bluuebunny/crossref_metadata_2025 huggingface dataset:
A new model to assess analgesic activity: Pain‐induced functional impairment in the rat (PIFIR)
Authors: López‐Muñoz Francisco J. , Salazar Luis A. , Castañeda‐Hernández Gilberto , Villarreal Julián E.
Published: January 2005

A new experimental model to assess analgesic activity of both analgesic and non‐steroidal antiinflammatory drugs in described. It uses the unilateral intra‐articular knee injection of an uric acid suspension in mineral oil to produce acute inflammation, pain, and functional motor impairment. The model, named “pain‐induced functional impairment in the rat” (PIFIR) assesses analgesic activity by measuring the capacity to walk with the injured extremity. The procedure determines both the potencies of analgesic drugs and the time course of the effect. Analgesia of selected reference agents was followed for 4 h and the effect versus time curves were constructed. The area under the curve (effect versus time), an expression of the overall activity during the observation period, increased in a dose‐dependent manner. The area under the curve, Emax, TEmax, and ED50 of reference agents tested are reported. The PIFIR procedure was sensitive to opiate and nonopiate analgetics (nonsteroidal antiinflammatory drugs) and possibly steroidal antiinflammatory drugs. These characteristics make it suitable for screening purposes. © 1993 Wiley‐Liss, Inc.
Properties of recombinant adenosine receptors
Authors: Linden Joel , Tucker Amy L. , Robeva Anna S. , Graber Stephen G. , Munshi Ravi
Published: January 2005

Four subtypes of adenosine receptors have been cloned in several laboratories. The receptors all interact with G proteins and span the plasma membrane 7 times. They range in size from 319 to 412 amino acids. Conservation of structure among 10 different receptor clones for various species suggests that ligand recognition sites involve amino acids in the 2, 3, and 7 transmembrane segments of receptors. Species differences in ligand binding to A1 receptors in tissues are very similar; for bovine receptors the affinity is R‐PIA ≫ NECA, for canine receptors NECA ≥ R‐PIA. Purified bovine A1 receptors functionally couple to the pertussis toxin sensitive recombinant G proteins, Gi1, Gi2, Gi3, and Go. © 1993 Wiley‐Liss, Inc.
Adenosine system in the heart
Authors: Belardinelli Luiz
Published: January 2005

The adenosine system in the heart consists of three components : (1) a mechanism formation, (2) a receptor‐effector coupling system, and (3) a mechanism for degradation. Selective pharmacological modification of this system with drug such as nucleoside uptake inhibitors osine. The action of adenosine in the heart are mediated by specific cell surface receptors of at least two subtypes. The A1 receptor subtype mediates the actions of adenosine that decrease O2 consumption (e.g, slowing of heart rate), whereas the A2 receptor subtype mediates the well‐known coronary vasodilatory effects of adenosine and thereby increases O2 supply. Adenosine formation is increased when O2 demand exceeds O2 supply. Thus, in the heart adenosine may serve as a negative‐feedback signal to adjust myocardial balance between O2 supply and consumption. In this brief review we describe the cardiovascular effects of adenosine, its mechanism(s) of action, and metabolism. © 1993 Wiley‐Liss, Inc.
Mechanism of the negative dromotrophic effect of adenosine 5′‐triphosphate in the guinea pig heart in vivo
Authors: Xu Jiang , Wang Li , Hurt Carl , Pelleg Amir
Published: January 2005

To test the hypothesis that the vagus nerve does not play a major mechanistic role in the cardiac electrophysiologic action of adenosine 5′‐triphosphate (ATP), the negative dromotropic actions of the nucleotide and adenosine on atrioventricular (AV) nodal conduction were quantitated in an in vivo guinea pig model. Anesthetized animals were divided into three groups. In group 1, ATP and adenosine (0.1–10.0 μmol/kg, iv) were given at random as a rapid bolus during right atrial pacing (paced cycle length 220–270 msec). This protocol was repeated following the administration of atropine (0.2 mg/kg, iv) followed by propranolol (1 mg/kg, iv). In group 2, ATP and adenosine (1.6 μmol/kg, iv) were given in the absence and presence of the selective A1‐adenosine receptor antagonist, N6‐endonorbornan‐2‐yl‐9‐methyladenine (N‐0861, 30 μmol/kg, iv), and in group 3, ATP and adenosine were given as in group 2 but instead of N‐0861, an adenosine transport blocker, dipyridamole (250 μg/kg, iv), was used. Standard lead I and II electrocardiogram, right atrial, right ventricular, and His bundle electrogram as well as systemic arterial blood pressure were continuously monitored and recorded. AV nodal conduction time was quantitated as AH interval. ATP and adenosine were equipotent in suppressing AV nodal conduction. For example, maximal AH interval following the highest dose of ATP and adenosine was 102 ± 10 and 112 ± 7 msec, respectively. These effects were not significantly altered by either muscarinic cholinergic or β‐adrenergic blockade. Furthermore, N‐0861 attenuated and dipyridamole enhanced the effects of ATP and adenosine similarly. It was concluded that the electrophysiologic action of ATP in the guinea pig AV node in vivo is independent of the vagus nerve and mediated by its degradation to adenosine and the action of the latter on A1‐adenosine receptors. © 1993 Wiley‐Liss, Inc.
Mechanism of the effector function of adenosine in asthma and rhintis
Authors: Crimi Nunzio , Polosa Riccardo , Mistretta Antonino
Published: January 2005

Adenosine, a purine nucleoside which may be formed following immunological activation, may act as an autacoid by modulating the function of a variety of cells. In asthmatic and rhinitic subjects, but not in normals, exposure to adenosine causes marked responses, which are markedly reduced by pretreatment with histamine‐H1 receptor antagonists. Although the mechanism by which adenosine induces changes in the function of the lower and upper airways are not clear this form of provocation of the airways may serve as a convenient tool in investigating the characteristic pathophysiological changer of asthma and rhinitis. © 1993 Wiley‐Liss, Inc.
Nucleoside transport inhibition for cardioprotection: New perspectives for the clinic
Authors: Van Belle Herman
Published: January 2005

