bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinin‐induced chloride permeability changes in colony 29 epithelia estimated from 125I− efflux and MEQ fluorescence
Authors: MacVinish L.J. , Reancharoen T. , Cuthbert A.W. 
Published: July 2012

The changes in apical Cl− permeability of Colony 29 human colonic epithelial monolayers were estimated from the rate constant of 125I− efflux from tissues loaded with the isotope.
Forskolin was used to increase intracellular concentrations of adenosine 3:5′ cyclic‐monophosphate (cyclic AMP), and A23187 to increase intracellular free Ca2+ (Cai). Both treatments increased the rate constant for 125I− efflux, indicating an increase in apical Cl− permeability.
Lysylbradykinin (LBK) also increased the rate constant for 125I− efflux, sometimes biphasically. Chelation of intracellular Ca2+ with BAPTA or prevention of prostaglandin formation with piroxicam, attenuated but did not eliminate the effect of LBK. It is concluded that LBK affects 125I− efflux through the agency of both cyclic AMP and Ca2+.
Ba2+ attenuated the effect of LBK and A23187 on 125I− efflux, but had no effect on the action of forskolin. It is concluded that Ca2+ has a major effect on K+ channels, the resulting hyperpolarization increasing the driving force for 125I− efflux. A secondary effect on Ca2+‐sensitive Cl− channels is possible. By contrast, cyclic AMP exerts it major effect on apical Cl− channels.
Using a Cl− sensitive fluorescent dye, MEQ, the intracellular chloride concentration, Cli was estimated to be around 30 mm, which was increased to around 50 mm by forskolin, suggesting cyclic AMP could activate the Na‐K‐2Cl co‐transporter.
MEQ fluorescence was used to estimate Cl− influx and efflux rates of epithelial cells. These were increased three fold by forskolin and dibutyryl cyclic AMP and two fold by LBK and histamine.
It is concluded that LBK increases electrogenic chloride secretion in Colony 29 epithelia through the generation of second messengers cyclic AMP and Ca2+, each of which may act on both apical and basolateral membranes.
Cibenzoline inhibits diazoxide‐ and 2,4‐dinitrophenol‐activated ATP‐sensitive K+ channels in guinea‐pig ventricular cells
Authors: Sato Toshiaki , Wu Bowei , Nakamura Sunao , Kiyosue Tatsuto , Arita Makoto 
Published: July 2012

We have investigated the effects of diazoxide (a sulphonamide derivative) and cibenzoline (a class I antiarrhythmic drug) on ATP‐sensitive K+ currents in guinea‐pig ventricular cells, using whole‐cell clamp techniques.
Diazoxide (50 μm) produced a marked shortening of action potential duration which was antagonized by 1 μm glibenclamide, an ATP‐sensitive K+ channel blocker.
Diazoxide (50 μm) increased the quasi‐steady state outward current elicited by a ramp voltage protocol (−20 mV s−1) at potentials positive to about − 70 mV. This effect was completely prevented in the presence of glibenclamide (1 μm), thereby suggesting that diazoxide opens ATP‐sensitive K+ channels.
Cibenzoline (5 μm) depressed the diazoxide‐induced increases in the outward current and the pretreatment with this agent prevented the development of the diazoxide‐induced outward current.
Cibenzoline (10 μm) reversed the 2,4‐dinitrophenol (50 μm)‐induced shortening of the action potential duration partially but significantly.
These results suggest that diazoxide activates ATP‐sensitive K+ channels of guinea‐pig ventricular cells and that cibenzoline, at therapeutic concentrations, inhibits this channel.
Fendiline inhibits L‐type calcium channels in guinea‐pig ventricular myocytes: a whole‐cell patch‐clamp study
Authors: Tripathi O. , Schreibmayer W. , Tritthart H.A. 
Published: July 2012

