic activation of mTOR by mobilizing intracellular Ca2+ stores that upregulate mitochondrial dehydrogenases and result in enhanced ATP production. ATP can then modulate KATP channels, serve as a substrate for adenylyl cyclase, and possibly directly regulate mTOR activation.     

人结肠癌细胞株HCT116中雌激素受体β与mTOR基因相互作用的初步研究

目的:探讨雌激素受体β(ERβ)在人结肠癌细胞株HCT116中的表达及其与mTOR基因的相互关系。方法:分别采用ERβ质粒转染(联合或不联合ERβ激动剂)、siRNA干扰mTOR基因、5-氮脱氧胞苷(5-aza-dC)处理HCT116细胞株;通过实时定量PCR法检测各处理组细胞中之mTOR、ERβ和cyclinD1的mRNA表达;蛋白印迹法检测p-mTOR、mTOR、ERβ和cyclinD1的蛋白表达。结果:HCT116细胞株转染ERβ质粒后,无论是否存在ERβ激动剂,都可明显下调p-mTOR和cyclinD1的蛋白表达水平,但是mTOR蛋白的表达却无变化。siRNA干扰细胞的mTOR基因后,ERβ表达明显增加而cyclinD1的mRNA和蛋白表达水平均下降。5-aza-dC处理后,能明显促进HCT116细胞株中ERβ的表达,mTOR基因在mRNA和蛋白水平的表达都无明显差异,但p-mTOR的蛋白水平降低,cyclinD1的mRNA和蛋白表达水平都下降。结论:ERβ和mTOR之间具有负相互调节作用;HCT116细胞中亦存在ERβ启动子甲基化的现象。这为ERβ及其特异性激动剂和mTOR抑制剂的联合应用防治结肠肿瘤提供了初步的实验依据。     

Role of mammalian target of rapamycin signaling in compensatory renal hypertrophy

Loss of functioning nephrons stimulates the growth of residual kidney tissue to augment work capacity and maintain normal renal function. This growth largely occurs by hypertrophy rather than from hyperplasia of the remaining nephrons. The signaling mechanisms that increase RNA and protein synthesis during compensatory renal hypertrophy are unknown. This study found that the remaining kidney hypertrophied 42% by 16 d after unilateral nephrectomy (UNX) in DBA/2 mice. Immunoblotting analysis revealed increased phosphorylation of the 40S ribosomal protein S6 (rpS6) and the eukaryotic translation initiation factor (eIF) 4E-binding protein 1 (4E-BP1), the two downstream effectors of the mammalian target of rapamycin (mTOR). The highly specific mTOR inhibitor rapamycin blocked UNX-increased phosphorylation of both rpS6 and 4E-BP1. UNX increased the content of not only 40S and 60S ribosomal subunits but also 80S monosomes and polysomes in the remaining kidney. Administration of rapamycin decreased UNX-induced polysome formation and shifted the polysome profile in the direction of monosomes and ribosomal subunits. Pretreatment of the mice with rapamycin inhibited UNX-induced hypertrophy. These studies demonstrate that activation of the mTOR signaling pathway in the remaining kidney after UNX plays an essential role in modulating RNA and protein synthesis during development of compensatory renal hypertrophy.     

Dopamine D2-like receptor agonist bromocriptine protects against ischemia/reperfusion injury in rat kidney