In this review the role of adenosine, produced in the myocardium in response to ischemia, as a “natural defense” system is briefly summarized. In contrast with exogenous adenosine or adenosine agonists, interference with adenosine metabolism will restrict the action of endogenous adenosine to when and where it is produced (site and event specificity). In this respect, Nucleoside transport inhibition seems to be the preferred strategy because of a dual effect, namely, attenuation of catabolism during ischemia and delay of the washout upon reperfusion. In a variety of experimental studies in animals, nucleoside transport inhibition has been documented to afford marked cardioprotection. Failure in humans thus far may be due to the shortcomings of the few existing drugs. The development of draflazine, a new transport inhibitor with a more appropriate pharmacokinetic profile may open new perspectives for therapy based on this concept. © 1993 Wiley‐Liss, Inc.
Adenosine outflow from hippocampal slices evoked by ischemic‐like conditions: Effect of the excitatory amino acid antagonists
Authors: Pedata Felicita , Latini Serena , Pazzagli Marta , Pepeu Giancarlo
Published: January 2005

The effect of amino acid receptor antagonists on adenosine and inosine outflow evoked by 5 or 10 min ischemia‐like conditions “in vitro” (glucose‐free Krebs solution gassed with 95% N2/5% CO2) was investigated on rat hippocampal slices. The viability of the slices after ischemia was evaluated by extracellular recording of the evoked synaptic responses in the CA1 region. The NMDA receptor antagonist D(−)‐2‐amino‐7‐phosphonoheptanoic acid (D‐AP7 100 μM) and the non‐NMDA receptor antagonist 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX 10 μM) did not significantly decrease the adenosine and inosine outflow evoked by ischemia. The glutamate uptake blocker dihydrokainate (500 μM) also did not affect the outflow of adenosine and inosine. It is concluded that ischemia‐like conditions “In vitro” evoke and adenosine and inosine outflow, through a mechanism which does not involve excitatory amino acids. © 1993 Wiley‐Liss, Inc.
Manipulation of endogenous adenosine affects seizure susceptibility
Authors: Murray Thomas F. , Zhang Ge , Franklin Paul H.
Published: January 2005

A1 adenosine receptors in rat prepiriform cortex (PPC) play an important role in the inhibition of bicuculline methiodide (BMI)‐induced convulsions. In the present study, we evaluated the manipulation of endogenous adenosine in this brain area as a strategy to effect seizure suppression. All compounds evaluated were unilaterally microinjected into the PPC. Focal administration of 5′NH25′dADO and dilazep were found to be highly efficacious as anticonvulsants with respective ED50 values of 2.6±0.8, and 5.6±1.6 nmol. In contrast, 2′DCF was both less potent and less efficacious. These results suggest that accumulation of endogenous adenosine may contribute to seizure suppression, and that adenosine kinase and adenosine transport may play a pivotal role in the regulation of extracellular levels of adenosine in the CNS. © 1993 Wiley‐Liss, Inc.
Cellular mechanisms underlying the excitatory actions of ATP in vascular smooth muscle
Authors: Kennedy Charles
Published: January 2005

It is now clear that noradrenaline (NA) is not the sole excitatory cotransmitter in perivascular sympathetic nerves, as both adenosine 5′‐triphosphate (ATP) and neuropeptide Y (NPY) are co‐stored with NA in synaptic vesicles and co‐released during nerve stimulation. The relative contribution of these compounds to neurogenic contractions is dependent upon the species, vessel and parameters of stimulation studied. Stimulation of the perivascular nerves evokes excitatory junction potentials (ejps) which, in most vessels are resistant to α‐adrenoceptor antagonists. The ejps are mediated by ATP, as they are selectively abolished by desensitisation of the P2x‐purinoceptor by α,β‐MeATP or by the selective P2‐antagonist, suramin. In many vessels a component of the neurogenic contraction also shows resistance to β‐adrenoceptor blockade but can be inhibited by α,β‐MeATP or suramin. In the limited number of vessels studied to date, ATP has been found to act via several ionic mechanisms, including an increasing in a non‐specific, cationic current and an increase in a chloride current. These currents appear to have a variable distribution and are not all present in all vessels. This may allow vessels a differential response to ATP depending on their function. However, the distribution, role and relative importance of these effects is not yet known. As well as its direct contractile effects, ATP also interacts in a synergistic manner with NA and NPY. The mechanisms which underlie these effects are unclear but may involve an increase in the current through L‐type calcium channels. Clearly, vascular neurotransmission is not the simple process previously envisaged. © 1993 Wiley‐Liss, Inc.
ACE inhibition versus angiotensin II, AT1 receptor antagonism: A review of effects on intimal lesion formation in animal models of vascular injury, restenosis, and atherosclerosis
Authors: Prescott Margaret Forney , Sawyer Wilbur K.
Published: January 2005

