bluuebunny/crossref_metadata_2025_split huggingface dataset:
Actions of general anaesthetics on a neuronal nicotinic acetylcholine receptor in isolated identified neurones of Lymnaea stagnalis
Authors: McKenzie D. , Franks N.P. , Lieb W.R. 
Published: July 2012

Completely isolated identified neurones from the right parietal ganglion of the pond snail Lymnaea stagnalis were studied under two‐electrode voltage‐clamp. Neuronal nicotinic acetylcholine receptor currents were studied at low acetylcholine (ACh) concentrations (≤ 200 nM). At these levels, control currents were non‐desensitizing and proportional to the square of the ACh concentration.
IC50 concentrations were determined for the steady‐state inhibition of the ACh‐activated current by 31 general anaesthetics plus the non‐anaesthetic alcohol n‐tridecanol. The general anaesthetics included inhalational agents, n‐alcohols, n‐alkane‐(α,ω)‐diols, cycloalcohols and an n‐alkane.
Anaesthetic inhibition was independent of voltage and consistent with two anaesthetic‐binding sites on the receptor.
IC50 concentrations for inhibiting the neuronal nicotinic ACh receptor correlated well (r = 0.97) with EC50 concentrations for general anaesthesia. The maximum deviation from the line of identity was less than fourfold. The inhalational agents tended to be more potent as inhibitors of the ACh receptor than as general anaesthetics, while the alcohols and diols were less potent.
The inhibition of the ACh‐induced current by the homologous series of n‐alcohols exhibited a cutoff at the same position (just after dodecanol) as found for the induction of general anaesthesia in tadpoles.
Polarity profile maps of the anaesthetic‐binding sites on the neuronal nicotinic ACh receptor were calculated from IC50 concentrations for the homologous series of n‐alcohols and n‐alkane‐(α,ω)‐diols. They reveal amphiphilic sites with apolar regions capable of accommodating the hydrocarbon chains of n‐alcohols as large as decanol. A striking resemblance was found to profiles previously calculated from data for tadpole general anaesthesia.
Quinidine‐induced open channel block of K+ current in rat ventricle
Authors: Clark R.B. , Sanchez‐Chapula J. , Salinas‐Stefanon E. , Duff H.J. , Giles W.R. 
Published: July 2012

The effects of quinidine on calcium‐independent outward K+ currents in rat ventricular myocytes were studied using whole‐cell patch clamp techniques.
Quinidine sulphate (6 μm) significantly prolonged repolarization of the ventricular action potential. This effect was larger during early repolarization (25% level) than at later times (90% level).
Quinidine reduced the amplitude of a transient outward current, and accelerated its rate of decay by approximately 4 fold at membrane potentials between 0 to +50mV. Quinidine also reduced the amplitude of a slowly inactivating, tetraethylammonium‐sensitive ‘pedestal’ component of the outward current.
The quinidine‐induced block of the transient outward current was dependent on time and membrane potential. Maximal block occurred with depolarizations of about 100 ms duration, and longer depolarizations (up to 1.5 s) produced little additional block. The membrane potential dependence of quinidine‐induced block was very similar to the membrane potential dependence of activation of the transient outward current. The membrane potential dependence of steady‐state inactivation of the transient outward current was not significantly affected by quinidine.
These results show that quinidine blocks outward K+ currents in rat ventricular cells. The time and potential dependence of this block suggests that quinidine blocks the transient outward K+ current by acting primarily on the open state of these channels.
Effect of nitric oxide on integrity, blood flow and cyclic GMP levels in the rat gastric mucosa: modulation by sialoadenectomy
Authors: Tripp M.A. , Tepperman B.L. 
Published: July 2012

