bluuebunny/crossref_metadata_2025_split huggingface dataset:
A pertussis toxin‐sensitive mechanism of endothelin action in porcine coronary artery smooth muscle
Authors: Kasuya Yoshitoshi , Takuwa Yoh , Yanagisawa Masashi , Masaki Tomoh , Goto Katsutoshi 
Published: July 2012

Endothelin‐1 (ET‐1)‐induced contraction of porcine coronary artery strips may be mediated via at least two intracellular signalling mechanisims, the activation of dihydropyridine‐sensitive voltage‐dependent Ca2+ channels and the stimulation of phosphoinositide breakdown. Here we have investigated the possible involvement of pertussis toxin (PT)‐sensitive guanosine‐5′‐triphosphate (GTP)‐binding proteins (G‐proteins) in ET‐1‐induced activation of these two signalling pathways in porcine coronary artery smooth muscle.
Increase in extracellular K+ concentration (10, 15 mm) shifted the dose‐response relationship for the ET‐1‐induced contraction to the left.
The dihydropyridine Ca2+ channel blocker, nifedipine (10−8 m), induced a rightward shift in the dose‐response curve for ET‐1. Pretreatment of the arterial strips with PT (0.1 μg ml−1) induced a similar rightward shift of the ET‐1 dose‐response curve but not of the KCl response. Nifedipine (10−8 m) did not further attenuate the ET‐1‐induced contraction in the PT‐pretreated strips.
The pretreatment with PT significantly reduced 45Ca2+ uptake of the arterial strips stimulated by ET‐1, but had no effect on ET‐1‐induced production of inositol phosphates.
The contractile response of the arterial strips to phorbol dibutyrate, an active phorbol ester, was not significantly affected by 10−8 m nifedipine.6 We confirmed that the pretreatment of the tissue with PT induced ADP‐ribosylation of a 41 kDa membrane protein.7 These findings indicate that activation of dihydropyridine‐sensitive voltage‐dependent Ca2+ channels by ET‐1 in this tissue is mediated via a PT‐sensitive G‐protein in a manner apparently independent of the ET‐1‐induced activation of protein kinase C. It is concluded that the action of ET‐1 in porcine coronary artery is mediated via two distinct signal transduction pathways, which are coupled to PT‐sensitive and PT‐insensitive GTP‐binding proteins, respectively.
Agonist analysis of 2‐(carboxycyclopropyl)glycine isomers for cloned metabotropic glutamate receptor subtypes expressed in Chinese hamster ovary cells
Authors: Hayashi Yasunori , Tanabe Yasuto , Aramori Ichiro , Masu Masayuki , Shimamoto Keiko , Ohfune Yasufumi , Nakanishi Shigetada 
Published: July 2012

2‐(Carboxycyclopropyl)glycines (CCGs) are conformationally restricted glutamate analogues and consist of eight isomers including l‐ and d‐forms. The agonist potencies and selectivities of these compounds for metabotropic glutamate receptors (mGluRs) were studied by examining their effects on the signal transduction of representative mGluR1, mGluR2 and mGluR4 subtypes in Chinese hamster ovary cells expressing the individual cloned receptors.
Two extended isomers of l‐CCG, l‐CCG‐I and l‐CCG‐II, effectively stimulated phosphatidylinositol hydrolysis in mGluR1‐expressing cells. The rank order of potencies of these compounds was l‐glutamate > l‐CCG‐I > l‐CCG‐II.
l‐CCG‐I and l‐CCG‐II were effective in inhibiting the forskolin‐stimulated adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) accumulation in mGluR2‐expressing cells. Particularly, l‐CCG‐I was a potent agonist for mGluR2 with an EC50 value of 3 × 10−7 m, which was more than an order of potency greater than that of l‐glutamate.
l‐CCG‐I evoked an inhibition of the forskolin‐stimulated cyclic AMP production characteristic of mGluR4 with a potency comparable to l‐glutamate.
In contrast to the above compounds, the other CCG isomers showed no appreciable effects on the signal transduction involved in the three mGluR subtypes.6 This investigation demonstrates not only the importance of a particular isomeric structure of CCGs in the interaction with the mGluRs but also a clear receptor subtype specificity for the CCG‐receptor interaction, and indicates that the CCG isomers would serve as useful agonists for investigation of functions of the mGluR family.
Capsazepine: a competitive antagonist of the sensory neurone excitant capsaicin
Authors: Bevan S. , Hothi S. , Hughes G. , James I.F. , Rang H.P. , Shah K. , Walpole C.S.J. , Yeats J.C. 
Published: July 2012