We recently demonstrated that the angiotensin converting enzyme inhibitor (ACEi) benazepril reduced balloon‐induced lesion formation solely by inhibiting smooth muscle cell (SMC) migration, whereas the Ang II, AT1 antagonist losartan reduced lesion formation by inhibiting both SMC migration and proliferation [Prescott et al. (1991): Am J Pathol 139:1291–1296.]. We thus proposed that in order for both SMC migration and proliferation to be reduced by ACEi treatment, a dose must be selected which is greater than the dose necessary to reduce blood pressure. Recent evidence that ACEi prevention of early intimal lesion formation following balloon injury can be reversed by simultaneous administration of the bradykinin antagonist, Hoe 140 [de‐Blois et al. (1992): Circulation 86 [Suppl I]:I‐226.] raises the possibility that low doses of ACEi treatment may be sufficient to inhibit lesion formation via mechanisms independent of effects on Ang II production but that high doses of ACEi treatment are necessary to prevent the local formation of Ang II. The present review therefore analyzes the results of ACEi treatment on lesion formation following balloon catheterization, vascular stenting, or angioplasty. Effects on lesion formation are correlated with the importance of SMC migration vs. proliferation in the specific model employed. In addition, we present evidence to support our speculation that ACEi reduction of both atherosclerosis and restenotic lesions in the hypercholesterolemic rabbit is primarily due to inhibition of monocyte emigration into the vessel wall and is independent of effects on SMC migration or proliferation. Finally, we present preliminary results from our efforts to develop a rabbit angioplasty model in which macrophage‐derived foam cells are not the primary component of either the initial “atherosclerotic” lesion or the restenotic lesion post‐angioplasty. © 1993 Wiley‐Liss, Inc.
Is there a functional cardiovascular role for AT2 receptors?
Authors: Keiser Joan A. , Major Terry C. , Lu Gina H. , Davis Leslie S. , Panek Robert L.
Published: January 2005

The presence of at least two major subtypes of mammalian angiotensin II (Ang II) receptors has been convincingly demonstrated with the use of selective non‐peptide receptor ligands. Subtype selective peptide ligands have also been identified. The role of AT1 receptors in mediating angiotensin II‐induced vascular smooth muscle contraction, aldosterone secretion and a host of other responses has been well documented. However, the role of the AT2 receptor has remained an enigma. The purpose of the studies presented here was to examine the potential role of AT2 receptors in cardiovascular responses in young animals in which the AT2 receptor predominates, and to examine Ang II responses in animals chronically treated with an AT2 receptor ligand. Ang II receptor binding assays and Ang II contractile responses were assessed in aortic tissue from neonatal rats; aortic binding was compared to liver binding in tissues from the same animals. Although AT2 receptors were expressed in neonatal aorta, the AT2 selective ligand PD 123319 had no effect on Ang II‐induced contractile responses in aortic rings from these neonatal rats. In adult rats acute administration of PD 123319 failed to inhibit Ang II‐induced increases in blood pressure; however, in rats treated for 10–12 days with PD 123319 Ang II‐induced pressor responses were inhibited roughly 40% compared to vehicle treated control rats. These data demonstrate that the AT2 receptor in the neonate may not play a role in Ang II induced vascular tone. However, there may be some resetting or interaction of Ang receptor subtypes in adults rats chronically exposed to an AT2 receptor ligand such that Ang‐II pressor responses are impaired. © 1993 Wiley‐Liss, Inc.
Captopril decreases accelerated atherosclerosis in hypertensive one kidney one clip rats fed cholesterol
Authors: Kowala Mark C.
Published: January 2005

The effect of captopril treatment on early atherosclerosis was determined in cholesterol‐fed rats with acute renovascular hypertension. Three groups were established: normotensive rats, hypertensive one kidney one clip (1K1C) rats, and 1K1C rats treated with 27 mg/kg/day of captopril. Animals in the 3 groups received chow containing 4% cholesterol and 1% cholic acid. Cholesterol feeding and drug treatment were started immediately following surgery, then after 1 or 2 weeks, mean arterial pressure, heart rate, and plasma lipids were measured; and the thoracic aorta was perfused with formalin. One or 2 weeks after surgery, mean arterial pressure increased by 17% to 22% in the 1K1C group compared to the normotensive animals. Captopril decreased blood pressure in the 1K1C rats by 22% to 25% compared to the hypertensive 1K1C group. In the 3 sets of rats, plasma cholesterol was similarly elevated from 109 to 531 mg/dl. Early atherosclerosis and endothelial cell proliferation in the thoracic aorta were quantified from en face specimens that were stained with hematoxylin and oil red O. Compared to the normotensive group, hypertensive 1K1C rats (1 and 2 weeks) had a 463% to 647% increase in the number of subendothelial macrophage‐foam cells/mm2. In 1K1C rats, foam cell accumulation was dense and widespread compared to a focal distribution of leukocytes in normotensive animals. Endothelial cell mitoses increased by 444% in hypertensive 1K1C rats at 1 week compared to the normotensive group. One or 2 weeks of captopril treatment of 1K1C rats reduced macrophage‐foam cells/mm2 by 62% to 72% compared to the hypertensive 1K1C group. Captopril decreased the rate of endothelial cell mitoses in 1K1C rats (1 week) by 62% compared to the hypertensive animals. The results indicate that macrophage‐foam cell accumulation was accelerated in the hypertensive 1K1C rats, and this was accompanied by an increased rate of endothelial cell turnover. Captopril lowered blood pressure, decreased the number of foam cells and inhibited the proliferation of arterial endothelial cells in 1K1C rats. © 1993 Wiley‐Liss, Inc.
Pharmacological and mechanistic aspects concerning the use of heparin and β‐cyclodextrin tetradecasulfate for the treatment of vascular restenosis
Authors: Reilly Christopher F. , Fujita Tsuneo , McFall Rosemary C. , Stabilito Inez I. , Eng Wai‐Si , Johnson Robert G.
Published: January 2005

