bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functional effects and ligand binding of chimeric galanin‐neuropeptide Y (NPY) peptides on NPY and galanin receptor types
Authors: Kahl Ulrika , Langel Ülo , Bartfai Tamas , Grundemar Lars 
Published: July 2012

The effects and binding characteristics of a series of chimeric galanin‐neuropeptide Y (NPY) peptides were examined in various preparations known to contain a predominant population of either Y1 or Y2 receptors for NPY or galanin receptors.
NPY suppressed the electrically stimulated twitches of the rat vas deferens (Y2 receptors), while galanin enhanced the electrically stimulated twitches. The galanin‐NPY peptides m 32 (galanin(1–13)‐NPY(25–36)), M69A (galanin(1–13)‐Lys‐[εNH‐Gly‐NPY(4‐1)]NPY(25–36)) and M88 (galanin(1–12)‐Ala‐NPY(25–36)) evoked a concentration‐dependent suppression of the electrically stimulated twitches. These chimeric peptides were about equipotent with NPY, while NPY (13–36) was about five times less potent than NPY itself. Also a stochiometric combination of the N‐ and C‐terminal fragments NPY (1–24)NH2 and NPY (25–36) (each at 1 μm) was inactive in vas deferens. M120 (galanin (1–13)‐NPY(14–36) (1 μm) did not affect the NPY‐mediated suppression of the stimulated twitches.
NPY evoked a concentration‐dependent contraction in the guinea‐pig isolated caval vein (Y1 receptors), while galanin (≤ 1 μm) was inactive. M32, M69A and M88 induced a slight contraction at very high concentrations only (≥ 0.3 m), while M120 was inactive at 1 μm. None of the four chimeric peptides affected the contraction evoked by NPY.
Since the number of NPY receptors in the rat vas deferens and guinea‐pig caval vein were too low, the affinities of the galanin‐NPY peptides for [3H]‐NPY binding sites were examined in membranes from rat brain areas known to contain predominant populations of Y1 receptors (cerebral cortex) and Y2 receptors (hippocampus), respectively. The chimeric peptides M32, M69A, M88, M120 and NPY (13–36) all had higher affinities for hippocampal binding sites than for cerebral cortical binding sites. These peptides were 90–440 times less potent than NPY at cerebral cortical binding sites and 15–125 times less potent than NPY at hippocampal binding sites. The most selective chimeric peptide was M32, which had a 20 fold higher affinity for hippocampal than for cerebral cortical binding sites.
At hypothalamic [125I]‐galanin binding sites M32, M88 and M69A were equipotent with galanin, while M120 was about 10 times less potent than galanin. M32, M88 and M69A, like galanin contracted the rat isolated jejunum.
The N‐terminal portion (1–12) of galanin seems to permit a steric conformation of the attached NPY (25–36) part of the chimeric galanin‐NPY peptides, which results in a facilitated Y2 but not Y1 receptor recognition and activation. None of the galanin‐NPY peptides appeared to act as antagonists at either type of NPY receptor, probably due to their low affinity. Instead, they displayed a very high affinity for hypothalamic galanin receptors and probably act as galanin agonists in the rat jejunum.
The effects of propofol and enflurane on single calcium channel currents of guinea‐pig isolated ventricular myocytes
Authors: Takahashi H. , Puttick R.M. , Terrar D.A. 
Published: July 2012