Capsazepine is a synthetic analogue of the sensory neurone excitotoxin, capsaicin. The present study shows the capsazepine acts as a competitive antagonist of capsaicin.
Capsazepine (10 μm) reversibly reduced or abolished the current response to capsaicin (500 nm) of voltage‐clamped dorsal root ganglion (DRG) neurones from rats. In contrast, the responses to 50 μm γ‐aminobutyric acid (GABA) and 5 μm adenosine 5′‐triphosphate (ATP) were unaffected.
The effects of capsazepine were examined quantitatively with radioactive ion flux experiments. Capsazepine inhibited the capsaicin (500 nm)‐induced 45Ca2+ uptake in cultures of rat DRG neurones with an IC50 of 420 ± 46 nm (mean ± s.e.mean, n = 6). The 45Ca2+ uptake evoked by resiniferatoxin (RTX), a potent capsaicin‐like agonist was also inhibited. (Log concentration)‐effect curves for RTX (0.3 nm‐1 μm) were shifted in a competitive manner by capsazepine. The Schild plot of the data had a slope of 1.08 ± 0.15 (s.e.) and gave an apparent Kd estimate for capsazepine of 220 nm (95% confidence limits, 57–400 nm).
Capsazepine also inhibited the capsaicin‐ and RTX‐evoked efflux of 86Rb+ from cultured DRG neurones. The inhibition appeared to be competitive and Schild plots yielded apparent Kd estimates of 148 nm (95% confidence limits, 30–332 nm) with capsaicin as the agonist and 107 nm (95% confidence limits, 49–162 nm) with RTX as agonist.
A similar competitive inhibition by capsazepine was seen for capsaicin‐induced [14C]‐guanidinium efflux from segments of adult rat vagus nerves (apparent Kd = 690 nm; 95% confidence limits, 63 nm‐1.45 μm). No significant difference was noted in the apparent Kd estimates for capsazepine in assays on cultured DRG neurones and vagus nerve as shown by the overlap in the 95% confidence limits.6 Capsazepine, at concentrations up to 10 μm, had no significant effects on the efflux of 86Rb+ from cultured DRG neurones evoked either by depolarization with high (50 mm) K+ solutions or by acidification of the external medium to pH 5.0–5.6. Similarly capsazepine had no significant effect on the depolarization (50 mm KCl)‐induced efflux of [14C]‐guanidinium from vagus nerve preparations.7 Ruthenium Red was also tested for antagonism against capsaicin evoked [14C]‐guanidinium release from vague nerves and capsaicin induced 45Ca2+ uptake in cultures of DRG neurones. In contrast to capsazepine the inhibition by Ruthenium Red (10–500 nm in DRG and 0.5–10 μm in vagus nerve experiments) was not consistent with a competitive antagonism, but rather suggested a more complex, non‐competitive inhibition.
Hepoxilins sensitize blood vessels to noradrenaline—stereospecificity of action
Authors: Laneuville Odette , Couture Réjean , Pace‐Asciak Cecil R. 
Published: July 2012

