bluuebunny/crossref_metadata_2025_split huggingface dataset:
A quantitative investigation into the dependence of Ca2+ mobilisation on changes in inositol 1,4,5‐trisphosphate levels in the stimulated neutrophil
Authors: Thompson Neil T. , Bonser Robert W. , Tateson James E. , Spacey Graham D. , Randall Roger W. , Hodson Harold F. , Garland Lawrence G. 
Published: July 2012

The coupling of N‐formyl‐methionyl‐leucyl‐phenylalanine (fMet‐Leu‐Phe) receptor stimulation to Ca2+ mobilisation has been investigated in the human neutrophil by measuring the concentration‐effect curves for inositol 1,4,5‐trisphosphate (IP3) formation and Ca2+ mobilisation.
fMet‐Leu‐Phe‐dependent mobilisation of intracellular Ca2+ has been monitored in fluo‐3‐loaded human neutrophils by measuring increases in the cytoplasmic free Ca2+ concentration ([Ca2+]i) in the presence of extracellular EGTA. Fluo‐3 was used in preference to fura‐2 because it was found to be more sensitive to the high Ca2+ levels seen in stimulated neutrophils.
fMet‐Leu‐Phe induced a rapid mobilisation of intracellular Ca2+ (EC50 = 2.9 ± 0.1 nm) and increased [Ca2+]i to a maximum of 1286 ± 184 nm.
The amount of IP3 in fMet‐Leu‐Phe‐stimulated neutrophils was determined by competition with [3H]‐IP3 for a specific IP3 binding protein isolated from bovine adrenocortical microsomes. Basal IP3 levels of 13.3 ± 2.0 pmol per 107 cells were increased nearly 4 fold by maximally effective concentrations of fMet‐Leu‐Phe.
The EC50 for the IP3 response (95 ± 18 nm) was much higher than that for mobilisation of intracellular Ca2+, such that only a doubling in the concentration of IP3 was required to fully mobilise intracellular Ca2+.
As a result of this relationship IP3 production was more sensitive than Ca2+ mobilisation to inhibition by demethoxyviridin, an inhibitor of phospholipase activation.
(+)‐Isradipine but not (−)‐Bay‐K‐8644 exhibits voltage‐dependent effects on cat adrenal catecholamine release
Authors: López Manuela G. , Michelena Pedro , Gandía Luis , García Antonio G. 
Published: July 2012

Catecholamine release from cat adrenal glands perfused at a high rate (4 ml min−1) at 37°C with polarizing (1.2 or 5.9 mm K+) or depolarizing (17.7, 35, 59 or 118 mm K+) solutions, was triggered by 5 or 10 s pulses of Ca2+ (0.5 or 2.5 mm) in the presence of various concentrations of K+.
In polarized glands, secretion was greater the higher the K+ concentration present during the secretory K+/Ca2+ test pulse. Thus, in 17.7 mm K+, catecholamine released was 162 ± 27 ng per pulse, while in 118 mm K+ secretion rose to 1839 ± 98 ng per pulse. In depolarized glands, secretion reached a peak of around 1000 ng per pulse in 35–59 mm K+; in 118 mm K+, secretion did not increase further, suggesting that voltage changes are implicated in the control of the secretory process.
Blockade of secretion by increased concentrations of (+)‐isradipine was much more manifest in polarized glands. The higher the degree of depolarization was (35, 59 or 118 mm K+), the lower the IC50s were. So, the ratios between the IC50s in polarized and depolarized glands rose from 3.92 in 35 mm K+ to 26.7 in 118 mm K+.
In contrast, the Ca2+ channel activator (−)‐Bay K 8644 potentiated catecholamine release evoked by K+/Ca2+ pulses equally well in polarized or depolarized glands. The ratios between EC50s in polarized or depolarized glands were, respectively, 0.30,0.59 and 0.69 for 17.7, 35 and 118 mm K+.
In simultaneous experiments, the two enantiomers of Bay K 8644 exhibited opposite effects on secretion. (+)‐Bay K 8644 (a Ca2+ channel blocker) inhibited secretion better in depolarized than in polarized glands, whilst (−)‐Bay K 8644 potentiated secretion in a voltage‐independent manner.
Potentiation of secretion by (−)‐Bay K 8644 was concentration‐dependent from 10−8 to 10−6 m. At 10−5 m, such potentiation largely disappeared in both polarized and depolarized glands. However, this dual effect of (−)‐Bay K 8644 was better seen in depolarizing conditions, suggesting that using the same enantiomer, the voltage‐dependence is only seen when blockade of secretion dominates.
In the presence of increasing concentrations of (−)‐Bay K 8644 (3 × 10−9, 3 × 10−8 and 3 × 10−7 m), the concentration‐response curves for (+)‐isradipine to inhibit secretion were displaced to the right. However, a Schild plot of (dose ratio −1) against (−)‐Bay K 8644 concentrations gave a slope of 0.6, suggesting that the interactions between (+)‐isradipine and (−)‐Bay K 8644 were non‐competitive in nature. The pA2 for (−)‐Bay K 8644 was 9.13.
Overall, the results suggest that potentiation of secretion by (−)‐Bay K 8644 (a voltage‐independent phenomenon), and blockade by (+)‐isradipine or (+)‐Bay K 8644 (a voltage‐dependent phenomenon) might be exerted through binding of the dihydropyridines activators and blockers to separate sites on chromaffin cell L‐type Ca2+ channels.
Evidence that the unilateral activation of 5‐HT1D receptors in the substantia nigra of the guinea‐pig elicits contralateral rotation
Authors: Higgins G.A. , Jordan C.C. , Skingle M. 
Published: July 2012

