bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adenosine A1 receptor‐mediated changes in basal and histamine‐stimulated levels of intracellular calcium in primary rat astrocytes
Authors: Peakman Marie‐Claire , Hill Stephen J. 
Published: July 2012

The effects of adenosine A1 receptor stimulation on basal and histamine‐stimulated levels of intracellular free calcium ion concentration ([Ca2+]i) have been investigated in primary astrocyte cultures derived from neonatal rat forebrains.
Histamine (0.1 μm‐l mM) caused rapid, concentration‐dependent increases in [Ca2+]i over basal levels in single type‐2 astrocytes in the presence of extracellular calcium. A maximum mean increase of 1,468 ±94 nM over basal levels was recorded in 90% of type‐2 cells treated with 1 mM histamine (n = 49). The percentage of type‐2 cells exhibiting calcium increases in response to histamine appeared to vary in a concentration‐dependent manner. However, the application of 1 mM histamine to type‐1 astrocytes had less effect, eliciting a mean increase in [Ca2+]i of 805 ± 197 nM over basal levels in only 30% of the cells observed (n = 24).
In the presence of extracellular calcium, the A1 receptor‐selective agonist, N6‐cyclopentyladenosine (CPA, 10 μm), caused a maximum mean increase in [Ca2+]i of 1,110 ± 181 nM over basal levels in 30% of type‐2 astrocytes observed (n = 53). The size of this response was concentration‐dependent; however, the percentage of type‐2 cells exhibiting calcium increases in response to CPA did not appear to vary in a concentration‐dependent manner. A mean calcium increase of 605 ± 89 nM over basal levels was also recorded in 23% of type‐1 astrocytes treated with 10 μm CPA (n = 30).
In the absence of extracellular calcium, in medium containing 0.1 mM EGTA, a mean increase in [Ca2+]i of 504 ±67 nM over basal levels was recorded in 41% of type‐2 astrocytes observed (n = 41) after stimulation with 1 μm CPA. However, in the presence of extracellular calcium, pretreatment with the A1 receptor‐selective antagonist, 8‐cyclopentyl‐1,3‐dipropylxanthine, for 5–10 min before stimulation with 1 μm CPA, completely antagonized the response in 100% of the cells observed.
In type‐2 astrocytes, prestimulation with 10 nM CPA significantly increased the size of the calcium response produced by 0.1 μm histamine and the percentage of responding cells. Treatment with 0.1 μm histamine alone caused a mean calcium increase of 268 ±34 nM in 41% of the cells observed (n = 34). After treatment with 10 nM CPA, mean calcium increase of 543 ±97 nM was recorded in 100% of the cells observed (n = 33).
These data indicate that adenosine A1 receptors couple to intracellular calcium mobilization and extracellular calcium influx in type‐1 and type‐2 astrocytes in primary culture. In addition, the simultaneous activation of adenosine A1 receptors on type‐2 astrocytes results in an augmentation of the calcium response to histamine H1 receptor stimulation.
Regenerative caffeine‐induced responses in native rabbit aortic endothelial cells
Authors: Rusko J. , Wang X. , van Breemen C. 
Published: July 2012