Summary
. The vascular activity of two stereoisomers of hepoxilin A3 (HxA3) (8R and 8S) and of its glutathione conjugate, hepoxilin A3‐C (HxA3‐C) (8R and 8S), was investigated on rat helicoidal strips of thoracic aorta and longitudinal strips of portal vein.
. Neither of the hepoxilins tested had a direct effect on the tone of the aortic strip or on the spontaneous contractions of the portal vein. However, the noradrenaline (NA)‐induced response of these vessels, as expressed by the dose required for half maximal contraction, (EC50) was greater in HxA3 (8S)‐ and HxA3‐C (8R)‐treated aorta. Increased frequency and strength of spontaneous contractions of the portal vein were detected at lower concentrations of NA in the presence of hepoxilins.
. The threshold dose for both hepoxilins was 10−8 m and their effect was not dose‐related beyond 10−8 m. The effect of hepoxilin appeared after a 45 min incubation period and could be observed even if the compounds were washed out after 15 min.
. Stereochemical specificity was observed. The 8S isomer of HxA3 was active in potentiating the NA‐induced contraction of these vessels while the 8R isomer was inactive. In contrast, the 8R isomer of HxA3‐C was active while the 8S isomer was inactive. In both tissues, HxA3 (8S) was more potent than its glutathione conjugate, HxA3‐C (8R).
. In calcium‐free buffer or in the presence of a calcium channel blocker (nifedipine 1 μm), no potentiation of NA‐induced contraction by hepoxilins could be observed, suggesting the involvement of extracellular calcium in the actions of hepoxilins.
. These experiments suggest that hepoxilins may be involved in the modulation of vascular tone and contractility.
Myocardial hypertrophy, cardiac β‐adrenoceptors and adenylate cyclase activity during sinoaortic denervation in dogs
Authors: Galinier Michel , Sénard Jean‐Michel , Valet Philippe , Dréan Géraldine , Planat Valerie , Arias Agustin , Tran Marie‐Antoinette , Montastruc Jean‐Louis 
Published: July 2012

Summary
. The long‐term effects of sinoaortic denervation on the development of left ventricular hypertrophy (assessed by the measurement of the ratio (R): heart weight/total body weight and LVT: left ventricular thickness), myocardial β‐adrenergic receptivity (measured by [125I]‐cyanopindolol binding and adenylate cyclase activity) and plasma catecholamine levels (measured by h.p.l.c.) were investigated in three groups of dogs: normotensive controls (group 1), dogs made hypertensive by sinoaortic denervation and evaluated 1 (group 2) and 18 months (group 3) later.
. Noradrenaline (NA) and adrenaline (A) plasma levels were 461 ± 54 and 85 ± 45 pg ml−1 in controls, 861 ± 185 and 191 ± 23 pg ml−1 in group 2 (P < 0.05). They were normal in group 3 (426 ± 132 and 110 ± 16 pg ml−1).
. R and LVT values were significantly (P < 0.05) higher in sinoaortic denervated dogs (R = 7.7 ± 0.1 and 7.8 ± 0.2; LVT = 13.6 ± 1.3 and 14.2 ± 0.9 mm in groups 2 and 3 respectively) than in normotensive dogs (group 1: R = 6.7 ± 0.1, LVT = 9.3 ± 0.8 mm).
. In group 1, the total number of β‐adrenoceptors (Bmax) was 37 ± 11 and 29 ± 6 fmol mg−1 protein in the left ventricle (LV) and right auricle (RA) respectively. In group 2, Bmax was significantly lower (10 ± 3 in LV and 13 ± 2 fmol mg−1 protein in RA, P < 0.05) than in group 1. There was no difference between group 1 and group 3 (37 ± 3 fmol mg−1 prot in LV and 31 ± 3 fmol mg−1 protein in RA).
. The percentage of β1‐adrenoceptors was 82 ± 4 in LV and 75 ± 5 in RA in group 1. It was significantly lower (P < 0.05) in groups 2 (LV: 33 ± 6 and RA: 33 ± 5) and 3 (LV: 59 ± 3 and RA: 55 ± 4).
. Basal values of adenylate cyclase activity in LV significantly decreased after sinoaortic denervation. Isoprenaline alone or in the presence of a β2‐adrenoceptor antagonist (ICI 118551, 1 μm) failed to stimulate adenylate cyclase activity 1 (but not 18) month after sinoaortic denervation.
. These data show that sinoaortic denervation is associated with left ventricular hypertrophy which appears early (1 month) and persists until 18 months despite the normalization of plasma catecholamine levels. The total number of myocardial β‐adrenoceptors is closely related to catecholamine levels but a selective decrease in β1‐adrenoceptors is observed during cardiac hypertrophy. The fall in basal adenylate cyclase activity suggests that cardiac hypertrophy is associated with an impairment of transmembrane signalling.
Differential inhibitory effects of opioids on cigarette smoke, capsaicin and electrically‐induced goblet cell secretion in guinea‐pig trachea
Authors: Kuo H.‐P. , Rohde J.A.L. , Barnes P.J. , Rogers D.F. 
Published: July 2012

