bluuebunny/crossref_metadata_2025 huggingface dataset:
Involvement of Nitric Oxide in Fading of 5‐Hydroxytryptamine‐Induced Vasocontraction
Authors: Wakabayasbi Ichio
Published: March 2009

Abstract:This investigation was done to determine whether vascular nitric oxide is involved in the fading of 5‐hydroxytryptamine (5‐HT)‐induced contraction of isolated aortic strips from rats. The 5‐HT (100 μM)‐induced contractile response showed a gradual decrease in tension after a plateau level had been attained. The degree of the fadeaway was less in strips without endothelium than in those with endothelium. Pretreatment with nitro‐L‐arginine (100 μM) or haemoglobin (10 μM) suppressed the fadeaway of 5‐HT contraction in both types of strips, although the effect was less in strips without endothelium. In contrast to 5‐HT contraction, phenylephrine (10 μM) contraction in the presence of endothelium did not begin fading away for at least 1 hr after stimulation. In strips precontracted with 5‐HT (100 μM), relaxation induced by sodium nitroprusside (1‐50 nM) was significantly higher than in those precontracted with phenylephrine (10 μM). There was no significant difference between the cyclic GMP levels at 1 hr after stimulation with phenylephrine (10 μM) and 5‐HT (100 μM). These results suggest that decrease in vascular tone in rat aorta after the plateau of 5‐HT contraction has been reached is in part due to nitric oxide derived from vascular endothelial and non‐endothelial cells. The vascular tone decreases more quickly after the plateau in the case of 5‐HT contraction than of phenylephrine contraction, which may be due to higher sensitivity of 5‐HT contraction to nitric oxide.
Involvement of Nitric Oxide and Peptides in the Inhibitory Non‐Adrenergic, Non‐Cholinergic (NANC) Response in Bovine Mesenteric Artery**
Authors: Leckström Arnold , Ahlner Johan , Grundström Nils , Axelsson Krister L.
Published: March 2009

Abstract:The cyclic GMP mediated non‐adrenergic non‐cholinergic (NANC) relaxation in field stimulated bovine mesenteric artery and its modulation by various factors was studied. Electrical field stimulation of precontracted (Phe 2.5 μM or histamine 5 μM) bovine mesenteric arteries resulted in relaxations varying between 10‐70% in different preparations. Tetrodotoxin (3 μM) completely blocked the inhibitory NANC response. Preincubation with high concentrations (100 μM − 1 mM) of NG‐nitro‐L‐arginine for 15 min. significantly reduced the relaxation induced by electrical field stimulation. Blockade of cyclooxygenases and prostaglandin synthesis by indomethacin had no effect on the relaxatory response to electrical field stimulation. Neither the α2‐adrenoceptor selective antagonist yohimbine (1 μM) nor the α2‐adrenoceptor selective agonist UK 14,304 (1 μM) had any significant effect on the electrical field stimulation‐induced relaxation. Pertussis toxin (100 ng/ml) was without effect on relaxations elicited by electrical field stimulation. GTP in the concentration range 10 μM − 1 mM slightly potentiated the relaxant response. N‐carboxymethyl‐Phe‐Leu (an inhibitor of enkephalinase) or aprotinin (an inhibitor of several proteases) had no significant effect on the electrical field stimulation response. Addition of trypsin (100 U/ml) in combination with chymotrypsin (20 U/ml) significantly reduced the electrical field stimulation‐induced relaxation. In the present study we have found indications for the involvement of nitric oxide and possibly also peptides in mediating the inhibitory NANC response (relaxation) in bovine mesenteric arteries.
Implementation of a Radioreceptor Assay for Dexmedetomidine
Authors: Salonen Markku , Maze Mervyn
Published: March 2009

Abstract: We have implemented a radioreceptor assay for dexmedetomidine, a novel α2‐adrenoceptor agonist. Receptor‐bearing membranes were prepared from rat cerebral cortex and 3H‐clonidine, 4 nM, was used as the labeled ligand. Dexmedetomidine displaced 3H‐clonidine in a linear fashion over a concentration of 2 × 10‐10 to 2 × 10‐8 M. The detection limit of dexmedetomidine (i.e. 10% of radiolabeled ligand displaced) in this assay was 50 pg.ml‐1 which is comparable to that seen with the reference method which utilizes gas chromotography with mass spectrometer (GC/MS) in series (Vuorilehto et al. 1989). Endogenous catecholamines, which can displace the radiolabeled ligand from its binding site, could easily be eliminated with a one‐step extraction procedure. A comparison was made with the reference method (GC/MS) in 47 human plasma samples; the correlation coefficient (r2) was 0.61 (P<0.001). The radioreceptor assay was also successfully applied for determining dexmedetomidine concentration in rabbit samples. These data indicate that the radioreceptor assay can be utilized for characterizing the pharmacokinetics of novel α2 agonists which are now being introduced into the clinical practice of anaesthesia.
Acute Toxicity of Tedisamil, a New Potassium Channel Blocking Drug
Authors: Hayes E. , Courtice I. D. , Abraham S. , Walker M. J. A.
Published: March 2009