Fendiline, a diphenylalkylamine type of antianginal drug, was examined for its effects on L‐type calcium channels in guinea‐pig ventricular myocytes by the whole‐cell patch‐clamp technique.
Fendiline (0.3–100 μm) applied extracellularly inhibited the calcium channel current (ICa) in a concentration‐ and time‐dependent manner. The IC50 of fendiline was 17.0 ± 2.43 μm and the Hill slope was 1.39 ± 0.23.
Inhibition of ICa by fendiline appeared with an onset of less than 3 s.
Fendiline inhibited ICa at all the membrane potentials tested and shifted the current‐voltage curve upwards. The overall calcium channel conductance (gCa) of the cell was reduced and conductance‐voltage curve was shifted to the left in the presence of fendiline.
Isoprenaline (0.5–1 μm), a β‐adrenoceptor agonist, partially reversed the inhibitory effect of fendiline on ICa.
It is suggested that fendiline applied extracellularly blocks L‐type calcium channels and reduces calcium channel conductance of the cell. The calcium channels thus inhibited are, nevertheless, still available for β‐adrenoceptor stimulation.
Nitric oxide affects mammalian distal colonic smooth muscle by tonic neural inhibition
Authors: Middleton S.J. , Cuthbert A.W. , Shorthouse M. , Hunter J.O. 
Published: July 2012

The role of the l‐arginine‐nitric oxide (NO) pathway in tonic neural inhibition of spontaneous mechanical activity of distal colonic circular smooth muscle (DCCSM) was investigated in male Wistar rats.
Muscle strips were mounted in organ baths and spontaneous contractions recorded with isometric force transducers. They were characterized as low frequency (LFCs) 0.41 ± 0.03 N cm−2 or high frequency contractions (HFCs) 0.22 ± 0.04 N cm−2. The latter occurred intermittently to produce summation contractions (SCs) range 0.5–12 N cm−2.
Tetrodotoxin (100 nm) increased the forces of LFCs and SCs. Increase in force to tetrodotoxin did not occur after incubation of the muscle with NG‐monomethyl‐l‐arginine (l‐NMMA) 500 μm, an inhibitor of NO biosynthesis.
l‐NMMA but not its enantiomer d‐NMMA increased the force of LFCs (EC50:200 μm) and SCs (EC50:175 μm) in a concentration‐dependent manner which was reversed by l‐arginine but not by d‐arginine.
Muscle, precontracted by acetylcholine, relaxed to sodium nitroprusside (EC50:1.8 μm) NO gas (EV50:70 μl) and NO solutions (EC50:4 μm) in a concentration‐dependent manner. Guanosine 3′:5′‐cyclic monophosphate tissue concentrations (pmol mg−1 protein) were elevated in muscle after relaxation by sodium nitroprusside (500 μm) from 0.32 ± 0.06 to 1.2 ± 0.37 and by 1 ml of NO gas from 0.49 ± 0.05 to 1.54 ± 0.14.
These data suggest that DCCSM is under tonic neural inhibition mediated by NO biosynthesis.
Postnatal changes in N‐methyl‐D‐aspartate receptor binding and stimulation by glutamate and glycine of [3H]‐MK‐801 binding in human temporal cortex
Authors: Slater P. , McConnell S.E. , D'Souza S.W. , Barson A.J. 
Published: July 2012

