Calcineurin inhibition eliminates the normal inverted U curve,enhances acquisition and prolongs memory in a mammalian 3′-5′-cyclic AMP–dependent learning paradigm

The role protein phosphatase 2B (calcineurin, CaN) plays in learning and memory has received a significant amount of attention due to its promotion of the dephosphorylation of 3′-5′-cyclic AMP response element binding protein (CREB). Researchers have ascertained that overexpression of CaN is associated with memory retention deficits [Foster TC, Sharrow KM, Masse JR, Norris CM, Kumar A (2001) Calcineurin links Ca²⁺ dysregulation with brain aging. J Neurosci 21:4066–4073; Mansuy IM, Mayford M, Jacob B, Kandel ER, Bach ME (1998) Restricted and regulated overexpression reveals calcineurin as a key component in the transition from short-term to long-term memory. Cell 92:39–49], while CaN inhibition enhances learning and memory [Gerdjikov TV, Beninger RJ (2005) Differential effects of calcineurin inhibition and protein kinase A activation on nucleus accumbens amphetamine-produced conditioned place preference in rats. Eur J Neurosci 22:697–705; Ikegami S, Inokuchi K (2000) Antisense DNA against calcineurin facilitates memory in contextual fear conditioning by lowering the threshold for hippocampal long-term potentiation induction. Neuroscience 98:637–646]. The present study hypothesized that infusion of a CaN inhibitor (FK506) bilaterally into the olfactory bulbs of postnatal day 6 Sprague Dawley rat pups would prolong the duration of a conditioned odor preference and retard cyclic AMP response element binding protein dephosphorylation. A 2 mg/kg s.c. injection of isoproterenol (ISO, β-adrenoceptor agonist) was paired with a 10 min exposure to peppermint and subsequently an infusion of FK506. Immunohistochemistry for phosphorylated 3′-5′-cyclic AMP response element binding protein (pCREB) revealed that unilateral infusion of FK506 resulted in an amplification of phosphorylated CREB in the olfactory bulb 40 min after training compared with saline-infused bulbs. Pups infused bilaterally with FK506 maintained a learned preference for peppermint 48, 72 and 96 h after training. CaN inhibition also modified the conventional inverted U curve obtained when ISO is used to replace stroking, as the unconditioned stimulus. When pups were infused with FK506, learning occurred with sub- and supra-optimal doses of ISO indicating that CaN overcomes non-optimal effects ISO may have on learning. We demonstrate that CaN inhibition can extend the duration of conditioned olfactory memory and may provide a target for memory prolongation that is superior to even phosphodiesterase inhibition observed in previous studies.     

八味沉香散对异丙肾上腺素诱导心肌缺血损伤大鼠抗氧化作用

目的研究八味沉香散对异丙肾上腺素(ISO)诱导大鼠心肌缺血损伤组织病理学、氧化-抗氧化系统的影响。方法大鼠50只,随机分为正常对照组,模型对照组,阳性对照组(心得安0.02 g.kg-1),八味沉香散1.0 g.kg-1和0.5 g.kg-1组。均灌胃给药,每天1次,连续10 d。除正常对照组外,其余各组均于第8,9,10 d灌胃给药30 m in后腹腔注射ISO 5 mg.kg-1,每天1次,连续3 d。末次给ISO后24 h,取心观察组织形态学改变,同时测定心肌组织大鼠SOD、GSH-Px、NOS活性以及NO和MDA含量。结果与正常对照组比,模型对照组心肌SOD和GSH-Px活性明显降低,iNOS活性、MDA和NO含量明显升高,心肌组织严重受损;预先给予八味沉香散可明显升高心肌SOD和GSH-Px活性,降低MDA、NO含量和iNOS活性,并减轻心肌组织损伤。结论八味沉香散对ISO致大鼠心肌缺血损伤具有保护作用,其作用机制与减少活性氧产生,增强抗氧化剂活性,阻断脂质过氧化有关。     

Types of Adrenoreceptors Mediating Responses of Rabbit Gastric Muscularis Mucosae

This study investigated adrenoreceptor-mediated responses of muscularis mucosae from the fundic and antral ends of the rabbit gastric corpus. Norepinephrine-induced fundic muscularis mucosae contractions were enhanced by propranolol and converted to relaxations by phentolamine. Methoxamine, but not clonidine, elicited large fundic contractions. Fundic muscle responded to low isoproterenol concentrations with atenolol- and butoxamine-resistant relaxations, and to high concentrations with atenolol-sensitive contractions. Norepinephrine evoked propranolol-resistant relaxations of antral muscularis mucosae that were enhanced by phentolamine. Methoxamine and clonidine elicited small antral contractions. Lower concentrations of isoproterenol caused atenolol-resistant antral relaxations that were enhanced by butoxamine; higher concentrations produced weak excitation. Fundic and antral relaxations to isoproterenol were abolished by cyanopindolol. Fundic muscularis mucosae possesses excitatory ₁-, ₁- and inhibitory ₃-adrenoreceptors. Excitatory ₂- and inhibitory ₃-adrenoreceptors predominate in the antral region. The heterogeneous adrenoreceptor-mediated responses of the gastric muscularis mucosae suggest that adrenergic modulation of its motor activity is unlikely to be linked to acid secretion.     