Abstract:The acute intravenous toxicity of tedisamil, a new potassium channel blocker, was assessed by infusing it at various rates (1.5 to 10 mg/kg/min.) to ventilated or spontaneously breathing rats subjected to blockade of their peripheral somatic and autonomic nervous systems. The lethal doses for ventilated rats (including pithed animals) were 2–3 times higher than those for spontaneously breathing animals. In spontaneously breathing rats death appeared to be due to respiratory depression which was possibly of central origin since the lethality of tedisamil was not markedly altered by vagotomy, bilateral carotid artery ligation, nor by autonomic nervous system blockade. On the other hand, in all of the artificially ventilated groups, death occurred at higher doses and was related to direct cardiac actions, possibly involving blockade of cardiac potassium and sodium channels. The cardiovascular responses to infusions of tedisamil included tachyarrhythmias, bradycardia, blood pressure changes, increased QRS width and Q‐T interval duration. Arrhythmias occurred at sublethal doses and were eliminated by autonomic blockade and pithing. However, the bradycardia, ECG and blood pressure changes induced by tedisamil infusions were unaltered by the various treatments. Thus tedisamil may induce arrhythmias by actions on the autonomic system.
Kainic Acid‐Induced Seizures and Brain Damage in the Rat: Different Effects of NMDA‐ and AMPA Receptor Antagonists
Authors: Berg M. , Bruhn T. , Johansen F. F. , Diemer N. H.
Published: March 2009

Abstract:We have studied the effect of two glutamate receptor antagonists on seizures and hippocampal neurone loss in the rat after systemic kainic acid administration. Intraperitoneal injection of the novel AMPA (α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolproprionic acid) receptor antagonist NBQX (6‐nitro‐7‐sulphamoylbenzo(f)quinoxaline‐2,3‐dione) (30 mg/kgx3 and 15 mg/kgx3) administered 30 and 15 min. before and simultaneously with injection of kainic acid (5 mg/kg) intraperitoneally, dramatically enhanced the toxicity of kainic acid leading to death of all animals. When the NBQX dose was reduced to 8 mg/kg x 3, all animals survived and neurone damage in the hippocampus did not differ from control animals. When NBQX (30 mg/kg x 3) was administered 30 ‐ or 60 min after injection of kainic acid (8 mg/kg) intraperitoneally, no changes were observed concerning survival rates, seizure generation and neurone loss. Postkainic acid treatment with the non‐competitive NMDA receptor antagonist MK‐801 (0.5 mg/kg and 1.0 mg/kg), 30 and 60 min. after intraperitoneally injection of kainic acid 8 mg/kg, abolished seizures in all animals and the neurone damage in the hippocampus was completely prevented. The results emphasize the importance of the NMDA‐receptor activation for seizure generation and subsequent brain damage after intraperitoneally kainic acid. The paradoxical, unexpected effects of NBQX contrast to the protective effect of this compound after cerebral ischaemia and hypoglycaemia, conditions which are also characterized by glutamate‐mediated damage. One possible explanation of the lowered seizure threshold to kainic acid after NBQX could be that NBQX is blocking AMPA receptors on interneurones more efficiently than on pyramidal cells.
Interactions Between Cultured Bovine Arterial Endothelial and Smooth Muscle Cells: Studies on Uptake and Degradation of Low Density Lipoproteins by Smooth Muscle Cells
Authors: Xu Cang‐Bao , Stavenow Lars , Liao Wei , Erlinge David , Edvinsson Lars
Published: March 2009

Abstract: This study was designed to investigate the effects of substances released from non‐injured and injured bovine arterial endothelial cells on 125I‐low density lipoprotein uptake and degradation by smooth muscle cells in culture. It was demonstrated that endothelial cell‐released non‐dialysable (molecular weight cut off 12‐14000) substances significantly stimulated 125I‐low density lipoprotein uptake and degradation by smooth muscle cells. Endothelial cell‐released dialysable substances and endothelin‐1 did not cause this stimulation. The increase in 125I‐low density lipoprotein uptake and degradation by smooth muscle cells could be dissociated from cell proliferation. However, in endothelial cell‐smooth muscle cell co‐culture 125I‐low density lipoprotein uptake and degradation by smooth muscle cells were not stimulated. Injury to endothelial cells by lipid‐soluble smoke particles or ultraviolet light, which reduced total cellular protein by 15‐25%, enhanced the endothelial cell release of the substances stimulating 125I‐low density lipoprotein uptake. The results are discussed in relation to atherogenesis.
Pharmacokinetics and Dynamic Response of Plain and Slow Release Isradipine Formulations in Moderately Hypertensive Patients
Authors: Christensen Hanne R. , Simonsen Kim , Kampmann Jens P.
Published: March 2009

Abstract: The pharmacokinetic variables and antihypertensive effect of the calcium antagonist isradipine, were investigated in 30 hypertensive patients. Isradipine was given orally in parallel group design in plain and slow release formulations in doses of 2.5 mg twice daily and 5.0 mg once daily, respectively. Isradipine concentration in serum was measured by a sensitive RIA method after the first dose and after 6 weeks of treatment. The pharmacokinetics and concentration/effect relationship after the first dose and after 6 weeks of treatment were compared. No differences in pharmacokinetics were observed between single and multiple dosing. Data were in accordance with results from studies in healthy volunteers. Rate, but not extent of bioavailability differs between the two isradipine formulations. Antihypertensive efficacy of the two formulations was similar (16/11 and 19/15 mmHg), and a significant time dependent increase in Emax from 10/3 mmHg to 23/14 mmHg after 6 weeks of treatment was observed.
Inhibition of the Vitamin B12 Binding Capacity of Proteins by the Hydrolysis Product of Cyclophosphamide
Authors: Fenrych Wladyslaw , Szczodrowska Enid , Ignatowicz Ewa
Published: March 2009

Abstract: The inhibitory effect of cyclophosphamide hydrolysis product (CPHP) on vitamin B12 binding ability to proteins has been established. The ester N‐(2‐chloroethyl)‐N'‐(3‐phosphopropyl)‐etheylenediamine hydrochloride is probably responsible, in vitro, for blocking the protein binding sites. Preincubation of proteins with vitamin B12 prevents the inhibitory effect of CPHP.
Efficacy of Antidotes against Soman Poisoning in Female Physostigmine‐Protected Rats
Authors: Sket Duŝan
Published: March 2009