BACKGROUND: Dopamine, via activation of D1-like and D2-like receptors, plays an important role in the regulation of renal sodium excretion. Recently, we demonstrated that dopamine D2-like receptor agonist (bromocriptine) stimulates p44/42 mitogen-activated protein kinases (MAPKs) and Na+,K(+)ATPase (NKA) activity in proximal tubular epithelial cells. Since both these parameters are compromised in ischemia/reperfusion (I/R) injury to the kidney, we investigated whether bromocriptine protects against the injury. METHODS: In this study we used unilateral rat model of renal I/R injury. The Sprague-Dawley rats were divided into vehicle and bromocriptine groups. The vehicle and bromocriptine group was treated with vehicle and bromocriptine (500 microg/kg intravenously), respectively, 15 minutes before the induction of unilateral ischemia followed by 24- or 48-hour reperfusion. At the end of 24 or 48 hours the animals were sacrificed to collect control and ischemic kidney cortices, in which necrosis, apoptosis, NKA activity, NKA alpha1 subunit expression, and p44/42 MAPK phosphorylation were measured. RESULTS: We found extensive necrosis, apoptosis, and decreased NKA activity (with no change in alpha1 subunit) in the ischemic kidney cortex compared to the nonischemic cortex from the vehicle-treated rats as early as 24 hours post-reperfusion. In contrast, I/R injury-induced necrotic, apoptotic, and decrease in NKA activity were absent in the outer cortex of bromocriptine-treated rats after 24 or 48 hours. Interestingly, we detected significantly higher phosphorylation of p44/42 MAPKs in control and ischemic kidneys of bromocriptine-treated rats compared to those of vehicle-treated rats. CONCLUSION: Therefore, bromocriptine, a D1-like receptor agonist, may protect against I/R injury to proximal tubules of the kidney, via p44/42 MAPK activation.     

mTOR and rapamycin in the kidney: signaling and therapeutic implications beyond immunosuppression

The immunosuppressive drug rapamycin has helped to identify a large signaling network around the target of rapamycin (TOR) protein that integrates information on nutrient availability and growth factors to control protein synthesis and cell size. Studies using rapamycin in animal models of kidney disease indicate that mTOR deregulation has a role in glomerular disease, polycystic kidney disease, and renal cancer. The role of mTOR activation in podocytes is context dependent, and indirect evidence suggests that mTOR may have a role in chronic podocyte loss. Several lines of evidence show that cyst formation in polycystic kidney disease (PKD) involves mTOR activation and its upstream regulator TSC. Polycystin 1 regulates mTOR activity through different pathways, and TSC intersects with the primary cilium, a crucial cell organelle in the pathogenesis of PKD. Data from hamartoma syndromes provide clear evidence that mutation of members of the mTOR network results in renal cancers. The detailed analysis of renal cell carcinomas has revealed a positive feedback loop involving VHL and mTOR. Rapamycin and its derivatives have been approved for the treatment of advanced renal cancer and are being investigated for the treatment of PKD. Discrepancies exist between the effects of rapamycin in animal models and the clinical experience with patients, precluding the widespread use of mTOR inhibitors in kidney disease. The details of mTOR signaling in the kidney need to be clarified to hopefully develop targeted treatments for renal disease in the future.     

Chronic inhibition of mammalian target of rapamycin signaling downregulates insulin receptor substrates 1 and 2 and AKT activation: A crossroad between cancer and diabetes?

Overactivation of the mammalian target of rapamycin (mTOR) branch downstream of the phosphatidylinositol 3-kinase-AKT pathway critically modulates insulin and growth factor signaling by insulin receptor substrates (IRS). On the basis of in vitro studies, the mTOR inhibitor rapamycin has been reported to lead to enhanced activation of AKT by relieving this feedback inhibition on IRS function. In view of the critical role of AKT in insulin signaling and tumorigenesis, the in vivo expression and activation of this kinase and of IRS-1 and IRS-2 were explored in PBMC of 30 patients who were treated long term with rapamycin. A marked decrease of basal and insulin-stimulated AKT phosphorylation, which correlated with the increase of patients' insulin resistance, and a significant increase of IRS total protein expression, together with a lower (IRS-2) or absent (IRS-1) increase of insulin-induced tyrosine phosphorylation, were found. Therefore, contrary to the expectations, long-term exposure to rapamycin caused the impairment of IRS signaling and AKT activation, and this would help to explain the antiproliferative effect and the possible deterioration of glucose metabolism that are observed in rapamycin-treated patients. These findings may form a novel basis for improved understanding of the role of mTOR inhibition in human diseases, such as diabetes and cancer.     