The effects of the nitrosothiol, S‐nitroso N‐acetylpenicillamine (SNAP) which liberates nitric oxide (NO), on ethanol‐mediated gastric damage, blood flow and cyclic GMP levels in siaoloadenectomized (SALX) rats have been investigated.
Intraluminal instillation of ethanol (5–50% w/v) dose‐dependently induced haemorrhagic damage and decreased NO synthase activity in the gastric mucosa. Both the extent of mucosal damage and inhibition of NO synthase activity were exacerbated in SALX rats.
Epidermal growth factor administration (5 and 10 μg kg−1, s.c.) reduced mucosal damage but did not restore NO synthase activity in ethanol‐treated SALX rats.
SNAP infusion (0.01‐1.0 μg kg−1 min−1, i.v.) attenuated haemorrhagic damage in ethanol‐treated rats. The reduction in mucosal damage was significantly greater in SALX rats.
SNAP administration also caused an increase in gastric mucosal blood flow and cyclic GMP levels in control rats and both responses were augmented in SALX animals.
These data suggest that SALX is associated with increases in mucosal susceptibility to ethanol‐mediated damage and reduces mucosal NO synthase activity. Epidermal growth factor does not appear to influence mucosal NO synthase in ethanol‐treated rats. Furthermore, SALX augments the responsiveness of the gastric mucosa to NO administration. Therefore, factors from the salivary glands influence gastric NO formation and mucosal responsiveness to a NO donor.
Pharmacological activity of the C‐terminal and N‐terminal domains of secretory leukoprotease inhibitor in vitro
Authors: Masuda Kenichi , Kamimura Takashi , Watanabe Kunihito , Suga Tetsuya , Kanesaki Masaharu , Takeuchi Akiko , Imaizumi Atsushi , Suzuki Yoji 
Published: July 2012

In order to characterize the physiological functions of the domain structure of secretory leukoprotease inhibitor (SLPI), the biological capacities of half‐length SLPIs, (Serl‐Pro54)SLPI and (Asn55‐Ala107)SLPI, were investigated and compared with those of full‐length SLPI.
The activities of these inhibitors against several serine proteases were determined using synthetic chromogenic substrates. The inhibitory capacity of the C‐terminal domain, (Asn55‐Ala107)SLPI, was as strong as that of full‐length SLPI against human neutrophil elastase (NE), cathepsin G and chymotrypsin. It possessed less trypsin inhibitory activity than intact SLPI. For the N‐terminal domain of SLPI, (Serl‐Pro54)SLPI, no inhibitory activity could be detected against the serine proteases tested in this study.
The inhibitory activity of (Asn55‐Ala107)SLPI against the proteolysis of the natural substrates elastin and collagen by NE was comparable with that of full‐SLPI (elastin, IC50 = 907±31 nM for SLPI, 767±33nM for (Asn55‐Ala107)SLPI; collagen, IC50 = 862 ± 36 nM for SLPI, 727 ±47 nM for (Asn55‐Ala107)SLPI).
The binding affinities of full‐ and half‐length SLPIs for heparin were measured by affinity column chromatography. Full‐length SLPI showed high affinity for heparin while the binding capacities of both half‐length SLPIs were lower. (Concentration of NaCl for elution, 0.45 m for SLPI, 0.24 m for (Serl‐Pro54)SLPI, 0.27 m for (Asn55‐Ala107)SLPI).
The effects of full‐SLPI and (Asn55‐Ala107)SLPI on blood coagulation were measured using the activated partial thromboplastin time (APTT). Full‐length SLPI prolonged clotting time dose‐dependently (1.25, 2.5 and 5.0 um), whereas (Asn55‐Ala107)SLPI had no effect even at the highest concentration.
In conclusion, the C‐terminal domain of SLPI is a promising candidate for the treatment of inflammatory diseases in which participation of neutrophil proteases has been suggested.
A novel receptor for diadenosine polyphosphates coupled to calcium increase in rat midbrain synaptosomes
Authors: Pintor Jesús , Miras‐Portugal M. Teresa 
Published: July 2012