Homogenates of human infant and adult temporal cortex were used to measure [3H]‐TCP and [3H]‐MK‐801 binding to the N‐methyl‐d‐aspartate (NMDA)‐coupled ion channel phencyclidine site.
Both [3H]‐TCP and [3H]‐MK‐801 binding increased in infant cortex by> 100% between term and 26 weeks suggesting that the numbers of NMDA receptors increase during postnatal brain development.
[3H]‐MK‐801 binding was measured under non‐equilibrium conditions in temporal cortex homogenates with the addition of 100 μm of l‐glutamate plus a range of concentrations (0.05 μm−100 μm) of glycine. Glutamate and glycine increased [3H]‐MK‐801 binding by stimulating NMDA receptors and improving [3H]‐MK‐801 access to ion channel binding sites; maximum stimulation in adult and infant temporal cortex was achieved with 100 μm glutamate plus 5 μm glycine; a higher concentration of glycine (50 μm) reduced [3H]‐MK‐801 binding to below maximum.
The stimulation by 100 μm glutamate plus 5 μm glycine of [3H]‐MK‐801 binding in infant temporal cortex was affected by postnatal age. For example, although the stimulation of [3H]‐MK‐801 binding in 5–6 week infant cortex (236% of basal) was similar to adult cortex (230% of basal), in samples taken from infants aged 5–6 months glycine (plus glutamate) stimulation of [3H]‐MK‐801 binding (392% of basal) was substantially greater than that measured in adult temporal cortex.
The binding of [3H]‐glycine to the glycine modulatory site associated with the NMDA receptor in infant cortex also increased with postnatal age by > 100% between term and 26 weeks.
It is concluded that NMDA receptors in infant cortex increase to levels greater than those in adult cortex during postnatal development. The results do not exclude the possibility that the transiently increased NMDA receptor‐ion channel complex in infant cortex shows enhanced responses to agonists and modulators.
l‐Arginine exerts a dual role in nociceptive processing in the brain: involvement of the kyotorphin‐Met‐enkephalin pathway and NO‐cyclic GMP pathway
Authors: Kawabata Atsufumi , Umeda Nahoko , Takagi Hiroshi 
Published: July 2012

Intracerebroventricular (i.c.v.) administration of l‐arginine (l‐Arg), at 10–100 μg per mouse, produced antinociception in mice, as assessed by the tail flick test; this antinociception was reversed by pretreatment (s.c.) with naltrindole (NTI), a δ‐selective opioid antagonist, and by co‐administered l‐leucyl‐l‐arginine (Leu‐Arg), a kyotorphin (endogenous Met‐enkephalin releaser) receptor antagonist.
l‐NG‐nitroarginine methyl ester (l‐NAME), a NO synthase inhibitor, but not d‐NG‐nitroarginine methyl ester, given i.c.v. at 3–10 μg per mouse, exhibited antinociceptive activity that was resistant to naloxone (s.c.), NTI (s.c.) and Leu‐Arg (i.c.v.).
The l‐NAME (i.c.v.)‐induced antinociception was not reversed by l‐Arg (i.c.v.), which was antinociceptive by itself, but was abolished by combined injection of l‐Arg plus Leu‐Arg (i.c.v.) or by l‐Arg (i.c.v.) after NTI (s.c.).
Methylene blue (MB), a soluble guanylate cyclase inhibitor, at 0.1–1 μg per mouse, produced antinociception by i.c.v. administration. The antinociception induced by MB (i.c.v.) or l‐NAME (i.c.v.) was reversed by co‐administered dibutyryl cyclic GMP.
These findings suggest that l‐Arg plays a dual role in nociceptive processing in the brain, being antinociceptive via the kyotorphin‐Met‐enkephalin pathway and nociceptive via the NO‐cyclic GMP pathway.
The Leu13‐motilin (KW‐5139)‐evoked release of acetylcholine from enteric neurones in the rabbit duodenum
Authors: Kitazawa Takio , Ishii Akio , Taniyama Kohtaro 
Published: July 2012

Involvement of cholinergic mechanisms in the contractile response to Leu13‐motilin (LMT, KW‐5139) was investigated in rabbit duodenal segments, and longitudinal muscle‐myenteric plexus (LM‐MP) preparations preincubated with [3H]‐choline.
Contractile response to LMT (0.1 nm −1 μm) consisted of an initial rapid (phasic) contraction and a tonic contraction slowly fading to a sustained plateau. LMT caused a concentration‐dependent phasic contraction of rabbit isolated duodenal segments. The EC50 value was 2.5 nm and the maximum amplitude of the contraction was 103% of the response induced by acetylcholine (ACh, 100 μm). Neither tetrodotoxin nor atropine changed the EC50 value or the maximum amplitude of the response to LMT.
Both atropine and tetrodotoxin decreased the amplitude and accelerated fading of the tonic contraction produced by LMT.
LMT (30 nm−3 μm) induced an increase of 3H‐outflow, in a concentration‐dependent manner. The LMT‐induced increase of 3H‐outflow was prevented by removal of external Ca2+ or by the presence of tetrodotoxin.
Porcine motilin (10 nm −1 μm) also stimulated the release of 3H at a similar concentration‐range to that seen with LMT.
Pretreatment with LMT (3 μm for 20 min) decreased LMT‐ and the porcine motilin‐evoked release of 3H but did not alter the high K+‐evoked release.
Our results suggest that LMT and porcine motilin stimulate the release of ACh from enteric neurones through the same receptor, and that the release of ACh plays a role in tonic components of contraction in the rabbit duodenum.
Blockade by calmodulin inhibitors of Ca2+ channels in smooth muscle from rat vas deferens
Authors: Nakazawa Ken , Higo Katsuya , Abe Kazuho , Tanaka Yoshio , Saito Hiroshi , Matsuki Norio 
Published: July 2012