mTOR通路调控肾间质成纤维细胞活化的机制

目的 探讨mTOR信号通路在肾间质成纤维细胞增生活化过程中的调控作用,并研究其抑制剂在抗肾纤维化治疗中的可行性.方法 用8周龄雌性C57BL/6小鼠构建单侧输尿管结扎(UUO)肾间质纤维化动物模型(n=30),按数字随机法分为雷帕霉素组(n=15)及UUO组(n=15).雷帕霉素组术前1d开始腹腔注射雷帕霉素(2 mg·kg-1·d-1)至实验结束;UUO组注射生理盐水.分别于术后1、3、7、14 d处死小鼠(n=3),留肾组织进行相关检测.同时,体外实验评估雷帕霉素对TGF-β诱导鼠成纤维细胞株(NIH3T3细胞)活化的干预作用.结果 UUO小鼠肾组织中活化的肌成纤维细胞[α肌动蛋白(α-SMA)阳性]高表达mTOR通路下游效应因子pS6K.雷帕霉素显著抑制pS6K表达及肾间质中肌成纤维细胞的活化,改善肾小管间质损伤及纤维化程度.实时荧光定量PCR结果提示雷帕霉素组小鼠肾皮质组织中成纤维细胞特异蛋白1 (FSP1)、转化生长因子β(TGF-β)、结缔组织因子(CTGF)及Ⅳ型胶原蛋白基因α1 (Col 4A1)的mRNA水平显著下降.体外实验结果示TGF-β诱导小鼠成纤维细胞株( NIH3T3)的mTOR通路显著活化,并大量合成α-SMA.雷帕霉素能够明显抑制mTOR通路活性,降低细胞的纤维化活性.结论 肾间质纤维化过程中成纤维细胞内的mTOR信号通路高度活化.抑制mTOR通路能够显著降低成纤维细胞的活性,改善肾间质纤维化程度.     

Effect of chronic atropine administration on the rat urinary bladder

Micturition is accomplished via a coordinated contraction of the urinary bladder body mediated primarily by muscarinic receptor stimulation. Theoretically, bladder function may be modified by pharmacologically altering either the muscarinic receptor density and/or the magnitude of the response to receptor activation. In the central nervous system, autonomic receptor density can be modified by chronic administration of specific receptor agonists and antagonists. The chronic administration of receptor agonists induces a decrease in the specific receptor density whereas the chronic administration of antagonists induces an increase in the specific receptor density. Although these induced alterations in receptor density occur in the CNS, there have been few studies on peripheral tissue. For the current study, we have administered L-atropine chronically to rats (five mg./kg./day) using implanted osmotic pumps. Using direct radioligand binding techniques, the muscarinic receptor density of the rat brain (cortex) and urinary bladder were determined following six hours, 12 hours, one, two, four, seven, 11 and 14 days of atropine administration. In addition, we have also determined the effect of atropine administration on bladder weight and the response of isolated strips of the bladder to bethanechol, a specific muscarinic agonist. For both the brain and the bladder, the receptor density increased progressively and reached a maximum by seven days. At 14 days of atropine administration, the density of muscarinic receptors in rat brain increased significantly (p less than .05) from 2956 +/-74 fmoles/mg. protein to 3800 +/-170 fmoles/mg. protein. The muscarinic receptor density of the rat urinary bladder increased significantly from 115 +/-10 fmole/mg. protein to 165 +/-14 fmole/mg. protein. Although there was a 42% increase in bladder mass, the contractile response of isolated strips to bethanechol did not change significantly. This study demonstrates that the urinary bladder can respond to the chronic administration of atropine with a significant increase in the density of muscarinic receptors. The magnitude of the increase observed was slightly greater than the magnitude observed for muscarinic receptors isolated from the brain cortex.     