Diadenosine polyphosphates, AP4A and Ap5A, as well as ATP, α,β‐MeATP and ADP‐β‐S, were able to elicit variable intrasynaptosomal Ca2+ increases in rat midbrain synaptic terminals. The origin of the Ca2+ increment was the extrasynaptosomal space since the elimination of extracellular Ca2+ abolished the effect of all the agonists.
The P2‐purinoceptor antagonist, suramin, did not affect the Ca2+–increase evoked by diadenosine polyphosphates but dramatically blocked the Ca2+ entry induced by ATP and its synthetic analogues.
The actions of Ap5A and ATP on the intrasynaptosomal Ca2+ increase did not cross‐desensitize.
Concentration‐response studies for diadenosine polyphosphates showed pD2 values of 54.5 ±4.2 μm and 55.6 ±3.8 μm for AP4A and Ap5A, respectively.
The entry of calcium induced by diadenosine polyphosphates could be separated into two components. The first represented a selective voltage‐independent Ca2+ entry; the second, a sustained phase which was voltage‐dependent.
Studies on the voltage‐dependent Ca2+–channels involved in the effects of the diadenosine polyphosphates, demonstrated that Ω‐conotoxin G‐VI‐A inhibited the sustained Ca2+–entry, suggesting the participation of an N‐type Ca2+–channel. This toxin was unable to abolish the initial cation entry induced by AP4A or Ap5A. Ω‐Agatoxin IV‐A, tetrodotoxin, or nifedipine did not inhibit the effects of the diadenosine polyphosphates.
The effect of ATP on Ca2+–entry was abolished by nifedipine and Ω‐conotoxin G‐VI‐A, suggesting the participation of L‐ and N‐type Ca2+–channels in the response to ATP. 8 These data suggest that AP4A, Ap5A and ATP activate the same intracellular Ca2+ signal through different receptors and different mechanisms. AP4A and Ap5A induce a more selective Ca2+–entry in a voltage‐independent process. This is the first time that a selective action of diadenosine polyphosphate through receptors other than P1 and P2‐purinoceptors has been described.
Mode of action of thrombin in the rabbit aorta
Authors: Godin Denis , Rioux Francis , Marceau François , Drapeau Guy 
Published: July 2012

Thrombin is a vasoactive protease that elicits the contraction of the rabbit aorta by activating a G‐protein coupled receptor through cleavage of its N‐terminal extracellular domain. Synthetic peptides corresponding to the newly exposed N‐terminus, following thrombin cleavage, have been shown to reproduce some of the activities of thrombin in the rabbit aorta.
Intracellular pathways involved in the contractile response of the rabbit aorta to thrombin and synthetic peptides were examined by use of a series of inhibitors. A similar method was applied to characterize the mitogenic effect of thrombin on cultured smooth muscle cells (SMCs) derived from the same tissue.
Results from this study indicate that the contractile response of the rabbit aorta to thrombin is dependent on the activation of protein kinase C (PKC) and independent of extracellular calcium. The contractile response to thrombin can be fully reproduced by peptide agonists related to the N‐terminal receptor sequence. However, subtle differences seem to exist between the mechanism of the contractile effect of thrombin and of the synthetic peptides, as both PKC activation and extracellular calcium were found to participate in the contractile effect of the synthetic peptides.
In cultured SMCs, both thrombin and the synthetic peptides increased inositol phosphate turnover; however, only thrombin elicited a mitogenic effect, which occurs at thrombin concentrations well below those needed to increase inositol phosphate turnover significantly. Activation of a tyrosine kinase pathway is involved in the mitogenic effect of thrombin on aortic SMCs.
Altogether these results suggest the existence of subtle differences between the mode of action of thrombin and of synthetic peptides related to the N‐terminal thrombin receptor sequence, in the rabbit aorta.
Characterization of acute homologous desensitization of μ‐opioid receptor‐induced currents in locus coeruleus neurones
Authors: Osborne P.B. , Williams J.T. 
Published: July 2012