Single native aortic endothelial cells obtained by enzymatic dispersion of the rabbit aortic endothelium were held under voltage clamp using patch pipette and whole‐cell membrane currents were measured. In parallel experiments performed on cells from the same batches, the free internal calcium concentration, [Ca2+]i, in the cell was estimated by use of the Ca2+‐sensitive fluorescent dye, fura‐2.
Caffeine (20 mM) applied to the cell evoked an outward current and an initial peak in [Ca2+]1 followed by a lower sustained rise (plateau). Ca2+‐free, EGTA‐containing solution applied outside the cells did not reduce these responses.
Following caffeine stimulation there was a biphasic rising phase of outward current both in the presence and absence of extracellular Ca2+.
Application of graded doses of caffeine revealed all‐or‐none type responses of both the outward current and the rise in [Ca2+]i.
Preincubation with lower doses of caffeine reduced the magnitude of both the outward current and the [Ca2+]i transient evoked by 20 mM caffeine.
Tetraethylammonium (3 mM) applied to the bathing solution blocked unitary and spontaneous transient outward currents (STOCs) stimulated by Ca2+‐free solution, but only reduced the outward current evoked by caffeine (20 mM).
In conclusion, our results reveal the all‐or‐none nature of Ca2+ release from the endoplasmic reticulum (ER) in native aortic endothelial cells. Lower concentrations of caffeine (0.4‐0.5 mM) may deplete intracellular Ca2+ stores. Extracellular Ca2+ is not necessary for maintaining the activity of spontaneous and caffeine‐induced outward currents in native aortic endothelial cells. Spontaneous outward currents are believed to represent the sporadic release of calcium from store sites independent of both extracellular Ca2+ and the caffeine‐sensitive Ca2+ stores which stimulate the outward current.
Ramipril‐induced decrease in renal lithium excretion in the rat
Authors: Barthelmebs Mariette , Grima Michele , Imbs Jean‐Louis 
Published: July 2012

The interaction of ramipril, an inhibitor of angiotensin I converting enzyme, with renal lithium handling was analysed in conscious normotensive Wistar rats and compared with the known increase in renal tubular lithium reabsorption induced by the non‐steroidal anti‐inflammatory drug, indomethacin.
The rats were treated for five days with ramipril (1 mg kg−1 day−1 orally), indomethacin (2.5 mg kg−1 day−1 intramuscularly) or their solvents. Lithium chloride (16.7 mg kg−1 intraperitonealy) was given as a single dose on the fifth day and renal functions were measured.
Ramipril induced a decrease in renal lithium clearance which was correlated with the decrease in the quantity of filtered lithium and the increase in the tubular fractional reabsorption of the metal. Ramipril also reduced the systolic blood pressure of the rats by about 15 mmHg.
In the absence of any effect on creatinine clearance or systolic blood pressure, indomethacin increased renal fractional lithium reabsorption and led to an increase in plasma lithium levels, as previously reported by our group. 5 In conclusion, our results indicate that ramipril decreases renal lithium excretion in Wistar rats, when given orally at a dose of 1 mg kg−1 day−1 over five days.
Central cardiovascular effects of acetylcholine in the conscious dog
Authors: Brefel C. , Lazartigues E. , Tran M.A. , Gauquelin G. , Geelen G. , Gharib C. , Montastruc J.L. , Montastruc P. , Rascol O. 
Published: July 2012

The effects of central cholinomimetic drugs on cardiovascular and vasoactive hormonal responses (blood pressure, heart rate, catecholamines, vasopressin, atrial natriuretic factor, neuropeptide Y plasma levels and plasma renin activity) were investigated in conscious Beagle dogs. For this purpose a catheter was chronically implanted into each dog's cisterna magna to allow repeated central injections in the awake animals.
Intracisternal acetylcholine (20 μg kg−1) significantly increased systolic and diastolic blood pressure. These changes were accompanied by an initial short term tachycardia followed by a long lasting bradycardia. Intracisternal acetylcholine also increased noradrenaline, adrenaline and vasopressin plasma levels, decreased plasma renin activity but did not modify plasma levels of neuropeptide Y and atrial natriuretic factor.
The effects of acetylcholine were completely abolished by pretreatment with intracisternal injection of the muscarinic antagonist, atropine (5 μg kg−1) but not by the intracisternal injection of the nicotinic antagonist, mecamylamine (25 μg kg−1).
The present results demonstrate that there are qualitative and quantitative differences between the central cardiovascular effects of acetylcholine in conscious dogs compared to what we previously reported, using a comparable protocol, in anaesthetized dogs. Under both conditions, we observed a central cholinergically mediated increase in blood pressure secondary to an increase in sympathetic tone and vasopressin release but these responses were shorter (less than 10 min) in the conscious dogs than in anaesthetized dogs (more than 10 min). Moreover, we detected in the response to the central cholinergic stimulation in the conscious dogs a significant increase in plasma adrenaline levels and biphasic changes in heart rate which were not described previously in the anaesthetized dog.
Inhibition by halothane of potassium‐stimulated acetylcholine release from rat cortical slices
Authors: Griffiths R. , Greiff J.M.C. , Haycock J. , Elton C.D. , Rowbotham D.J. , Norman R.I. 
Published: July 2012

