bluuebunny/crossref_metadata_2025 huggingface dataset:
A series of novel, highly potent and selective agonists for the κ‐opioid receptor
Authors: Hayes A.G. , Birch P.J. , Hayward N.J. , Sheehan M.J. , Rogers H. , Tyers M.B. , Judd D.B. , Scopes D.I.C. , Naylor A.
Published: July 2012

This paper describes the opioid receptor pharmacology and in vivo activity of several novel benzeneacetamidopiperidine and benzeneacetamidopiperazine analogues.

These compounds all showed potent, naloxone‐reversible, full agonist activiy in the field‐stimulated rabbit vas deferens, indicating that they are κ‐opioid agonists; but showed very little activity in the rat or hamster vas deferens, indicating good selectivity with regard to μ‐ and δ‐opioid receptors.

They were all potent antinociceptive agents, the most potent compound, GR103545, having an ED50 value in the mouse abdominal constriction test of 0.25 μg kg−1 s.c. The compounds also produced sedation and diuresis, but had little effect on respiration rate or gastrointestinal motility.

It is concluded that the seven novel compounds described are all potent and selective agonists for the κ‐opioid receptor.
Prevention of myocardial enzyme release by ranolazine in a primate model of ischaemia with reperfusion
Authors: Allely M.C. , Alps B.J.
Published: July 2012

In control anaesthetized baboons subjected to 30 min occlusion of the left anterior descending coronary artery, followed by 5.5 h reperfusion, total plasma levels for creatine kinase (CK) and lactate dehydrogenase (LDH) were markedly elevated in a time‐related manner. In a second group of baboons pretreated 10 min prior to ischaemia with ranolazine [(±)‐N‐(2,6‐dimethyl‐phenyl)‐4[2‐hydroxy‐3‐(2‐methoxyphenoxy)propyl]‐1‐piperazine acetamide dihydrochloride; RS‐43285–193] at 500 μg kg−1 i.v., followed by continuous infusion of 50 μg kg−1 min−1, neither enzyme was significantly elevated at any time point. Similarly, serum levels of the cardiospecific isoenzyme CK2 were 8 fold greater in the controls than in the ranolazine‐treated animals at 6 h. The results indicate that ranolazine pretreatment abolished cardiac enzyme release over a 5.5 h reperfusion period, indicating a potential protective effect.
Chronic diazepam treatment in rats causes long‐lasting changes in central [3H]‐5‐hydroxytryptamine and [14C]‐γ‐aminobutyric acid release
Authors: Hitchcott P.K. , File Sandra E. , Ekwuru M. , Neal M.J.
Published: July 2012

The effects of chronic diazepam administration to rats on the central release of [3H]‐5‐hydroxytryptamine ([3H]‐5‐HT) and [14C]‐γ‐aminobutyric acid ([14C]‐GABA, ex vivo) were examined. Chronic (5 and 21 days) administration of diazepam (4 mg kg−1 i.p. daily for 21 days) reduced the K‐evoked (20 mm KCl) release of [3H]‐5‐HT from frontal cortex by approximately 50%. Remarkably, this decrease was still present 1 week after diazepam withdrawal. Chronic diazepam treatment did not significantly affect hippocampal [3H]‐5‐HT release but after 21 days the K‐evoked release of [14C]‐GABA was more than doubled and remained elevated 30 h after withdrawal; it returned to control levels after 1 week, and decreased below control levels after 2 weeks. This study indicates that chronic diazepam treatment produces striking changes in transmitter release in rats that persist long after treatment has ceased.
Phannacokinetic‐pharmacodynamic modelling of the anticonvulsant effect of oxazepam in individual rats
Authors: Dingemanse Jasper , Voskuyl Rob A. , Langemeijer Mariska W.E. , Postel‐Westra Ineke , Breimer Douwe D. , Meinardi Harry , Danhof Meindert
Published: July 2012

The purpose of this investigation was to examine in vivo drug‐concentration anticonvulsant effect relationships of oxazepam in individual rats following administration of a single dose.

Whole blood concentration vs time profiles of oxazepam were determined following administration of doses of 4, 8 and 12 mg kg−1. The pharmacokinetics could be described by an open 2‐compartment pharmacokinetic model. Following 12 mg kg−1 the values (mean ± s.e., n = 11) of clearance and volume of distribution were 28 ± 2 ml min−1 kg−1 and 2.6 ± 0.31 kg−1, respectively, and were not significantly different from the values obtained at the other doses.

The anticonvulsant effect was quantitated by a new technique which allows repetitive determination of the convulsive threshold by direct cortical stimulation within one rat. Significant dose‐dependent elevations of the seizure threshold were observed.