Acute homologous desensitization of μ‐opioid receptor‐induced currents was pharmacologically characterized in locus coeruleus (LC) neurones by use of intracellular and whole cell recording in superfuised brain slices.
Following desensitization of opioid receptors by perfusion with a high concentration of [Met5] enkephalin (ME) for 5 min, there was a reduction in the maximum response and a rightward shift of the concentration ‐ response curves for ME, [D‐Ala2, N‐MePhe4, Gly ‐ ol] enkephalin (DAMGO) and nor‐morphine.
By simultaneously fitting the operational model to the paired pre‐ and post‐desensitization concentration‐response data for each agonist, estimates of the level of desensitization were obtained. The values obtained for the three agonists (between 88% and 96%) were similar and did not vary according to the efficacy of the agonist used.
Use of whole cell patch recording techniques caused a slow rundown in the amplitude of ME currents (approx. 40% reduction over 60 min) but did not greatly affect the expression of acute desensitization of opioid currents.
When included in the patch recording solution, the phosphatase inhibitors, microcystin (50 nM‐4 μm) and okadaic acid (1 μm) had no effect on the induction of desensitization or the normal ability of opioid or α2‐adrenoceptors to produce currents. Microcystin decreased the rate of recovery of the ME (300 nM) currents following desensitization; however, okadaic acid had little effect on the rate of recovery from desensitization.
Strong calcium buffering with BAPTA (10–20 mM) had no effect on desensitization or the recovery from desensitization.
These results suggest that acute homologous desensitization of μ‐opioid receptors in LC neurones entails a rapid loss of responsiveness that involves a majority of the receptor population. The mechanism by which desensitization is reversed may involve a non‐calcium‐dependent protein phosphatase but the processess that cause desensitization remain unclear.
Ca2+‐dependent and ‐independent mechanism of cyclic‐AMP reduction: mediation by bradykinin B2 receptors
Authors: Sipma Henk , den Hertog Adriaan , Nelemans Adriaan 
Published: July 2012

Bradykinin caused a transient reduction of about 25% in the cyclic AMP level in forskolin prestimulated DDT1 MF‐2 smooth muscle cells (IC50: 36.4 ±4.9 nM) and a pronounced, sustained inhibition (40%) of the isoprenaline‐stimulated cyclic AMP level (IC50: 37.5 ±1.1 nM).
The Ca2+ ionophore, ionomycin, mimicked both the bradykinin‐induced transient reduction in the forskolin‐stimulated cyclic AMP level and the sustained reduction in the isoprenaline‐stimulated cyclic AMP level.
The Ca2+‐dependent effect on cyclic AMP induced by bradykinin was mediated solely by Ca2+ release from internal stores, since inhibition of Ca2+ entry with LaCl3 did not reduce the response to bradykinin.
The involvement of calmodulin‐dependent enzyme activities, protein kinase C or an inhibitory GTP binding protein in the bradykinin‐induced responses was excluded since a calmodulin inhibitor, calmidazolium, a PKC inhibitor, staurosporine and pertussis toxin, respectively did not affect the decline in the cyclic AMP level.
Bradykinin enhanced the rate of cyclic AMP breakdown in intact cells, which effect was not mimicked by ionomycin. This suggested a Ca2+‐independent activation of phosphodiesterase activity by bradykinin in DDT1 MF‐2 cells.
The bradykinin B1 receptor agonist, desArg9–bradykinin, did not affect cyclic AMP formation in isoprenaline prestimulated cells, while the bradykinin B2 receptor antagonists, Hoe 140 (D‐Arg[Hyp3, Thi5, D‐Tic7, Oic8]‐BK) and D‐Arg[Hyp3, Thi5–8, D‐Phe7]‐BK completely abolished the bradykinin response in both forskolin and isoprenaline prestimulated cells.
Bradykinin caused an increase in intracellular Ca2+, which was antagonized by the bradykinin B2 receptor antagonists, Hoe 140 and D‐Arg[Hyp3, Thi5,8, D‐Phe7]‐BK. The bradykinin B2 receptor agonist, desArg9–bradykinin, did not evoke a rise in cytoplasmic Ca2+.
It is concluded, that stimulation of bradykinin B2 receptors causes a reduction in cellular cyclic AMP in DDT1 MF‐2 cells. This decline in cyclic AMP is partly mediated by a Ca2+/calmodulin independent activation of phosphodiesterase activity. The increase in [Ca2+]i mediated by bradykinin B2 receptors inhibited forskolin‐ and isoprenaline‐activated adenylyl cyclase differently, most likely by interfering with different components of the adenylyl cyclase signalling pathway.
A role for mast cells in adenosine A3 receptor‐mediated hypotension in the rat
Authors: Hannon J.P. , Pfannkuche H.J. , Fozard J.R. 
Published: July 2012