The effects of the anaesthetics, propofol (100 μm) and enflurane (3%, 1.46 mm), on single L type calcium channel currents were investigated in single myocytes isolated from guinea‐pig ventricles. Channel activity was recorded from membrane patches by use of the ‘cell‐attached’ patch‐clamp technique (pipette solution containing 110 mm BaCl2, 5 μm Bay K 8644, 5 μm HEPES, pH 7.4; temperature 36°C).
Channel conductance was calculated from the slope of the relationship between single channel current and membrane potential during step depolarizations to activate the channel over a range of approximately − 20 to + 20 mV. Neither propofol (6 cells) nor enflurane (7 cells) caused any significant reduction in channel conductance.
Both propofol (7 cells) and enflurane (9 cells) decreased the probability of the channel being open during depolarizations to + 10 mV (measured from histograms of the fraction of time spent by the channel at different current levels, taking areas under the Gaussian curves fitted to the open and closed components of the distributions to represent the proportion of time spent in the two states).
A fraction of the current traces showed no detectable channel openings in response to step depolarizations to + 10 mV. Both propofol and enflurane significantly increased the fraction of silent traces.
Transitions across a threshold halfway between the open and closed levels were used to define periods spent in the open and closed states. Both propofol (7 cells) and enflurane (9 cells) reduced the mean open times and increased the mean closed times of the calcium channel.
Histograms were plotted showing the distributions of times spent by the channels in the open and closed states. Two exponentials were fitted to the open and closed time distributions. Both propofol (7 cells) and enflurane (9 cells) shortened both time constants fitted to the open times and lengthened both time constants fitted to the closed times.
It is concluded that both propofol and enflurane appear to alter the kinetics of opening and closing of calcium channels to favour shut channels without altering channel conductance. This effect would be expected to result in a reduction of the macroscopic calcium current and thus contribute to the negative inotropic action of these anaesthetics.
Reduction of endothelial function with age in the mesenteric arterial bed of the normotensive rat
Authors: Atkinson Jeffrey , Tatchum‐Talom Rabelais , Capdeville‐Atkinson Christine 
Published: July 2012

Age‐related changes in endothelial vasodilator function were studied in an in vitro preparation of the mesenteric arterial bed removed from male, normotensive, Wistar rats.
Animals were killed at 2, 12 or 22 months of age, the superior mesenteric artery was cannulated and the gut removed. The mesenteric arterial bed was perfused at a constant flow rate of 4 ml min−1and perfusion pressure was taken as an index of arteriolar tone.
The muscarinic agonist, carbachol, antagonized noradrenaline‐induced vasoconstriction in the presence, but not in the absence, of endothelium. This cholinoceptor agonist‐induced release of endothelial‐derived relaxing factor (EDRF) was impaired in 22 month old rats.
Noradrenaline‐induced vasoconstriction increased following removal of endothelium suggesting that agonist‐induced release of EDRF attenuates vasoconstrictor responses to noradrenaline measured in the presence of endothelium.
Removal of endothelium had less effect on noradrenaline‐induced vasoconstriction in old rats suggesting once again that agonist‐induced release of EDRF is impaired in old rats.
The noradrenaline dose‐response curve established in the presence of endothelium was shifted to the left in 22 month old rats.
In conclusion, aging in the rat appears to lead to a reduction in endothelial vasodilator function in a resistance vessel.
NMDA antagonists increase recovery of evoked potentials from slices of rat olfactory cortex after anoxia
Authors: Yassin Maged , Scholfield C.N. 
Published: July 2012