雷帕霉素靶蛋白及其底物在自体移植静脉中的表达及意义

目的研究雷帕霉素靶蛋白（mammalian target of rapamycin,mTOR）及其底物——核糖体蛋白s6激酶（p70s6k）、真核细胞启动子4E结合蛋白1（4E—BP1）在自体移植静脉中表达的动态变化规律,探讨其与内膜增生的关系及意义。方法Wistar大鼠64只,建立自体静脉移植模型,随机分为8组,分别在移植后6h,1、3d,1、2…468周切取移植静脉。逆转录-聚合酶链反应（RT—PCR）联合原位杂交方法检测移植血管中mTOR及其底物pT0s6k和4E—BPI的mRNA表达,Western蛋白印迹或免疫组化方法检测mTOR、pT0s6k和4E—BP1的蛋白产物表达,同时检测增殖细胞核抗原（PCNA）的表达。结果静脉移植1—3d即出现mTOR和pT0s6k的mRNA表达增强,3d-2周达到高峰,与其他组比较差异有统计学意义（P〈0．01）,6—8周逐渐恢复正常;而4E—BP1的mRNA表达在移植后1d开始降低,1周表达最低,之后表达开始增强,4～6周为表达高峰,与其他组比较差异有统计学意义（P〈0．01）。Western蛋白印迹提示mTOR和pT0s6k蛋白产物在移植后1周表达明显增加,2～4周达到高峰,8周恢复至正常水平;而4E—BP1蛋白产物在移植后1周表达最少,4—6周增加达到高峰,8周仍维持一定的表达量。原位杂交及免疫组化结果提示阳性细胞多定位于移植静脉新生内膜和中膜血管平滑肌细胞,mTOR及其底物与PCNA分布基本一致。结论mTOR信号通路在血管移植后即被激活并与内膜增生关系密切,可能成为防治移植血管狭窄、闭塞的有效靶点。     

The evidence for hippocampal long-term potentiation as a basis of memory for simple tasks

Long-term potentiation (LTP) is the enhancement of postsynaptic responses for hours, days or weeks following the brief repetitive afferent stimulation of presynaptic afferents. It has been proposed many times over the last 30 years to be the basis of long-term memory. Several recent findings finally supported this hypothesis: a) memory formation of one-trial avoidance learning depends on a series of molecular steps in the CA1 region of the hippocampus almost identical to those of LTP in the same region; b)hippocampal LTP in this region accompanies memory formation of that task and of another similar task. However, CA1 LTP and the accompanying memory processes can be dissociated, and in addition plastic events in several other brain regions(amygdala, entorhinal cortex, parietal cortex) are also necessary for memory formation of the one-trial task, and perhaps of many others.     

Ventromedial prefrontal cortex is obligatory for consolidation and reconsolidation of object recognition memory

Once consolidated, a long-term memory item could regain susceptibility to consolidation blockers, that is, reconsolidate, upon its reactivation. Both consolidation and reconsolidation require protein synthesis, but it is not yet known how similar these processes are in terms of molecular, cellular, and neural circuit mechanisms. Whereas most previous studies focused on aversive conditioning in the amygdala and the hippocampus, here we examine the role of the ventromedial prefrontal cortex (vmPFC) in consolidation and reconsolidation of object recognition memory. Object recognition memory is the ability to discriminate the familiarity of previously encountered objects. We found that microinfusion of the protein synthesis inhibitor anisomycin or the N-methyl-D-aspartate (NMDA) receptor antagonist D,L-2-amino-5-phosphonovaleric acid (APV) into the vmPFC, immediately after training, resulted in impairment of long-term (24 h) but not short-term (3 h) recognition memory. Similarly, microinfusion of anisomycin or APV into the vmPFC immediately after reactivation of the long-term memory impaired recognition memory 24 h, but not 3 h, post-reactivation. These results indicate that both protein synthesis and NMDA receptors are required for consolidation and reconsolidation of recognition memory in the vmPFC.     