Effects of three compounds which are used as calmodulin inhibitors (trifluoperazine, W‐7 and calmidazolium) on Ca2+ channels were investigated in smooth muscle from rat vas deferens.
All three calmodulin inhibitors relaxed the smooth muscle precontracted by a high concentration of KCl (63.7 mm). The order of potency for the relaxation was trifluoperazine > W‐7 > calmidazolium.
In binding studies using a microsomal fraction of vas deferens, all these calmodulin inhibitors displaced specific [3H]‐nimodipine binding. Trifluoperazine and W‐7 inhibited the binding at concentrations that relaxed the smooth muscle whereas calmidazolium inhibited at concentrations much lower than those necessary for muscle relaxation.
Ba2+ current flowing through voltage‐gated Ca2+ channels was measured under whole‐cell voltage‐clamp conditions in isolated smooth muscle cells. The Ba2+ current was suppressed by the three calmodulin inhibitors in the concentration‐range where inhibition of [3H]‐nimodipine binding was observed. Neither voltage‐dependence nor the inactivation time course of Ba2+ current were affected by these compounds.
The results suggest that the calmodulin inhibitors directly block Ca2+ channels in the smooth muscle cells. The channel inhibition by trifluoperazine and W‐7, but perhaps not that by calmidazolium, may be responsible for the muscle relaxation observed with these compounds.
A non‐peptide NK1‐receptor antagonist, RP 67580, inhibits neurogenic inflammation postsynaptically
Authors: Moussaoui S.M. , Montier F. , Carruette A. , Blanchard J.C. , Laduron P.M. , Garret C. 
Published: July 2012

The non‐peptide neurokinin NK1‐receptor antagonist, RP 67580 (3aR, 7a), a perhydroisoindolone derivative, powerfully reduced plasma extravasation in rat hind paw skin induced by local application of xylene (ID50 = 0.03 mg kg−1, i.v.) or capsaicin (ID50 = 0.06 mg kg−1, i.v.), or by i.v. injection of exogenous substance P (SP) or septide ([pGlu6,Pro9]SP(6–11)) (ID50 = 0.04–0.05 mg kg−1, i.v.). RP 67580 (1 mg kg−1, i.v.) also abolished capsaicin‐induced nasal fluid hypersecretion (by 82 ± 5%). These effects were found to be stereospecific, the enantiomer, RP 68651 (3aS, 7aS), being inactive at 1 mg kg−1, i.v.
In rats neonatally treated with capsaicin (50 mg kg−1, s.c.), plasma extravasation induced by SP was significantly increased (by 43 ± 7%). RP 67580 (1 mg kg−1, i.v.) completely inhibited the SP‐induced plasma extravasation in capsaicin neonatally treated‐animals, as it did in control animals. This result suggests that RP 67580 acts at the postsynaptic level for the inhibition of plasma extravasation.
Opioid receptor agonists, μ‐(morphine) and κ‐(PD‐117302) at 10 mg kg−1, s.c., in contrast to NK1‐receptor antagonists, did not inhibit plasma extravasation induced by exogenous SP. They were, however, partially effective against plasma extravasation induced by electrical nerve stimulation (74 ± 4% and 48 ± 9% inhibition at 10 mg kg−1, s.c. of morphine and PD‐117302, respectively, compared to 90 ± 3% inhibition obtained with RP 67580, 3 mg kg−1, s.c.). These results indicate the presynaptic action of opioid receptor agonists, in contrast to the postsynaptic action of NK1‐preceptor antagonists for the inhibition of plasma extravasation.
Ligature of the saphenous nerve distal to the point of electrical stimulation, local application of lignocaine to the saphenous nerve, neonatal capsaicin pretreatment, and colchicine at very low doses (120 μg kg−1 day−1 given for 3 days) were found to prevent plasma extravasation elicited by electrical nerve stimulation.
The foregoing results demonstrate that the non‐peptide NK1‐receptor antagonist, RP67580, is a potent inhibitor of plasma extravasation induced in skin by NK1‐receptor agonists, by local application of chemical irritants (capsaicin or xylene) or by electrical nerve stimulation. Moreover, opioid receptor agonists and colchicine inhibit plasma extravasation induced by electrical nerve stimulation but not that elicited by exogenous SP. Therefore, it is possible to inhibit neurogenic inflammation either at the presynaptic level with opioid receptor agonists and colchicine, or at the postsynaptic level with NK1‐receptor antagonists, and that the new non‐peptide NK1‐receptor antagonists may have a great potential for alleviation of inflammation in various pathological syndromes in man.
The diuretic action of 8‐cyclopentyl‐1,3‐dipropylxanthine, a selective A1 adenosine receptor antagonist
Authors: Knight R.J. , Bowmer C.J. , Yates M.S. 
Published: July 2012

