Antisense knockdown of the Shaker-like Kv1.1 gene abolishes the central stimulatory effects of amphetamines in mice and rats.

Amphetamine (AMPH) is an indirect sympathomimetic compound classified as a substrate-type releaser that distinguishes it from other stimulants that act as uptake 1 blockers, such as cocaine (COC). In mammals, AMPH elicits central stimulation, hypermotility, anorexia, analgesia and analeptic activity, mainly through the increase of extracellular brain dopamine (DA). The inversion of vesicular transporters and/or intravesicular alkalinization is assumed to have a role in AMPH-induced exocytosis. However, the action mechanism of this compound has not yet been completely clarified. Recent evidence on the action of AMPHs indicates potassium channel-blocking properties in peripheral tissues. We investigated the possible involvement of a Shaker-like Kv1.1 channel subtype in the central effects of AMPH, using an antisense oligodeoxyribonucleotide (aODN) that specifically and reversibly inhibits the expression of these channels in the brain. The effect of aODN pretreatments was studied by evaluating the modification of behavioral effects induced in mice through the intracerebroventricular administration of AMPH, COC, or other compounds. The aODN in mice almost completely blocked the stimulatory effects of AMPH and other releasers but was ineffective in reducing the central activity of COC. In aODN-pretreated rats a strong reduction of the AMPH, but not of the COC-stimulated DA efflux from nucleus accumbens was observed. Our results suggest that the stimulant effects of AMPH and chemically related compounds, but not COC, require the presence of functionally active Kv1.1 channels in the brain.     

Restoration of cardiomyocyte functional properties by angiotensin II receptor blockade in diabetic rats

Recent evidence suggests that blockade of the renin-angiotensin system ameliorates diabetes-induced cardiac dysfunction, but the mechanisms involved in this process remain elusive. We investigated the effect of treatment with an angiotensin II receptor blocker, losartan, on the metabolic and electrophysiological properties of cardiomyocytes isolated from streptozotocin-induced diabetic (STZ) rats. Glucose uptake and electrophysiological properties were measured in ventricular cardiomyocytes from normoglycemic and STZ-induced diabetic rats given vehicle or 20 mg x kg(-1) x day(-1) losartan for 8 weeks. Insulin and beta-adrenergic stimulation failed to increase the glucose uptake rate in STZ cardiomyocytes, whereas the alpha-adrenergic effect persisted. Concurrently, a typical prolongation of action potential duration (APD) and a decrease of transient outward current (I(to)) were recorded in patch-clamped STZ myocytes. Treatment with losartan did not affect body weight or glycemia of diabetic or control animals. However, in losartan-treated STZ-induced diabetic rats, beta-adrenergic-mediated enhancement of glucose uptake was completely recovered. APD and I(to) were similar to those measured in losartan-treated control rats. A significant (P < 0.0001) correlation between metabolic and electrophysiological parameters was found in control, diabetic, and losartan-treated diabetic rats. Thus, angiotensin receptor blockade protects the heart from the development of cellular alterations typically associated with diabetes. These data suggest that angiotensin receptor blockers may represent a new therapeutic strategy for diabetic cardiomyopathy.     

The reduction of food intake induced in mice by benzylamine and its derivatives

Characterisation of the pharmacological profile of non-physiological amine oxidase substrates could help to identify the endogenous role of this class of enzymes. Previous studies have suggested that benzylamine, a common non-physiological substrate for monoamine and tissue-bound or soluble benzylamine oxidases, could behave as a potassium channel blocking agent. Potassium channel blockers are known to modify several forms of animal behaviour including food consumption. To characterise further the pharmacological profile of benzylamine and the role of amine oxidases, we have studied the effect of benzylamine on mice food intake. Our results confirm that benzylamine produces a reduction in mice feeding in a similar manner to that obtained by amphetamine. The anorectic effect of benzylamine and amphetamine in mice was potentiated by pretreatment with amine oxidase inhibitors. In addition, the introduction of substituents in the aromatic ring of benzylamine did not produce compounds with a higher anorectic potency than the one measured with benzylamine.     

Endogenous substrates of the semicarbazide-sensitive amine oxidase increased nitric oxide production in rat white adipocytes

Inflammation Research -     

Sulfhydryl groups and peroxidase-like activity of albumin as scavenger of organic peroxides

The concentration, the reactivity of sulfhydryl (SH) groups and the peroxidase-like activity (PLA) of bovine serum albumin (BSA) have been determined in vitro after treatment with peroxides. Tert-butylhydroperoxide (tBOOH), cumene hydroperoxide (CuOOH), benzoyl hydroperoxide (BOOH) and hydrogen peroxide reacted with BSA, decreasing the titratable SH group concentration and increasing the value of the ratio between the reaction rate and the concentration of albumin SH groups in the sulfhydryl-disulfide exchange reaction. This value was defined as reaction constant (Kr). PLA of albumin was independent of the presence of the SH group, as SH depleted BSA maintained the same activity as the control. From our findings it derives that albumin may have two possibilities of scavenging peroxides: PLA and the SH group. The plasma SH concentration, Kr and PLA of albumin were also determined in carrageenan paw edema and in experimental adjuvant-arthritis in rats. A decrease in SH concentration, an increase in Kr and PLA of rat plasma albumin were observed in both inflammatory processes.     