The effects of various 5‐hydroxytryptamine (5‐HT) receptor agonists were examined following unilateral infusion into the substantia nigra (SN) of the guinea‐pig.
The 5‐HT1 receptor agonists, 5‐carboxamidotryptamine (5‐CT) (2–25 μg), sumatriptan (10–25 μg) and RU24969 (25 μg) all induced a marked contralateral rotation. In contrast, the selective 5‐HT1A receptor agonist 8‐hydroxy‐2‐(di‐n‐propylamino)tetralin (8‐OH DPAT, 10–25 μg) produced only a very small response, whilst the selective 5‐HT1C/5‐HT2 receptor agonist (±)‐1‐(4‐iodo‐2,5‐dimethoxyphenyl)‐2‐aminopropane hydrochloride ((±)‐DOI) (25 μg) and the 5‐HT3 receptor agonist, 2‐methyl 5‐HT (2‐Me5‐HT, 25 μg) were without effect.
The contralateral rotation induced by 5‐CT (10 μg) was attenuated following pretreatment with the non‐selective 5‐HT1/5‐HT2 receptor antagonists methiothepin (1 mg kg−1, s.c.) and metergoline (5–10 mg kg−1, s.c.) but not the 5‐HT1C/5‐HT2 antagonist ritanserin (1 mg kg−1, s.c.) or the 5‐HT3 antagonist, ondansetron (0.5 mg kg−1, s.c). An involvement of dopaminergic systems in the rotational response to 5‐CT was implied by the antagonism of 5‐CT‐induced rotation by haloperidol (0.3 mg kg−1, s.c).
At doses lower than those required to produce contralateral rotation, 5‐CT (0.08–0.4 μg) and sumatriptan (2 μg) induced a small, but nonetheless consistent, ipsilateral rotation.
The data with agonists and antagonists taken together suggest that 5‐CT‐induced contralateral rotation may be mediated by 5‐HT1D receptor activation but definitive classification of the receptor will not be possible until selective 5‐HT1D‐antagonists become available. This may therefore represent the first model to study this receptor subtype in vivo.
Effect of thyrotropin releasing hormone (TRH) on acetylcholine release from different brain areas investigated by microdialysis
Authors: Giovannini M.G. , Casamenti F. , Nistri A. , Paoli F. , Pepeu G. 
Published: July 2012