Abstract:Female rats have been found much more sensitive to lethal effects of soman than male rats. Therefore it was of interest to examine the efficacy of different antidotes against soman poisoning in females which are usually not being used in soman poisoning studies. The effects of acetylcholinesterase (AChE) non‐reactivating antidotes atropine and diazepam were analyzed in combination with physostigmine prophylaxis against supralethal doses of soman. Physostigime prophylaxis was much more effective when supplemented by atropine and diazepam therapy, applied at the onset of the first signs of poisoning. The interval between the injection of a supralethal dose of soman and the appearance of signs of poisoning was shorter in physostigmine pretreated animals than in non‐pretreated controls poisoned with the same supralethal dose of soman. The prophylactic effect of physostigmine (used at maximal dose) disappeared in about 120 min. The addition of HI‐6, an AChE‐reactivating oxime, to atropine+diazepam therapy further increased the survival in soman‐poisoned and physostigmine‐pretreated rats, yielding the highest protective ratio of 6.4. Pretreatment with physostigmine offered marked protection against inhibition of AChE by soman, as shown by enzyme activity determination in different brain regions and in diaphragm muscle. Application of HI‐6 in addition to the combination of the above mentioned antidotes even preserved more AChE activity in the skeletal muscle but did not influence inhibition of the enzyme in brain.
Comparison of Hepatic Drug‐Oxidizing Activity after Simultaneous Administration of Two Probe Drugs, Caffeine and Trimethadione, to Human Subjects
Authors: Tanaka Einosuke , Ishikawa Akio , Yamamoto Yuji , Osada Akira , Tsuji Katsuhisa , Fukao Katashi , Iwasaki Youji
Published: March 2009

Abstract: Pharmacokinetic interactions between caffeine 2 mg/kg and trimethadione 4 mg/kg were evaluated in 10 healthy volunteers. Whether administered alone or together, the total body clearance (CL), the apparent volume of distribution (Vd) and half‐life (t1/2) of caffeine and trimethadione were the same, however, there was a weak correlation between the CL of caffeine and trimethadione [alone: r = 0.51 (P<0.05); coadministered: r = 0.56 (P<0.05)]. There were also weak correlations between the CL of trimethadione and the area under the serum concentration‐time curves (AUC) of theobromine (r= —0.61, P<0.05), paraxanthine (r = −0.69, P<0.05) and theophylline (r = −0.60. P<0.05), when the two drugs were administered alone. After combined administration, the correlation between the CL of trimethadione and the AUCs of the metabolites of caffeine were as follows: theobromine r = −0.63 (P<0.05); paraxanthine r = −0.68 (P<0.05); theophylline r = −0.65 (P<0.05). These findings suggest that caffeine and trimethadione metabolism in healthy subjects is mediated by only in part by a form(s) of P450 enzymes involved.
Further Evidence for the Existence of Two Forms of α2B‐Adrenoceptors in Rat
Authors: Xia Yun , Uhlén Staffan , Chhajlani Vijay , Lien Eric J. , Wikberg Jarl E. S.
Published: March 2009

Abstract:Analysis of saturation isotherms of the novel α2‐adrenoceptor antagonist radioligand [3H]‐MK 912 revealed that the ligand labelled a homogenous population of α2B‐adrenoceptors in the neonatal rat lung with a Kdof 0.77 nM and a Bmaxof 231 fmol/mg protein. In rat kidney, combined saturation and competition experiments, using [3H]‐MK 912 and the α2A‐adrenoceptor selective drug guanfacine, revealed that ~ 81% of the sites labelled by [3H]‐MK 912 were α2B‐adrenoceptors and ~ 19% α2A‐adrenoceptors; the Kds of [3H]‐MK 912 being. 1.1 and 2.0 nM and the Bmax134 and 33 fmol/mg protein, respectively. The kidney α2B‐adrenoceptors were studied separately by using ~ 1.5 nM [3H]‐MK 912 in the presence of 0.32 μM guanfacine, the latter which blocked ligand binding to α2A‐adrenoceptors completely. Analysis of drug competition curves obtained during these conditions revealed that 18 out of 20 different agonists and antagonists yielded steep and uniphasic competion curves which modelled best into one site fits. However, both guanoxabenz and LT 11 appeared to inhibit [3H]‐MK 912 binding at two sites; the Kds of guanoxabenz differing ~ 120‐fold and that of LT 11 differing ~ 35‐fold for the two sites. Moreover, the addition of mutual fixed concentrations of either 20 μM guanoxabenz or 20 μM LT 11 completely prevented the binding of the other compound to its high affinity site, indicating that both compounds labelled the same site with the high affinity. The analysis indicated that 29% of the sites were of high and 71% of low affinity. However, in the neonatal rat lung guanoxabenz and LT 11 (as well as 15 other compounds) yielded competition curves which modelled only into one site fits. The Kds obtained in the lung correlated well with the Kds obtained in the kidney for α2B‐adrenoceptors; for guanoxabenz and LT 11 the values from the lung were close to those determined in the kidney for the low affinity site for guanoxabenz and LT 11. Moreover, when the rat RNG α2B‐adrenoceptor was expressed in COS‐7 cells and its binding properties tested using [3H]‐MK 912 binding, guanoxabenz, LT 11 as well as a number of other drugs inhibited the ligand binding at a single α2‐adrenoceptor site; the drug Kds being practically the same as those found for the neonatal rat lung. It is suggested that rat α2B‐adrenoceptors may exist in two forms: α2B1and α2B2. The α2B1‐form, which shows high affinity for guanoxabenz and LT 11, is present in the adult rat kidney. The α2B2‐form, which shows low affinity for guanoxabenz and LT 11, is present in the neonatal rat lung as well as in the adult rat kidney and it is encoded by the RNG gene.
Cardiotoxic Effects of Nitrofurantoin and Tertiary Butylhydroperoxide in Vitro: Are Oxygen Radicals Involved?
Authors: Biel Bettina , Ounces Maged , Brasch Helmut
Published: March 2009

