bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of KATP channels in intact mammalian skeletal muscle fibres
Authors: Barrett‐Jolley Richard , McPherson Grant A. 
Published: January 2005

The aim of this study was to characterize the KATP channel of intact rat skeletal muscle (rat flexor digitorum brevis muscle). Changes in membrane currents were recorded with two‐electrode voltage‐clamp of whole fibres.
The KATP channel openers, levcromakalim and pinacidil (10–400 μM), caused a concentration‐dependent increase in whole‐cell chord conductance (up to approximately 1.5 mScm−2). The activated current had a weak inwardly rectifying current‐voltage relation, a reversal potential near EK and nanomolar sensitivity to glibenclamide – characteristic of a KATP channel current. Concentration‐effect analysis revealed that levcromakalim and pinacidil were not particularly potent (EC50 ∼186 μM, ∼30 μM, respectively), but diazoxide was completely inactive.
The ability of both classical KATP channel inhibitors (glibenclamide, tolbutamide, glipizide and 5‐hydroxydecanoic acid) and a number of structurally related glibenclamide analogues to antagonize the levcromakalim‐induced current was determined. Glibenclamide was the most potent compound with an IC50 of approximately 5 nM. However, the non‐sulphonylurea (but cardioactive) compound 5‐hydroxydecanoic acid was inactive in this preparation.
Regression analysis showed that the glibenclamide analogues used have a similar rank order of potency to that observed previously in vascular smooth muscle and cerebral tissue. However, two compounds (glipizide and DK13) were found to have unexpectedly low potency in skeletal muscle.
These experiments revealed KATP channels of skeletal muscle to be at least 10× more sensitive to glibenclamide than previously found; this may be because of the requirement for an intact intracellular environment for the full effect of sulphonylureas to be realised. Pharmacologically, KATP channels of mammalian skeletal muscle appear to resemble most closely KATP channels of cardiac myocytes.

British Journal of Pharmacology (1998) 123, 1103–1110; doi:10.1038/sj.bjp.0701727
Comparison of anaesthetic and non‐anaesthetic effects on depolarization‐evoked glutamate and GABA release from mouse cerebrocortical slices
Authors: Liachenko Serguei , Tang Pei , Somogyi George T. , Xu Yan 
Published: January 2005

Investigation with substances that are similar in structure, but different in anaesthetic properties, may lead to further understanding of the mechanisms of general anaesthesia.
We have studied the effects of two cyclobutane derivatives, the anaesthetic, 1‐chloro‐1,2,2‐trifluorocyclobutane (F3), and the non‐anaesthetic, 1,2‐dichlorohexafluorocyclobutane (F6), on K+‐evoked glutamate and γ‐aminobutyric acid (GABA) release from isolated, superfused, cerebrocortical slices from mice, by use of h.p.l.c. with fluorescence detection for quantitative analysis.
At clinically relevant concentrations, the anaesthetic, F3, inhibited 40 mM K+‐evoked glutamate and GABA release by 72% and 47%, respectively, whereas the structurally similar non‐anaesthetic, F6, suppressed evoked glutamate release by 70% but had no significant effects on evoked GABA release. A second exposure to 40 mM KCl after a ∼30 min washout of F3 or F6 showed recovery of K+‐evoked release, suggesting that F3 and F6 did not cause any non‐specific or irreversible changes in the brain slices.
Our findings suggest that suppression of excitatory neurotransmitter release may not be directly relevant to the primary action of general anaesthetics. A mechanism involving inhibitory postsynaptic action is implicated, in which a moderate suppression of depolarization‐evoked GABA release by the anaesthetic may be consistent with the enhancement of postsynaptic GABAergic activities.