Cholinergic neurones in the basal forebrain are linked to cortical activation and arousal.
The present study was designed to examine the hypothesis that clinically relevant doses of halothane (0.1 to 5%) would significantly reduce depolarization‐evoked acetylcholine (ACh) release from rat cortical slices.
ACh release was measured from rat cortical slices by a chemiluminescent technique.
Depolarization‐evoked ACh release was inhibited significantly by halothane with an IC50 of 0.38%. This value equates to 0.3 MAC (the minimum alveolar concentration at which no movement occurs to a standard surgical stimulus in 50% of subjects) for the rat.
The potent effect of halothane on ACh release suggests that this mechanism may be a target for the action of volatile anaesthetic agents. This in vitro effect on ACh release is consistent with effects of halothane reported in vivo.
Regulation by phosphodiesterase isoenzymes of non‐adrenergic non‐cholinergic contraction in guinea‐pig isolated main bronchus
Authors: Spina D. , Harrison S. , Page C.P. 
Published: July 2012

We have investigated the role of phosphodiesterase isoenzymes in modulating electric field stimulation (EFS), substance P and capsaicin‐induced contraction of the guinea‐pig isolated main bronchus.
Non‐adrenergic non‐cholinergic contractile responses were elicited by EFS (3 Hz, 20 s) in the guinea‐pig isolated main bronchus in the presence of the non‐selective muscarinic antagonist, atropine (0.1 μm), the non‐selective, β‐adrenoceptor antagonist, propranolol (1 μm), the neutral endopeptidase inhibitor, thiorphan (10 μm) and the cyclooxygenase inhibitor, indomethacin (5 PM). The type III, type III/IV, type IV and type V phosphodiesterase isoenzyme inhibitor, SKF 94836, benzafentrine, Ro‐20–1724 and zaprinast respectively, significantly attenuated the contractile response to EFS. The IC50 (95% confidence limits) value for SKF 94836, benzafentrine, Ro‐20–1724 and zaprinast was 8.3 μm (0.89‐78); 0.7, μm (0.1–4.5); 0.5 μm (0.2‐1.2) and 13 μm (2–87) respectively.
The phosphodiesterase isoenzyme inhibitors, SKF 94836, Ro‐20–1724 and zaprinast, partially attenuated the contractile response to substance P (10 nM). Benzafentrine significantly inhibited the contractile response to substance P. yielding an IC50 value of 1.9 μm (0.9‐3.8).
The phosphodiesterase isoenzyme inhibitor, Ro‐20–1724 (0.1–100 μm) failed to reduce significantly the contractile potency of capsaicin (P>0.05). In contrast, SKF 94836 (1 μm), benzafentrine (10 μm) and zaprinast (100 μm) significantly reduced the contractile potency of capsaicin (P<0.05).
The selective phosphodiesterase isoenzyme inhibitors, SKF 94836, benzafentrine, Ro‐20–1724 and zaprinast (0.01–100 μm) reversed in a concentration‐dependent manner the contractile response to exogenously administered capsaicin (EC50) yielding IC50 values of 3.91 μm (0.68‐22); 3.37 μm (1.86‐6.11); 0.366 μm (0.201‐0.564) and 50.1, μm (18.6–135) respectively.
In conclusion, phosphodiesterase isoenzymes appear to regulate the contractile response to electrical field stimulation and our results provide circumstantial evidence for a regulatory role of phosphodiesterase type IV isoenzyme on sensory nerve function in vitro.
Mediation by prostaglandins of the nitric oxide‐induced neurogenic vasodilatation in rat skin
Authors: Holzer Peter , Jociĉ Milana , Peskar Bernhard A. 
Published: July 2012