By pharmacokinetic‐pharmacodynamic modelling, a log‐linear relationship was found between concentration and anticonvulsant effect. Following 12 mg kg−1 the values (mean ± s.e., n = 11) of the pharmacodynamic parameters slope and minimal effective concentration (Cmin) were 243 ± 27 μA and 0.11 ± 0.02 mg l−1, respectively and not significantly different from the values obtained at the other doses.

In a repeatability study the pharmacodynamic parameters were determined twice on two different occasions with an interval of two weeks in the same group of 11 rats. The inter‐animal variability in the pharmacodynamic parameter slope was 46%, whereas the intra‐animal variability was 24 ± 18%. The value of the minimal effective concentration was in each animal and on each occasion close to zero within the relatively narrow range of 0.01–0.30 mgl−1.

The results of this study showed that it is possible to determine in vivo concentration‐anticonvulsant effect relationships of oxazepam under non‐steady‐state conditions in individual rats. The anti‐convulsant effect of oxazepam appeared to be a rapidly reversible direct effect and acute tolerance did not develop within the time frame of the experiments.
Reversal of the anorectic effect of (+)‐fenfluramine in the rat by the selective cholecystokinin receptor antagonist MK‐329
Authors: Cooper S.J. , Dourish C.T. , Barber D.J.
Published: July 2012

Experiments were conducted to determine whether or not the effect of (+)‐fenfluramine (3.0 mg kg−1, i.p.) on food intake can be antagonized by the selective cholecystokinin receptor antagonist MK‐239 (formerly L364/718; (3S(−)‐N‐(2,3‐dihydro‐1‐methyl‐2‐oxo‐5‐phenyl‐1‐H‐1,4‐benzodiazepin‐3‐yl)‐1H‐indole‐2‐carboxamide). Two feeding paradigms were employed. In the first, non‐deprived rats were familiarized with eating a highly palatable, sweetened mash in a 30 min test. In the second, freely‐feeding rats were trained to consume powdered chow in their home‐cages, and their intake was monitored over the first 6 h of the night‐period.

In doses of 30.0 and 100.0 μg kg−1, s.c., MK‐329 almost completely blocked the anorectic effect of (+)‐fenfluramine in the palatable food intake test. These doses of MK‐329 have previously been reported to antagonize the anorectic effect produced by exogenous cholecystokinin‐octapeptide (CCK8) in rats. Both doses of MK‐329 were also effective in significantly attenuating the anorectic effect of (+)‐fenfluramine in nocturnal free‐feeding animals over a 6 h‐period.

MK‐329 (10.0–100.0 μg kg−1, s.c.) failed to antagonize the anorectic effect of either the specific dopamine D2‐receptor agonist quinpirole (0.3 mg kg−1, s.c.) or the β‐carboline FG 7142 (10.0 mg kg−1, i.p.) in the palatable food intake test.

MK‐329 (10.0–300.0 μg kg−1, s.c.) had no effect, when administered alone, on the level of palatable food intake in non‐deprived rats, even when substantial satiation was produced by a pre‐feeding procedure. Furthermore, MK‐329 had no effect, when administered alone, on nocturnal food intake in freely‐feeding rats.

In conclusion, not only was MK‐329 a potent antagonist of the effect of CCK8 on food intake, it also blocked the effect of (+)‐fenfluramine to a significant degree. The effect of MK‐329 was selective in that the anorectic effects of either quinpirole or FG 7142 remained unaffected. Administered alone, MK‐329 did not affect food intake, indicating that its reversal of (+)‐fenfluramine‐induced anorexia was not secondary to an intrinsic hyperphagic effect. The results provide some evidence that the depressant effect of (+)‐fenfluramine on food intake depends on the activity of endogenous CCK.
κ‐Opioid‐receptor agonists modulate the renal excretion of water and electrolytes in anaesthetized rats
Authors: Ashton N. , Balment R.J. , Blackburn T.P.
Published: July 2012

Subcutaneous injection of the κ‐opioid agonists U50,488 (10 mg kg−1) and tifluadom (3.5 mg kg−1) into Inactin‐anaesthetized, saline‐infused rats was associated with a diuresis, antinatriuresis and anti‐kaliuresis which lasted for up to 2h. A high (5 mg kg−1), but not low (0.1 mg kg−1), dose of naloxone blocked the renal effects of U50,488.

U50,488 administration in anaesthetized, vasopressin‐deficient Brattleboro DI rats was associated with an attenuated diuresis, though the antinatriuretic response remained intact.

The diuretic action of U50,488 was associated with an increase in glomerular filtration rate while fractional fluid reabsorption remained steady. In contrast, fractional sodium and potassium reabsorption were increased.

These data suggest that κ‐opioid agonists alter renal handling of both water and electrolytes. This appears to be mediated by two separate mechanisms: increased fluid loss largely reflects altered glomerular events while the fall in electrolyte excretion results from altered tubular handling.
Pharmacological subclassification of α1‐adrenoceptors in vascular smooth muscle
Authors: Muramatsu Ikunobu , Ohmura Tsuyoshi , Kigoshi Shigeru , Hashimoto Shigeki , Oshita Masafumi
Published: July 2012

We examined whether α1‐adrenoceptors in various blood vessels can be divided into subtypes by antagonist affinity or by susceptibility to chloroethylclonidine or nifedipine.

Noradrenaline or phenylephrine produced concentration‐dependent contractions in all the tissues tested, which were competitively inhibited by phentolamine, yohimbine, prazosin, WB4101 and HV723. However, there were large differences between the tissues in the pA2 values for all the antagonists except phentolamine.

The blood vessels could be classified into three groups (I, II and III) on the basis of their affinity variation. In group I (dog mesenteric artery and vein, saphenous vein), the pA2 values for HV723 were greater than 9, and those for HV723 and WB4101 were approximately 1 log unit higher than for prazosin. This rank order of affinity reversed in group II (dog carotid artery and rat thoracic aorta), where prazosin was more potent (pA2 values greater than 9.5) than HV723 or WB4101. In group III (rabbit mesenteric artery, thoracic aorta and carotid artery and guinea‐pig thoracic aorta), on the other hand, prazosin, HV723 and WB4101 inhibited the noradrenaline response with a similar affinity (pA2 values ranging from 8 to 9).

Yohimbine inhibited the responses to noradrenaline and phenylephrine with a lower affinity than prazosin, HV723 or WB4101. The pA2 values for yohimbine were similar in groups I and II (the values greater than 6.5), which were greater than those in group III (values less than 6.4).

The α1‐adrenoceptors in group II were selectively affected by chlorethylclonidine, resulting in an irreversible attenuation of noradrenaline responses in the dog carotid artery and a persistent contraction in the rat thoracic aorta.

Nifedipine either produced no effect or a slight inhibition of α1‐adrenoceptor‐mediated contractions in all the blood vessels; these effects were not correlated to the above groups.

These results suggest that α1 ‐adrenoceptors of blood vessels can be divided into three subtypes (designated as α1H, α1L and α1N) by antagonist affinity and their susceptibility to chloroethylclonidine but not to nifedipine: the characteristics of each subtype are summarized in Table 3. Subtypes α1H, α1L and α1N may be predominantly involved in the contractile responses to noradrenaline or phenylephrine of the blood vessels in groups II, III and I, respectively.
Evaluation of the effect of azapropazone on neutrophil migration in anaesthetized swine using a multichamber blister suction technique
Authors: Mousa S.A. , Brown R. , Chan Y. , Hsieh J. , Smith R.D.
Published: July 2012

The purpose of this study was to determine the in vivo inhibitory efficacy of azopropazone on neutrophil migration. The effects of azapropazone given at a dose of 100 mg kg−1 i.v. every 2 h on the neutrophil migration into skin inflammation sites (blister fluid) as well as into an autologous serum (± chemoattractant) placed above the blister surface (2nd chamber) were determined.

Azapropazone treatment schedule maintained blood levels at 70–100 μg ml−1 throughout the time course (360 min) of the experiment.

Azapropazone significantly inhibited (48 ± 6%) neutrophil migration into the blister fluid (as evident from the decrease in myeloperoxidase activity).

Azapropazone significantly inhibited the neutrophil migration into the autologous serum either with (65 ± 5%) or (35 ± 6%) without the chemoattractant, formyl‐methionyl‐leucyl‐phenylalanine (FMLP). The chemoattractant, FMLP, markedly increased neutrophil migration into the autologous serum by approximately 1.5 to 2 times the non‐FMLP treated group. Azapropazone was more efficacious in inhibiting the neutrophil migration in the presence of FMLP than in its absence.

We conclude that azapropazone is an effective inhibitor of neutrophil migration into topically inflamed sites in anaesthetized swine.
Phorbol esters inhibit smooth muscle contractions through activation of Na+ ‐K+ ‐ATPase
Authors: Sasaguri Toshiyuki , Watson Stephen P.
Published: July 2012

The role of protein kinase C (PKC) in agonist‐induced contractions of guinea‐pig ileum longitudinal smooth muscle has been investigated.

The phorbol esters, phorbol 12,13‐dibutyrate (PDBu), phorbol 12,13‐diacetate (PDA) and phorbol 12‐myristate 13‐acetate (PMA), relaxed tissues precontracted by submaximal concentrations of carbachol, histamine or substance P.

This inhibitory action of the phorbol esters was reversed following the application of ouabain, a specific inhibitor of Na+‐K+‐ATPase. Similarly, pretreatment with ouabain inhibited the ability of phorbol esters to relax tissues precontracted by the above agonists.

The slow relaxation of the tonic component of contraction induced by submaximal concentrations of carbachol and histamine, and all concentrations of substance P, was abolished in the presence of ouabain.

In Na+‐loaded tissues, PDBu and carbachol caused a concentration‐dependent increase of Na+‐K+‐ATPase activity, assessed by ouabain‐sensitive 86Rb+‐uptake. Extrusion of Na+, assessed by the cellular content of the ion, was also stimulated by PDBu (the effect of carbachol was not investigated).

We conclude that phorbol esters inhibit the tonic component of contractions induced by submaximal concentrations of these agonists through activation of Na+‐K+‐ATPase. We suggest that PKC may exert feedback control over the tonic component of agonist contractions through stimulation of the pump.
Vasopressin and stress‐induced antinociception in the mouse
Authors: Hart S.L. , OluyomiXY1 A.O.
Published: July 2012

Arginine vasopressin produced antinociception in the hot‐plate test after intracerebroventricular injection (0.5 μg) and in the acetic acid abdominal constriction test after intraperitoneal injection (0.1 mg kg−1).

The antinociception produced by arginine vasopressin was sensitive to deamino(CH2)5Tyr(Me) arginine vasopressin (0.5 μg i.c.v.; 0.1 mg kg−1 i.p.) but not to naloxone (5 μg i.c.v.; 2 mg kg−1 i.p.)

Arginine vasopressin when administered by the intracerebroventricular route, but not by the intraperitoneal route, produced characteristic behaviour which was sensitive to deamino(CH2)5Tyr(Me) arginine vasopressin (0.5 μg, i.c.v.).

A 3 min swim at 20°C produced antinociception on the hot‐plate which was sensitive to naloxone (0.4 mg kg−1, i.p.) but not to deamino(CH2)5Tyr(Me) arginine vasopressin (0.5 μg, i.cv.).

The reduction in the number of acetic acid‐induced abdominal constrictions produced by a 30 s swim at 30°C was not sensitive to either naloxone (2 mg kg−1, i.p.) or deamino(CH2)5Tyr(Me) arginine vasopressin (0.1 mg kg−1, i.p.).

Arginine vasopressin, at high doses, is antinociceptive in the mouse but does not appear to mediate stress‐induced antinociception in this species.
Changes in preganglionic sympathetic nerve function following chronic morphine treatment in rats
Authors: Leung Christopher M.K. , Dai Soter , Ogle Clive W.
Published: July 2012

The effects of acute or chronic morphine treatment on the changes in blood pressure and pulse rate in response to ganglionic stimulation or blockade and to vagal stimulation, and of isolated atria to field stimulation or noradrenaline, were studied.

In pithed rats, intravenously injected hexamethonium significantly depressed the blood pressure responses to sympathetic nerve stimulation. The ganglionic blocking effects of hexamethonium were significantly greater in chronically morphine‐treated rats, but were not significantly affected by acute morphine administration in naive animals.

Intravenous administration of nicotine dose‐dependently increased blood pressure and pulse rate. The magnitudes of these changes were not significantly affected by acute or chronic morphine pretreatment.

Studies with rat isolated atrial preparations revealed that the changes in atrial contractile rate and force in response to noradrenaline or field stimulation were not influenced by either acute or chronic morphine treatment.

Cervical vagal stimulation produced voltage‐ or frequency‐dependent decreases in pulse rate and blood pressure. The responses were not significantly affected by chronic morphine treatment.

These findings suggest that the site of the changes in sympathetic function following prolonged exposure to the opiate appears to be on the preganglionic nerve fibres.
Modulation of seizure susceptibility in the mouse by the strychnine‐insensitive glycine recognition site of the NMDA receptor/ion channel complex
Authors: Singh L. , Oles R.J. , Tricklebank M.D.
Published: July 2012

In order to determine whether the strychnine‐insensitive glycine modulatory site on the N‐methyl‐d‐aspartate (NMDA) receptor/ion channel complex is fully activated in vivo, the ability of the selective glycine receptor agonist, d‐serine, to modulate seizure susceptibility in the mouse has been examined.

d‐Serine (10–200 μg per mouse, i.c.v.) dose‐dependently increased the potency of NMDLA in inducing seizures in Swiss Webster mice by approximately 3 fold. l‐Serine was without significant effect.

The potency of pentylenetetrazol in inducing seizures was also enhanced by d‐, but not l‐serine, although the magnitude of the shift (1.6 fold) was considerably less than for NMDLA.

Similar doses of d‐serine were also able to block the anticonvulsant effect of the non‐selective glycine receptor antagonist, kynurenic acid, against seizures induced by NMDLA, but were without effect on the anticonvulsant effect of the competitive NMDA receptor antagonist, 3‐((+)‐2‐carboxypiperazin‐4‐yl)‐propyl‐1‐phosphonic acid (CPP).

d‐Serine completely antagonized the protective effect of the selective glycine receptor antagonist, 7‐chlorokynurenic acid, against sound‐induced seizures in DBA/2 mice, but was less effective in this model against the less selective antagonist, kynurenic acid.

The results indicate that in vivo, NMDA receptors are not maximally potentiated by endogenous glycine and suggest an important involvement of the glycine modulatory site on the NMDA receptor/ion channel complex in the pathophysiology of epilepsy.
Developmental changes in β‐adrenergic and cholinergic interactions on calcium‐dependent slow action potentials in rat ventricular muscles
Authors: Kojima Michio , Sada Hideaki , Sperelakis Nicholas
Published: July 2012

Developmental changes in the effect of isoprenaline (Iso) and acetylcholine (ACh) interactions on Ca2+‐dependent slow action potentials (APs) were studied in the ventricular muscles of foetal (12–20 days post‐gestation), neonatal (0–20 days old), and adult (2–3 months old) rats. The slow APs were recorded at 0.2 Hz in partially depolarized preparations (an extracellular K+ concentration of 25 mm).

Iso (1 nm to 10 μm) began to increase the of the slow APs (an approximate indicator of Ca2+ current) on foetal day 18; its potentiating effect became greater with age and reached the adult level about 2 weeks after birth.

ACh (10 μm) abolished the Iso (1 μm)‐induced increased in the observed in the late foetal and neonatal periods.

The inhibitory effect of ACh on the was antagonized by atropine but not by pirenzepine, suggesting that ACh reduces Ca2+ current (in the presence of β‐adrenoceptor agonists) by stimulating muscarinic (M2) cholinoceptors.

These results suggest that developmental changes in the modulatory effects of β‐adrenoceptor and cholinoceptor agonists on Ca2+ channels occur from a few days before birth to 2 weeks after birth and that the functional coupling between muscarinic cholinoceptors and Ca2+ channels has already been established when the coupling between β‐adrenoceptors and Ca2+ channels starts to operate.
Inhibition of Na+ ‐K+ pump activity by divalent cations in intact peritoneal mast cells of the rat
Authors: Knudsen Trorben , Berthelsen Henrik C. , Johansen Torben
Published: July 2012

The inhibition by the divalent cations magnesium, barium and strontium and the trivalent ion lanthanum of the Na+‐K+ pump in the plasma membrane of rat peritoneal mast cells was studied in pure mast cell populations by measurement of the ouabain‐sensitive uptake of the radioactive potassium analogue, 86rubidium (86Rb+).

Exposure of the cells to magnesium induced a time‐ and concentration‐dependent decrease in the ouabain‐sensitive K+(86Rb+)‐uptake of the cells without influencing the ouabain‐resistant uptake. The time‐dependent decrease was apparent after incubation of the cells for 10 min or more, but no decrease was observed after 2 min incubation when the cells are supposed to be loaded with sodium due to the cell isolation procedure.

Barium and strontium caused concentration‐dependent decreases in the ouabain‐sensitive K+‐(86Rb+) ‐uptake of the cells but the ouabain‐resistant uptake was not changed. Half maximum decrease in the ouabain‐sensitive K+(86Rb+)‐uptake was observed with 1.8 mm magnesium, 1.2 mm barium and 0.7 mm strontium.

The trivalent ion lanthanum blocked almost completely the ouabain‐sensitive K+(86Rb+)‐uptake at a concentration of 1 μm as does 1 mm calcium. Combining either of these ions with magnesium had no further inhibitory effect on the ouabain‐sensitive uptake.

In conclusion, in addition to the previously suggested modulation by calcium of the activity of the Na+‐K+ pump, evidence is provided in this investigation that the modulation may be a more general effect of divalent and polyvalent cations present in the extracellular space through their influence on the sodium permeability of the plasma membrane.
Endogenous nitric oxide as a modulator of rabbit skeletal muscle microcirculation in vivo
Authors: Persson M.G. , Gustafsson L.E. , Wikludn N.P. , Hedqvist P. , Moncada S.
Published: July 2012

Intravital microscopy of rabbit tenuissimus muscle microvasculature was used for in vivo studies of the role of endogenous nitric oxide (NO) in local vascular control. Derivatives of arginine were applied topically in order to modulate the formation of NO from l‐arginine.

l‐NG‐monomethylarginine (l‐NMMA) (10–100 μm), but not d‐NG‐monomethylarginine (d‐NMMA), dose‐dependently reduced microvascular diameters. The vasoconstriction induced by l‐NMMA (100 μm) was prevented by pretreatment with l‐arginine (1 mm) but not with d‐arginine (1 mm). Intravenous infusions of l‐arginine (300 mg kg−1) reversed the effect of l‐NMMA (100 μm). l‐Arginine or d‐arginine applied topically at 1 mm per se had no effect on microvascular diameters.

Vasodilatation by acetylcholine (0.03‐3 μm) was significantly inhibited by l‐NMMA (100 μm), whereas vasodilatation by adenosine (0.1–100 μm) or sodium nitroprusside (100 nm) was not affected.

The hyperaemic response after tenuissimus muscle contractions induced by motor nerve stimulation was unaffected by the presence of l‐NMMA (100 μm).

Aggregates of platelets and white blood cells were seen in venules during superfusion with l‐NMMA (100 μm), but not with d‐NMMA (100 μm).

Our results suggest that endogenous NO formed from l‐arginine is a modulator of microvascular tone and platelet and white cell‐vessel wall interaction in vivo. Nitric oxide does not, however, appear to play a role in the mediation of functional hyperaemia in this tissue.
Effects of butanedione monoxime on neuromuscular transmission
Authors: Gage P.W. , McArdle J.J. , Saint D.A.
Published: July 2012

The amplitude of endplate potentials was increased by concentrations of butanedione monoxime (BDM, 5–20 mm) that typically caused muscle paralysis.

Although BDM slowed the decay of spontaneous miniature endplate currents, the effect was insuffient to explain most of the large increase in amplitude of endplate potentials.

The quantal content of endplate potentials was increased by BDM in a reversible, concentration‐dependent manner.

The frequency of miniature endplate potentials was not changed by 10 mm BDM in the presence of normal or raised potassium concentrations, indicating that BDM does not change quantal content by a direct effect on calcium channels or on steady‐state intracellular calcium concentration.

A change in the time course of the extracellularly recorded nerve terminal action potential caused by BDM was similar to the change produced by 4‐aminopyridine (4‐AP).

The increase in quantal content produced by BDM was only slightly reduced in the presence of 1 mm tetraethylammonium (TEA) but was significantly reduced in the presence of 0.5 to 1 mm 4‐AP.

It was concluded that BDM blocks a 4‐AP‐sensitive potassium conductance in motor nerve terminals and, by increasing the duration of the action potential in this way, increases evoked transmitter release.
Bradykinin induces elevations of cytosolic calcium through mobilisation of intracellular and extracellular pools in bovine aortic endothelial cells
Authors: Buchan Kevin W. , Martin William
Published: July 2012

In the presence of 1.8 mm extracellular calcium, bradykinin (0.3 nm–100 nm) induced a biphasic elevation of intracellular calcium ([Ca2+]i) in bovine aortic endothelial cells, consisting of an initial, large transient component followed by a lower sustained component.

When endothelial cells were bathed in nominally calcium‐free solution containing 0.5 mm EGTA, bradykinin induced only a transient elevation of [Ca2+]i: the magnitude of this was significantly smaller than that obtained in the presence of extracellular calcium and the sustained phase was abolished. In the continued presence of bradykinin, re‐addition of extracellular calcium to achieve a level of around 1.8 mm resulted in the induction of a biphasic elevation of [Ca2+]i consisting of a large initial component followed by a lower sustained component.

In the presence of 1.8 mm extracellular calcium, caffeine (5 mm) induced a small elevation of [Ca2+]i. When endothelial cells were bathed in nominally calcium‐free solution containing 0.5 mm EGTA, the caffeine‐induced elevation of [Ca2+]i was almost completely abolished.

In the presence of 1.8 mm extracellular calcium, treatment of endothelial cells with the calcium influx blocker, nickel chloride (4 mm), had no effect on resting [Ca2+]i or on the magnitude of the bradykinin‐induced initial transient elevation of [Ca2+]i but abolished the sustained component.

In the presence of 1 mm extracellular calcium, treatment with the calcium chelator EGTA (2 mm; 1 min) had no effect on resting [Ca2+]i but the magnitude of the bradykinin‐induced initial transient elevation of [Ca2+]i was significantly reduced. Increasing the exposure time or concentration of EGTA resulted in no further reduction in the magnitude of the bradykinin‐induced transient component.

Treatment of endothelial cells with the putative inhibitor of intracellular calcium release, 3,4,5‐trimethoxybenzoic acid 8‐(diethylamino)octyl ester (TMB‐8, 0.1 mm) increased resting [Ca2+]i slightly but had no effect on the magnitude of the bradykinin‐stimulated elevation of [Ca2+]i.