The role of glutamate in producing tissue damage during cerebral anoxia was investigated in brain slices using antagonists to the NMDA and AMPA receptor types.
Tissue function was assessed by field recordings of the synaptically evoked potentials elicited by stimulating the main afferent input to the olfactory cortex, the lateral olfactory tract. Anoxia was produced by bathing the slice in glucose‐free solution equilibrated with 95% N2/5% CO2.
The amount of recovery of the evoked potential was inversely dependent on the period of anoxia and temperature: at 24°C, 15 min of anoxia followed by reoxygenation produced a 14.6 ± 4.1% recovery whereas there was no recovery at 35°C.
Dizocilpine and ketamine had no effect on synaptic transmission in oxygenated media but following anoxia they produced an increased recovery of the responses: from 14.6 ± 4.1% to 48.3 ± 7.8% for dizocilpine (10 μm) and 21.6 ± 7.7% to 87.2 ± 7.1% for ketamine (200 μm); the tissue endurance to anoxia was increased by around 5 min.
Blockade of the AMPA receptors did not influence recovery in spite of the depressed synpatic transmission. A similar synaptic attenuation produced by lignocaine provided some increase in post‐anoxic recovery.
The NMDA receptor antagonist, AP5, antagonized NMDA at 50 μm by 3.7 fold and at 200 μm by 15 fold but only 200 μm increased post‐anoxic recovery. This suggests that a substantial degree of NMDA antagonist is required before anoxic tissue damage due to NMDA receptor activation can be nullified. The antagonist to the glycine binding site, 7‐chlorokynurenic acid also increased recovery.
These in vitro experiments confirm the idea that NMDA receptor activation makes a substantial contribution to cerebral tissue damage and that this can be reduced by a substantial blockade of these receptors.
Time‐dependent enhancement or inhibition of endotoxin‐induced vascular injury in rat intestine by nitric oxide synthase inhibitors
Authors: Laszlo F. , Whittle B.J.R. , Moncada S. 
Published: July 2012

The effects of the nitric oxide (NO) synthase inhibitors, NG‐nitro‐l‐arginine methyl ester (l‐NAME) and NG‐monomethyl‐l‐arginine (l‐NMMA), on the vascular damage induced by the endotoxin, E. coli lipopolysaccharide (LPS), in the ileum and colon were investigated in the conscious rat over a 5 h period.
Administration of LPS (3 mg kg−1, i.v.) increased ileal and colonic vascular injury after a lag period of 2 h, as determined by the leakage of radiolabeled albumin.
Administration of l‐NAME (1–5 mg kg−1, s.c.) concurrently with LPS, produced a dose‐dependent increase in vascular albumin leakage in the intestinal tissues, when determined over a 5h period. Vascular albumin leakage with LPS and l‐NAME (5 mg kg−1) was substantially increased after 1 h, reached maximal levels 3 h after administration, and then slowly declined.
l‐NMMA (50 mg kg−1, s.c.), likewise elevated intestinal albumin leakage when administered concurrently with LPS, but this reached maximal levels after 1 h and rapidly declined over the subsequent 2 h.
In control rats, in the absence of LPS challenge, neither l‐NAME (5 mg kg−1, s.c.) nor l‐NMMA (50 mg kg−1, s.c.) increased intestinal vascular leakage of albumin over a 5h period.
By contrast, when l‐NAME (1–5 mg kg−1, s.c.) or l‐NMMA (12.5–50 mg kg−1, s.c.) was injected 3 h after LPS, a dose‐dependent reduction in the LPS‐provoked vascular albumin leakage was observed.
Pretreatment with l‐arginine (300 mg kg−1, s.c.) 15 min prior to the NO synthase inhibitors, reversed either the potentiation or the inhibition by l‐NAME (5 mg kg−1, s.c.) or l‐NMMA (50 mg kg−1, s.c.) of the LPS‐induced intestinal vascular damage.
These findings indicate that initial suppression of the constitutive NO synthase by l‐NAME or l‐NMMA following challenge with LPS aggravates the acute vascular injury in the ileum and colon, suggesting a defensive role of NO. By contrast, the delayed administration of NO synthase inhibitors, at a time of known expression of the inducible NO synthase, provides protection against the subsequent damage to the intestinal vasculature.
Activation of chloride current by P2‐purinoceptors in rat ventricular myocytes
Authors: Kaneda M. , Fukui K. , Doi K. 
Published: July 2012