Intraplantar administration of the nitric oxide (NO) donor, sodium nitroprusside (SNP), induces hyperaemia in the rat paw skin, which is in part due to release of calcitonin gene‐related peptide (CGRP) from afferent nerve fibres. The present study examined whether prostaglandins or other inflammatory mediators participate in the neurogenic vasodilatation caused by SNP. Blood flow in the plantar hindpaw skin of urethane‐anaesthetized rats was measured by laser Doppler flowmetry.
The hyperaemic responses to intraplantar administration of the NO donors SNP (150 pmol) and 3‐morpholinosydnonimine (SIN‐1, 15 nmol) were attenuated by 45% and 61%, respectively, after injection of the CGRP antagonist, CGRP8–37 (50 nmol kg−1, i.v.) which did not significantly change baseline blood flow.
The NO synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME, 15 mg kg−1, i.v.), the bradykinin antagonist Hoe‐140 (100 nmol kg−1, i.v.) and the histamine antagonists, pyrilamine (2 mg kg−1, i.v.) plus cimetidine (10 mg kg−1, i.p.) were without effect on baseline blood flow and the vasodilatation caused by SNP.
The cyclooxygenase inhibitors, indomethacin (10 mg kg−1, i.p.) and flurbiprofen (5 mg kg−1, i.p.) depressed the SNP‐induced hyperaemia by 65% and 42%, respectively, without altering baseline blood flow. The ability of CGRP8–37 to inhibit the vasodilator response to SNP was lost in indomethacin‐treated rats. 5 Intraplantar administration of prostaglandin E2 (PGE2, 15 pmol) evoked cutaneous vasodilatation which was attenuated by 66% after administration of CGRP8–37 but remained unaltered by indomethacin or L‐NAME. 6 These data indicate that the neurogenic hyperaemia which in rat skin is induced by intraplantar administration of NO donors involves the formation of prostaglandins which in turn cause release of the vasodilator peptide, CGRP, from perivascular afferent nerve fibres.
Nitric oxide synthase in dog urethra: a histochemical and pharmacological analysis
Authors: Takeda Masayuki , Lepor Herbert 
Published: July 2012

To examine the presence of nitric oxide synthase (NOS) activity in female dog urethra, pharmacological experiments were performed using electrical field stimulation (EFS), guanethidine, atropine, NG‐nitro‐L‐arginine methyl ester and L‐arginine, NOS immunohistochemistry using specific anti‐NOS antibody, and reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase staining were also performed.
EFS caused frequency‐dependent contractions in all urethral preparations, but in the presence of guanethidine and atropine, EFS caused significant relaxation in the proximal urethra and was without effect on the distal urethra.
In the presence of guanethidine, atropine, and NG‐nitro‐L‐arginine methyl ester, small contractions to EFS were re‐established in the proximal urethra, but not in the distal urethra. NG‐nitro‐D‐arginine methyl ester had no such effect.
In the presence of guanethidine, atropine, and NG‐nitro‐L‐arginine methyl ester, the addition of L‐arginine, restored the EFS‐elicited relaxant responses previously seen with guanethidine and atropine alone in the proximal urethra (at 30 Hz; 12.89 ± 5.27% to −2.44 ± 4.43%, mean ± s.e., P<0.05). D‐Arginine had no such effect.
In the distal urethra, the addition of NG‐nitro‐L‐arginine methyl ester and then L‐arginine had no effect on responses to EFS in preparations treated with guanethidine and atropine.
Sodium nitroprusside caused relaxation in both the proximal and distal urethra. The relaxant responses per cm2 cross sectional area in the proximal and distal urethra were 1.23 ± 0.29, and 2.02 ± 0.54 g cm−2 cross sectional area (mean ± s.e.), respectively: there was no significant difference between them.
Both NOS and NADPH diaphorase‐positive neurones were present in dog urethra, the densities of both being higher in the proximal urethra than in the distal urethra.
These results show that female dog urethra possesses NOS nerves and that endogenous NO may play a role in relaxation in the proximal but not the distal urethra.
Calcium homeostasis in mouse fibroblast cells: affected by U‐73122, a putative phospholipase Cβ blocker, via multiple mechanisms
Authors: Grierson Jeremy P. , Meldolesi Jacopo 
Published: July 2012