Aberrant smooth muscle cell (SMC) growth within the intimal tissues of the arterial wall plays a major role in the development of restenosis which commonly occurs following coronary bolloon angioplasty. Studies from several laboratories have demonstrated that heparin reduced neointimal formation in response to balloon denudation in vivo and that heparin also inhibits the growth and migration of cultured SMC in vitro. In this paper, data will be presented demonstrating that heparin markedly inhibits neointimal thickening and bromodexyuridine incorporation into newly synthesized DNA in a fully characterized rat model of arterial injury. Heparin treatment begun at the time of angioplasty and continued for as little as 2–4 days resulted in substantial inhibiton of neointimal formation 14 days later. The relevance of the rat model to human restenosis and the positive and negative aspects concerning the use of heparin and heparin‐like molecules for the treatment of vascular restenosis will be discussed. In addition, we will show that heparin recognizes specific binding sites on the surface of cultured aortic SMC which is a feature possibly associated with the anti‐proliferative mechanism of action of heparin. Finally, a highly sulfated cyclic polysaccharide, β‐cyclodextrin tetradecasulfate (S‐β‐CD), was found to significantly inhibit neointimal formation in the rat model of arterial injury. S‐β‐CD retains several positive aspects but lacks some of the negative features associated with the chronic use of heparin for the treatment of vascular restenosis. © 1993 Wiley‐Liss, Inc.
Novel signal transduction targets in cardiovascular disease: Role of platelet‐derived growth factor in vascular smooth muscle cell proliferation
Authors: Molloy Christopher J.
Published: January 2005

Proliferation and directed migration of vascular smooth muscle cells (VSMCs) are important components in such processes as hypertension‐induced vascular remodeling, vascular restenosis, and atherosclerosis. However, the cellular mechanisms involved in the control of VSMC growth and migration at the tissue level remain largely undefined. Platelet‐derived growth factor (PDGF) has been identified as one of the most potent endogenous VSMC mitogens/chemoattractants. PDGF consists of disulfide‐linked polypeptide dimers composed of two distinct gene products, designated A‐chain and B‐chain. These are assembled as either heterodimers (e.g., AB) or homodimers (e.g., AA, BB). Two distinct PDGF‐receptor genes have been identified, designated α and β. Elevated vascular expression of PDGF‐A and ‐B chains and PDGF‐receptors has been observed in cardiovascular disorders and their related animal models, including restenosis and atherosclerosis. For example, in the rat ballon‐injury model, infusion of PDGF greatly increases intimal thickening and migration of VSMC [Jawien et al. (1992): J Clin Invest 89:507–511]. Furthermore, in a similar model, PDGF‐neutralizing antibodies significantly reduce intimal thickening following balloon injury [Ferns et al. (1991): Science 253:1129–1132]. Thus, PDGF may have a pivotal role in the pathophysiology of hyperproliferative vascular diseases. Pharmacological antagonism of PDGF can be directed at distinct cellular sites, related to the biochemical signaling pathways involved in PDGF‐initiated signal transduction. These include inhibition of ligand binding to high‐affinity surface receptors, inhibition of activated PDGF‐receptor tyrosine kinases, interruption of intracellular PDGF‐receptor‐protein interactions, and inhibition of secondary signaling enzymes. Future development of specific PDGF antagonists will allow precise elucidation of the role of this potent growth factor in cardiovascular diseases. © 1993 Wiley‐Liss, Inc.
Effect of protocatechualdehyde, a metabolite of the novel antirheumatic agent ACP, on chondrocyte metabolism
Authors: Watanabe Koju , Hayashi Haruhisa , Mori Yo
Published: January 2005

We investigated PAL (protocatechualdehyde), one of the metabolites of ACP (3,4‐diacetoxy benzylidene diacetate) which is a candidate novel antirheumatic agent. Specifically, we studied the effect and mechanism of action of PAL on chondrocyte metabolism using a primary culture of chondrocytes from rabbit articular cartilage. Proteoglycan (PG) depletion in the chondrocyte matrix was induced by the addition of human recombinant interleukin‐1α (hrlL‐1α) or phorbol myristate acetate (PMA). PAL (10–100 μM) significantly reduced the induced PG depletion and [35S]‐PG release in the chondrocyte matrix. The matrix metalloproteinase (MMPs) inhibitor, 1,10‐phenanthroline, and protein kinase C (PKC) inhibitor, H‐7, also blocked PG depletion and [35S]‐PG release. Furthermore, H‐7 reduced the production of MMPs induced by hrlL‐1α in the culture media of chondrocytes. These results indicate that hrlL‐1α causes MMPs production by the activation of PKC, which is followed by [35S]‐PG release in the chondrocyte matrix. While PAL also resulted in significant inhibition of MMPs production, which might be mediated by PKC activation, it had no direct influence on PKC activity. These results suggest that PAL affects chondrocyte metabolism by the inhibition of MMPs production. ©1993 Wiley‐Liss, Inc.
Effect of calcium binding protein modulators on myofibrillar MgATPase activity and cGMP‐inhibitable phosphodiesterase activity from human cardiac muscle
Authors: Pagani Edward D. , O'Connor Bernard , Allen Paul D. , Hille Darcy , Silver Paul J.
Published: January 2005