Tert-aminoalkyl derivatives of 3-methyl-6,8-diazaquinoxaline-2(1H)-ones. Effect on the acquisition and modification of a conditioned avoidance response in rats

By condensating ethyl pyruvate with 4-dialkylaminoalkyl-5-aminopyrimidine, obtained by hydrogenolysis of the corresponding 6-chloroderivatives, were prepared 3-methyl-6,8-diazaquinoxalinee-2(1H)-ones which carry on position 1 a tert-aminoalkyl chain (dimethylaminoethyl-, morpholinylethyl-, dimethylaminopropyl- and N-methylpiperazinylpropyl-). The synthetized compounds were tested to verify the effects on acquisition and modification of a conditioned avoidance response (C.A.R.) in rats. In these tests 1-dimethylaminoethyl-3-methyl-6,8-diazaquinoxalin-2(1H)-one, shows activity comparable with that of the cloropromazine.     

Relationship between SH group reactivity and concentration of bovine serum albumin and rat plasma

This study revealed that SH group reactivity (R) and concentration (C) of bovine serum albumin (BSA) and rat plasma are proportional in the sulphydryl-disulfide (SH-SS) exchange reaction with 5-5' dithiobis (2nitrobenzoic acid) (DTNB). The existence of the R/C proportionality suggests the use of Kr ratio and C as parameters for characterizing the biological properties of plasma SH groups. Moreover it was found that the electrophilic agents, diethylmaleate (DEM) and ethacrynic acid (ETHAC) that react with SH groups, determine an in vitro decrease in plasma SH group concentration and a Kr increase. The Kr increase seemed to be independent of SH group blocking as results obtained with sodium dodecyl sulfate (SDS) and SDS plus DEM indicated. The Kr biological significance might be related to a conformational change of albumin. In vivo treatment with 0.6 and 1.2 ml/kg of DEM confirmed the plasmatic linear relationship between R and C and showed a Kr increase in accordance with in vitro results. In carrageenan paw edema, decreased SH group plasma levels and an increased Kr were obtained.     

1,4-Disubstituted 1,3-dihydro-2H-1,5-benzo- and chlorobenzodiazepin-2-ones with activity on the central nervous system

In pursuing the study on pyridodiazepinone derivatives, in order to verify the variation of biological activity induced by replacement of the heteroaromatic with an aromatic nucleus and by the introduction of chlorine on the benzene ring, a series of 1-[(dialkylamino)alkyl]-4-phenyl-1,3-dihydro-2H-1,4-benzodiazepin- 2-ones and of 7-chloro-analogues were prepared. Some benzodiazepinones and their 7-chloro-analagous were subjected to pharmacological experimentation in order to evaluate and compare their effect upon mice with regard to exploratory activity, motor coordination and spontaneous motility. In addition their anti-strychnine, anti-cardiazole, anti-amphetamine and anti-reserpine activities were also evaluated.     

5-Acyl-6-aryl-4-nitro-3(2H)pyridazinones and related 4-amino compounds: synthesis and pharmacological evaluation

Several 4-nitro- and 4-amino-5-acyl-6-aryl-3(2H)pyridazinones were prepared and their in vitro and ex vivo antiaggregatory properties were evaluated. 4-Nitro derivatives 3 generally showed good activity in vitro towards arachidonic acid (AA)-induced human blood platelet aggregation. The 4-amino compound 4a, which has weak in vitro activity, exhibited antiplatelet activity, particularly on adenosine dephosphate (ADP)-induced aggregation ex vivo in rabbit. Moreover, the same compound was shown to be active in platelet-activating factors (PAF)-induced rat paw hyperalgesia and to be endowed with low acute oral toxicity. The 4-amino derivatives 4a-m and the other pyridazinones 5-9 administered orally to rats were also found to be more potent antiinflammatory agents than acetyl salicylic acid (ASA). Compounds 3a and 4a, tested in vitro on lipopolysaccharide (LPS)-stimulated rat peritoneal macrophages, were seen to be active in the inhibition of prostaglandin E2 (PGE2) production and interleukin-1 activity. Structure-activity relationship studies in the series of antiaggregating pyridazinones 3 have shown the primary importance of the nitro and acetyl substituents at positions 4 and 5, respectively. Hydrophobic substituents at position 2 were also required for better activity.