The inhibitory effects of the putative phospholipase Cβ inhibitor, U‐73122, on ligand‐induced and thapsigargin‐induced [Ca2+]i transients were investigated in mouse fibroblast cells (the L line).
Ca2+ release from intracellular stores was stimulated either by ATP (and also by UTP or ADP) working through the activation of a P2U receptor, or by lysophosphatidic acid, which elicited a more pronounced response.
U‐73122 inhibited the Ca2+ mobilization produced by all the agonists in a dose‐dependent manner, consistent with a mode of action involving phospholipase C inhibition.
In addition, however, U‐73122 slowed the kinetics of intracellular Ca2+ release induced by the Ca2+‐ATPase inhibitor, thapsigargin, and reduced the influx of Ca2+ across the plasma membrane, following stimulation of store‐dependent influx by the latter.
We conclude that U‐73122 has multiple sites of action, all of which can lead to a change in Ca2+ homeostasis. Thus, particular caution is recommended when employing this agent and when interpreting the results obtained.
Subtypes of tachykinin receptors on tonic and phasic neurones in coeliac ganglion of the guinea‐pig
Authors: Zhao F.‐Y. , Saito K. , Yoshioka K. , Guo J.‐Z. , Murakoshi T. , Konishi S. , Otsuka M. 
Published: July 2012

Intracellular recording techniques were used to investigate the characteristics of tachykinin receptors and their subtypes in tonic and phasic neurones, which constituted two major neuronal populations in the coeliac ganglion of the guinea‐pig.
In 95% of phasic neurones a long‐lasting after‐hyperpolarization (LAH), 5–8s in duration and 10–20 mV in amplitude, was observed following action potentials evoked by passing a train of depolarizing current pulses into the neurones. In contrast, LAH was observed in only 4% of tonic neurones.
In most tonic neurones, substance P (SP), neurokinin A (NKA) and senktide induced depolarizations, whereas in phasic neurones they usually inhibited LAH but rarely induced depolarization.
Tonic and phasic neurones were further classified into three groups based on their responses (depolarization for tonic neurones and LAH inhibition for phasic neurones) to these tachykinin receptor agonists: (1) neurones responsive to SP, NKA and senktide (71–78%); (2) those responsive to senktide but not to SP and NKA (12–23%) and (3) those not responsive to any of the three agonists (7–11%).
GR71251 (5 μM), an NK1‐selective tachykinin receptor antagonist, depressed the depolarization in tonic neurones and the LAH inhibition in phasic neurones induced by SP and NKA, but not those induced by senktide.
Selective NK2 receptor agonists, [Nle10]NKA4‐10, [β‐Ala8]NKA4‐10 and GR64349, were without effect in both tonic and phasic neurones. Furthermore, an NK2 receptor antagonist, L659,877, did not inhibit the depolarization induced by NKA, SP or senktide in tonic neurones.
It is suggested that NK1 and NK3 receptors are present on a large proportion of coeliac ganglion neurones. In tonic neurones both subtypes of tachykinin receptors are coupled to membrane depolarization, whereas in phasic neurones activation of these receptors leads to inhibition of LAH. The present study also suggests that NKA evokes the depolarization in tonic neurones and the LAH inhibition in phasic neurones via NK1, but not NK2 receptors.
Involvement of tachykinins in plasma extravasation induced by bradykinin and low pH medium in the guinea‐pig conjunctiva
Authors: Figini Michela , Javdan Panthea , Cioncolini Fabio , Geppetti Pierangelo 
Published: July 2012