The effect of thyrotropin releasing hormone (TRH) administration upon acetylcholine (ACh) release in freely moving rats was investigated by means of transversal microdialysis coupled to h.p.l.c. TRH administered either s.c. or via local perfusion increased the ACh release from the cortex and hippocampus but not from the striatum. The increase in ACh release was maintained after 7 days of s.c. administration of TRH.
After s.c. injection of the neuropeptide, the increase in ACh release was dose‐dependent and reached a maximum at 40 min after administration. The maximal percentage increases were 18, 52, 66 and 89% at doses of 1, 2.5, 5 and 10 mg kg−1 and 35, 48 and 54% at doses of 2.5, 5 and 10 mg kg−1 in the cortex and hippocampus, respectively. The effect of TRH was dependent on neuronal activity since it was completely inhibited by perfusion with tetrodotoxin (TTX), 5 × 10−7 m.
Perfusion with TRH, 2.5 μg μl−1, caused 198% and 150% increase in ACh release 60 and 80 min after the beginning of the perfusion in the cortex and hippocampus, respectively. After this initial peak, a 100% increase in ACh release persisted throughout the perfusion.
Systemic TRH administration was followed by marked hyperactivity and stereotyped behaviour that showed a time course shorter than that of the increase in ACh release.
These findings demonstrate that TRH exerts a strong stimulant action on cortical and hippocampal cholinergic pathways.
Studies of three non‐peptide cholecystokinin antagonists (devazepide, lorglumide and loxiglumide) in human isolated alimentary muscle and guinea‐pig ileum
Authors: D'Amato M. , Stamford I.F. , Bennett A. 
Published: July 2012

Three recently described non‐peptide cholecystokinin (CCK) antagonists (devazepide, lorglumide, loxiglumide) have been studied for their antagonism of the contraction to cholecystokinin‐octapeptide (CCK‐OP) in human alimentary muscle and guinea‐pig intestine.
Each antagonist caused a concentration‐dependent inhibition of the contraction induced by CCK‐OP, regardless of regional and species differences.
The potencies of each drug, estimated by use of an adaptation of the Cheng & Prusoff equation, were similar in the different regions of human alimentary tract (weighted mean apparent pKB, ± s.e.mean: devazepide, 5.76 ± 0.08, n = 20; lorglumide, 5.82 ± 0.04, n = 25; loxiglumide, 5.87 ± 0.07, n = 24).
In contrast, the potencies differed markedly in the guinea‐pig ileum. Apparent pKB values obtained by the same method as with human tissues were, mean ± s.e.mean: devazepide, 10.61 ± 0.61; lorglumide, 7.43 ± 0.20; loxiglumide, 6.67 ±0.12. pKB values obtained from classical competition experiments were: devazepide, 10.09 ± 0.09; lorglumide 7.70 ± 0.12; loxiglumide 6.08 ± 0.22.
The CCK receptors in human gut muscle from different regions seem to be similar, but there appear to be species differences.
Pharmacological profile of various κ‐agonists at κ‐, μ‐ and δ‐opioid receptors mediating presynaptic inhibition of neurotransmitter release in the rat brain
Authors: Mulder A.H. , Burger D.M. , Wardeh G. , Hogenboom F. , Frankhuyzen A.L. 
Published: July 2012

The potency, relative efficacy and selectivity of a series of κ‐opioid receptor agonists at the μ‐, δ‐ and κ‐opioid receptors mediating inhibition of electrically‐induced (radiolabelled) neurotransmitter release from superfused rat brain slices was determined.
With regard to their potencies at κ‐receptors mediating inhibition of striatal [3H]‐dopamine release, the highest pD2 value (8.7) was found for bremazocine and the lowest (7.1) for U50488; the pD2 values for ethylketocyclazocine (EKC), tifluadom, U69593 and PD117302 were between 8.0 and 8.3. There were no marked differences between the relative efficacies of the κ‐agonists (maximum inhibition being 60–70%). In contrast to the other κ‐agonists, at a concentration of 1 μm, PD117302 caused a significant (25–40%) increase of the spontaneous efflux of tritium.
None of the κ‐agonists significantly affected striatal [14C]‐acetylcholine (ACh) release, with the exception of a slight inhibitory effect of EKC. The δ‐receptor‐mediated inhibitory effect of [d‐Ala2, d‐Leu5] enkephalin (DADLE) on [14C]‐ACh release was antagonized in a concentration‐dependent manner by bremazocine (0.1 and 1.0 μm) and also partially by EKC (1 μm), but not by the other κ‐agonists. The pA2 value for bremazocine as an antagonist at the δ‐receptors involved was 8.0, compared to 7.6 for naloxone.
None of the κ‐agonists significantly affected cortical [3H]‐noradrenaline (NA) release, with the notable exception of tifluadom, which strongly inhibited release by activating μ‐receptors. The μ‐receptor‐mediated inhibitory effect of Tyr‐d‐Ala‐Gly‐(NMe)Phe‐Gly‐ol (DAMGO) on [3H]‐NA release was antagonized in a concentration‐dependent manner by bremazocine and EKC, but not by the other κ‐agonists. The pA2 value for bremazocine as an antagonist at the μ‐receptors involved was 8.2, compared to 8.6 for naloxone.
Thus, whereas U69593 and PD117302 display high potency and selectivity towards κ‐opioid receptors, the potent benzomorphan κ‐agonists bremazocine and EKC also appear to be strong μ‐opioid receptor antagonists.
Selective and competitive antagonism by suramin of ATP‐stimulated catecholamine‐secretion from PC12 phaeochromocytoma cells
Authors: Inoue Kazuhide , Nakazawa Ken , Ohara‐Imaizumi Mica , Obama Tomoko , Fujimori Kannosuke , Takanaka Akira 
Published: July 2012