British Journal of Pharmacology (1998) 123, 1274–1280; doi:10.1038/sj.bjp.0701728
Evidence that inducible nitric oxide synthase is involved in LPS‐induced plasma leakage in rat skin through the activation of nuclear factor‐κB
Authors: Iuvone Teresa , D'Acquisto Fulvio , Van Osselaer Nancy , Di Rosa Massimo , Carnuccio Rosa , Herman Arnold G. 
Published: January 2005

Rats challenged with lipopolysaccharide (LPS) produce large amounts of nitric oxide (NO) following the induction of the inducible NO‐synthase (iNOS) in several tissues and organs. Recent studies have shown that the expression of iNOS is regulated at the transcriptional level by a transcription nuclear factor‐κB (NF‐κB). In this study we investigated the role of NO in a model of LPS‐induced plasma‐leakage in rat skin and the involvement of NF‐κB.
Plasma leakage in the rat skin was measured over a period of 30 min to 2 h as the local accumulation of intravenous (i.v.) injection of [125I]‐human serum albumin ([125I]‐HSA) in response to intradermal (i.d.) injection of LPS. LPS (1, 10, 100 μg/site) produced a dose‐related increase in plasma extravasation (18.2±3.2, 27.2±2.9, 40.4±9.6 μl/site) as compared to saline control (11.4±2.2 μl/site). This increase was maximal after 2 h; therefore this time point and the dose of LPS 10 μg/site was used in all the successive experiments.
To investigate the role of NO in LPS‐induced plasma leakage in rat skin, the non‐selective NOS inhibitor NGnitro‐l‐arginine‐methyl ester (l‐NAME) or the more selective iNOS inhibitor S‐methyl‐isothiourea (SMT) was injected i.d. with LPS. l‐NAME and SMT (0.01, 0.1 and 1 μmol/site) inhibited LPS‐induced plasma leakage in a dose‐related fashion (l‐NAME: 26.0±5.5, 20.2±1.6, 18.0±2.0 μl/site; SMT: 19.5±1.5, 17.0±1.6, 15.0±2.6 μl/site) as compared to LPS alone (27.2±2.9 μl/site). At the lowest concentration used (0.01 μmol/site), SMT significantly reduced plasma leakage by 30%±0.7 while l‐NAME (0.01 μmol/site) was not effective.
Treatment with increasing concentrations of pyrrolidinedithyocarbamate (PDTC) (0.01, 0.1, 1 μmol/site), an inhibitor of NF‐κB activation, injected i.d. 30 min before LPS challenge, inhibited in a concentration‐dependent fashion LPS‐induced plasma leakage by 9.0±0.6, 33±4.0, 51±2.0% respectively. Moreover, PDTC (0.1, 1 μmol/site) suppressed LPS‐induced NF‐κB DNA‐binding.
Western blot analysis showed significant levels of iNOS proteins in the skin samples of LPS‐treated rats, as compared to basal levels present in saline‐injected rat skin. PDTC (0.1, 1.0 μmol/site) dose‐dependently decreased the amount of iNOS protein expression induced by LPS.
Our results indicate that LPS‐induced plasma leakage in rat skin is modulated by NO mainly produced by the inducible isoform of NOS. Furthermore, the suppression of plasma leakage by PDTC, an inhibitor of NF‐κB activation, is correlated to the inhibition of iNOS protein expression.

British Journal of Pharmacology (1998) 123, 1325–1330; doi:10.1038/sj.bjp.0701730
Quantification and distribution of α1‐adrenoceptor subtype mRNAs in human proximal urethra
Authors: Nasu Kimio , Moriyama Nobuo , Fukasawa Ritsu , Tsujimoto Gozoh , Tanaka Teruo , Yano Junichi , Kawabe Kazuki 
Published: January 2005

We performed RNase protection assays and in situ hybridization to investigate the ratio of the three α1‐adrenoceptor subtype mRNAs, α1a, α1b and α1d, in human proximal urethra, and their localization in urethral cross‐sections. As revealed by the RNase protection assays, α1a was the predominant subtype mRNA in both male and female urethral samples. α1d mRNA was detected only in the female sample, and α1b mRNA was not detected in any of the samples tested. The ratio of the abundance of the subtype mRNAs, α1a : α1b : α1d, was 100 : 0 : 0 in the male urethra and 90 : 0 : 10 in the female urethra.
In situ hybridization studies showed no significant differences in the cross‐sectional distribution of α1‐adrenoceptor subtype mRNAs between male and female urethras. Intense α1a staining was observed in the smooth muscle of the urethra, but α1b and α1d staining was much less intense.
Of the three cloned α1 subtypes, α1a is the most likely to be responsible for the contraction of the human urethra. Owing to the side effects of nonselective α1 drugs, α1‐selective drugs may be clinically superior to nonselective drugs for the treatment of urethral disorders.