These findings suggest that, in bovine aortic endothelial cells, the bradykinin‐induced initial transient elevation of [Ca2+]i is completely dependent upon release of calcium from intracellular stores and the sustained component is due to calcium influx. They further suggest the possible existence of two intracellular calcium pools, one which is rapidly depleted in the absence of extracellular calcium and a second which is resistant to such depletion.
The effects of calcitonin gene‐related peptide on submucosal gland secretion and epithelial albumin transport in the ferret trachea in vitro
Authors: Webber S.E. , Lim J.C.S. , Widdicombe J.G.
Published: July 2012

We have examined the effect of calcitonin gene‐related peptide (CGRP) on basal mucus volume, lysozyme and albumin outputs from the ferret whole trachea in vitro, and on the outputs produced by methacholine and substance P (SP). We have also examined the effect of inhibiting neutral enkephalinase with thiorphan on the responses to CGRP.

CGRP (1–100 nm) produced small concentration‐dependent increases in basal mucus volume, lysozyme and albumin outputs. These effects of CGRP were enhanced by thiorphan. The increases in basal outputs with CGRP and the potentiation by thiorphan were considerably less than previously observed with SP and neurokinin A (NKA). CGRP had no significant effect on potential difference (PD) across the trachea.

CGRP produced a concentration‐dependent inhibition of methacholine‐ and SP‐induced lysozyme output but a concentration‐dependent increase in methacholine‐ and SP‐induced albumin output. The effects of CGRP on methacholine‐induced lysozyme and albumin outputs were enhanced by thiorphan. CGRP weakly inhibited methacholine‐induced mucus volume output and weakly enhanced SP‐induced mucus volume output.

Thus, CGRP weakly stimulates basal serous cell secretion and epithelial albumin transport, but does not alter epithelial integrity. CGRP inhibits the serous cell secretion due to methacholine or SP, but potentiates the epithelial albumin transport produced by these agents. The interaction between CGRP and other sensory neuropeptides or muscarinic agonists on airway submucosal glands and epithelium may be important in the normal airway and in inflammatory airway diseases where release of sensory neuropeptides is enhanced.
Comparison of the effects of neuropeptide Y and noradrenaline on rat gastric mucosal blood flow and integrity
Authors: Tepperman B.L. , Whittle B.J.R.
Published: July 2012

The effects of neuropeptide Y (NPY) and noradrenaline on rat gastric mucosal blood flow, as estimated by laser Doppler flowmetry (LDF), have been examined. In addition, the ability of NPY and noradrenaline to induce acute mucosal haemorrhagic damage has also been assessed.

Close‐arterial infusion of NPY (0.05–0.2 nmol kg−1 min−1) for 10 min in the anaesthetized rat induced a dose‐dependent fall in LDF, but had minimal effects on systemic arterial blood pressure. Higher doses of NPY did not produce any further reduction in LDF.

Close‐arterial infusion (0.1–0.4 nmol kg−1 min−1) of the structurally related peptide YY (PYY) or pancreatic polypeptide (PP), had inconsistent actions in decreasing LDF.

Close‐arterial infusion of noradrenaline (30–90 nmol kg−1 min−1) dose‐dependently reduced gastric LDF.

Local infusion of NPY (0.1 and 0.2 nmol kg−1 min−1) or noradrenaline (45 and 60 nmol kg−1 min−1) resulted in dose‐related increases in the area of mucosal hemorrhagic damage.

Pretreatment with the α1‐adrenoceptor antagonist, prazosin (0.1 mg kg−1, i.v.) significantly reduced the effect of noradrenaline, but not NPY, on both LDF and mucosal damage.

These findings indicate that NPY and noradrenaline act directly on the gastric microvasculature to induce vasoconstriction and both can induce acute mucosal damage. Therefore endogenous NPY, like noradrenaline could play a modulatory role in regulating vascular tone and may influence mucosal integrity.
Prejunctional nicotinic receptors involved in facilitation of stimulation‐evoked noradrenaline release from the vas deferens of the guinea‐pig
Authors: Todorov L. , Windisch K. , Shersen H. , Lajtha A. , Papasova M. , Vizi E.S.
Published: July 2012

In guinea‐pig prostatic vas deferens loaded with [3H]‐noradrenaline ([3H]‐NA), nicotinic receptor agonists, nicotine and dimethylphenylpiperazinium (DMPP) enhanced the resting and facilitated the stimulation‐evoked release of [3H]‐NA in a concentration‐dependent fashion. The effect of nicotine on both contraction of vas deferens and release of NA in response to field stimulation was stereospecific in favour of the naturally occurring (−)‐enantiomer. Prolonged (15 min) exposure to (−)‐nicotine resulted in a cessation of the facilitatory effect on NA release and on responses of the vas deferens to field stimulation.