The diuretic effect of the selective A1 adenosine receptor antagonist, 8‐cyclopentyl‐1,3‐dipropylxanthine (CPX), was investigated in anaesthetized rats.
CPX (0.1 mg kg−1, i.v.) produced significant increases in urine flow, and the excretion rate and fractional excretion of both sodium and chloride. By contrast, CPX administration did not result in any significant change in the excretion of potassium.
The diuretic effect of CPX was accompanied by a transient increase in inulin clearance although p‐amino‐hippurate clearance was unaffected, indicating the CPX induced a temporary elevation of glomerular filtration rate but no change in renal blood flow.
The fractional excretion of lithium (a marker of delivery of fluid out of the proximal tubule) was also significantly increased by CPX. However, other measures of tubular function derived from lithium clearance indicated that there were no changes in the handling of sodium or water in the distal regions of the nephron.
CPX did not significantly alter the relationship between either free water reabsorption or free water clearance and the distal delivery of sodium, which suggests that CPX does not affect the renal concentration/dilution mechanism.
The results of this study show that the diuresis and increased excretion of sodium and chloride induced by CPX (0.1 mg kg−1) in the rat, occurs with only transient elevation in glomerular filtration rate and no change in renal blood flow. The primary reason for the diuresis appears to be inhibition of sodium reabsorption in the proximal tubule. Furthermore, the results provide evidence that production and release of endogenous adenosine modifies renal excretory function via stimulation of the A1 receptor subtype.
Thermodynamics of antagonist binding to rat muscarinic M2 receptors: antimuscarinics of the pridinol, sila‐pridinol, diphenidol and sila‐diphenidol type
Authors: Waelbroeck M. , Camus J. , Tastenoy M. , Lambrecht G. , Mutschler E. , Kropfgans M. , Sperlich J. , Wiesenberger F. , Tacke R. , Christophe J. 
Published: July 2012