mTOR partly mediates insulin resistance by phosphorylation of insulin receptor substrate-1 on serine residues after burn

Mammalian target of rapamycin (mTOR) is an important mediator for cross talk between nutritional signals and metabolic signals of insulin by downregulating insulin receptor substrate proteins. Therefore, mTOR inhibition could become a therapeutic strategy in insulin-resistant states, including insulin resistance induced by burn. We tested this hypothesis in the rat model of 30% TBSA full thickness burn, using the mTOR inhibitor rapamycin. Rapamycin (0.4 mg/kg, i.p.) was injected 2 h before euglycemic-hyperinsulinemic glucose clamps at 4 days after burn. IRS-1, phospho-serine³⁰⁷, phospho-tyrosine of IRS-1 and phospho-mTOR in muscle tissue were determined by immunoprecipitation and Western blot analysis or immunohistochemistry. Plasma TNF-α, insulin and C-peptide were determined before and after euglycemic-hyperinsulinemic glucose clamps. Our data showed that TNF-α, insulin and C-peptide significantly increased in the early stage after burn (P < 0.01). The infused rates of total 10% glucose (GIR, mg/kg min) significantly decreased at 4 days after burn. The level of IRS-1 serine³⁰⁷ phosphorylation in muscle in vivo significantly increased after burn (P < 0.01), while insulin-induced tyrosine phosphorylation of IRS-1 significantly decreased (P < 0.01). Inhibition of mTOR by rapamycin inhibited the phosphorylation of mTOR, reduced serine³⁰⁷ phosphorylation, elevated tyrosine phosphorylation and partly prevented the decrease of GIR after burn. However, TNF-α, insulin and C-peptide were not decreased by rapamycin treatment postburn. Taken together, these results indicate that the mTOR pathway is an important modulator of the signals involved in the acute regulation of insulin-stimulated glucose metabolism, and at least, partly contributes to burn-induced insulin resistance. mTOR inhibition may become a therapeutic strategy in insulin-resistant states after burn.     

Inhibition of mTOR pathway decreases the expression of pre‐meiotic and meiotic markers throughout postnatal development and in adult testes in mice

Rapamycin (mTOR inhibitor) has been reported to have negative effect on human male gonadal function. Previously, we showed that mTOR signalling molecules are expressed during early spermatogenesis in mice. The objective of this study was to investigate the role of mTOR signalling in meiosis both during the first wave of spermatogenesis and also during adult spermatogenesis. Day 5 post‐partum mice were administered rapamycin and retinoic acid (RA; a Stra8 activator), and expression of p‐p70S6K and Stra8 proteins was evaluated. p‐p70S6K and Stra8 protein expressions decreased in post‐natal testes after rapamycin treatment. Stra8 protein expression increased after RA and rapamycin+RA administrations in post‐natal testes. In adult mice, rapamycin was administrated for 1 or 4 weeks. Morphological analysis for testicular damage and TUNEL assay was performed. After rapamycin administration, germ cell loss increased in adult testes. Ultrastructural analysis revealed disorganised testicular morphology and vacuolisation. The number of apoptotic germ cells increased after 4 weeks rapamycin administration. Stra8 and Dmc1 expressions decreased in 4 weeks rapamycin group, whereas Sycp3 and VASA expression did not change. Our findings suggest that mTOR pathway has an important role in meiotic progress of male germ cells both during first wave of spermatogenesis and in adult mice.     