Cardiac muscle force development and shortening result from the interaction between actin and myosin within the myofibrillar contractile unit. This interaction is dependent upon intracellular Ca2+ and is controlled by the troponin‐tropomyosin regulatory proteins situated along the length of the actin thin filament. Enhancing the Ca2+ sensitivity of cardiac contractile protein interactions has been proposed as a novel mechanism for some positive inotropic agents. These myofibrillar Ca2+ sensitizers have variable effects on myofibrillar MgATPase activity among nonhuman animal species, and different effects between myofibrils from failed nonhuman hearts are evident. In this study, we have evaluated several myofibrillar calcium sensitizers, at maximal testable concentrations, for their effects on the calcium‐activated MgATPase of myofibrils prepared from normal human hearts and from hearts of patients with congestive heart failure. Bepridil (100 μM) increased MgATPase at pCA 9.0 (basal activity) and pCa 6.5 (an intermediate concentration of Ca2+ which stimulated activity 42–56% of maximal), with no effect at pCa 5.0 (maximal Ca2+ activity) in both normal and failing hearts. APP 201–533 (300 μM) increased MgATPase at pCa 6.5 in all hearts, but increased MgATPase at pCa 5.0 only in normal hearts. Pimobendan (100 μM) increased MgATPase at pCa 6.5 only in normal hearts and increased activity at pCa 5.0 only in failing hearts. In contrast, trifluoperazine (100 μM) reduced MgATPase at pCa 5.0 and pCa 9.0 in all hearts and at pCa 6.5 in failing hearts. The stimulating effects of bepridil, APP 201–533, and pimobendan (approximately 7–17%) were less than those observed in studies with nonhuman cardiac myofibrils (typically 30–40%). These data suggest that some myofibrillar Ca2+ sensitizers can have either modest stimulatory or inhibitory activity on human cardiac myofibrillar MgATPase activity. While these (Ca+‐sensitizing) effects on MgATPase activity are statistically significant, the biological relevance with respect to enhancing cardiac contractility is equivocal. Furthermore, both pimobendan and APP 201–533 inhibited cAMP‐phosphodiesterase III purified from failing human hearts with IC50 values of 0.35 and 2.0 μM, respectively. Since other inotropic mechanisms, such as cAMP‐phosphodiesterase inhibition, are also evident at much lower concentrations with some of these agents, the relevance of myofibrillar Ca2+ sensitization as the predominant inotropic mechanism of action of these compounds is questionable. © 1993 Wiley‐Liss, Inc.
Pharmacology of cyanodothiepin (BTS 56 424), a selective 5‐hydroxytryptamine reuptake inhibitor
Authors: Luscombe Graham P. , Buckett W. Roger
Published: January 2005

The pharmacological profile and antidepressant potential of cyanodothiepin (BTS 56 424) have been compared to those of dothiepin, cianopramine, and imipramine. Rat brain synaptosomes and human platelets were used to measure the effects of drugs on radiolabeled monoamine uptake in vitro. The 2‐nitrile substitution converted the actions of dothiepin from nonselective inhibition of 5‐hydroxytryptamine (5‐HT) and noradrenaline uptake to those of cyanodothiepin, a potent and very selective 5‐HT uptake inhibitor (Ki = 4.8 and 597 nM vs. 5‐HT and noradrenaline uptake, respectively; rat brain synaptosomes). Nitrile substitution similarly conferred in vitro 5‐HT selectivity on cianopramine (Ki = 0.71 and 15 nM vs. 5‐HT and noradrenaline) compared to imipramine. The selectivity of cyanodothiepin as a 5‐HT reuptake inhibitor was maintained in vivo in a variety of rodent models. Cianopramine was a more potent but less selective 5‐HT reuptake inhibitor than cyanodothiepin in these paradigms. In monoamine‐depletor based tests for antidepressant activity, cyanodothiepin was weakly active compared to cianopramine and imipramine; cyanodothiepin was active in the Porsolt test for antidepressants. Compared to cianopramine, cyanodothiepin showed weaker affinity for muscarinic cholinergic and 5‐HT2 receptors in vitro and in vivo, and for α1‐adrenergic, dopamine (D1 and D2) receptors in vitro. Cyanodothiepin was less sedative than cianopramine and was also a weaker enhancer of drug‐induced loss of righting reflex in mice. Overall, cyanodothiepin is a potent and selective 5‐HT reuptake inhibitor which exhibits antidepressant potential and probably possesses a lower propensity to induce side effects associated with tricyclic antidepressants. © 1993 Wiley‐Liss, Inc.
8‐(3‐Isothiocyanatostyryl)caffeine is a selective, irreversible inhibitor of striatal A2‐Adenosine receptors
Authors: Ji Xiao‐Duo , Gallo‐Rodriguez Carola , Jacobson Kenneth A.
Published: January 2005

8‐(3‐Isothiocyanatostyryl)caffeine (ISC) was synthesized and shown to inhibit selectively the binding of [3H]CGS 21680 (an A2a‐selective agonist) at adenosine receptors in striatal membranes. The Ki value at A2a‐receptors was found to be 110 nM (rat), with selectivity ratios for A2a versus A1‐receptors in rat, guinea pig, bovine, and rabbit striatum of >100‐fold. Preincubation of membranes with ISC caused a dose‐dependent, irreversible antagonism of the binding of [3H]CGS 21680, with an IC50 value of 3 μM. The irreversibility is likely due to the presence of the chemically reactive isothiocyanate group, since the binding of the corresponding analogue in which the isothiocyanate was replaced with a chloro group was completely reversible. The potency of ISC to irreversibly inhibit the binding of [3H]CGS 21680 in several species varied in the order rat ≈︁ guinea pig > bovine ≈︁ rabbit. In all four species, binding of the A1‐selective agonist [3H]R‐N6‐phenylisopropyladenosine was not diminished by pre‐treatment with 2 μM ISC. The kinetics of irreversible inhibition of rat A2a‐receptors by 2 μM ISC gave a t1/2 of approximately 3 min. Following partial inactivation, the remaining rat A2a‐binding sites retained the same Kd value as in control membranes for saturatin by [3H]CGS 21680. Thus, ISC appears to be a selective affinity label for A2a‐ versus A1‐receptors in the brain. © 1993 Wiley‐Liss, Inc.
MS‐551: Pharmacological profile of a novel class III antiarrhythmic agent
Authors: Kamiya Joji , Ishii Masaaki , Yoshihara Kanji , Oyabe Akihiro , Banno Hitoshi , Katakami Tstutomu
Published: January 2005