Suramin, a putative P2‐antagonist, (10 to 300 μm) inhibited the adenosine 5′‐triphosphate (ATP)‐stimulated secretion of [3H]‐noradrenaline or endogenous dopamine from phaeochromocytoma PC12 cells in a concentration‐dependent manner. Suramin (300 μm) did not affect the dopamine‐secretion stimulated by high K+ or nicotine.
Suramin shifted the concentration‐response curve for ATP to the right. The antagonism was competitive with a pA2 value of 4.52.
ATP also stimulated an increase in intracellular Ca2+ concentration as determined by fura‐2 methods. Suramin antagonized this effect over the same concentration range that antagonized the ATP‐stimulated catecholamine secretion.
These results suggest that suramin can be used as a selective and competitive antagonist of ATP in experiments concerning mechanisms of catecholamine‐secretion.
A comparison of the relative activities of a number of GABAB antagonists in the isolated vas deferens of the rat
Authors: Hills Judith M. , Larkin Madelene M. , Howson William 
Published: July 2012

A series of GABAB receptor antagonists were tested against (±)‐baclofen for activity on the presynaptic GABAB receptor in the rat vas deferens.
All the antagonists tested caused a rightward shift in the concentration‐response curve to (±)‐baclofen.
pA2 values calculated from full Schild analysis were as follows: phaclofen, pA2 = 4.3; δ‐amino valeric acid, pA2 = 4.4; 3‐aminopropyl(diethoxymethyl)phosphinic acid (CGP 35348), pA2 = 5.0; 3‐aminopropyl(n‐hexyl)phosphinic acid (3‐APHPA), pA2 = 4.5.
These results show that none of the above compounds possess potent antagonist activity at the GABAB receptor (i.e. pA2 > 6) in this peripheral tissue. In addition, the more recently available phosphinic acid antagonists, appear to offer no great advance over the GABAB antagonists previously available.
Pharmacology of a cholecystokinin receptor on 5‐hydroxytryptamine neurones in the dorsal raphe of the rat brain
Authors: Boden P.R. , Woodruff G.N. , Pinnock R.D. 
Published: July 2012

The effect of bath application of sulphated cholecystokinin octapeptide (CCK‐8) was studied on neurones in slices containing rat raphe nucleus.
Intracellular recordings were made from neurones in the dorsal raphe nucleus. Some of the neurones with the characteristics of 5‐hydroxytryptamine (5‐HT)‐containing cells which were inhibited by 5‐HT and excited by noradrenaline were excited by cholecystokinin. The response to cholecystokinin was dose‐dependent over the range 10 to 1000 nm.
The response to CCK‐8 persisted in the presence of tetrodotoxin. Either reduction of extracellular calcium or addition of 25 mm magnesium did not block the CCK response, suggesting it was mediated by receptors located on the membrane of the raphe neurones.
The agonist and antagonist specificity of the CCK response was determined. The CCKB selective agonist, pentagastrin, was inactive when applied at concentrations up to 10 μm. the CCKA receptor antagonist L‐364,718 (1 to 100 nm) blocked the response to cholecystokinin. Much higher (1–10 μm) concentrations of the CCKB receptor antagonist L‐365,260 were required for inhibition of the CCK response.
These data support the existence of a CCK receptor, located on raphe neurones in the rat, with a pharmacological profile very similar to that described for the CCKA type.
Differential effect of R 56865 on ouabain binding to isolated sarcolemma and intact atrial tissue of guinea‐pig
Authors: Heers Cara , Scheufler Eckhard , Wilhelm Doris , Wermelskirchen Detlef , Wilffert Bob , Peters Thies 
Published: July 2012

R 56865 (N‐[1‐[4‐(4‐fluorophenoxy)‐butyl]‐4‐piperidinyl]‐N‐methyl‐2‐benzothiazolamine) is a compound known to antagonize cardiac glycoside intoxication. Therefore, the effect of the compound on ouabain binding to intact cardiac tissue as well as cardiac membrane preparations was investigated.
The binding of ouabain to highly purified sarcolemmal membranes was not influenced by R 56865 1 × 10−6 mol l−1 (ouabain: KD = 1.3 × 10−7 mol l−1, Bmax = 160 pmol mg−1; ouabain + R 56865: KD = 1.4 × 10−7 mol l−1, Bmax = 168 pmol mg−1).
In contrast to the results in purified membranes, the binding of ouabain (10−8 mol l−1 to 5 × 10−7 mol l−1) to intact atria was significantly reduced.
Ouabain, 5 × 10−7 mol l−1, led to a transient positive inotropic effect of about 220% followed by a developing negative inotropic effect after 3 h. R 56865, 10−7 mol l−1, led to a maximal positive inotropic effect of about 290% also followed by a delayed decline of contractile force. A tenfold higher concentration of R 56865 led to sustained positive inotropic effect of about 250% in the same time interval.
The different effects of R 56865 on ouabain binding in subcellular preparations and intact tissue do not support the view that R 56865 interferes directly with the action of ouabain on Na/K‐ATPase. An indirect effect, which may be mediated by a lowered intracellular sodium load is discussed.
Anti‐arrhythmic activities of opioid agonists and antagonists and their stereoisomers
Authors: Sarne Y. , Flitstein A. , Oppenheimer E. 
Published: July 2012

A series of opioid agonists, antagonists and their (+)‐stereoisomers were tested for antiarrhythmic activity in the rat coronary artery occlusion model.
Naloxone (0.01–2 mg kg−1) significantly reduced the incidence and severity of cardiac arrhythmias, in accordance with previous published studies.
The non‐opioid stereoisomer, (+)‐naloxone, was equipotent with naloxone against occlusion‐induced arrhythmia.
Similar non‐stereospecific antiarrhythmic effects were induced by another opioid antagonist, Win 44,441–3 and its stereoisomer Win 44,441–2.
The opioid agonists, morphine and levorphanol, protected against occlusion‐induced arrhythmia as did the opioid antagonists, and the (+)‐stereoisomer, dextrorphan, was equipotent to levorphanol.
It is concluded that the antiarrhythmic effects of opioid drugs are not mediated by opioid receptors. A direct effect on ionic currents in cardiac muscle is suggested as the mechanism of opioid antiarrhythmic activity.
Comparison of the effects of intra‐arterial and aerosol administration of endothelin‐1 (ET‐1) in the guinea‐pig isolated lung
Authors: Pons Françoise , Touvay Caroline , Lagente Vincent , Mencia‐Huerta Jean Michel , Braquet Pierre 
Published: July 2012

Intra‐arterial injection of endothelin‐1 (ET‐1, 400 pmol; 1 μg) in guinea‐pig isolated perfused lungs, induced increases in pulmonary inflation pressure (PIP) and perfusion pressure (PPP), associated with oedema formation and thromboxane B2 (TxB2) release but not with the generation of sulphidopeptide leukotrienes or release of histamine. In contrast, aerosol administration of ET‐1 (3, 6, 10 μg ml−1, for 2 min) evoked a dose‐dependent increase in PIP, without significant changes in PPP, oedema formation or TxB2 release.
Addition of indomethacin (5 μm) or BW 755C (10 or 100 μm), but not nordihydroguaiaretic acid (NDGA, 50 μm) or FPL 55712 (10 μm), to the perfusion medium led to a significant inhibition of the increases in PIP and PPP, TxB2 release and oedema formation evoked by intra‐arterial injection of 400pmol ET‐1. In contrast, indomethacin (5 μm), BW 755C (100 μm) or FPL 55712 (10 μm), added to the perfusion medium 10 min prior to challenge, did not affect the increase in PIP induced by a 2‐min aerosol of a solution of ET‐1 10 μg ml−1.
In vivo aerosol administration of indomethacin (100 mg ml−1, for 20 min) to non‐anaesthetized guinea‐pigs, 15 min before lung removal, did not modify the bronchopulmonary response evoked in isolated perfused lungs by an aerosol of ET‐1 10 μg ml−1. However, under the same experimental conditions, indomethacin significantly inhibited TxB2 release evoked by aerosolized arachidonic acid (2 mg ml−1).
In conclusion, the present study shows that when injected by the intra‐arterial route, ET‐1 effects are mediated primarily via the generation of cyclo‐oxygenase metabolites of arachidonic acid, whereas when the aerosol route is used, the peptide appears to act on airway smooth muscle cells, through an indomethacin‐insensitive process which may involve some other, as yet unidentified, mediator(s).
Effect of the leukotriene receptor antagonists FPL 55712, LY 163443, and MK‐571 on the elimination of cysteinyl leukotrienes in the rat
Authors: Denzlinger C. , Grimberg M. , Kapp A. , Haberl C. , Wilmanns W. 
Published: July 2012

Leukotriene elimination via bile and urine is an important mechanism of inactivation for these potent lipid mediators. We investigated whether the elimination of cysteinyl leukotrienes is a target for the action of leukotriene receptor antagonists.
Experiments were performed in male rats under deep thiopentone anaesthesia. The bile duct and the urinary bladder were cannulated. Tritium labelled leukotrienes and leukotriene receptor antagonists were given via central venous catheters. Elimination of leukotrienes produced in vivo was studied following stimulation of endogenous leukotriene biosynthesis by operative trauma. 3H‐leukotriene metabolites were identified by h.p.l.c. analysis. Leukotrienes produced in vivo were measured by combined use of h.p.l.c. and RIA.
Under control conditions, 49 ± 12% of the injected 3H‐leukotriene radioactivity was recovered in bile and 1 ± 0.8% in urine within 90 min. Operative trauma resulted in initial hepatobiliary secretion of 887 ± 206 pmol kg−1 h−1 of the endogenous leukotriene metabolite N‐acetyl leukotriene E4 (LTE4NAc).
FPL 55712 strongly inhibited hepatobiliary elimination of 3H‐leukotriene radioactivity in a dose‐dependent manner after i.v. injection of [3H]‐LTC4, [3H]‐LTD4 or [3H]‐LTE4, respectively. Biliary [3H]‐LTD4 was reduced most effectively. The leukotriene antagonist potently prevented biliary elimination of LTE4NAc produced in vivo. Bile flow and elimination from blood into bile of [3H]‐ouabain were also impaired by FPL 55712, but to a lesser extent.
LY 163443 reduced biliary [3H]‐LTD4 after i.v. administration of [3H]‐LTD4. However, the total elimination of 3H‐leukotriene metabolites into bile was not significantly inhibited by the drug.
MK‐571 reduced the biliary concentration of tracer after administration of 3H‐leukotrienes most potently with respect to [3H]‐LTD4. In contrast, the total recovery of 3H‐leukotrienes in bile tended to increase. This is explained by a drug‐induced increase in bile flow.
Urinary elimination of 3H‐leukotrienes, quantitatively less important in the rat, was not significantly influenced by the leukotriene receptor antagonists. Recovery of 3H‐leukotriene radioactivity in liver and kidneys was quantitatively insignificant.
From our data, we conclude that leukotriene receptor antagonists have the potential to affect leukotriene elimination by a mechanism not necessarily related to receptor blockade. Inhibition of elimination by the receptor antagonists may prolong the biological half life of leukotrienes. This effect may counteract the antagonistic properties of these drugs.