Goblet cell secretion in guinea‐pig airways is under neural control. Opioids have previously been shown to inhibit neurogenic plasma exudation and bronchoconstriction in guinea‐pig airways. We have now examined the effects of morphine and opioid peptides on tracheal goblet cell secretion induced by either electrical stimulation of the cervical vagus nerves, exogenous capsaicin, or acute inhalation of cigarette smoke. The degree of goblet cell secretion was determined by a morphometric method and expressed as a mucus score which is inversely related to mucus discharge.
Morphine, 1 mg kg−1, completely blocked goblet cell secretion induced by electrical stimulation of the vagus nerves. Morphine also inhibited the response to cigarette smoke given either at a low dose (10 breaths of 1:10 diluted in air), which principally activates cholinergic nerves, or at a high dose (20 breaths of undiluted), which activates capsaicin‐sensitive sensory nerves, by 100% and 73% respectively. In contrast, morphine had no significant inhibitory effect on capsaicin‐induced goblet cell secretion. The inhibitory effect of morphine was reversed by naloxone.
Selective μ‐ or δ‐opioid receptor agonists, [d‐Ala2, NMePhe4, Glyol5]enkephalin (DAMGO) or [d‐Pen2, d‐Pen5]enkephalin (DPDPE) respectively, caused a dose‐related inhibition of low dose cigarette smoke‐induced goblet cell discharge, with DPDPE more potent than DAMGO. A κ‐receptor agonist, trans‐3,4‐dichloro‐N‐methyl‐N‐(2‐(1‐pyrollidinyl)cyclohexyl) benzeneacetamine (U‐50,488H), had no inhibitory effect. DPDPE had no inhibitory effect on goblet cell secretion induced by exogenous methacholine.
DAMGO dose‐dependently blocked the response to high dose cigarette smoke with a maximal inhibition of 95% at 2 × 10−7 mol kg−1. Neither DPDPE nor U‐50,488H had any significant inhibitory effect. The increase in goblet cell secretion induced by exogenous substance P was not affected by DAMGO.
We conclude that opioids inhibit neurally‐mediated goblet cell secretion via actions at prejunctional δ‐ and μ‐receptors on cholinergic nerves and at μ‐receptors on sensory nerve endings, and that capsaicin activation of sensory nerves is via a different mechanism from that of electrical or cigarette smoke activation.
Evidence for multiple endothelin receptors in the guinea‐pig pulmonary artery and trachea
Authors: Cardell Lars Olaf , Uddman Rolf , Edvinsson Lars 
Published: July 2012

The responses of the three peptides, endothelin 1 (ET‐1), endothelin 2 (ET‐2) and endothelin 3 (ET‐3) were analysed on isolated circular segments of pulmonary arteries and trachea from the guinea‐pig.
In the pulmonary artery, the vasomotor responses to the endothelins, expressed as the maximum contraction (Emax%), had the order ET‐1 > ET‐2 > ET‐3 while the order of potency (pD2) was ET‐1 = ET‐2 > ET‐3. ET‐1 and ET‐2 caused cross‐desensitization, but did not affect the responses to ET‐3. ET‐3 did not cause cross‐desensitization to ET‐1 or ET‐2 although it induced homologous desensitization. Finally, the effects of ET‐1 and ET‐2 were additive to those of ET‐3. The additive effect of ET‐3 to those of ET‐1 or ET‐2 was more difficult to demonstrate, given the profound contraction produced by ET‐1 and to a lesser extent by ET‐2.
In the trachea, the rank order of potency, additivity and desensitization were different from the pulmonary artery. Basically, all three peptides were equipotent but less potent than ET‐1 in the artery. There was no evidence for additivity and only a slight tendency to tachyphylaxis was seen.
The guinea‐pig pulmonary artery appears to be endowed with one receptor type which is sensitive to ET‐1/ET‐2 and with another receptor type which responds preferentially to ET‐3. In the trachea, neither of these receptors appears to be present since all three peptides apparently act on a homogeneous population of receptors with characteristics different from those of the two arterial receptors. This suggests a third non‐isopeptide selective type of endothelin receptor.
Effects of systemic non‐steroidal anti‐inflammatory drugs on nociception during tail ischaemia and on reperfusion hyperalgesia in rats
Authors: Gelgor Linda , Butkow Neil , Mitchell Duncan 
Published: July 2012

