Role of the ERK pathway in psychostimulant-induced locomotor sensitization

BACKGROUND: Repeated exposure to psychostimulants results in a progressive and long-lasting facilitation of the locomotor response that is thought to have implications for addiction. Psychostimulants and other drugs of abuse activate in specific brain areas extracellular signal-regulated kinase (ERK), an essential component of a signaling pathway involved in synaptic plasticity and long-term effects of drugs of abuse. Here we have investigated the role of ERK activation in the behavioral sensitization induced by repeated administration of psychostimulants in mice, using SL327, a brain-penetrating selective inhibitor of MAP-kinase/ERK kinase (MEK), the enzyme that selectively activates ERK. RESULTS: A dose of SL327 (30 mg/kg) that reduced the number of activated ERK-positive neurons by 62 to 89% in various brain areas, had virtually no effect on the spontaneous locomotor activity or the acute hyperlocomotion induced by cocaine or D-amphetamine. Pre-treatment with SL327 (30 mg/kg) prior to each drug administration prevented the locomotor sensitization induced by repeated injections of D-amphetamine or cocaine. The SL327 pre-treatment abolished also conditioned locomotor response of mice placed in the context previously paired with cocaine or D-amphetamine. In contrast, SL327 did not alter the expression of sensitized response to D-amphetamine or cocaine. CONCLUSION: Altogether these results show that ERK has a minor contribution to the acute locomotor effects of psychostimulants or to the expression of sensitized responses, whereas it is crucial for the acquisition of locomotor sensitization and psychostimulant-conditioned locomotor response. This study supports the important role of the ERK pathway in long-lasting behavioral alterations induced by drugs of abuse

Реконструкция котла ПК-38 на Назаровской ГРЭС в г. Назарово Красноярского края

В работе рассматривается реконструкция котла ПК-38, работающего на твердом топливе Назаровского месторождения. Приведены конструктивные характеристики топки и всех поверхностей нагрева, произведен поверочный расчет котельного агрегата.The paper reviews the reconstruction of the PK-38 boiler, which operates on solid fuel at the Nazarovo deposit. The design characteristics of the furnace and all heating surfaces are presented, and the boiler unit is calibrate

THE JOURNAL OF BIOLOGICAL CHEMISTRY Microsomal Enzymes of Cholesterol Biosynthesis from Lanosterol PURIFICATION AND CHARACTERIZATION OF A7-STEROL 5-DESATURASE OF RAT LIVER MICROSOMES*

Microsomal A7-sterol 5-desaturase of cholesterol biosynthesis is a multienzyme system which catalyzes the introduction of the A6-bond into A'-cholestenol to form 7-dehydrocholesterol. The detergent-solubilized 5-desaturase has been purified more than 70-fold and resolved from electron carriers and other rat liver microsomal enzymes of sterol biosynthesis by chromatography on DEAE-Sephacel, CM-Sepharose, and immobilized cytochrome b,; the 5-desaturase had not been fully resolved from cytochrom b6 reductase in earlier work. A functional electron transport system for the 5-desaturase has been reconstituted by combining the purified 5-desaturase and electron carriers with egg phosphatidylcholine liposomes. Optimizations of conditions for reconsitution have been obtained; both cytochrome b, and NADH-cytochrome b, reductase serve as electron carriers. A pyridine nucleotide-dependent flavoprotein is required and the requirement can be satisfied with either purified cytochrome bK reductase or cytochrome P-450 reductase. Cyanide and ironchelators strikingly inhibit the 5-desaturase activity, thus suggesting that 5-desaturase is a metalloenzyme as are other well-characterized cytochrome bK-dependent oxidases. 5-Desaturase is resolved from 4-methyl sterol oxidase activity of cholesterol biosynthesis by chromatography on the immobilized cytochrome b,. This resolution of the two oxidases not only indicates that introduction of the A6-bond and oxidation of 4a-methyl groups are catalyzed by different terminal oxidases, but resolution affords enzymes of sufficient purity to carry out reconstitution experiments. A novel assay based on substrate-dependent increments of oxidation of a-NADH has been developed for measurement of 5-desaturase activity. Measurement of stoichiometry of 5-desaturase demonstrates that for each equivalent of cis-desaturation of A7-cholestenol, 1 eq of NADH is consumed. Along with strict dependence upon oxygen, this observation confirms, as suggested by previous workers, that the 5-desaturation is catalyzed by a mixed function oxidase rather than a dehydrogenase. The biotransformation of lanosterol to cholesterol proceeds in a multiple process involving reduction of the AZ4-bond in the side chain, removal of three methyl groups from C-4 and * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact

A Necessity for MAP Kinase Activation in Mammalian Spatial Learning

Although the biochemical mechanisms underlying learning and memory have not yet been fully elucidated, mounting evidence suggests that activation of protein kinases and phosphorylation of their downstream effectors plays a major role. Recent findings in our laboratory have shown a requirement for the mitogen-activated protein kinase (MAPK) cascade in hippocampal synaptic plasticity. Therefore, we used an inhibitor of MAPK activation, SL327, to test the role of the MAPK cascade in hippocampus-dependent learning in mice. SL327, which crosses the blood-brain barrier, was administered intraperitoneally at several concentrations to animals prior to cue and contextual fear conditioning. Administration of SL327 completely blocked contextual fear conditioning and significantly attenuated cue learning when measured 24 hr after training. To determine whether MAPK activation is required for spatial learning, we administered SL327 to mice prior to training in the Morris water maze. Animals treated with SL327 exhibited significant attenuation of water maze learning; they took significantly longer to find a hidden platform compared with vehicle-treated controls and also failed to use a selective search strategy during subsequent probe trials in which the platform was removed. These impairments cannot be attributed to nonspecific effects of the drug during the training phase; no deficit was seen in the visible platform task, and injection of SL327 following training produced no effect on the performance of these mice in the hidden platform task. These findings indicate that the MAPK cascade is required for spatial and contextual learning in mice

Regulation of extracellular signal-regulated kinase by cannabinoids in hippocampus.

Endocannabinoids form a novel class of intercellular messengers, the functions of which include retrograde signaling in the brain and mediation or modulation of several types of synaptic plasticity. Yet, the signaling mechanisms and long-term effects of the stimulation of CB1 cannabinoid receptors (CB1-R) are poorly understood. We show that anandamide, 2-arachidonoyl-glycerol, and Delta9-tetrahydrocannabinol (THC) activated extracellular signal-regulated kinase (ERK) in hippocampal slices. In living mice, THC activated ERK in hippocampal neurons and induced its accumulation in the nuclei of pyramidal cells in CA1 and CA3. Both effects were attributable to stimulation of CB1-R and activation of MAP kinase/ERK kinase (MEK). In hippocampal slices, the stimulation of ERK was independent of phosphatidyl-inositol-3-kinase but was regulated by cAMP. The endocannabinoid-induced stimulation of ERK was lost in Fyn knock-out mice, in slices and in vivo, although it was insensitive to inhibitors of Src-family tyrosine kinases in vitro, suggesting a noncatalytic role of Fyn. Finally, the effects of cannabinoids on ERK activation were dependent on the activity of glutamate NMDA receptors in vivo, but not in hippocampal slices, indicating the existence of several pathways linking CB1-R to the ERK cascade. In vivo THC induced the expression of immediate-early genes products (c-Fos protein, Zif268, and BDNF mRNAs), and this induction was prevented by an inhibitor of MEK. The strong potential of cannabinoids for inducing long-term alterations in hippocampal neurons through the activation of the ERK pathway may be important for the physiological control of synaptic plasticity and for the general effects of THC in the context of drug abuse.In VitroJournal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe