bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation into the mechanism of capsaicin‐induced oedema in rabbit skin
Authors: Newbold P. , Brain S.D. 
Published: July 2012

Oedema formation induced by intradermal capsaicin has been studied in rabbit skin. The effect of the anti‐inflammatory steroid dexamethasone and also of a range of known inhibitors of oedema formation have been investigated in order to elucidate mechanisms involved in capsaicin‐induced oedema formation.
Oedema formation, in response to intradermally‐injected test agents, was measured by the local extravascular accumulation of intravenously injected 125I‐labelled albumin. In separate experiments skin blood flow was assessed by the clearance of intradermally‐injected 133xenon.
Oedema formation induced by intradermal histamine (3 nmol) and bradykinin (1 nmol), when in the presence of vasodilator doses of calcitonin gene‐related peptide (CGRP) (3 pmol) or prostaglandin E1, (PGE1) (10 pmol), was significantly inhibited (P < 0.01) in rabbits pretreated with intravenous dexamethasone (3 mg kg−1, −4h). In contrast dexamethasone had no effect on capsaicin (3 μmol)‐induced oedema formation or, on capsaicin (30–100 nmol)‐induced blood flow.
Oedema formation observed in response to intradermal capsaicin (3 μmol) was significantly inhibited (P < 0.01) when the selective capsaicin antagonist, ruthenium red (3 nmol) was co‐injected. This suggests that the mechanism of capsaicin‐induced oedema involves activation of sensory nerves. However, oedema was not inhibited when capsaicin was co‐injected with the neurokinin NK1 receptor antagonist, RP67580 (10 nmol), the NK2 antagonist SR48960 (10 nmol) or the CGRP antagonist CGRP8–37 (300 pmol).
Oedema formation induced by capsaicin was not inhibited when co‐injected with the histamine H1 receptor antagonist, mepyramine (3 nmol), the PAF antagonist, WEB 2086 (100 nmol), the bradykinin B2 receptor antagonist, Hoe140 (1 nmol), or the cyclo‐oxygenase inhibitor, indomethacin (10 nmol), suggesting that these mediators do not play a major role in the capsaicin‐induced response.
Histological analysis of capsaicin‐treated skin sites revealed undamaged, intact microvessels and lack of haemorrhage. Further, co‐injection of capsaicin with the hydrogen peroxide remover, catalase (2,200 u), had no effect on oedema formation. This suggests that capsaicin does not induce oedema formation secondary to free radical‐induced damage.
These results indicate that capsaicin‐induced oedema in rabbit skin involves activation of sensory nerves. However, the oedema is not inhibited by pretreatment with the anti‐inflammatory steroid, dexamethasone. Further the mechanisms which lead to the oedema formation observed after intradermal capsaicin remain unknown.
Effect of crilvastatin, a new cholesterol lowering agent, on unesterified LDL‐cholesterol metabolism into bile salts by rat isolated hepatocytes
Authors: Clerc Thierry , Sbarra Véronique , Diaconescu Nicolas , Lafont Huguette , Jadot Guy , Laruelle Claude , Chanusso Françoise 
Published: July 2012

The aim of these experiments was to determine the effect of crilvastatin, a new cholesterol lowering agent, on the metabolism of unesterified low density lipoprotein (LDL)‐cholesterol by rat freshly isolated hepatocytes. This preclinical model was developed as an alternative to in vivo experiments, to mimic the metabolic effects of a molecule on its target cells and to define optimal conditions for future experimentation on human hepatocytes.
Cells were obtained from normolipidaemic or hypercholesterolaemic rats, hypercholesterolaemia was nutritionally induced. Incubations were performed in a medium containing 600 μm taurocholate and 50 μm or 300 μm crilvastatin.
This molecule was shown in vitro to be carried by physiological transporters, i.e., albumin‐bile salt micellar associations and LDL. Crilvastatin induced a significance increase in the synthesis and secretion by hepatocytes of bile salts resulting from the metabolism of unesterified LDL‐cholesterol in both normolipidaemic and hypercholesterolaemic rats. Stimulation involved non‐conjugated as well as tauro‐ and glyco‐conjugated bile salts. These findings corroborate preliminary studies showing in vivo that crilvastatin enhances the secretion of bile acids by stimulating the uptake and incorporation of LDL‐cholesterol by the liver.
Influence of age on the signal transduction pathway of non‐adrenergic non‐cholinergic neurotransmitters in the rat gastric fundus
Authors: Smits Geert J.M. , Lefebvre Romain A. 
Published: July 2012

The influence of aging on the relaxant response and the change in cyclic nucleotide content induced by vasoactive intestinal polypeptide (VIP), nitric oxide (NO), electrical field stimulation of the non‐adrenergic non‐cholinergic neurones and substances acting at different levels of the cyclic AMP and cyclic GMP transduction pathways was studied in longitudinal muscle strips of the rat gastric fundus.
The relaxant responses to VIP, sustained electrical stimulation, forskolin and 3‐isobutyl‐1‐methylxanthine were reduced with age, while the responses to dibutyryl cyclic AMP were not. The increase in cyclic AMP content induced by sustained electrical stimulation and forskolin was lower in old rats.
The relaxant responses to NO and to short train electrical stimulation were similar in the three age groups. The inhibitory effect of NG‐nitro‐1‐arginine methyl ester on relaxations induced by short train electrical stimulation was more pronounced in old rats. The relaxant responses to sodium nitroprusside (SNP), 8‐bromo‐cyclic GMP and zaprinast were reduced with age. SNP induced a similar elevation of the cyclic GMP content in the three age groups.
These results suggest that aging differentially affects the cyclic AMP and cyclic GMP pathway for relaxation by VIP and NO in the rat gastric fundus, as the defect seems to occur at the level of the adenylate cyclase and cyclic GMP‐dependent protein kinase respectively.
Relaxation and decrease in [Ca2+]i by hydrochlorothiazide in guinea‐pig isolated mesenteric arteries
Authors: Pickkers Peter , Hughes Alun D. 
Published: July 2012

We examined the effect of the thiazide diuretic, hydrochlorothiazide, on intracellular calcium concentration ([Ca2+]i) and tone in guinea‐pig mesentery arteries. Vessels were mounted on a microvascular myograph and loaded with the Ca2+‐sensitive fluorescent dye, Fura‐2.
Hydrochlorothiazide caused relaxation of noradrenaline‐precontracted arteries associated with a fall in [Ca2+]i. Preincubation of arteries with hydrochlorothiazide inhibited both contraction and rise in [Ca2+]i in response to noradrenaline. Hydrochlorothiazide did not affect tone and [Ca2+]i when this was elevated by a combination of depolarizing potassium solution and noradrenaline.
Hydrochlorothiazide‐induced vasorelaxation and decrease of [Ca2+]i was abolished by charybdotoxin, a blocker of large conductance Ca2+‐activated K channels.
The rise in [Ca2+]i elicited by caffeine in Ca2+‐free physiological salt solution, and presumably reflecting Ca2+ release from intracellular stores, was not altered by preincubation with hydrochlorothiazide.
Under depolarizing conditions hydrochlorothiazide did not alter the relationship between the extracellular concentration of Ca2+ and [Ca2+]i; however, hydrochlorothiazide caused a small reduction in the contraction produced for a given rise in [Ca2+]i suggesting hydrochlorothiazide may cause a slight desensitization of the contractile machinery.
These findings suggest that hydrochlorothiazide opens Ca2+‐activated K channels leading to hyperpolarization and consequent closing of voltage‐operated calcium channels. The result of this is an impaired influx of extracellular Ca2+, a decrease in [Ca2+]i and vasorelaxation.
Functional identification of rat atypical β‐adrenoceptors by the first β3‐selective antagonists, aryloxypropanolaminotetralins
Authors: Manara Luciano , Badone Domenico , Baroni Marco , Boccardi Giovanni , Cecchi Roberto , Croci Tiziano , Giudice Antonina , Guzzi Umberto , Landi Marco , Le Fur Gérard 
Published: July 2012

We have assessed the relative abilities of compounds belonging to the new aryloxypropanolaminotetralin (APAT) class and of the reference β‐adrenoceptor‐blocking agent, alprenolol, to antagonize functional responses in vitro and in vivo involving atypical (β3) or conventional (β1 and β2) β‐adrenoceptors.
The range of pA2 values for three representative APATs against inhibition of spontaneous motility in the rat isolated colon by the selective β3‐adrenoceptor agonist, SR 58611A (8.1–8.8), was well above similarly calculated values for non‐competitive antagonism of guinea‐pig trachea relaxation by salbutamol (β2, 6.5–6.9) and the atrial chronotropic response by isoprenaline (β1, 6.7‐7.3). Alprenolol, however, was substantially more potent in antagonizing atrial (pA2, 8.2) and tracheal (pA2, 8.9) responses than SR 58611A mediated inhibition of colonic motility (pA2, 6.8).
Several APAT isomers with different configurations at the chiral carbons, when tested on isolated organs, presented stringent stereochemical requirements for β3‐selectivity, including high antagonist potency‐ratios between active and inactive enantiomers.
In vivo, the inhibition of colonic motility and the thermogenic response of brown adipose tissue elicited in rats by the selective β3‐adrenoceptor agonists SR 58611A and BRL 37344 respectively were substantially diminished by the representative APAT, SR 59230A, at oral doses (≤5 mg kg−1) well below those half maximally effective (ID50) for preventing β1‐(isoprenaline tachycardia ≥80 mg kg−1) or β2‐(salbutamol bronchodilatation, 44 mg kg−1) mediated responses. Alprenolol, as expected, was a less potent and nonselective antagonist of the putative β3‐responses.
These findings support APATs as the first potent, orally effective selective antagonists at β3‐adrenoceptors, and provide final unambiguous evidence that β3‐adrenoceptors underlie inhibition of colonic motility and brown adipose tissue thermogenesis in rats
Characterization of Ca2+‐activated 86Rb+ fluxes in rat C6 glioma cells: a system for identifying novel IKCa‐channel toxins
Authors: de‐Allie Frank A. , Bolsover Steven R. , Nowicky Alex V. , Strong Peter N. 
Published: July 2012

The pharmacological characteristics of a putative Ca2+ activated K+ channel (IKCa channel) in rat glioma C6 cells were studied in the presence of the Ca2+ ionophore, ionomycin and various K+ channel blockers, 86Rb+ being used as a radioisotopic tracer for K+.
The resting 86Rb+ influx into C6 cells was 318±20 pmol s−1. The threshold for ionomycin activation of 86Rb+ influx was approx. 100 nM. At ionomycin concentrations above the activation threshold, the initial rate of 86Rb+ influx was proportional to ionophore concentration. Ionomycin‐activated 86Rb+ flux was saturable (EC50 = 0.62±0.03 μm) and was not inhibited by ouabain.
Intracellular Ca2+ increased within 30 s from a basal level of 42±2 nM to 233±17 nM, after addition of 2 μm ionomycin. During this period, intracellular pH fell from 7.03±0.04 to 6.87±0.03 and the cell hyperpolarized from −34±10 mV to −76±2 mV.
Single channel conductance measurements on inside‐out patches in physiological K+ solutions identified a 14±3 pS Ca2+ ‐activated K+ current between −25 mV and +50 mV. In symmetrical (100 mM) K+, the single channel conductance was 26 pS.
Externally applied quinine (IC50 = 0.12±0.34 mM) and tetraethylammonium chloride (IC50 = 10±1.9 mM) inhibited 86Rb+ influx into C6 cells in a concentration‐dependent manner. Charybdotoxin (IC50 = 0.5±0.02 nM) and iberiotoxin (IC50 = 800±150 nM), as well as the crude venoms from the scorpions Leiurus quinquestriatus and Mesobuthus tamulus, also inhibited 86Rb+ influx. In contrast, apamin and toxin I had no inhibitory effects on 86Rb+ flux. A screen of fractions from cation exchange h.p.l.c. of Mesob. tamulus venom revealed the presence of at least four charybdotoxin‐like peptides. One of these was iberiotoxin; the other three are novel toxins.
The ionomycin‐activated 86Rb+ influx into rat C6 glioma cells has proved to be a valuable pharmacological assay for the screening of toxins and crude venoms which modify intermediate conductance, Ca2+ activated K+ channel activity.
Role of opioid receptors in the spinal antinociceptive effects of neuropeptide FF analogues
Authors: Gouardères Christine , Jhamandas Khem , Sutak Maaja , Zajac Jean‐Marie 
Published: July 2012

Neuropeptide FF (NPFF) has been shown to produce antinociceptive effects and enhance morphine‐induced antinociception after intrathecal (i.t.) injection. In this study, the spinal effects of two NPFF analogues, [D‐Tyr1, (NMe)Phe3]NPFF (1DMe) and [D‐Tyr1, D‐Leu2, D‐Phe3]NPFF (3D), which are resistant to degradation and exhibit a high affinity for NPFF binding sites, were examined in tests of thermal and mechanical nociception.
1DMe and 3D produced potent dose‐dependent spinal antinociception in the tail‐flick test. On a molar basis, 1DMe was 20 and 50 times more potent than 3D and morphine, respectively, and high doses of 1DMe and 3D produced a sustained antinociceptive effect without visible signs of motor impairment.
Spinal antinociceptive effects produced by 1DMe (0.86 nmol) or 3D (8.6 nmol) were significantly reduced by i.t. co‐administration of naloxone (11 nmol) or i.t. pre‐administration of D‐Phe‐Cys‐Tyr‐D‐Trp‐Orn‐Thr‐Pen‐Thr‐NH2 (CTOP, 9.25 nmol) or β‐funaltrexamine (β‐FNA, 2 nmol) or naltrindole (2.2 nmol). The doses of the μ‐antagonists (CTOP and β‐FNA) or the δ‐antagonist (naltrindole) used in 1DMe and 3D experiments blocked the antinociceptive effects of μ‐or δ‐receptor‐selective agonists.
When administered in combination with antinociceptive doses of the μ‐receptor agonist, morphine (13.2 nmol) or the δ‐receptor agonist, [D‐Ala2]deltorphin I (20 nmol), sub‐effective dose of 1DMe or 3D (0.009 nmol) enhanced and prolonged the spinal effects of these opioid agonists.
The results of this study show that spinal μ‐and δ‐opioid receptors play a role in antinociception produced by NPFF analogues. These results also suggest a role for NPFF in modulation of nociceptive signals at the spinal level.
Modulating effect of the nootropic drug, piracetam on stress‐ and subsequent morphine‐induced prolactin secretion in male rats
Authors: Matton A. , Engelborghs S. , Bollengier F. , Finne E. , Vanhaeist L. 
Published: July 2012

The effect of the nootropic drug, piracetam on stress‐ and subsequent morphine‐induced prolactin (PRL) secretion was investigated in vivo in male rats, by use of a stress‐free blood sampling and drug administration method by means of a permanent indwelling catheter in the right jugular vein.
Four doses of piracetam were tested (20, 100, 200 and 400 mg kg−1), being given intraperitoneally 1 h before blood sampling; control rats received saline instead. After a first blood sample, rats were subjected to immobilization stress and received morphine, 6 mg kg−1, 90 min later.
Piracetam had no effect on basal plasma PRL concentration.
While in the non‐piracetam‐treated rats, stress produced a significant rise in plasma PRL concentration, in the piracetam‐pretreated rats PRL peaks were attenuated, especially in the group given 100 mg kg−1 piracetam, where plasma PRL concentration was not significantly different from basal values. The dose‐response relationship showed a U‐shaped curve; the smallest dose had a minor inhibitory effect and the highest dose had no further effect on the PRL rise.
In unrestrained rats, morphine led to a significant elevation of plasma PRL concentration. After the application of immobilization stress it lost its ability to raise plasma PRL concentration in the control rats, but not in the piracetam‐treated rats. This tolerance was overcome by piracetam in a significant manner but with a reversed dose‐response curve; i.e. the smaller the dose of piracetam, the higher the subsequent morphine‐induced PRL peak.
There is no simple explanation for the mechanism by which piracetam induces these contradictory effects. Interference with the excitatory amino acid system, which is also involved in opiate action, is proposed speculatively as a possible mediator of the effects of piracetam.
Inhibition of prostanoid formation in intact cells by 2,5‐di‐(tert‐butyl)‐1,4‐benzohydroquinone, a blocker of Ca2+‐ATPases
Authors: Leis Hans J. , Zach Doris , Huber Evelyn , Ziermann Laszlo , Gleispach Helmut , Windischhofer W. 
Published: July 2012

The blocker of endoplasmic reticulum Ca2+‐ATPase, 2,5‐di‐(tert‐butyl)‐1,4‐benzohydroquinone (BHQ) was shown to inhibit formation of prostaglandin E2 and prostacyclin in the osteoblast‐like cell lines, MC3T3‐E1 and ROS 17/2.8, respectively, in a dose‐dependent manner with an IC50 of 0.5‐1 μm. Inhibition was observed with various stimuli (arachidonic acid, bradykinin, melittin and calcium ionophore, A23187).
This effect was also observed in human platelets, where BHQ dose‐dependently blocked thromboxane biosynthesis and formation of 12‐hydroxy‐heptadecatrienoic acid after stimulation with arachidonic acid, but not formation of 12‐hydroxy‐eicosatetraenoic acid.
Inhibition of prostaglandin E2 formation in MC3T3‐E1 cells was not observed with thapsigargin after stimulation with arachidonic acid, A23187 or melittin, whereas bradykinin‐induced prostaglandin E2 biosynthesis was blocked.
Taken together, the results suggest a direct inhibitory action of BHQ on the cyclo‐oxygenase in these three cell systems.
Comparison of the profiles of agonists as stimulants of the β3‐adrenoceptor in vitro with their gastroprotective effects in the conscious rat
Authors: Bahl A.K. , Clayton N.M. , Coates J. , Martin D.P. , Oakley I.G. , Strong P. , Trevethick M.A. 
Published: July 2012