British Journal of Pharmacology (1998) 123, 1289–1293; doi:10.1038/sj.bjp.0701731
ATP stimulation of Ca2+‐dependent plasminogen release from cultured microglia
Authors: Inoue Kazuhide , Nakajima Kazuyuki , Morimoto Takako , Kikuchi Yoshiaki , Koizumi Schuichi , Illes Peter , Kohsaka Shinichi 
Published: January 2005

ATP (10–100 μm), but not glutamate (100 μm), stimulated the release of plasminogen from microglia in a concentration‐dependent manner during a 10 min stimulation. However, neither ATP (100 μm) nor glutamate (100 μm) stimulated the release of NO. A one hour pretreatment with BAPTA‐AM (200 μm), which is metabolized in the cytosol to BAPTA (an intracellular Ca2+ chelator), completely inhibited the plasminogen release evoked by ATP (100 μm). The Ca2+ ionophore A23187 induced plasminogen release in a concentration‐dependent manner (0.3 μm to 10 μm).
ATP induced a transient increase in the intracellular calcium concentration ([Ca2+]i) in a concentration‐dependent manner which was very similar to the ATP‐evoked plasminogen release, whereas glutamate (100 μm) had no effect on [Ca2+]i (70 out of 70 cells) in microglial cells. A second application of ATP (100 μm) stimulated an increase in [Ca2+]i similar to that of the first application (21 out of 21 cells).
The ATP‐evoked increase in [Ca2+]i was totally dependent on extracellular Ca2+, 2‐Methylthio ATP was active (7 out of 7 cells), but α,β‐methylene ATP was inactive (7 out of 7 cells) at inducing an increase in [Ca2+]i. Suramin (100 μm) was shown not to inhibit the ATP‐evoked increase in [Ca2+]i (20 out of 20 cells). 2′‐ and 3′‐O‐(4‐Benzoylbenzoyl)‐adenosine 5′‐triphosphate (BzATP), a selective agonist of P2X7 receptors, evoked a long‐lasting increase in [Ca2+]i even at 1 μm, a concentration at which ATP did not evoke the increase. One hour pretreatment with adenosine 5′‐triphosphate‐2′, 3′‐dialdehyde (oxidized ATP, 100 μm), a selective antagonist of P2X7 receptors, blocked the increase in [Ca2+]i induced by ATP (10 and 100 μm).
These data suggest that ATP may transit information from neurones to microglia, resulting in an increase in [Ca2+]i via the ionotropic P2X7 receptor which stimulates the release of plasminogen from the microglia.

British Journal of Pharmacology (1998) 123, 1304–1310; doi:10.1038/sj.bjp.0701732
Desensitization and resensitization of δ‐opioid receptor‐mediated Ca2+ channel inhibition in NG108‐15 cells
Authors: Morikawa Hitoshi , Fukuda Kazuhiko , Mima Hiroyuki , Shoda Takehiro , Kato Shigehisa , Mori Kenjiro 
Published: January 2005

To approach the mechanisms underlying desensitization of the opioid receptor‐mediated Ca2+ channel inhibition, the effects of prolonged application of [D‐Ala2, D‐Leu5]enkephalin (DADLE) on Ba2+ currents (IBa) through Ca2+ channels were analysed in NG108‐15 neuroblastoma × glioma hybrid cells.
Inhibition of IBa by 100 nM DADLE desensitized by 57% with a time constant of 4.4 min.
Maximal desensitization of the δ‐opioid receptor‐Ca2+ channel coupling was attained by 1 μM DADLE. The EC50 value for desensitization was estimated to be 78 nM.
RNA blot hybridization analysis and immunoblot analysis revealed the expression of β‐adrenoceptor kinase‐1 (βARK1) in NG108‐15 cells.
Heparin, an inhibitor of βARK, significantly reduced the magnitude and rate of desensitization, whereas Rp‐cyclic AMPS and PKI (14‐24)amide, inhibitors of cyclic AMP‐dependent protein kinase (PKA), or long‐term treatment with phorbol 12‐myristate 13‐acetate to induce down‐regulation of protein kinase C (PKC) had no significant effect.
Recovery from desensitization (resensitization) proceeded with a time constant of 6.7 min. Okadaic acid, an inhibitor of serine/threonine phosphatases 1 and 2A, significantly attenuated the degree of resensitization.
In summary, we have characterized the time course and concentration‐dependence of the desensitization of DADLE‐induced IBa inhibition in NG108‐15 cells. This desensitization was reversible after removal of DADLE. It is suggested that βARK, but neither PKA nor PKC, is involved in desensitization, while serine/threonine phosphatases mediate resensitization.