We studied the effect of temperature on the binding to rat heart M2 muscarinic receptors of antagonists related to the carbon/silicon pairs pridinol/sila‐pridinol and diphenidol/sila‐diphenidol (including three germanium compounds) and six structurally related pairs of enantiomers [(R)‐ and (S)‐procyclidine, (R)‐ and (S)‐trihexyphenidyl, (R)‐ and (S)‐tricyclamol, (R)‐ and (S)‐trihexyphenidyl methiodide, (R)‐ and (S)‐hexahydro‐diphenidol and (R)‐ and (S)‐hexbutinol]. Binding affinities were determined in competition experiments using [3H]‐N‐methyl‐scopolamine chloride as radioligand. The reference drugs were scopolamine and N‐methyl‐scopolamine bromide.
The affinity of the antagonists either increased or decreased with temperature, van 't Hoff plots were linear in the 278–310°K temperature range. Binding of all antagonists was entropy driven. Enthalpy changes varied from large negative values (down to −29 kJ mol−1) to large positive values (up to + 30 kJ mol−1).
(R)‐configurated drugs had a 10 to 100 fold greater affinity for M2 receptors than the corresponding (S)‐enantiomers. Enthalpy and entropy changes of the respective enantiomers were different but no consistent pattern was observed.
When silanols (R3SiOH) were compared to carbinols (R3COH), the affinity increase caused by C/Si exchange varied between 3 and 10 fold for achiral drugs but was negligible in the case of chiral drugs. Silanols induced more favourable enthalpy and less favourable entropy changes than the corresponding carbinols when binding. Organogermanium compounds (R4Ge) when compared to their silicon counterparts (R4Si) showed no significant difference in affinity as well as in enthalpy and entropy changes.
Exchange of a cyclohexyl by a phenyl moiety was associated with an increase or a decrease in drug affinity (depending on the absolute configuration in the case of chiral drugs) and generally also with a more favourable enthalpy change and a less favourable entropy change of drug binding.
Replacement of a pyrrolidino by a piperidino group and increasing the length of the alkylene chain bridging the amino group and the central carbon or silicon atom were associated with either an increase or a decrease of entropy and enthalpy changes of drug binding. However, there was no clear correlation between these structural variations and the thermodynamic effects.
Taken together, these results suggest that hydrogen bond‐forming OH groups and, to a lesser extent, polarizable phenyl groups contribute significantly to the thermodynamics of interactions between these classes of muscarinic antagonists and M2 muscarinic receptors.
Blockade by glibenclamide of the flow‐evoked endothelial release of ATP that contributes to vasodilatation in the pulmonary vascular bed of the rat
Authors: Hasséssian Haroutioun , Bodin Philippe , Burnstock Geoffrey 
Published: July 2012

The effect of step augmentation of flow rate on the level of adenosine −5′‐triphosphate (ATP) measured in the Krebs perfusate was investigated, and the effect of glibenclamide on the release of ATP was tested in the rat pulmonary vascular bed.For flow rates between 10.38 ± 1.18 and 28.88 ± 2.08 ml min−1(n= 8) 1 μmsuramin, a P2‐purinoceptor antagonist, significantly (P< 0.05) increased vascular resistance under conditions of step augmentation of flow rate. This suggests that endogenous ATP released during increases in flow rate dilates pulmonary vessels.In response to a step augmentation in flow rate from 9.13 ± 0.97 to 18.3 ± 1.69 ml min−1(n= 4) ATP levels were up to 23 fold higher (P< 0.05) for 15 s, and gradually dropped to a level of about half the initial rise. Once the ATP levels had stabilized, another step augmentation of flow rate to 27.00 ± 3.49 ml min−1was able to evoke a corresponding increase of ATP release. The ability of the vascular bed to respond with increased ATP release after the initial ATP responses had tapered, demonstrates that the drop in ATP levels after the initial rise is not due to depletion of ATP. Furthermore, the maximal ATP response directly precedes the vasodilatation observed following each jump in perfusion pressure produced with each step increase in flow rate.In response to two 3 fold step augmentations of flow rate (8.41–27.29 ml min−1) spaced 30 min apart there were two increases in the level of ATP which were not significantly different from each other. However, perfusion with 1 μmglibenclamide between the first and the second step augmentation of flow rate (8.08–24.67 ml min−1) significantly (P< 0.05;n= 6) blocked the increase in ATP release. This suggests that the release of intracellular ATP is mediated by glibenclamide‐sensitive K+channels.A concentration of 1 μmglibenclamide perfused for 30 min was without effect on vascular pressure at constant flow. However, under conditions where flow was augmented in a stepwise manner (between 11.50 and 36.45 ml min−1) perfusing with 1 μmglibenclamide increased vascular resistance (P< 0.10).It is concluded that flow‐induced ATP release is mediated by a glibenclamide‐sensitive K+channel, and that the release of ATP from endothelial cells probably functions to vasodilate the pulmonary vascular bed of the rat.