The adenosine A3 receptor agonist, N6–2‐(4‐aminophenyl)ethyladenosine (APNEA) induces hypotension in the anaesthetized rat. The present experiments were carried out to explore the role of mast cells in the response.
Intravenous injection of APNEA (1–30 μg kg−1 to rats in which the A3 receptor‐mediated response had been isolated by pretreatment with 8‐(p‐sulphophenyl) theophylline (8‐SPT)), induced dose‐related falls in blood pressure accompanied at higher doses by small falls in heart rate. Responses to the mast cell degranulating agent, compound 48/80 (10–300 μg kg−1, i.v.) were qualitatively similar to those to APNEA.
Pretreatment with sodium cromoglycate (0.25‐20 mg kg−1, i.v.) induced dose‐related, although incomplete, blockade of the hypotensive responses to APNEA. At 20 mg kg−1, sodium cromoglycate also inhibited the cardiovascular response to compound 48/80 but had no effects on those to the selective A1 receptor agonist, N6–cyclopentyladenosine (CPA) or the selective A2A receptor agonist, 2‐[p‐(2‐carboxyethyl)phenylamino]‐5′‐N‐ethylcarboxamidoadenosine (CGS 21680). Lodoxamide (0.01–20 mg kg−1) also blocked selectively but incompletely the response to APNEA.
The cardiovascular responses to compound 48/80 (10–300 μg kg−1, i.v.) were markedly suppressed in animals which had received repeated doses of the compound by the intraperitoneal route. Similarly APNEA was essentially devoid of cardiovascular activity in such preparations. In contrast, responses to CPA were similar in animals treated repeatedly with compound 48/80 to those obtained in control animals.
Plasma and serum histamine concentrations were markedly increased associated with the pronounced hypotensive responses induced by intravenous injections of APNEA (30 or 100 μg kg−1) in the presence of 8‐SPT, or compound 48/80 (300 μg kg−1).
Taken together the data implicate the mast cell in a key role in adenosine A3 receptor‐mediated hypotension in the anaesthetized rat.
Potentiation, activation and blockade of GABAA receptors of clonal murine hypothalamic GT1‐7 neurones by propofol
Authors: Adodra Snehal , Hales Tim G. 
Published: July 2012

The actions of GABA and the intravenous general anaesthetic propofol (2,6‐düsopropylphenol) on GABAA receptors of self‐replicating GT1‐7 hypothalamic neurones were investigated by the patch clamp technique.
GABA (1 μm‐1 mM) dose‐dependently activated inward currents with an EC50 of 27 μm, recorded from whole cells voltage‐clamped at —60 mV. GABA (100 μm)‐activated currents reversed at the Cl− equilibrium potential.
Propofol (0.1 −100 μm) dose‐dependently potentiated GABA (100 μm)‐evoked currents with an EC50 of 5 μm.
In the absence of GABA, propofol (10 μm‐1 mM) activated small inward currents with a reversal potential similar to the CI− equilibrium potential. The peak current amplitudes activated by propofol were only 31% of those activated by GABA in the same cells.
Like GABA (100 μm)‐activated currents, propofol (100 μm)‐activated currents were inhibited by the GABAA receptor antagonist, bicuculline (10 μm) and were abolished by Zn2+ (100 μm).
Propofol (10, 30 and 100 μm) dose‐dependently activated currents in the absence of GABA. However, the peak amplitude of currents activated by propofol declined with concentrations > 100 μm. The cessation of application of a high dose of propofol (1 mM) was associated with a current ‘surge’.
The surge current, seen after application of propofol (1 mM), had a reversal potential similar to the CI− equilibrium potential. The ratio between peak current amplitude in the presence of propofol (1 mM) and surge current amplitude after propofol application, were not dependent on holding potential. Thus, it is unlikely that the surge current represents reversal of a voltage‐dependent block of GABAA receptors by propofol.
The amplitude of the surge current exceeded the amplitude of the initial propofol (1 mM)‐evoked current following brief applications, but declined after prolonged applications of the drug.
The observed modulatory actions of propofol may be due to separate potentiation, activation and inhibitory sites for this anaesthetic agent on GT1‐7 cell GABAA receptors.
Application of a model to explore interspecies differences in acetylcholine M‐receptor‐stimulated gastric acid secretion
Authors: Welsh Nicola J. , Shankley Nigel P. , Black James W. 
Published: July 2012