British Journal of Pharmacology (1998) 123, 1111–1118; doi:10.1038/sj.bjp.0701733
Heterogeneity and underlying mechanism for inotropic action of endothelin‐1 in rat ventricular myocytes
Authors: Katoh Hideki , Terada Hajime , Iimuro Masaru , Sugiyama Shiho , Qing Ke , Satoh Hiroshi , Hayashi Hideharu 
Published: January 2005

To clarify the mechanisms underlying the positive inotropic action of endothelin‐1 (ET‐1), we investigated the effect of ET‐1 on twitch cell shortening and the Ca2+ transient in rat isolated ventricular myocytes loaded with a fluorescent Ca2+ indicator indo‐1.
There was a cell‐to‐cell heterogeneity in response to ET‐1. ET‐1 (100 nm) increased twitch cell shortening in only 6 of 14 cells (44 %) and the increase in twitch cell shortening was always accompanied by an increase in the amplitude of the Ca2+ transient.
The ETA‐ and ETB‐receptors antagonist TAK‐044 (100 nm) almost reversed both the ET‐1‐induced increases in twitch cell shortening and in the Ca2+ transient. In the ET‐1 non‐responding cells, the amplitude of the Ca2+ transient never increased.
Intracellular pH slightly increased (∼0.08 unit) after 30 min perfusion of ET‐1 in rat ventricular myocytes. However, ET‐1 did not change the myofilament responsiveness to Ca2+, which was assessed by (1) the relationship between the Ca2+ transient amplitude and twitch cell shortening, and by (2) the Ca2+ transient‐cell shortening phase plane diagram during negative staircase.
We concluded that there was a cell‐to‐cell heterogeneity in the positive inotropic effect of ET‐1, and that the ET‐receptor‐mediated positive inotropic effect was mainly due to an increase in the Ca2+ transient amplitude rather than to an increase in myofilament responsiveness to Ca2+.

British Journal of Pharmacology (1998) 123, 1343–1350; doi:10.1038/sj.bjp.0701743
Differential responses of pulmonary arteries and veins to histamine and 5‐HT in lung explants of guinea‐pigs
Authors: Shi Weibin , Wang Chong‐Gang , Dandurand Ron J. , Eidelman David H. , Michel René P. 
Published: January 2005

The mechanisms by which histamine and 5‐HT differentially contract pulmonary arteries and veins are unclear. In lung explants from 26 guinea‐pigs, we compared responses of pulmonary arteries and vein to histamine, 5‐HT and KCl, and examined potential determinants for the differential responses. Lungs were filled with agarose, sectioned into ∼1 mm thick slices, and vascular luminal areas measured by image analysis.
Histamine and 5‐HT produced a concentration‐dependent constriction in arteries and veins, greater in the latter. KCl constricted arteries and veins equally.
The histamine H1 antagonist chlorpheniramine (10−4 M) abolished contractions to histamine; the H2 antagonist cimetidine enhanced maximal responses and sensitivity of arteries and veins to histamine, and diminished the differences between their maximal responses; the NO synthase inhibitor Nω‐nitro‐L‐arginine (L‐NOARG) increased the maximal responses of arteries and veins, and the differences between their responses; indomethacin had no effect.
Contractions to 5‐HT were abolished in arteries and markedly reduced in veins by the 5‐HT2 antagonist ketanserin (10−4 M); L‐NOARG potentiated the maximal responses of arteries but not of veins; indomethacin increased the maximal responses of arteries but reduced them in veins.
By morphometry, arteries had a greater medial thickness and luminal diameter than veins.
The data suggest that in guinea‐pigs, H2 receptors are responsible for the differential contractile responses of pulmonary arteries and veins to histamine, whereas endothelium‐derived vasoactive substances are responsible for their differential contractile responses to 5‐HT.

British Journal of Pharmacology (1998) 123, 1525–1532; doi:10.1038/sj.bjp.0701759
Enhanced involvement of endothelin in the haemodynamic sequelae of endotoxaemia in conscious, hypertensive, transgenic ((mRen‐2)27) rats
Authors: Gardiner S. M. , Kemp P. A. , March J. E. , Bennett T. 
Published: January 2005

Age‐matched (3–4 months old) male, heterozygous, hypertensive, transgenic ((mRen‐2)27) rats (abbreviated to TG rats) and the normotensive control animals (homozygous, Hannover Sprague‐Dawley rats (abbreviated to SD rats), were chronically instrumented for the assessment of regional haemodynamic responses to continuous lipopolysaccharide (LPS) infusion (150 μg kg−1 h−1, i.v.)
The early (1–2 h) hypotension in SD rats (−11±3 mmHg; n=7) was significantly less than that in TG rats (−35±3 mmHg; n=8), but by 24 h mean arterial blood pressure (MAP) in both strains of rat was not different from the pre‐LPS value (SD rats: baseline, 108±3 mmHg; 24 h LPS, 112±4 mmHg; TG rats: baseline, 171±2 mmHg; 24 h LPS, 169±3 mmHg). At this stage in the SD rats there was a renal vasodilatation (Δ vascular conductance, 29±10 [kHz mmHg−1]103) but not in TG rats (Δ vascular conductance 2±3[kHz mmHg−1]103).
Co‐infusion of LPS and the non‐selective endothelin receptor antagonist, SB 209670 (600 μg kg−1 bolus, 600 μg kg−1 h−1) between 24 and 31 h in SD rats caused a fall in MAP of 16±2 mmHg accompanied by hindquarters vasodilatation (Δ vascular conductance 11±3 (kHz mmHg−1)103). In TG rats, under the same conditions, the fall in MAP was −60±6 mmHg, and there were renal, mesenteric and hindquarters vasodilatations (Δ vascular conductance, 23±5, 32±7, and 14±4 (kHz mmHg−1)103, respectively). All effects, except the hindquarters vasodilatation, were greater in TG than in SD rats.
In TG rats infused with LPS alone for 31 h, between 24 and 31 h the fall in MAP was −17±4 mmHg, and the changes in renal, mesenteric and hindquarters vascular conductances were 5±3, −4±5, and 12±4 (kHz mmHg−1)103, respectively.
Administration of the angiotensin (AT1)‐receptor antagonist, losartan (10 mg kg−1, i.v.) following co‐infusion of LPS and SB 209670 between 24 and 31 h caused similar falls in MAP in SD and TG rats (−12±3 and −14±4 mmHg, respectively).
These results, together with previous findings, are consistent with a relative enhancement of the contribution of endothelin to the maintenance of cardiovascular status in endotoxaemic TG rats, particularly through a mesenteric vasoconstrictor action.

British Journal of Pharmacology (1998) 123, 1403–1408; doi:10.1038/sj.bjp.0701762
Two imidazoquinoxaline ligands for the benzodiazepine site sharing a second low affinity site on rat GABAA receptors but with the opposite functionality
Authors: Im Haesook K. , Bin Im Wha , Pregenzer Jeffrey F. , Stratman Nancy C. , VonVoigtlander Philip F. , Jon Jacobsen E. 
Published: January 2005

Imidazoquinoxaline PNU‐97775 and imidazoquinoline PNU‐101017 are benzodiazepine site ligands with a second low affinity binding site on GABAA receptors, the occupancy of which at high drug concentrations reverses their positive allosteric activity via the benzodiazepine site, and may potentially minimize abuse liability and physical dependence.
In this study we discovered, with two imidazoquinoxaline analogues, that the functionality of the second site was altered by the nitrogen substituent on the piperazine ring moiety: PNU‐100076 with a hydrogen substituent on the position produced a negative allosteric effect via the second low affinity site, like the parent compounds, while PNU‐100079 with a trifluoroethyl substituent produced a positive allosteric response.
These functional characteristics were monitored with Cl− currents measurements in cloned rat αxβ2γ2 subtypes of GABAA receptors expressed in human embryonic kidney 293 cells, and further confirmed in rat cerebrocortical membranes containing complex subtypes of GABAA receptors with binding of [35S]‐TBPS, which is a high affinity ligand specific for GABAA receptors with exquisite sensitivity to allosteric modulations.
This structure‐functional relationship could be exploited to further our understanding of the second allosteric site of imidazoquinoxaline analogues, and to develop more effective benzodiazepine site ligands without typical side effects associated with those currently available on the market.