Rat ventricular myocytes were dissociated and their responses to extracellularly applied ATP were recorded using patch pipettes under the whole cell configuration.
ATP initially induced an inward current followed by an outward current at − 50 mV. With a Cs‐rich pipette solution the late outward current was blocked, leaving a sustained inward current (IATPs) suggesting that a K+conductance underlies the late response.
When the extracellular Cl−concentration was changed, the reversal potential of IATPs corresponded well to the shift of the Cl−equilibrium potential. IATPs was reversibly blocked by the chloride channel blocker, 4,4′‐diisothiocyanatostilbene‐2,2′‐disulphonic acid (DIDS).
The concentration‐response curve of IATPs had a Hill coefficient of 0.98 and an EC50 value of 5.2 × 10−6m.
ATP was more potent than ADP, while AMP and adenosine were ineffective, suggesting that P2‐purinoceptor activation induced IATPs.
The activation of IATPs was depressed by depleting the extracellular Mg2+and increased by adding Mg2+.
Our results strongly suggest that P2‐purinoceptor activation by ATP induces both a Cl−‐conductance (IATPs) and a K+‐conductance in rat ventricular myocytes.
Characterization and transduction mechanisms of purinoceptors in activated rat microglia
Authors: Langosch J.M. , Gebicke‐Haerter P.J. , Nörenberg W. , Illes P. 
Published: July 2012

Purinoceptor agonist‐induced currents in untreated (proliferating) and lipopolysaccharide‐ (LPS; 100 ng ml−1) treated (non‐proliferating) rat microglial cells were recorded by the whole‐cell patch‐clamp technique.
In non‐proliferating microglia, adenosine (0.01–100 μm), 2‐methylthio ATP (3–3000 nm), ATP (0.1–1000 μm), and ATP‐γ‐S (1–10 μm), but not α,β‐methylene ATP (α,β‐MeATP; 100 μm) produced a slow outward current at a holding potential of 0 mV. When K+ was replaced in the pipette solution by an equimolar concentration of Cs+ (150 mm), the 2‐methylthio ATP‐ (300 nm) induced outward current disappeared. The effect of 2‐methylthio ATP (300 nm) did not depend on the presence of extracellular Mg2+ (1 mm). The outward current response to 2‐methylthio ATP (300 nm) was larger in proliferating than in non‐proliferating microglia.
ATP (1–1000 μm) evoked a fast inward current at a holding potential of − 70 mV in non‐proliferating microglia, while adenosine (100–1000 μm) was inactive. When the effects of ATP were compared at 0 and − 70 mV, it became evident that ATP is much more potent in evoking the outward current.
The 2‐methylthio ATP‐ (300 nm) induced outward current was blocked by suramin (300 μm), but not by 8‐(p‐sulphophenyl)‐theophylline (100 μm), while the adenosine‐ (1 μm) induced outward current had the reverse sensitivity to these antagonists.
The 2‐methylthio ATP‐ (300 nm) induced outward current was inhibited by inclusion of GDP‐β‐S (200 μm) into the pipette solution or by preincubation of microglial cells with pertussis toxin (50 ng ml−1) for 12 h. The 2‐methylthio ATP‐ (300 μm) induced inward current was not changed by intracellular GDP‐β‐S (200 μm). The outward current response to adenosine (1 μm) was also abolished after pretreatment with pertussis toxin (50 ng ml−1).
Rat microglia possess both ATP‐sensitive P2Y‐ and adenosine‐sensitive P1‐purinoceptors. The ATP‐evoked inward current is mediated by P2Y‐purinoceptors, while the ATP‐ and adenosine‐evoked outward currents are mediated by P2Y‐ and P1‐purinoceptors, respectively. The transduction mechanisms of the outward, but not the inward current activation involve a pertussis toxin‐sensitive G protein.
Neuropeptide Y in rat detrusor and its effect on nerve‐mediated and acetylcholine‐evoked contractions
Authors: Iravani M.M. , Zar M.A. 
Published: July 2012