We have investigated the effects of five non‐steroidal anti‐inflammatory drugs (NSAIDs) on nociception during ischaemia and on reperfusion hyperalgesia in rats.
We induced tail ischaemia in conscious rats by applying a tourniquet at the base of the tail until the rats exhibited co‐ordinated escape behaviour when we released the tourniquet.
We assessed hyperalgesia by measuring the tail flick latency following tail immersion in water at 49°C, before applying and immediately after releasing the tourniquet, and then at 30 min intervals for 2 h.
Intraperitoneal injection of NSAIDs prior to applying the tourniquet had no effect on the co‐ordinated escape behaviour during ischaemia, nor on tail flick latency in the absence of prior ischaemia. However all the drugs attenuated reperfusion hyperalgesia in a log dose‐dependent manner. Doses required to abolish hyperalgesia, were indomethacin 5 mg kg−1, diclofenac sodium 42 mg kg−1, ibuprofen 54 mg kg−1, dipyrone 168 mg kg−1 and paracetamol 170 mg kg−1.
We conclude that the mechanisms underlying nociception during ischaemia are not the same as those underlying reperfusion hyperalgesia. Moreover our procedure provides a rapid and more humane method for measuring the antinociceptive potency of NSAIDs.
Blockade of delayed rectifier K+ currents in neuroblastoma × glioma hybrid (NG 108–15) cells by clofilium, a class III antidysrhythmic agent
Authors: Reeve Helen L. , Peers Chris 
Published: July 2012

The whole‐cell patch‐clamp technique was used to examine the effects of the class III antidysrhythmic agent, clofilium, on voltage‐activated delayed rectifier K+ currents (IKv) in undifferentiated mouse neuroblastoma × rat glioma hybrid (NG 108–15) cells. Ca2+‐activated K+ currents also seen in these cells were abolished by bath application of 4 mm Co2+.
Bath application of clofilium (0.3 to 70 μm) caused dose‐dependent, irreversible inhibition of IKv in these cells. Under control conditions, activated currents were sustained during 200 ms depolarizing steps, but in the presence of clofilium, or after its wash‐out, currents were reduced in amplitude and showed a time‐dependent decay.
Clofilium blockade of IKv was voltage‐dependent: the degree of current inhibition increased with increasing depolarizations. The transient nature of IKv seen in the presence of clofilium was also more apparent at higher test potentials.
The effects of clofilium were use‐dependent: when cells were left unstimulated during drug application, and then depolarizations were resumed, several pulses were required for clofilium blockade to reach a steady level. Similar results were obtained post‐clofilium, when cells were unstimulated during application and then removal of clofilium, suggesting that although the blocking action of the drug was use‐dependent, it bound to the closed, delayed rectifier K+ channel.
High concentrations (100 or 300 μm) of sotalol, another class III antidysrhythmic agent, were without discernible effects on IKv in NG 108–15 cells.
The effects of clofilium on a neuronal IKv described here, and its possible mechanism of action, are compared with previously reported effects of clofilium on the cardiac IKv.
Adenosine modulation of calcium currents in postganglionic neurones of avian cultured ciliary ganglia
Authors: Bennett Max R. , Kerr R. , Khurana G. 
Published: July 2012