Tubular Reabsorption of Glucose During Pregnancy

Continuous infusion of isoproterenol or electric stimulation of left stellate ganglion in atropinized dogs changed the cardiac response to high aortic blood pressure. In thoracotomized dogs, cardiac output rose when ventricular systolic blood pressure was increased from 100 to more than 200 mm Hg by constriction of the descending aorta. Myocardial dimensions as measured by ultrasonic distance gauges implanted one cm apart in the left myocardium (myocardial distance) showed only slight changes. In control experiments at normal inotropic levels, or after blocking β-receptors by propranolol, the effect of increasing aortic pressure was maintenance or reduction of cardiac output. Myocardial distances were increased with reductions in amplitude of the beat-to-beat oscillations. In unanesthetized dogs, angiotensin infusion reduced cardiac output and increased myocardial dimensions under control conditions. During infusion of isoproterenol the response to angiotensin at similar increments of blood pressure was an increase in cardiac output and nearly no increase in myocardial dimensions. These studies show that the cardiac response to increased blood pressure is dependent on the level of inotropy.     

Ablation of p21-activated kinase-1 in mice promotes isoproterenol-induced cardiac hypertrophy in association with activation of Erk1/2 and inhibition of protein phosphatase 2A

Earlier investigations in our lab indicated an anti-adrenergic effect induced by activation of p21-activated kinase (Pak-1) and protein phosphatase 2A (PP2A). Our objective was to test the hypothesis that Pak-1/PP2A is a signaling cascade controlling stress-induced cardiac growth. We determined the effects of ablation of the Pak-1 gene on the response of the myocardium to chronic stress of isoproterenol (ISO) administration. Wild-type (WT) and Pak-1-knockout (Pak-1-KO) mice were randomized into six groups to receive either ISO, saline (CTRL), or ISO and FR180204, a selective inhibitor of Erk1/2. Echocardiography revealed that hearts of the Pak-1-KO/ISO group had increased LV fractional shortening, reduced LV chamber volume in diastole and systole, increased cardiac hypertrophy, and enhanced transmitral early filling deceleration time, compared to all other groups. The changes were associated with an increase in relative Erk1/2 activation in Pak-1-KO/ISO mice versus all other groups. ISO-induced cardiac hypertrophy and Erk1/2 activation in Pak-1-KO/ISO were attenuated when the selective Erk1/2 inhibitor FR180204 was administered. Immunoprecipitation showed an association between Pak-1, PP2A, and Erk1/2. Cardiac myocytes infected with an adenoviral vector expressing constitutively active Pak-1 showed a repression of Erk1/2 activation. p38 MAPK phosphorylation was decreased in Pak-1-KO/ISO and Pak-1-KO/CTRL mice compared to WT. Levels of phosphorylated PP2A were increased in ISO-treated Pak-1-KO mice, indicating reduced phosphatase activity. Maximum Ca²⁺-activated tension in detergent-extracted bundles of papillary fibers from ISO-treated Pak-1-KO mice was higher than in all other groups. Analysis of cTnI phosphorylation indicated that compared to WT, ISO-induced phosphorylation of cTnI was blunted in Pak-1-KO mice. Active Pak-1 is a natural inhibitor of Erk1/2 and a novel anti-hypertrophic signaling molecule upstream of PP2A.     