Immunohistochemical and isolated organ bath techniques were used to detect the presence of neuropeptide Y (NPY) in the rat urinary bladder and to determine its effect on tone, spontaneous activity and contractile responses of the detrusor muscle to electrical field stimulation, acetylcholine and α,β‐methylene ATP (α,β‐MeATP).
A very rich presence of NPY‐immunoreactive nerve fibres was found mainly within the bundles of detrusor muscle cells. Chronic treatment with 6‐hydroxydopamine did not affect the density of NPY‐positive nerve fibres.
NPY (> 1 nm) enhanced the force and frequency of spontaneous contractions and generated a rise in the resting tone of the detrusor. These effects of NPY on the tone and the spontaneous activity remained unaffected by atropine (3 μm), indomethacin (10 μm) and aspirin (100 μm) but were abolished by Ca2+‐withdrawal from the bathing medium.
The enhancing effects of NPY on the spontaneous contractions and the resting tone were not prevented by the induction of purinoceptor desensitization.
NPY (1–250 nm) potentiated electrical field stimulation (EFS, 1–64 Hz, 0.1 ms pulses duration, 10s train duration)‐evoked, tetrodotoxin (0.5 μm)‐sensitive contractions. The atropine (3 μm)‐resistant component of EFS‐evoked contractions was also potentiated by NPY. By contrast, the nifedipine (1 μm)‐resistant but atropine‐sensitive component of EFS‐evoked contraction was inhibited by NPY.
NPY (250 nm) did not affect acetylcholine‐evoked contractions, but potentiated α,β‐MeATP‐evoked contractions.
It is concluded that NPY‐innervation of rat urinary bladder is largely confined to the detrusor muscle and is abundant and mainly non‐adrenergic. It is further concluded that the enhancing effect of NPY on detrusor spontaneous activity and tone is caused by Ca2+ influx through nifedipine‐sensitive Ca2+ channels and is not mediated through acetylcholine or cyclo‐oxygenase‐sensitive eicosanoids or ATP.
The results are consistent with the hypothesis that intrinsic NPY in the rat detrusor innervation contributes to the motor transmission in two ways: by promoting non‐cholinergic motor transmission and by inhibiting prejunctionally the cholinergic transmission.
Characterization of the 5‐hydroxytryptamine receptor type involved in inhibition of spontaneous activity of human isolated colonic circular muscle
Authors: Tam F.S.‐F. , Hillier K. , Bunce K.T. 
Published: July 2012

Experiments were carried out to characterize pharmacologically the 5‐hydroxytryptamine (5‐HT) receptor types which mediate inhibition of spontaneous contractions of the intertaenial circular muscle in human isolated colon.
5‐HT caused a reproducible concentration‐dependent inhibition of spontaneous contractions of the circular muscle of human colon in vitro with a mean EC50 value of 0.2 μm and 95% confidence limits of 0.1–0.5 μm. No evidence for a contractile action of 5‐HT was found. Tetrodotoxin (TTX, 1.5 μm) caused a rightward shift of the concentration‐response curve of 5‐HT with a concentration‐ratio of 2.9.
The inhibitory response to 5‐HT was mimicked by several indoles with the rank order of potency 5‐HT > 5‐methoxytryptamine = α‐methyl‐5‐HT > 5‐carboxamidotryptamine >> 2‐methyl‐5‐HT. 5‐Hydroxyindalpine was inactive.
The substituted benzamides were agonists with the following rank order of potency, 5‐HT > renzapride > zacopride > metoclopramide > cisapride.
The inhibitory responses to 5‐HT were not inhibited by methysergide (10 μm) or methiothepin (1 μm), which are antagonists selective for 5‐HT1‐like and 5‐HT2 receptors, nor by ondansetron (10 μ) which is an antagonist at 5‐HT3 receptors.
The inhibitory responses induced by 5‐HT and 5‐methoxytryptamine were competitively antagonized by a weak 5‐HT4 receptor antagonist, tropisetron, with pKB values of approximately 6. Tropisetron had no significant effect on the inhibitory response curve produced by isoprenaline (0.01–100 μm).
The pharmacological profile of the 5‐HT‐evoked relaxations of human colon circular muscle are consistent with activation of a 5‐HT4‐like receptor.
A novel antagonist, phenylbenzene ω‐phosphono‐α‐amino acid, for strychnine‐sensitive glycine receptors in the rat spinal cord
Authors: Saitoh T. , Ishida M. , Maruyama M. , Shinozaki H. 
Published: July 2012