This paper compares the activity of a range of agonists as stimulants of the β3‐adrenoceptor in rat isolated oesophagus with their ability to afford protection against indomethacin‐induced gastric damage in the conscious rat.
The β3‐adrenoceptor agonists, CL 316243 and BRL 37344, the non‐selective β‐adrenoceptor agonist, isoprenaline and the selective β2‐adrenoceptor agonist, salmeterol, all evoked concentration‐dependent relaxation of precontracted muscularis mucosa from rat oesophagus. The rank order of agonist potency was BRL 37344 > CL 316243 > isoprenaline > > salmeterol. The selective β1‐adrenoceptor agonist, denopamine, did not relax the preparation.
The relaxant responses to all agonists were resistant to blockade by atenolol (10 μm), and ICI 118551 (1 μm) thus suggesting that they were not mediated by either β1‐ or β2‐adrenoceptor stimulation. In contrast, cyanopindolol and propranolol did inhibit responses to BRL 37344, CL 316243 and isoprenaline, giving pA2 values or pKB estimates which were consistent with an interaction at β3‐adrenoceptors (i.e. approximately 8.0 and 6.5 respectively). However, responses to salmeterol were resistant to blockade by all the antagonists tested, which suggests that the high (> 1 μm) concentrations of salmeterol used exerted non‐specific relaxant effects.
The agonist effects of CL 316243 and BRL 37344 on β1‐ and β2‐adrenoceptors were assessed on guinea‐pig right atrium and precontracted trachea respectively. Both agonists had minimal activity as stimulants of heart rate, but did relax trachea, being 380 (CL 316243) and 21 (BRL 37344) fold less potent than isoprenaline.
CL 316243 and BRL 37344 were potent inhibitors of indomethacin‐induced gastric antral ulceration in the conscious rat (ED50 values = 0.24 and 0.09 μmol kg−1, p.o.) Salmeterol was approximately 100 times less potent than BRL 37344 as a gastroprotective agent and denopamine was without effect.
The gastroprotective effects of CL 316243 and BRL 37344 were resistant to blockade by ICI 118551 (10 mg kg−1, p.o.) and propranolol (10 mg kg−1, p.o.). In contrast, both antagonists caused dose‐related inhibition of the protective action of salmeterol (10 mg kg−1, p.o.). Cyanopindolol was not assessed as an antagonist in vivo because preliminary experiments revealed that it exacerbated indomethacin‐induced gastric damage in its own right.
In conclusion, the β3‐adrenoceptor agonists CL 316243 and BRL 37344 were potent inhibitors of indomethacin‐induced gastric antral ulceration in the rat. These data suggest that an agonist which is potent and selective for the human β3‐adrenoceptor may confer mucosal protection in man.
Allosteric interactions between cyclothiazide and AMPA/kainate receptor antagonists
Authors: Yamada Kelvin A. , Turetsky Dorothy M. 
Published: July 2012

Cyclothiazide blocks α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor desensitization and potentiates AMPA receptor gated currents. Interactions between cyclothiazide, and the non‐competitive antagonist GYKI52466 (GYKI) and competitive antagonist 2,3‐dihydroxy‐6‐nitro‐7‐sulphamoyl‐benzo (F) quinoxaline (NBQX) were studied at native and recombinant AMPA/kainate receptors using whole‐cell recording in order to characterize the modulation by cyclothiazide of these two antagonist sites.
GYKI 100 μm, which is sufficient to eliminate virtually hippocampal kainate (100 μm) currents, failed to prevent access of cyclothiazide to its site of potentiation, and was unable to enhance removal of cyclothiazide potentiation. However, cyclothiazide reduced GYKI (30 μm) block from 84±8.3% to 38±12%, and slowed the onset of the block with a time course much faster than the time course for onset and offset of potentiation induced by cyclothiazide. Cyclothiazide had qualitatively similar effects upon antagonism by NBQX 1 μm.
Kainate activated desensitizing currents in dorsal root ganglion (DRG) neurones, which were unaffected by cyclothiazide. GYKI blocked these kainate currents with lower affinity (IC50>120 μm) than for hippocampal neurones (IC50<30 μm), and cyclothiazide did not affect GYKI antagonism.
Steady‐state AMPA currents from homomeric GluRA‐Dflip receptors in HEK 293 cells were dramatically potentiated (up to 216 fold) by cyclothiazide via reduction of desensitization. In contrast, kainate‐gated currents in HEK 293 cells expressing GluR6R receptors exhibited pronounced desensitization that was unaffected by cyclothiazide. GYKI retains its inhibition at both recombinant AMPA and kainate receptors.
These results indicate that cyclothiazide allosterically influences two important antagonist sites on AMPA receptors. In addition, AMPA/kainate receptor subunit composition influences the affinity of GYKI for the receptor.