左旋卡尼汀对异丙肾上腺素致心肌损害的影响

目的:观察左旋卡尼汀对异丙肾上腺素致心肌损害的保护作用并探讨其机制。方法:采用大鼠皮下注射异丙肾上腺素造成心肌损害模型。心肌切片,HE染色,光镜下观察心肌损害程度;分离心肌线粒体,测定膜脂流动性（LFU）。结果:注射左旋卡尼汀可减轻心肌损害程度;改善线粒体的损伤,改善LFU。结论:左旋卡尼汀能减轻异丙肾对心肌的损害,对线粒体膜脂流动性损伤具有明显的保护作用。     

Selective Effect of High Arterial Pressure in Hypertension Upon Inhibition of cGMP Versus cAMP Mediated Vascular Relaxation

We tested the hypothesis as to whether elevated arterial pressure in hypertension alters cGMP, or cAMP, mediated vasorelaxation. Relaxation to nitroglycerin and isoproterenol was determined in isolated aortic rings from one-kidney, one clip hypertensive (1K1C), coarctation hypertensive (CH) and normotensive control (C) rats. Thoracic aortas from 1K1C and CH rats, as well as abdominal aortas from 1K1C rats, but not abdominal aortas from CH rats were exposed chronically (4–6 weeks) to elevated arterial pressure. Sensitivity of rings with and without endothelium to nitroglycerin was suppressed significantly only in vessels exposed chronically to high arterial pressure. Impaired sensitivity to nitroglycerin in abdominal rings from lKlC rats could not be abolished by exposure to 100 uM L-arginine, the substrate for production of NO by endothelial nitric oxide synthase, or 100 uM L-cysteine, the source of thiol groups required for the production of nitric oxide from nitroglycerin. Maximum relaxation to isoproterenol was impaired significantly in thoracic and abdominal rings, with and without endothelium, from lKlC and CH rats. Relaxation to 8-bromo-cGMP and dibutyryl cAMP was similar in abdominal rings from all groups. We conclude that impaired vasorelaxation to nitroglycerin and isoproterenol in hypertension involves mechanisms prior to activation of vascular smooth muscle cGMP-dependent and cAMP dependent protein kinase, respectively. Impaired cGMP, but not cAMP, mediated relaxation of aortas appears to result from their exposure to high arterial pressure per se. This effect does not appear to involve the vascular endothelium or vascular sources of thiols, but rather may reflect an effect of high arterial pressure to impair the ability of the artery to respond t o nitric oxide derived from nitroglycerin.     

葛根素对儿茶酚胺诱导大鼠心肌损伤时凋亡相关蛋白的影响

目的 :探讨在儿茶酚胺诱导的心肌损伤过程中 ,心肌细胞的凋亡相关基因 Fas和 Bcl 2的蛋白表达改变及葛根素干预的影响。方法 :5 0只健康雄性 SD大鼠随机分成 3组 :心肌损伤组 (2 0只 )、葛根素干预组 (2 0只 )和对照组 (10只 )。动物模型仿用异丙肾上腺素 (ISO)皮下注射致心肌损伤方法。心肌组织切片分别行 HE及 Fas和 Bcl 2蛋白表达的免疫组织化学染色检测。结果 :心肌损伤组 :Fas蛋白和 Bcl 2蛋白的表达等级均上调 (P均 <0 .0 0 1) ,Fas蛋白的表达水平更高 (P<0 .0 0 1)。葛根素干预组 :心肌组织的 HE病理损害等级明显减轻 (P<0 .0 5 ) ;Fas蛋白表达等级下调 (P<0 .0 5 )。结论 :在儿茶酚胺诱导的心肌损伤过程中 ,Fas和 Bcl 2的蛋白表达水平表现出高水平的差异 ,葛根素能抑制损伤过程中 Fas蛋白的表达。     

不同中医治法对异丙肾上腺素致大鼠心肌肥大的比较研究

目的观察不同中医治法对异丙肾上腺素致大鼠心肌肥大的干预作用。方法以异丙肾上腺素20 mg/kg1、0 mg/kg、5mg/kg递减皮下注射,3 mg/kg维持7 d制备大鼠心肌肥大模型,给予金匮肾气丸、真武汤、补阳还五汤及生脉饮5周,观察大鼠血流动力学指标、心输出量、心脏指数、左心室指数以及血清心房利钠肽(ANP)、脑钠肽(BNP)、血管紧张素Ⅱ(AngⅡ)及去甲肾上腺素(NE)含量的变化。结果异丙肾上腺素造模5周后,模型组大鼠血流动力学处于代偿状态,与正常组比较差异无统计学意义(P>0.05);但心输出量明显降低,血清ANP、BNP含量显著升高,心脏指数及左心室指数增加(P<0.05)。与模型组比较,补阳还五汤组及金匮肾气丸组能够有效提高心输出量,降低血清ANP、BNP水平,降低心脏指数(P<0.05)。生脉饮组和真武汤组能够降低血清ANP含量,对于模型大鼠心脏指数及血清BNP含量均无明显作用(P>0.05),但是有降低心输出量及心肌收缩功能的作用。结论益气活血法和温补肾阳法能够有效改善异丙肾上腺素致大鼠心肌肥大的血流动力学状况,改善过度激活的神经体液水平。