The class II antiarrhythmic agent properties of the novel compound MS‐551 (1,3‐dimethyl‐6‐{(2‐[N‐(2‐hydroxyethyl‐3‐(4‐nitrophenyl)propylamino]ethylamino} ) 2,4 (1H3H)‐pyrimidinedione hydrochloride) have been characterized in vitro and in vivo. Using isolated canine Purkinje fibers, the effect of MS551 on the action potentials was studied. MS‐551 (0.1‐10μg/ml) caused a uniform and concentration‐dependent increase in action potential duration without changing parameters of action potential depolarization. IN anesthetized open‐chested dogs. MS‐551 (0.1‐10 mg/kg i,v.) produced a dose‐dependent increase in both atrial and ventricular effective refractory periods 9ERP) with QTc prolongation. At 0.3 mg/kg i.v., atrial and ventricular ERP were significantly increased 28 ± 4 mec and 12 ± 2 msec, respectively, and the minimum e4ffective plasma concentration of MS‐551 for atrial ERP prolongation was approximately 0.1 μg/ml. However, MS‐551 did not slow intracardiac conduction time (A‐H, H‐V) even at the highest dose studied (30 mg/kg i.v.). These data suggest that MS‐551 has a “pure” class III electrophysioloigcal property in dogs. Furthermore, we compared the effects of MS‐551 on the hemodynamics in anesthetized dogs with those of d‐sotalol. MS‐551 (0.1‐3 mg/kg) produced dose‐dependent decrease in heart rate with QTc prolongation and slight increase in LVdP/dtmax. In contrast d‐sotalol (0.1‐10 mg/kg i.v.) depcreased heart rate, mean arterial pressure, LVdP/dtmax and aortic flow in a dose‐dependent manner. Moreover, we reassessed in anesthetized dogs the cardiovascular toxicity of continuously infused MS‐551 (2 mg/kg/min for 50 min). Ath the end of the infusion (total dose: MS‐551 100 mg/kg), LVdP/dtmax was decreased 23%, but QTc prolongation never exceeded 30%. Thus, arrhythmias, such as torsade de pointes, were not seen. In conclusion, MS‐551 appears to be a pure and potent class III antiarrhythmic agent with a favourable hemodhynamic profile. © 1993 wiley‐Liss, Inc.
Comparison of acute and repeated treatment with the 5‐HT1A receptor ligands 8‐OH‐DPAT and ipsapirone in animal models of anxiety and depression
Authors: De Vry Jean , Schreiber Rudy
Published: January 2005

The present study compared the 5‐HT1A receptor ligands 8‐OH‐DPAT and ipsapirone with diazpepam and imipramine in the shock induced ultrasonic vocalization anxiety test and the forced swimming depression test in the rat. Acutely, 8‐OH‐DPAT induced anxiolytic and antidepressive effects (ED50: 0.12 and 1.4 mg/kg, i.p., respectively), whereas ipsapirone induced anxiolytic (ED50: 0.6 mg/kg) and moderate antidepressive effects (33% at 3‐10 mg/kg). Virtually no tolerance developed for the anxiolytic effects after 2 weeks of treatment with 0.03‐1 mg/kg 8‐OH‐DPAT or 0.1‐10 mg/kg ipsapirone (i.p., b.i.d.), with 10 mg/kg/day ipsapirone (s.c., mini‐pumps), or with 1.5 μg/rat/hr 8‐OH‐DPAT (local infusion in the dorsal raphe nucleus, mini‐pumps). However, some tolerance developed for the antidepressive effects of 8‐OH‐DPAT (ED50: 0.6, 1.4, 2.5 and >3 mg/kg, after 2 weeks of pretreatment with vehicle, 0.3, 1, and 3 mg/kg 8‐OH‐DPAT, respectively, i.p., b.i.d.). In the case of ipsapirone, the dose‐effect curve in the forced swimming test was shifted to the left after 2 weeks of pretreatment with ipsapirone (0.3‐10 mg/kg, i.p., b.i.d.). Acutely, diazepam induced an anxiolytic effect (ED50: 3.6 mg/kg, i.p.), but failed to induce an antidepressive effect; whereas imipramine induced an antidepressive effect (ED50: 20.5 mg/kg) and a moderate anxiolytic effect (max. efficacy: 47% at 30 mg/kg). Upon repeated administration (2 weeks), diazepam (5 mg/kg) showed t0olerance for its anxiolytic effects and weak antidepressive effects emerged, whereas imipramine (20 mg/kg) showed weak sensitization for both effects. It is concluded that (a) with all compounds, tolerance, as well as sensitization can be observed, depending on the behavioral test, the dose and the type of compound; and (b) compared with the other compounds tested, relatively low doses of 5‐HT1A drugs offer the most attractive profile of mixed anxiolytic/antidepressive activity. © 1993 wiley‐Liss, Inc.
Tretinoin: A review of preclinical toxicological studies
Authors: Cohen Marvin
Published: January 2005

Tretinoin (all‐trans‐retinoic acid) has shown efficacy in the treatment of acute promyelocytic leukemia. The preclinical toxicological profile of tretinoin was similar to that of other retinoids. The compound had a relatively low acute toxicity; repeated doses resulted in a substantial increase in toxicity that was a function of dose and duration of exposure. Bone fractures, elevated alkaline phosphatase, and testicular degeneration were produced by repeated doses of tretinoin. Teratogenicity was demonstrated in several species. Tretinoin was inactive in the Ames test but appeared to induce sister‐chromatid exchanges in human diploid fibroblasts. Insufficient data are available to evaluate the carcinogenic potential of tretinoin. © 1993 wiley‐Liss, Inc.
Neurochemical mechanisms mediating the behavioral and cognitive effects of nicotine
Authors: Gray Jeffrey A. , Mitchell Stephen N. , Joseph Michael H. , Grigoryan Grigory A. , Dawe Sharon , Hodges Helen
Published: January 2005