Calcium currents in postganglionic neurones of cultured 7‐ to 10‐day embryonic avian ciliary ganglia were analyzed under whole‐cell voltage‐clamp and their modulation by 2‐chloroadenosine determined.
In the presence of tetrodotoxin (200 nm) in the medium to block the Na+ current and CsCl (105 mm) in the patch‐clamp electrode to block the K+ current, two different components of the calcium currents (transient and sustained) were identified on the basis of their voltage‐dependent kinetics as well as their sensitivity to the dihydropyridine agonist Bay K 8644 and antagonist nifedipine.
The sustained current inactivated very slowly (τ > 1000 ms; for test potentials from − 20 mV to + 40 mV) but was reactivated at a holding potential (Vh) of − 40 mV. The current was increased on average over 50% by 1 μm of Bay K 8644 at a test potential of 0 mV and decreased over 35% by 1 μm of nifedipine.
The transient current inactivated slowly (τ < 200 ms; for test potentials from −20 mV to +40 mV), and could be completely reactivated at a Vh of − 80 mV. This current was unaffected by Bay K 8644 (1 μm) but reduced on average by 8% with nifedipine (1 μm).
The sustained and transient currents were decreased more than 70% by 5 μm of ω‐conotoxin and decreased more than 50% by 250 μm verapamil.
2‐Chloroadenosine (1 μm) decreased the transient current by over 50% and the sustained current by less than 10%. In the presence of nifedipine (1 μm), 2‐chloroadenosine decreased the transient current by over 30% and the remaining sustained current by 35%. In the presence of 8‐phenyltheophylline (10 μm), 2‐chloroadenosine no longer decreased either the transient or sustained currents but did have a slight potentiating effect on both the transient and sustained currents.
These observations of the effects of 2‐chloroadenosine on the transient and sustained currents are discussed in relation to the different calcium channel types at preganglionic nerve terminals.
Combined dose‐ratio analysis of cholecystokinin receptor antagonists, devazepide, lorglumide and loxiglumide in the guinea‐pig gall bladder
Authors: Bishop L.A. , Gerskowitch V.P. , Hull R.A.D. , Shankley N.P. , Black J.W. 
Published: July 2012

Interactions between cholecystokinin octapeptide (CCK‐8) and CCKA‐receptor antagonists derived from benzodiazepines (devazepide) and glutamic acid (lorglumide and loxiglumide) have been examined in an improved bioassay using the guinea‐pig, isolated, gall bladder preparation.
The presence of CCKB‐receptors in the assay was provisionally‐ruled out on the basis of the low potency of pentagastrin in the assay. By applying analyses of both agonism and antagonism, pentagastrin was shown to behave as a partial agonist at the CCKA‐receptor.
Devazepide, lorglumide and loxiglumide behaved as simple competitive antagonists of CCKA‐receptors and pKB values of 9.98, 7.59 and 7.07 were estimated, respectively.
Application of a combined dose‐ratio analysis to the interactions between CCK‐8 and combinations of devazepide/lorglumide and devazepide/loxiglumide indicated that these molecules behave as syntopic, competitive, antagonists at the CCKA‐receptor.
We conclude that the guinea‐pig gall bladder assay contains a homogeneous population of CCKA‐receptors and offer an explanation for the differences between our results and those obtained recently by Maubach et al. (1991) which were taken as preliminary evidence for CCKA‐receptor heterogeneity.
The effect of monoclonal antibodies to calcitonin gene‐related peptide (CGRP) on CGRP‐induced vasodilatation in pig coronary artery rings
Authors: Shaw N.E. , Foulkes R. , Andrew D.P. , Brown D.T. , Hughes B. 
Published: July 2012

The modification of the vasodilator effect of calcitonin gene‐related peptide (CGRP) by a panel of monoclonal antibodies (MAbs), which map to discrete epitopes on the CGRP molecule, was investigated in pig coronary artery rings (PCA). The preparations were pre‐constricted with acetylcholine (3 × 10−7 m) and concentration‐response curves to CGRP (2 × 10−10 − 2.56 × 10−8 m) were obtained in the presence or absence of each MAb.
CGRP caused a concentration‐dependent relaxation of PCAs which reached a maximum (98.2 ± 4.8%, n = 25) at 1.28 × 10−8 m and gave an EC50 of 3.8 ± 0.8 × 10−9 m.
Two MAbs which map to the N‐terminal, CN1 and CRA3, did not affect the CGRP response whilst a third, CRA5, significantly inhibited its effect.
The C‐terminal MAb, CRA2, did not modify the CGRP response whilst, in contrast, CB3 (C‐terminal) potentiated its effect. A similar augmentation of the CGRP‐induced vasodilatation was seen in the presence of the middle‐region MAb, CRA8.
These results suggest that regional specific MAbs can modify the vasodilator effect of CGRP causing either inhibition (CRA5, N‐terminal) or potentiation (CB3, C‐terminal; CRA8, middle region).