3‐[2′‐Phosphonomethyl[1,1′‐biphenyl]‐3‐yl]alanine (PMBA) is a novel glycine antagonist at strychnine‐sensitive receptors. The chemical structure of PMBA, possessing both a glycine moiety and a phosphono group, is quite different from that of strychnine.
In the spinal motoneurone of newborn rats, glycine (100 μm‐1 mM) induced depolarizing responses in a concentration‐dependent manner. PMBA effectively inhibited depolarizing responses to glycine and other agonists, such as taurine and β‐alanine. The dose‐response curves for glycine were shifted to the right in an almost parallel manner (pA2 value: 5.30 ± 0.23, n = 5) by PMBA which was about 60 times less potent than strychnine (pA2 value: 7.08 ± 0.21, n = 5) as a glycine antagonist.
PMBA (1 − 100 μm) did not interact with modulatory glycine sites on N‐methyl‐D‐aspartate (NMDA) receptors, which suggests a high selectivity of PMBA for strychnine‐sensitive glycine receptors. At considerably high concentrations (0.1 mM‐1 mM), PMBA depressed responses to GABA (pA2 value: 3.57 ± 0.24, n = 3).
PMBA inhibited the binding of [3H]‐strychnine to synaptosomes from adult rat spinal cords; the IC50 values of PMBA, glycine and strychnine were 8 ± 2, 9 ± 3 and 0.08 ± 0.04 μm, respectively (n = 5) for [3H]‐strychnine (4.8 nM).
PMBA is a central excitant drug with relatively high potency and selectivity and should be useful as a pharmacological probe for analysing the mechanisms underlying physiological functions of glycine receptors.
Sensitization by dexamethasone of lymphocyte cyclic AMP formation: evidence for increased function of the adenylyl cyclase catalyst
Authors: Michel Martin C. , Knapp Jörg , Ratjen Hanna 
Published: July 2012

Glucocorticoids and elevations of intracellular adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) may affect lymphocyte activation, proliferation and effector functions in similar ways. Therefore, we have investigated the effects of the glucorticoid, dexamethasone, on human lymphocyte cyclic AMP formation.
Treatment of resting human lymphocytes with the glucocorticoid, dexamethasone, sensitized prostaglandin E2‐stimulated cyclic AMP accumulation in a time‐ and concentration‐dependent manner.
In membranes of lymphocytes treated for 24 h with 100 nm dexamethasone, maximal adenylyl cyclase activity stimulated by prostaglandin E2, isoprenaline, guanosine 5′‐triphosphate (GTP), forskolin and MnCl2 was significantly enhanced; the EC50 for these agents was not significantly altered.
β2‐Adrenoceptor density, immunodetectable α‐subunits of the G‐proteins Gs and Gi, and pertussis toxin‐substrates were not significantly altered by dexamethasone treatment.
In dexamethasone‐treated lymphocytes, prostaglandin E2‐mediated inhibition of concanavalin A‐induced Ca2+ elevations was doubled compared to control cells.
Based on these data and the observation that enhancement of forskolin‐ and MnCl2‐stimulated adenylyl cyclase activity could quantitatively account for the enhancement of prostaglandin E2‐, isoprenaline‐ or GTP‐stimulated adenylyl cyclase activity, we conclude that dexamethasone treatment sensitizes cyclic AMP formation in resting human lymphocytes by altering the adenylyl cyclase catalyst rather than G‐proteins or hormone receptors. This results in an enhanced capability of cyclic AMP generating agonists to inhibit early steps of lymphocyte activation.