Abstract: Langendorff rat hearts were perfused for 15, 30 or 75 min. with the oxygen radical generators nitrofurantoin (0.25 or 0.5 mmol/1) or tertiary butylhydroperoxide (0.25 mmol/1). Both agents reduced the force of contraction and increased the release of glutathione, oxidized glutathione, lactate dehydrogenase and creatine phosphokinase into the perfusion fluid. The tissue concentration of glutathione was reduced. While there were no signs of an increased production of conjugated dienes, the tissue concentration of malondialdehyde was greater than in control experiments. The variability of the latter effect was large, however, and in most cases the increase was not statistically significant. Addition of catalase (100 mU/ml) or catechin (0.5 mmol/1) to the perfusion medium abolished the nitrofurantoin induced release of oxidized glutathione but did not prevent or attenuate enzyme leakage from the cells and the development of a negative inotropic effect. These results suggest that the cardiotoxic effects of nitrofurantoin and tertiary butylhydroperoxide cannot be explained by the appearance of oxygen radicals alone and that an increased lipid peroxidation is not the mechanism which is primarily responsible for cell death.
Transmitter Role of Vasoactive Intestinal Peptide
Authors: Fahrenkrug Jan
Published: March 2009

Abstract: Vasoactive intestinal polypeptide (VIP) is a 28 amino acid with a wide‐spread neuronal localization. VIP fulfils many of the classical criteria for neurotransmission. In the cerebral cortex bipolar VIP neurones are involved in the coupling between energy metabolism, blood flow and neuronal activity. Furthermore, VIP in the brain plays a role in circadian rhythms and melatonin and pituitary hormone secretion. In the peripheral nervous system VIP is the transmitter of a number of non‐cholinergic, non‐adrenergic autonomic events. Thus, the peptide is involved in the control of smooth muscle tone and motility, blood flow and secretion in the digestive tract, respiratory tract and urogenital tract. The effects of VIP are mediated by a specific membrane‐bound receptor linked to adenylate cyclase via a stimulatory G‐protein. It is likely that impairment of VIP nerves is involved in some autonomic dysfunctions, an example being male impotence which is succesfully treated with VIP injections.
Potential Antidepressive Properties of Amantadine, Memantine and Bifemelane
Authors: Moryl Elzbieta , Danysz Wojciech , Quack Günter
Published: March 2009

Abstract: The effects of amantadine, its dimethyl derivative, memantine and the chemically unrelated compound bifemelane were tested for antidepressant activity. Reserpine‐induced hypothermia and the forced swim test (Porsolt test) were selected for this purpose. In the former test amantadine and bifemelane but not memantine were effective. In the forced swim test all three agents produced antidepressive‐like activity (decreased immobility time), but in case of bifemelane it was less pronounced. The effect in the forced swim test was specific i.e. it was apparently not the result of an increase in general activity as evidenced by control experiments in the open field. The mechanism of amantadine and memantine action may involve indirect dopaminomimetic activity resulting from the blockade of NMDA receptors. However in reserpine‐induced hypothermia this explanation is not valid considering the lack of effect of memantine and positive action of amantadine. Hence, amantadine may have an additional central sympathomimetic action that memantine is lacking. Bifemelane antidepressant‐like activity might be attributed to an enhancement of noradrenergic transmission. We suggested that amantadine and bifemelane could be particularly useful therapeutically when depressive symptoms are present in patients suffering from Parkinson's disease and dementia.
Effects of 5‐HT1A Receptor Agonists on Patterns of Rat Motor Activity in Relation to Effects on Forebrain Monoamine Synthesis
Authors: Ahlenius Sven , Hillegaart Viveka , Salmi Peter , Wijkström Agneta
Published: March 2009

Abstract: The effects of the 5‐HT1A receptor agonists 8‐OH‐DPAT (0.15–2.5 μmol kg−1 subcutaneously), flesinoxan (0.6–10.0 μmol kg−1 subcutaneously) and buspirone (1.9–30.0 μmol kg−1 subcutaneously) on spontaneous motor activity in male Sprague‐Dawley rats was examined in a photocell‐equipped open‐field arena. Following motor activity observations, the cerebral aromatic L‐amino acid decarboxylase inhibitor NSD‐1015 (100 mg kg−1 intraperitoneally) was administered and 30 min. later the animals were decapitated for subsequent analysis of the accumulated forebrain DOPA and 5‐HTP levels, as an estimate of the rate of monoamine synthesis. 8‐OH‐DPAT and flesinoxan produced a similar and characteristic pattern of changes of the spontaneous motor activity in normal animals i.e. a moderate decrease in locomotor activity, a marked suppression of rearing and an increase in the relative amount of forward locomotion and of activity in the periphery of the open‐field arena. This behavioural profile was closely related to a decrease in forebrain 5‐HTP accumulation, indicating 5‐HT receptor stimulation. In agreement with these observations buspirone also produced an increase in peripheral activity and a suppression of rearing. In contrast to effects by 8‐OH‐DPAT and flesinoxan, however, buspirone produced a further reduction of locomotor activity and reduced the forward locomotion. This difference in behavioural profile between buspirone and the other two compounds is probably explained by its DA receptor blocking properties, as indicated by an increased DOPA accumulation in the neostriatum. At least partially, 8‐OH‐DPAT, flesinoxan and buspirone, all antagonized reserpine‐induced (5 mg kg−1 subcutaneously – 16 hr) suppression of locomotor activity. This stimulation of locomotor activity in reserpine‐treated rats is in all probability related to 5‐HT1A receptor stimulation since concomitant DA D2 receptor blockade, in the case of buspirone, did not markedly affect this behavioural response.
Lactic Acid‐Induced Plasma Protein Extravasation in Rat Airways by Stimulation of Sensory Nerves and NK1 Receptor Activation
Authors: Auberson Serge , Lundberg Jan M.
Published: March 2009

Abstract:Locally applied lactic acid and capsaicin caused extravasation of Evans blue dye in trachea, main bronchi and nasal mucosa of anaesthetized rats. In animals pretreated with capsaicin to deplete sensory neuropeptides, the lactic acid response was abolished in main bronchi and highly reduced in trachea. Pretreatment with the NK1 receptor antagonist, RP 67580 (3 mgxkg−1intravenously), markedly inhibited the lactic acid‐induced extravasation at all levels; similar pretreatment with NK2 receptor antagonist, SR 48968 (0.5 mgxkg−1intravenously), was ineffective. Locally applied ruthenium red (a transmembrane Ca2+fluxes inhibitor), capsazepine (a capsacin receptor antagonist) and diclofenac intraperitoneally (a cyclooxygenase blocker) did not change the lactic acid effect, while the capsaicin response wasonlydiminishedin bronchiby local pretreatment with ruthenium red. In conclusion locally applied lactic acid in rat trachea and nasal cavity activated capsaicin sensitive sensory nerve endings producing plasma protein extravasation. This reaction was shown to be mediated by tachykinins acting on the NK1 receptor through a mechanism which appeared to be resistant to capsazepine and ruthenium red and independent of cyclooxygenase products. In comparison the effect of capsacin was partially ruthenium red‐sensitive but not influenced by capsazepine.
Acute Toluene Exposure Increases Extracellular GABA in the Cerebellum of Rat: A Microdialysis Study
Authors: Stengård K. , Tham R. , O'Connor W. T. , Höglund G. , Ungerstedt U.
Published: March 2009

Abstract: Effect of acute inhalation exposure of toluene or halothane anaesthesia on extracellular levels of gamma‐aminobutyric acid (GABA) was monitored within the cerebellum of rats by microdialysis. GABA increased during and after exposure to toluene (2000 p.p.m., 2 hr) in contrast, halothane had no noticeable effect on GABA levels. When tetrodotoxin was added to the perfusion medium basal concentrations of GABA decreased to about 74% of control concentrations. Extracellular GABA levels did not increase during exposure to toluene when tetrodotoxin was added to the perfusion medium. The results indicate that toluene increase GABA within the cerebellum by sodium dependent mechanisms, possibly by modulating the neuronal input from the mossy fibers to the cerebellar cortex.
Involvement of P450 1A1 in Benzo(a)Pyrene but Not in Benzo(a)Pyrene‐7,8‐Dihydrodiol Activation by 3‐Methylcholanthrene‐Induced Mouse Liver Microsomes
Authors: Bjelogrlic Nina , Peng Renxiu , Park Sang S. , Gelboin Harry V. , Honkakoski Paavo , Pelkonen Olavi , Vähäkangas Kirsi
Published: March 2009

Abstract:Synchronous fluorescence spetrophotometry for benzo(a)pyrene‐7,8‐diol‐9,10‐epoxide (BPDE)‐DNA adducts was used to study the activation pathway of benzo(a)pyrene in C57BL/6 mice. Benzo(a)pyrene but not benzo(a)pyrene‐7,8‐diol activation by 3‐methylcholanthrene‐induced mouse liver microsomes was inhibited by a monoclonal antibody (Mab 1–7–1) against CYP1A1/2 suggesting that 1A1 probably takes part in the first P450 reaction. However, aryl hydrocarbon hydroxylase activity, a classical measure of benzo(a)pyrene metabolism, was not inhibited by the same concentration of Mab 1–7–1. None of the other antibodies used, detecting 2A, 2B, 2C or 2E subfamilies, inhibited the adduct formation. Troleandomycin and gestodene, chemical inhibitors of human 3A4, inhibited benzo(a)pyrene‐7,8‐diol activation by 3‐methylcholanthrene‐induced microsomes to some extent only in high concentrations. Although liver microsomes from 3‐methylcholanthrene‐induced mice catalyzed the formation of BPDE‐DNAin vitroclearly more than uninduced microsomes, 3‐methylcholanthrene pretreatmentin vivodecreased the adduct formation in benzo(a)pyrene‐treated mice. These results emphasize the significance of detoxicating and DNA‐repairing pathwaysin vivo.Finally, synchronous fluorescence spectrophotometry for BPDE‐DNA measures the end‐point of the three‐step activation pathway while aryl hydrocarbon hydroxylase measures a one‐step hydroxylation. Thus, these methods should be used rather as corroborative than mutually exclusive assays.
Effects of Remoxipride's Metabolites on Dopamine D2Receptors and Receptor Functions in the Rat
Authors: Ögren Sven Ove , Hall Håkan , Widman Marianne , Ängeby‐Möller Kristina
Published: March 2009

Abstract:The main metabolites of remoxipride formed in rat and man were examined for their affinities for the [3H] SCH 23390‐labelled DA D1and [3H]‐raclopride‐labelled D2receptors in rat striatal homogenates. In addition, their effectiveness in blocking postsynaptic DA receptor activityin vivowas measured by the use of several different test models in the male rat. Phenolic metabolites formed mainly in the rat retained (similar to remoxipride) their selectivity for the D2receptor with very low affinities for the D1receptor. The pyrrolidone metabolites formed mainly in man showed very low affinities for both the D1and D2receptors. The ability of the metabolites to block postsynaptic DA receptor activityin vivocorrelated with their affinities for the D2receptor. Among the metabolites tested, the phenolic compounds FLA 797 (–) and FLA 908 (–) were much more effective than remoxipride in inducing catalepsy, which is consistent with a higher affinity for [3H] raclopride labelled striatal D2receptors. However, analysis of the effectiveness of the DA receptor blockade (blockade of d‐amphetamine locomotion or DA agonist hypothermia) after intraperitoneal or subcutaneous administration suggested that FLA 797 (–)/FLA 908 (–) may only contribute marginally to the D2receptor‐blocking activity of remoxipride in the rat. This conclusion was further supported by the observation that the atypical antipsychotic profile of remoxipride was not mimicked by the active metabolites. The weak DA D2blocking effect of the pyrrolidone metabolites indicated that remoxipride is responsible for the clinical action.
Neurochemical Mechanism of Action of Anorectic Drugs
Authors: Samanin Rosario , Garattini Silvio
Published: March 2009

Studies with dexfenfluramine, an anorectic agent which releases 5‐hydroxytryptamine (5‐HT) from nerve terminals and inhibits its reuptake, have considerably increased our knowledge of the role of 5‐HT in feeding control. 5‐HT1Breceptors mediate the satiating effect of dexfenfluramine, whereas the mechanism by which 5‐HT uptake inhibitors such as fluoxetine and sertraline cause anorexia is not clear. Anorexia induced by (+)‐amphetamine, phentermine, diethylpropion and phenylpropanolamine seems to be the result of their ability to increase the release of noradrenaline and/or dopamine from nerve terminals and inhibit their reuptake or, in the case of phenylpropanolamine, to stimulate directly α1‐adrenoceptors. It has been suggested that β‐ and α1‐adrenoceptors and D1dopamine receptors are involved in their effect on food intake. The difficulties of extrapolation across species limit our knowledge of the mechanism of the anorectic action in humans. Significant advances in the treatment of feeding pathology will be linked to identifying new receptor types and subtypes for neurotransmitters and quantifying and modelling eating disorders such as binge‐eating and food craving.
Effects of 2, 4‐Dichlorophenoxyacetic Acid (2, 4‐D) on Open‐Field Behaviour and Neurochemical Parameters of Rats *
Authors: Oliveira G. H. , Palermo‐Neto J.
Published: March 2009

The effects of the herbicide 2, 4‐dichlorophenoxyacetic acid (2, 4‐D) on the central nervous system (CNS) were studied in rats. Behavioural and neurochemical studies were performed. Results show that acute and oral administration of dimethylamine 2, 4‐D was able to decrease locomotion and rearing frequencies and to increase immobility duration of rats observed in an open‐field test. Treatment of rats with p‐chlorophenylalanine (PCPA) was unable to change rat's open‐field behaviour; 5‐hydroxytryptophan (5‐HTP) administration not only increased locomotion and rearing frequences but also decreased immobility duration. Pretreatment of the rats with PCPA and 5‐HTP decreased and increased dimethylamine 2, 4‐D effects, respectively. The herbicide was not able to change the striatal levels of dopamine and homovanilic acid but decreased the striatal levels of serotonin (5‐HT), as observed for the doses of 100 and 200 mg/kg and increased those of 5‐hydroxyindoleacetic acid (5‐HIAA) as measured after the 200 mg/kg dose treatment. When the levels of serotonin and 5‐HIAA were measured at the brain stem level, only those of 5‐HIAA were modified, being increased by diethylamine 2, 4‐D (60; 100 and 200 mg/kg); this increment on 5‐HIAA levels was observed even 1 hr after pesticide administration. Further analysis showed that 2, 4‐D concentrations chromatographycally detected both in serum and brain of the intoxicated animals were dose‐dependent, being found as early as 1 hr after the smaller dose of the herbicide used (10 mg/kg). The results suggest that diethylamine 2, 4‐D modify 5‐HT functional activity within the CNS. Thus, the effects of the herbicide on open‐field behaviour of rats could be attributed to a direct or indirect pesticide action on serotoninergic systems.
Detomidine Binding to Guinea Pig Liver Imidazoline Receptors (I‐Receptors) Shows Marked Positive Cooperativity
Authors: Rangel Ninfa , Uhlén Staffan , Wikberg Jarl E. S.
Published: March 2009

The binding of [3H]‐idazoxan to guinea pig liver membranes was measured in the presence of 3 μM rauwolscine, which prevented the binding [3H]‐idazoxan to α2‐adrenergic receptors. Under these conditions the radioligand bound to saturable imidazoline receptors (I‐receptors) with a Kdof 18 nM and a Bmaxof 665 fmol mg‐1protein. Six drugs which were used to compete for [3H]‐idazoxan in the liver caused competition curves of widely varying steepness. Fitting the competition curves to the standard four parameter logistic function showed that the Hill coefficients (nH) varied from 2.02 (detomidine) to 0.43 (UK‐14,304), The nH's obtained in liver for the six compounds correlated strongly (r = 0.99; P< 0.001) with the corresponding nH's obtained in a previous study on the guinea pig kidney where the drugs were also tested in competition with [3H]‐idazoxan (Wikberget al.1992). Good correlation was also found for the Log(Ki) values of drugs determined in the two tissues (r = 0.96; P< 0.005). Whereas the standard logistic function accurately described the competition curves of the 5 drugs tested in the liver for which the competition curve Hill coefficients varied between 0.43 to 1.41 (UK‐14,304, rilmenidine, histamine and d‐ and 1‐medetomidine), it did not accurately fit the detomidine competition curves. Instead the detomidine competition curves could be more accurately described by a model composed of the sum of two independent logistic functions. Using this model detomidine appeared to compete with [3H]‐idazoxan with two apparent affinity components, one with a Kiof 0.26 μM and an nHof 3.24 and the other with a Kiof 4.9 μM and an nHof 1.09. The proportion of the affinity components were 72% of the higher and 28% of the lower affinity. The data are discussed with the notion that guinea pig liver and kidney I‐receptors are similarly regulated by both positive and negative allosteric cooperative interactions.
Investigation of Acute Cardiovascular and Respiratory Toxicity of HLö 7 Dimethanesulfonate and HI 6 Dichloride in Anaesthetized Guinea‐Pigs
Authors: Worek Franz , Szinicz Ladislaus
Published: March 2009

The bis‐pyridinium dioxime HLö 7 is considered to possess promising therapeutic properties in the treatment of organophosphate poisoning. Acute circulatory and respiratory effects of HLö 7 and HI 6 were therefore compared in anaesthetized guinea‐pigs. Female Pirbright white guinea‐pigs were anaesthetized with urethane and the carotid artery, jugular vein and trachea were cannulated. Saline or atropine, 10 mg/kg, or HLö 7 or HI 6 (30 or 100 μmol/kg, each) or atropine plus oxime were injected intravenously after base line measurements. Respiratory and circulatory parameters were recorded for 60 min., then blood was drawn for AChE measurement. Injection of HLö 7 or HI 6 alone resulted in a temporary, dose‐dependent hypotension, an almost unchanged heart rate and a slight respiratory stimulation. A more severe hypotension appeared after the administration of atropine plus HLö 7 or HI 6. In these groups heart rate and respiration were markedly stimulated. Measurement of AChE activity in blood samples revealed no impairment by HLö 7 or HI 6 with or without atropine. These results suggest that HLö 7 has only transient effects on the cardiorespiratory system after intravenous administration and its safety regarding acute circulatory and respiratory toxicity is comparable to HI 6.
Dynamic Effects and Pharmacokinetics of Lemakalim in the Isolated Guinea‐Pig Heart
Authors: Mellemkjser Seven , Nielsen‐Kudsk Folmer
Published: March 2009

Myocardial effects of lemakalim were studied in the isolated retrogradely perfused and spontaneously beating guinea‐pig heart. Pharmacokinetic analysis of drug accumulation and disposition showed two‐compartment characteristics with phasic half‐times of about 0.27 and 2.1 min., respectively. Myocardial clearance was 6.8 ml min.‐1, and myocardial drug accumulation was 5‐fold. Dynamic parameters were studied during increasing lemakalim concentrations from 1.4 nM up to 10 μM. Dynamic steady‐states developed within 3‐4 min. Increase of coronary flowrate showed an Emaxof 185% with an EC50of 60 nM. Lemakalim produced biphasic inhibitory actions on contraction velocity and amplitude. Emax, and EC50for the two phases were: 48% and 47% and 100 nM and 65 nM, respectively, for the first phase and 100%) in both cases and 1.7 μM and 1.6 μM for the second phase. Heart frequency increased to a maximum of 15% above baseline at 0.3 μM. Oxygen consumption increased progressively at concentrations above 7 nM and reached a maximum of 175% at 0.3 μM. The frequency‐corrected QT‐interval was biphasically shortened to a maximal extent of 30% at the highest concentration. Myocardial efficiency expressed as the ratio of amplitude times frequency to oxygen consumption exhibited a progressive decline to about 20% of control values. PQ‐ and QRS‐intervals showed only minor or no changes, respectively. No arrythmogenic effects were observed. The study demonstrated a rapid and very moderate accumulation of lemakalim in the guinea‐pig heart accompanied by a marked increase in coronary flowrate and a progressive negative inotropic effect followed by reduced myocardial efficiency.
Influence of pH on the Uptake and Pharmacodynamics of Quinidine in the Isolated Perfused Rat Heart
Authors: Huang Jiu Li , Morgan Denis J.
Published: March 2009

Using the single‐pass isolated perfused rat heart preparation we examined the effect of perfusate pH (pH 7.05, 7.46, 7.71, 7.92) on quinidine output concentration (Cout) and ▵QT. Eight hearts were perfused at 2.5 ml/min. with quinidine (20 μM) for 35 min. followed by a 35‐40 min. washout period with drug‐free perfusate. This procedure was repeated four times in each preparation with the pH sequence varied and the same pH used in the first and last phases. Increasing pH slowed the rate of equilibration of Cout,the equilibration rate constant (k) decreasing from 0.273 min.‐1at pH 7.05 to 0.095 min.‐1at pH 7.92. A modified Kety‐Renkin‐Crone equation was fitted to the Coutversus time data for each pH. The estimated volume of distribution (V) increased significantly with pH from 11.5 × 1.1 to 32.5 × 2.9 ml/g, but the permeability surface product did not change with pH (mean 17.7 ml/min./g). There was a linear relationship between V and calculated un‐ionised quinidine Cout,with an intercept of 5.70 ml/g corresponding to the V of ionised drug. This indicates that ionised and un‐ionised drug readily enter the heart and that the slower equilibration with pH is due to the increased V which results from increased partitioning of un‐ionised quinidine into myocardial tissue. Perfusion pH did not directly affect baseline QT interval, but the rate of attainment of maximum ▵QT decreased with increasing perfusate pH. Plots of ▵QT versus calculated coronary output quinidine concentration did not change with pH, showing that this drug effect was due to both ionised and un‐ionised moieties. This study shows that myocardial permeability and pharmacodynamic effect (▵QT) of quinidine are not influenced by perfusion pH over the range 7.0 to 7.9, although rate of equilibration of both Coutand effect vary with pH.
Accumulation of the Recombinant Factor VIIa in Rat Bone: Importance of the Gla‐Domain and Relevance to Factor IX, another Vitamin K‐Dependent Clotting Factor
Authors: Thomsen Mads Krogsgaard , Wildgoose Peter , Nilsson Povl , Hedner Ulla
Published: March 2009

The vitamin K‐dependent clotting factors II, VII, IX, and X are proteins which undergo γ‐carboxylation of specific glutamic acid residues prior to secretion from the liver. These unique Ca2+binding amino acids allow the interaction of the proteins with cell surface phospholipids, a function that is crucial for expression of full procoagulant activity of the proteins. The N‐terminal region of the molecule contains the γ‐carboxylation sites and is termed the Gla‐domain. A preliminary observation in rats suggested that mineralized bone accumulated activated recombinant FVII (rFVIIa: NovoSeven™) as well as the non‐activated, single chain rFVII. The present study investigated the role of the Gla‐domain in the accumulation of rFVII in bone, as well as the influence of the activation state of FVII on this phenomenon. Rats were treated with 125I‐labelled rFVII, rFVIIa, Gla‐domainless rFVIIa, factor IX, iodide, or recombinant human growth hormone (rhGH). Following sacrifice, radioactivity was measured in mineralized bone, among other tissues. Following administration of 125I‐radiolabelled rFVII, rFVIIa and factor IX, but not Gla‐domainless rFVIIa, iodide or rhGH, extensive sequestration occurred in endochondrally as well as intramembranously ossified bones. The results indicate that the proteins containing a Gla‐domain, and only these, are sequestered in bone. Additionally, the normally occurring form of FVII in the circulation, the single‐chain FVII, exhibited similar kinetics in rat bone and plasma, as the two‐chain rFVIIa. The half‐life of rFVII/rFVIIa in mineralized bone was between 3 and 4 days, implying that significant bone accumulation of the factor will take place at steady state. However, the approach to steady state takes more than 2 weeks and the absolute amounts of accumulated rFVII are negligible with respect to bone matrix structure and function. Besides not being sequestered in bone, 125I‐labelled Gla‐domainless rFVIIa was present in larger amounts than rFVIIa in kidney tissue due to the charge and size properties of the molecule. In conclusion, accumulation in mineralized bone of the vitamin K‐dependent clotting factors seems to depend on the presence of a Ca2+‐binding Gla‐domain. The physiological implications of the phenomenon remain speculative at present but in theory, the bone compartment could be a storage site for e.g. factors VII and IX in dynamic equilibrium with the much higher plasma levels of the factors.
No Effect of the 5HT2‐Antagonist ICI 169,369 on Systolic, Ergotamine‐Induced Blood Pressure Changes in Man
Authors: Nielsen T. H. , Tfelt‐Hansen P.
Published: March 2009

The 5HT‐antagonistic effect of drugs in man is difficult to study because of side effects to 5HT. Ergotamine, however contracts human arteries, probably by acting on 5HT receptors. This effect can be antagonizedin vitroby the 5HT antagonist ICI 169,369. After an initial ergotamine challenge to select responders to ergotamine, 10 selected volunteers were given in a double blind study an oral dose of either placebo, 30 mg or 120 mg of ICI 169,369. After 2 hr an intravenous dose of 0.5 mg ergotamine tartrate was given. From 6 to 8 hr after the administration, ergotamine caused a mean decrease in the toe‐arm systolic gradient, measured by strain‐gauge plethysmography of 32 mmHg (P<0.001), which was not influenced by either 30 mg or 120 mg ICI 169,369 (P<0.4). The most likely explanation for our inability to detect any effect of ICI 169,369 on blood pressure changes, induced by ergotamine may be high binding (99%) of ICI 169,369 to plasma proteins. There was, however, indication of aper sevasodilatory effect of ICI 169,369 since the dose of 120 mg increased the toe‐arm systolic gradient by 4.7 mmHg.
Inhalation Kinetics of C8 to C10 1‐Alkenes and Iso‐Alkanes in the Rat after Repeated Exposures
Authors: Zahlsen K. , Eide I. , Nilsen A. M. , Nilsen O. G.
Published: March 2009

The toxicokinetic properties of C8 and C10 1‐alkenes and iso‐alkanes have been investigated in rats during inhalation of 100 p.p.m. of the single hydrocarbons for 3 days, 12 hr/day. The concentration of hydrocarbon was measured in blood, brain, liver, kidneys and perirenal fat at days 1, 2 and 3, immediately after exposure and 12 hr after exposure on day 3. The 1‐alkenes showed an efficient absorption to blood combined with extensive accumulation in organs, compared to the iso‐alkanes. The concentration of 1‐alkenes and iso‐alkanes in blood, brain, liver and fat increased with increasing number of carbon atoms. The C9 and C10 1‐alkenes and iso‐alkanes showed increasing concentration in fat during the exposure period and high concentrations 12 hr after cessation of exposure. The extensive accumulation in both blood and organs of 1‐alkenes compared to any of the other groups of hydrocarbons may have a toxicologic relevance. Products which contain 1‐alkenes should be handled carefully to minimize the risk of inhalation exposure.
Dose Dependent Transfer of 203Lead to Milk and Tissue Uptake in Suckling Offspring Studied in Rats and Mice
Authors: Hallén Ira Palminger , Oskarsson Agneta
Published: March 2009

The dose‐dependent transfer of 203Pb to milk and uptake in suckling rats and mice during a three‐day nursing period was studied. On day 14 of lactation, the dams were administered a single intravenous dose of lead, labelled with 203Pb, in four or five doses from 0.0005 to 2.0 mg Pb/kg b.wt. There was a linear relationship between Pb levels in plasma and milk of both species. The Pb milk:plasma ratios at 24 hr after administration were 119 and 89 in mice and rats, respectively. At 72 hr the Pb milk:plasma ratio had decreased to 72 in mice and 35 in rats. The tissue levels of lead in the suckling rats and mice were also linearly correlated with lead concentration in milk at 72 hr, showing that milk could be used as an indicator of lead exposure to the suckling offspring. It is concluded that lead is transported into rat and mouse milk to a very high extent and the excretion into milk is more efficient in mice than in rats. On the other hand, rat pups had higher lead levels in tissues than mice pups, which might be due to a higher bioavailability and/or a lower excretion of lead in rat pups. Thus, lead in breast milk could be used as a biological indicator of lead exposure in the mother as well as in the suckling offspring.