Concentration‐effect curves were obtained, in the absence and presence of histamineH2‐receptor blockade, to 5‐methylfurmethide (5‐MeF) and McN‐A 343, high efficacy and low efficacy acetylcholine (ACh) M‐receptor agonists, respectively, in isolated stomach preparations from the mouse and immature rat and guinea‐pig.
In the immature guinea‐pig assay, the responses to 5‐MeF and McN‐A 343 were abolished by histamineH2‐receptor blockade suggesting that the responses were totally dependent upon gastric mucosal histamine. However, in the mouse and immature rat assays, although the histamineH2‐receptor antagonists produced small but significant rightward shifts and, in some cases, depression of the maximum of the agonist concentration‐effect curves, a significant secretory response remained, presumed to be due to direct stimulation of oxyntic cells.
Previously, by assuming that the histamineH2‐receptor blockade alters the mode of agonist‐stimulated acid secretion from mainly an indirect action mediated by histamine release to direct stimulation of the oxyntic cell, we applied an operational model of agonism to similar data obtained in the mouse preparation. In that study we were able to account for the behaviour of 5‐MeF and McN‐A 343 by assuming that the agonists expressed 6 fold higher efficacy, τ in the operational model of agonism, at ACh M‐receptors on the histamine‐releasing cells than on the oxyntic cells. In this study it was possible to account for the variation in the behaviour of the agonists both between and within assays by simply varying the efficacy expressed by the agonists at each of the cells in the model. The efficacy variation could be due to receptor concentration variation.
The data and analysis are discussed in terms of contemporary models for the role of histamine in the regulation of gastric acid secretion.
Accumulation of endogenous inhibitors for nitric oxide synthesis and decreased content of L‐arginine in regenerated endothelial cells
Authors: Azuma Hiroshi , Sato Jun , Hamasaki Hidehisa , Sugimoto Akiko , Isotani Eiji , Obayashi Satoshi 
Published: July 2012

We examined regeneration of endothelial cells (ECs), neointima formation, decreased endothelium‐dependent relaxation (EDR) and changes in the contents of L‐arginine, NG–monomethyl‐L‐arginine (l‐NMMA), asymmetrical NG, NG–dimethylarginine (ADMA) and symmetrical NG, NG–dimethylarginine (SDMA) in the regnerated ECs, 6 weeks after balloon denudation of the rabbit carotid artery.
Regeneration of ECs was completed in 6 weeks and a significant neointima formation accompanied by the decreased EDR was observed.
L‐NMMA and ADMA contents in the regenerated ECs (23.5 ± 4.3 and 21.2 ± 2.0 pmol mg−1 DNA, respectively) were significantly (P<0.05 and P<0.01) higher than those in the control ECs (8.8 ± 3.0 and 7.4plusmn;1.9 pmol mg−1 DNA, respectively), whereas L‐arginine was significantly (P< 0.005) decreased in the regenerated ECs (31,470±1,050 pmol mg−1 DNA) as compared to that in the control ECs (47,870±1,890 pmol mg−1 DNA). SDMA content was below the assay limits.
L‐NMMA and ADMA, but not SDMA, inhibited the EDR induced by acetylcholine in a concentration‐dependent manner. The inhibition with L‐NMMA and ADMA was prevented by an addition of L‐arginine, but not by D‐arginine.
These results suggest that the accumulation of endogenous inhibitors for nitric oxide synthesis and decreased L‐arginine content are associated with decreased NO production/release from regenerated ECs and neointima formation.