Ischemic depolarization monitoring: evaluation of protein synthesis in the hippocampal CA1 after brief unilateral ischemia in a gerbil model

OBJECT: The authors investigate whether depolarization monitoring is an accurate index of ischemic damage in a gerbil model of unilateral ischemia and assess the effects of brief cerebral ischemia on protein synthesis in this model. METHODS: The authors evaluate the relationship between the duration of ischemic depolarization caused by unilateral carotid artery occlusion and ischemia-induced neuronal damage in the CA1 subregion 7 days after ischemia. When the depolarization period exceeded 210 seconds, some neuronal damage was detected, and almost complete neuronal damage was observed when the period exceeded 400 seconds. Uptake of [14C]valine was evaluated in ischemic and nonischemic CA1 subregions. Disturbances in protein synthesis were seen in all animals subjected to sublethal ischemia (< or = 210-second depolarization) after a 10-minute recirculation, and after 2 and 6 hours of recirculation in animals with 90 seconds or more of depolarization. Inhibition of protein synthesis was proportional to the length of the depolarization period. After 1 and 3 days of recirculation, protein synthesis returned to near normal, and some animals with depolarizations greater than 180 to 210 seconds showed an increase in protein synthesis. Protein synthesis in all animals returned to normal levels after 7 days of recirculation. CONCLUSIONS: In this study the authors demonstrate that monitoring of ischemic depolarization is a useful method to predict neuronal damage in the hippocampal CA1 in this model, and they identify subtle changes in protein synthesis after brief ischemia. Sublethal ischemia was divided into three categories by its depolarization period (< 90 seconds, 90-180 seconds, and > 180-210 seconds) with regard to changes in protein synthesis.     

Exendin-4对小鼠巨噬细胞一氧化氮生成和促炎/抗炎反应平衡的影响

目的：探讨新型糖尿病药物exendin-4（Ex-4）影响小鼠巨噬细胞一氧化氮（NO）生成和IL-10/IL-12分泌的量效-时效关系,以及是否经由PI3K/Akt/mTOR信号转导通路产生该作用.方法：体外培养小鼠RAW264.7巨噬细胞株,在有或者无细菌脂多糖（LPS）诱导下,给予不同浓度的Ex-4（1、10、50）nmol/L）刺激,并在培养4、8和24h收集上清,分别采用Griess和ELISA方法检测上清NO和IL-10/IL-12的分泌水平.此外,分别给予mTOR抑制剂雷帕霉素或PI3K抑制剂LY294002预处理巨噬细胞1且h,再给予低、中浓度Ex-4（1、10 nmol/L）刺激,观察巨噬细胞NO的产生和IL-10/IL-12的分泌是否发生改变.结果：无论是否存在LPS,Ex-4均能显著促进小鼠RAW264.7细胞分泌IL-10,同时抑制IL-12和NO的分泌,并且呈明显的时效-量效关系,中浓度Ex-4 已达最大效应（与低浓度比较,P〈0.05;与高浓度比较,P＞0.05）,该作用能被LY294002和雷帕霉素逆转（P〈0.05或P〈0.01）,尤以雷帕霉素最为显著.结论：Ex-4可通过PI3K/Akt/mTOR信号通路调控单核细胞NO的分泌,并影响IL-10/IL-12的平衡,可能是其参与免疫调节的机制之一.     

Dopamine modulation of hippocampal-prefrontal cortical interaction drives memory-guided behavior

Information gleaned from learning and memory processes is essential in guiding behavior toward a specific goal. However, the neural mechanisms that determine how these processes are effectively utilized to guide goal-directed behavior are unknown. Here, we show that rats utilize retrospective and prospective memory and flexible switching between these 2 memory processes to guide behaviors to obtain rewards. We found that retrospective memory is mainly processed in the hippocampus (HPC) but that this retrospective information must be incorporated within the prefrontal cortex (PFC) to be used to switch to an anticipatory response strategy involving prospective memory. Furthermore, switching between memory processes is regulated by the mesocortical dopamine (DA) system. Thus, DA D1 and D2 receptor activation in the PFC differentially affects retrospective memory processing within the HPC via an indirect feedback pathway. In contrast, D1, but not D2, receptor activation is crucial for incorporation of HPC-based retrospective information into the PFC. However, once this takes place, D2 receptor activation is required for further processing of information to effect preparation of future actions. These results provide a unique perspective on the mechanism of memory-based goal-directed behavior.