Data are reviewed, largely from experiments in the authors'laboratory, that suggest three modes of action of systemic nicotine in producing three different types of effect upon behavior and cognitive function. (1) Preexposure of a stimulus without consequence makes it harder subsequently to form associations to that stimulus, a form of selective attention known as latent inhibition. Latent inhibition is blocked by nicotine, an effect that is apparently mediated by a nicotine‐induced increase in dopamine release in the nucleus accumbens. (2) A single dose of nicotine proactively increases the partial reinforcement extinction effect measured several weeks later: that is, resistance to extinction is decreased by nicotine in animals that have been trained on a continuous reinforcement schedule, and increased in animals trained on a partial reinforcement schedule. This effect appears to be due to increased synthesis of tyrosine hydroxylase in the cell bodies of noradrenergic neurons in the locus coeruleus, followed by axonal transport to the hippocampus and increased synthesis and release of noradrenaline in that structure. (3) Nicotine improves vigilance in animals with cognitive deficits due to destruction of the forebrain cholinergic projection system, either as a consequence of excitotoxic lesions of the nuclei of origin of this system or after prolonged alcohol consumption; and also in human subjects with Alzheimer's disease (in which this system undergoes degeneration). This effect is most likely due to an action at denervated cholinergic synapses in the hippocampus and neocortex. © 1994 Wiley‐Liss, Inc.
Biochemical evidence for the involvement of central serotonergic neurotransmission in the action of the antidepressant drug Medifoxamine
Authors: Gillon Jean‐yves , Vitte Pierre‐Alain , Lemonnier Francoise , Kato Gabor
Published: January 2005

Medifoxamine, an antidepressant agent which has an original chemical structure, has been shown through in vitro studies, utilising radioligand binding in tissue homogenates, to bind with moderately high affinity to 5‐HT1c and 5‐HT2 receptor subtypes and to 5‐HT uptake sites (IC50 950, 980, and 1,500 nM, respectively). It has been shown to bind in vivo to rat brain 5‐HT2 receptors after acute treatment with high dose (50 mg/kg, i.e., 133.9 μmol/kg). After 14 days continuous treatment with low dose (20 mg/kg, 53.6 μmol/kg), a decrease in the capacity of [3H]‐5‐HT uptake and a dose‐dependent down‐regulation of 5‐HT2 receptors in rat cerebral cortex were observed. These results indicate that medifoxamine, which has been shown previously to act through dopaminergic systems, interacts also with central serotonergic neurotransmission and particularly with the 5‐HT2 receptors, which could contribute to its antidepressant effect.
Attenuation of experimental hypertension with agents that increase insulin sensitivity
Authors: Kotchen Theodore A.
Published: January 2005

Both in the human and in several experimental models, hypertension is associated with insulin resistance. Thiazolidinedione derivatives are a novel group of oral hypoglycemic agents that increase insulin sensitivity without stimulating endogenous insulin secretion. These agents have been shown to attenuate the development of hypertension in the following experimental rat models: the Dahl salt‐sensitive rat, the one‐kidney, one‐clip hypertensive rat, the obese Zucker rat, and blood pressure increases in rats fed high carbohydrate or high fat diets. Clofibrate, a lipid lowering agent that also increases insulin sensitivity, also prevents the development of hypertension in Dahl salt sensitive rats. Additional studies will be required to determine if attenuation of hypertension by these agents is specifically related to their capacity to increase insulin sensitivity.
Diabetic nephropathy, renal hemodynamics, and aldose reductase inhibitors
Authors: Oates Peter J.
Published: January 2005

Diabetic kidney disease or diabetic nephropathy is the leading cause of renal failure in the United States today. This review presents a brief overview of diabetic nephropathy—its current statistics, histopathology, natural history, and main risk factors, including hyperglycemia, hyperfiltration, and hypertension. Pathogenic mechanisms by which hyperglycemia, severe hyperfiltration, and capillary hypertension might cause renal injury are discussed. Evidence is reviewed indicating a potentially useful role for aldose reducatase inhibitors (ARIs) to normalize or reduce the impact of two possible risk factors for diabetic nephropathy, namely, elevated polyol pathway metabolism and severe hyperfiltration. Measurements in experimental models of whole kidney blood flow (57Co‐microspheres, clearance methods), superficial cortical blood flow (laser Doppler flowmetry), and single nephron hemodynamic parameters (renal micropuncture) concordantly indicate that the beneficial effect of ARIs on hyperfiltration is based on protection or restoration of normal renal microvascular resistance. Since ARIs affect neither blood sugar levels nor mean arterial pressure, ARIs have no increased risk attributable to hypoglycemia or hypotension. It is concluded that ARIs warrant further experimental and clinical research in early diabetic nephropathy.
Effect of 5‐HT2 receptor antagonist ergolines and their desisopropyl metabolites on rabbit platelet aggregation in vitro and ex vivo
Authors: Cohen Marlene L. , Bloomquist William
Published: January 2005

Amesergide and LY215840 are potent and long‐lasting 5‐HT2 receptor antagonists after oral administration to animals. In animals, these ergolines are metabolized to their desisopropyl ergoline congeners which have lower affinity (40–60 nM) at 5‐HT2 receptors in the rat relative to higher 5‐HT2 receptor affinity (2–3 nM) at the cloned human 5‐HT2 receptor. Because amesergide and LY215840 are effective in rabbit models of thrombosis, we asked whether their efficacy in the rabbit was related in part to the activity of both the parent and desisopropyl metabolites at rabbit platelet 5‐HT2 receptors. Platelet aggregation responses were first optimized to ADP and the combination of ADP and serotonin with regard to platelet number (300,000 platelets/μl of plasma) and time (70 to 140 min after platelet harvest). In ex vivo studies, both amesergide and LY215840 (3.0 mg/kg p.o.) showed similar and marked antagonism of rabbit platelet 5‐HT2 receptors at 1 and 24 h after their oral administration to rabbits. Furthermore, the desisopropyl ergoline metabolites of both amesergide and LY215840 inhibited serotonin‐amplified platelet aggregation responses in vitro as did amesergide and LY215840. Thus, these studies add support to the hypothesis that the desisopropyl metabolites of amesergide and LY215840 may contribute to the oral antithrombotic efficacy of the parent molecules in rabbits.
Regulatory considerations on the role of general pharmacology studies in the development of therapeutic agents
Authors: Proakis Anthony G.
Published: January 2005