The effect of bradykinin, capsaicin, substance P and low pH medium on plasma extravasation in the guinea‐pig conjunctiva has been studied. Evans blue dye was measured in the conjunctiva after local instillation of the agents into the conjunctival sac.
Bradykinin (2–50 nmol), capsaicin (20–50 nmol) and substance P (0.5‐5 nmol) caused a dose‐dependent increase in plasma extravasation with the following order of potency: substance P> bradykinin = capsaicin. The effect of capsaicin (50 nmol) and substance P (5 nmol) was abolished by the tachykinin NKX receptor antagonist, CP‐99,994 (8umolkg−1, i.v.) (P<0.01), whereas CP‐100,263 (8 umol kg−1, i.v.) the inactive enantiomer of CP‐99, 994 was without effect. CP‐99,994 inhibited by 70% (P<0.01) the effect of bradykinin.
The kinin B2 receptor antagonist, Hoe 140 (icatibant, 10 nmol kg−1, i.v.) abolished the response to bradykinin (50 nmol) (P<0.01), but did not affect the responses to capsaicin (50 nmol) or substance P (5 nmol). Plasma extravasation induced by low pH medium (pH 1) was abolished by CP‐99,994 (P<0.01) and by Hoe 140 (P<0.01).
The present findings suggest that: endogenous or exogenous tachykinins increase plasma extravasation in the guinea‐pig conjunctiva by activation of NK1 receptors; bradykinin‐induced plasma extravasation is mediated by tachykinin release from sensory nerve endings; low pH media cause plasma extravasation via release of kinins that by activation of B2 receptors release tachykinins from sensory nerve endings.
Effects of GTPγS on muscarinic receptor‐stimulated inositol phospholipid hydrolysis in permeabilized smooth muscle from the small intestine
Authors: Prestwich S.A. , Miyazaki H. , Bolton T.B. 
Published: July 2012

Smooth muscle fragments from the longitudinal layer of the small intestine of the guinea‐pig were permeabilized with Staphylococcus aureus alpha toxin (a‐toxin) and used to investigate the role of G‐protein activation in the regulation of muscarinic acetylcholine receptor (AChR)‐stimulated inositol phospholipid hydrolysis.
The efficiency of α‐toxin permeabilization was estimated by the release of [3H]‐2‐deoxyglucose ([3H]‐2DG) after prior loading or lactate dehydrogenase (LDH) enzyme release from the smooth muscle fragments.
In a‐toxin‐permeabilized smooth muscle, but not in non‐permeabilized muscle, GTPγS induced time‐and concentration‐dependent increases in labelled inositol phosphates. Carbachol (CCh) increased labelled inositol phosphates in both permeabilized and non‐permeabilized muscle, although the increases were greater in non‐permeabilized smooth muscle. The response to 100 γM CCh was severely reduced by 0.5 γM atropine.
In permeabilized muscle the effects of GTPγS or CCh on inositol phosphate levels were reduced by treatment with pertussis toxin (PTX) and completely inhibited by GDPβS.
GTPγS caused a concentration‐dependent inhibition of the CCh‐induced increases in the levels of labelled inositol phosphates. Dibutyryl cyclic AMP or Sp‐cAMPs (adenosine‐3′,5′‐cyclic phosphoro‐thiolate‐Sp) reduced the effects of CCh on inositol phosphate levels.
The results suggest that muscarinic AChR activation induces inositol phospholipid hydrolysis via more than one G‐protein in this smooth muscle and that several mechanisms may contribute to the modulation of both stimulatory and inhibitory responses observed.