British Journal of Pharmacology (1998) 123, 1490–1494; doi:10.1038/sj.bjp.0701763
Age and region‐dependent contraction to α‐adrenoceptor agonists in rat and guinea‐pig isolated trachea
Authors: Preuss Janet M. H. , Rigby Paul J. , Goldie Roy G. 
Published: January 2005

The influence of age and of region on α‐adrenoceptor‐mediated contraction to (−)‐adrenaline and (−)‐noradrenaline was examined in rat (4–136 weeks) and guinea‐pig (2–156 weeks) isolated tracheal ring preparations with particular emphasis on the early (up to 12 weeks) maturation phase.
In rat tracheal rings, significant regional variation was observed with respect to maximal (−)‐adrenaline‐induced contraction, such that the greatest activity was seen in ring preparations from the laryngeal end of the trachea. Tracheal rings from the carinal end responded very poorly or were unresponsive to (−)‐adrenaline, depending on animal age. These regional differences were seen across the age range. The potencies of (−)‐adrenaline and (−)‐noradrenaline remained unchanged with respect to animal age, but the maximum contractile tension that developed in response to these agonists increased with increasing animal age in all regions of the trachea.
In guinea‐pig isolated tracheal tissue, maximum contractile responses (Emax) to (−)‐adrenaline and (−)‐noradrenaline remained unchanged with increasing animal age. In addition, there was no evidence for a region‐dependence in the responsiveness of tracheal tissue to α‐adrenoceptor‐mediated contraction in this species.
In both guinea‐pig and rat isolated tracheal tissue, α‐adrenoceptor‐mediated contraction appeared to involve the activation of α1‐adrenoceptors.

British Journal of Pharmacology (1998) 123, 1541–1548; doi:10.1038/sj.bjp.0701765
PYY‐preferring receptor in the dorsal vagal complex and its involvement in PYY stimulation of gastric acid secretion in rats
Authors: Yang H. , Li W. P. , Reeve J. R. , Rivier J. , Taché Y. 
Published: January 2005

Microinjection of peptide YY (PYY, 7–46 pmol) into the dorsal vagal complex (DVC) stimulated gastric acid secretion in urethane‐anaesthetized rats. Using a variety of neuropeptide Y (NPY) and PYY derivatives, we characterized the pharmacological profile of the receptor mediating the acid secretory response to PYY.
[Pro34]rat(r)/porcine(p)PYY and [Pro34]human(h)PYY (23–117 pmol), microinjected unilaterally into the DVC resulted in a similar maximal increase in net acid secretion reaching 68±11 and 89±31 μmol 90 min−1 respectively.
Rat/hNPY and pNPY (47 pmol) microinjected into the DVC induced a similar net gastric acid secretion (27±8 and 23±8 μmol 90 min−1 respectively) and a higher dose (116 pmol) tended to reduce the response.
Pancreatic polypeptide (PP, 4–46 pmol), [Leu31,Pro34]r/hNPY (47 and 117 pmol) and the Y2 selective agonists, hPYY3‐36, pNPY5‐36 and pNPY13‐36 (25–168 pmol) microinjected into the DVC failed to influence basal gastric acid secretion.
The rank order of potency of PYY[Pro34]r/pPYY=[Pro34]hPYY>r/hNPY=pNPY to stimulate gastric acid secretion upon injection into the DVC and the ineffectiveness of PP, [Leu31,Pro34]NPY and C‐terminal NPY/PYY fragments suggest that a PYY‐preferring receptor subtype may be involved in mediating the stimulating effect.

British Journal of Pharmacology (1998) 123, 1549–1554; doi:10.1038/sj.bjp.0701767