In contrast to the well‐defined regulatory requirements for the conduct of animal toxicology studies, FDA regulations and guidelines for nonclinical pharmacodynamic studies are relatively general and do not require that any specific studies be conducted. General pharmacology studies are conducted to identify actions of a new agent in addition to those associated with the primary therapeutic utility. General pharmacology studies aimed at determining drug effects on cardiovascular, central nervous system, gastrointestinal, respiratory and pulmonary, renal, endocrine and metabolism, autonomic nervous system, and drug‐receptor functions were among the types of general pharmacology studies included in a sample of recent investigational new drug application (IND) and new drug application (NDA) submissions. Assessment of drug effects on cardiovascular, autonomic nervous system, and drug‐receptor interactions were given the greatest individual importance in identifying drug effects relevant to the assessment of a product's safety at the initial IND stage. At the NDA stage, general pharmacology studies find their greatest value in predicting drug‐drug interactions, defining mechanisms of action, characterizing the pharmacological correlates of drug‐overdose, identifying dose‐limiting effects for the chronic toxicity studies, and associating animal toxicity findings with known pharmacotoxic effects. General pharmacology studies provide valuable information to complement animal toxicity studies for evaluating a drug's potential risk to humans.
Surface of synergistic interaction between dipyrone and morphine in the PIFIR model
Authors: López‐Muñoz Francisco J.
Published: January 2005

The analgesic effects of dipyrone and morphine administered either separately or in 24 different combination were determined in the “Pain‐Induced Functional Impairment in the Rat” (PIFIR analgesic model). This allowed the detection of the profile of analgesic interaction of the various combinations. Furthermore, the optimal degree of potentiation obtained with a specific combination of the above drugs was determined by means of the “Surface of Synergistic Interaction” (SSI) of the combinations. This parameter was calculated from the total analgesic effect produced by the combination after having subtracted the analgesic effect produced by each drug alone. Over the dose‐ranges used, the analgesic activities of either dipyrone or morphine tended to be smaller than those of their respective combinations. Furthermore, 11 combinations showed various degrees of potentiation (P < 0.05), while the remainder (13) exhibited additive analgesic effects. The combination of dipyrone (562 mg/kg, sc) and morphine (5.6 mg/kg, sc) produced the maximum analgesic effect. However, dipyrone (178 mg/kg) with morphine (3.2 mg/kg) produced the highest potentiation effect (P < 0.001). The surface of synergistic interaction clearly showed which combination of analgesic drugs produced the highest degree of potentiation in the rat. This represents the first study to show that a specific ratio of combination of analgesic drugs can produce an optimal potentiation of their analgesic effects. These findings may have important implications for the treatment of pain. © 1994 Wiley‐Liss, Inc.
Scanning whole cells with phage‐display libraries: Identification of peptide ligands that modulate cell function
Authors: Fong Susan , Doyle Laura V. , Devlin James J. , Doyle Michael V.
Published: January 2005

A general strategy has been developed for rapidly identifying peptides that alter cellular function, which has revealed a series of peptides that inhibit platelet aggregation. First whole cells—platelets in this case—were used as an affinity matrix to isolate cell‐binding phage from a phage‐display, random‐peptide library. In this step 3 × 107 different filamentous phage, each encoding and displaying a different random peptide, were screened as a single pool. Since it is the peptide displayed on the surface of the phage that presumably causes a particular phage to bind specifically to a cell, synthetic peptides were then made based on the predicted sequences of the displayed peptides. Because the initial affinity selection step had focused attention on a handful of peptides, each of the 17 synthetic peptides could be individually tested in an appropriate functional assay, such as platelet aggregation. The majority of the 17 different peptides that we analyzed inhibited platelet aggregation; these peptides could be grouped into at least five different motifs including the expected RGD motif. It is believed that this strategy, which requires neither purification nor prior knowledge of a particular target receptor, will prove to be generally useful for identifying peptide ligands that influence cellular function. © 1994 Wiley‐Less, Inc.
Synthesis of support‐bound peptides carrying color labels
Authors: Câmpian Eugen , Sebestyén Ferenc , Major Ferenc , Furka Árpád
Published: January 2005

In order to check the possibility of labeling sub‐libraries, we synthesized a colored support by acylation of aminomethyl resin with a special Boc‐amino acid (a red azo dye). Syntheses of model peptides proved that the colored resin is suitable for solid phase peptide synthesis. Color labeling was also made by coupling resin‐bound peptides at their N‐termini with a blue dye. Colored resins as well as labeling at the N‐terminus offer a possibility to simplify the preparation of support‐bound peptide sub‐library kits and their use in sequence determination of bioactive peptides. © 1994 Wiley‐Less, Inc.
Identification of small peptides that interact specifically with a small organic dye
Authors: Lam Kit S. , Zhao Zhan‐Gong , Wade Shelly , Krchňák Viktor , Lebl Michal
Published: January 2005

Using a “one‐bead one‐peptide” combinatorial peptide library method, we have been able to identify peptide ligands that interact specifically with various macromolecular targets such as monoclonal antibodies, streptavidin, avidin, MHC‐Class I molecules, proteases, growth factor receptors, and gpIIb/IIIa integrin. In this paper, we test the hypothesis that small peptides that interact specifically with a small organic molecule can also be identified using this combinatorial peptide method. Using a small organic dye molecule, indigo carmine, as a color probe to screen a random L‐heptapeptide and two D‐hexa and octapeptide libraries, we were able to identify a specific peptide binding motif. Potential applications of this technology are described. © 1994 Wiley‐Less, Inc.