The rank order of agonist potency in facilitating NA release was DMPP = (−)‐nicotine > (+)‐nicotine. Cytisine had no agonistic activity. The dissociation constants (KD) of antagonists were 9.3 ± 0.6 and 31.4 + 2.4 μm for (+)‐tubocurarine and hexamethonium, respectively, when (−)‐nicotine was used as agonist. α‐Bungarotoxin had no antagonistic activity. These findings suggest that nicotinic receptors located on noradrenergic axon terminals are different from those located postsynaptically in striated muscle or ganglia but seem similar to those present on cholinergic axon terminals at the neuromuscular junction.

Cotinine, the breakdown product of nicotine failed to have any agonistic activity indicating that nicotine itself is responsible for the effects observed on axon terminals.

Stimulation of presynaptic muscarinic receptors by oxotremorine prevented the nicotine‐induced facilitation of [3H]‐NA release, indicating the presence of both inhibitory muscarinic and facilitatory nicotinic receptors on noradrenergic axon terminals.
Vascular 5‐HT1‐like receptors that mediate contraction of the dog isolated saphenous vein and carotid arterial vasoconstriction in anaesthetized dogs are not of the 5‐HT1A or 5‐HT1D subtype
Authors: Perren Marion J. , Feniuk Wasyl , Humphrey Patrick P.A.
Published: July 2012

There is controversy about whether 5‐HT1A receptors mediate contraction of isolated cerebral blood vessels. We have therefore compared the vascular actions of the 5‐HT1A receptor agonist, 8‐hydroxy‐2‐(di‐n‐propyl‐amino)‐tetralin (8‐OH‐DPAT) with those of the 5‐HT1‐like receptor agonist, sumatriptan, on the dog isolated saphenous vein, which contains a 5‐HT1‐like receptor similar to those on cerebral blood vessels, and in the carotid circulation of the anaesthetized dog.

5‐Hydroxytryptamine (5‐HT), sumatriptan and 8‐OH‐DPAT each caused contraction of dog isolated saphenous vein with a rank order of agonist potency of 5‐HT > sumatriptan > 8‐OH‐DPAT and EC50 values (95% confidence limits) of 0.06 (0.04–0.08), 0.3 (0.1–0.8) and 3.9 (2.0–7.5) μm respectively. The maximum contractile effect produced by each agonist was similar.

The contractile effects of 5‐HT, sumatriptan and 8‐OH‐DPAT in the dog isolated saphenous vein were resistant to antagonism by the 5‐HT1A receptor antagonists spiperone, spiroxatrine and pindolol (all 1 μm). The 5‐HT1D receptor ligands, metergoline (0.1 μm) rauwolscine (1 μm) and yohimbine (1 μm) had little or no antagonist activity. In contrast, the non‐selective 5‐HT1‐like receptor blocking drug, methiothepin (0.03–0.3 μm) potently antagonized the contractile effects of 5‐HT, sumatriptan and 8‐OH‐DPAT to a similar degree, suggesting that all three agonists act at the same receptor.

In ganglion‐blocked, anaesthetized dogs, intra‐carotid administration of 8‐OH‐DPAT (0.3–3 μg kg−1) and sumatriptan (0.1–1 μg kg−1), caused dose‐dependent carotid arterial vasoconstriction. The two agonists were approximately equipotent in this respect.

The carotid arterial vasoconstrictor actions of 8‐OH‐DPAT and sumatriptan were not modified by spiperone (1 mg kg−1, i.v.) but were antagonized to a similar extent by the subsequent administration of methiothepin (1 mg kg−1, i.v.).

These results suggest that 8‐OH‐DPAT contracts the dog isolated saphenous vein and constricts the carotid arterial circulation of anaesthetized dogs by activation of 5‐HT1‐like receptors which are not of the 5‐HT1A subtype, nor, on the basis of data with metergoline in the dog isolated saphenous vein, of the 5‐HT1D subtype. The receptor involved in these actions appears to be the same as that mediating the vasoconstrictor effects of sumatriptan. This receptor does not appear to be like any known 5‐HT1 ligand binding site; hence the current description, 5‐HT1‐like, remains the most appropriate.
Dicentrine, a natural vascular α1‐adrenoceptor antagonist, isolated from Lindera megaphylla
Authors: Teng Che‐Ming , Yu Sheu‐Meei , Ko Feng‐Nien , Chen Chien‐Chih , Huang Yu‐Ling , Huang Tur‐Fu
Published: July 2012

The pharmacological activity of dicentrine, isolated from Lindera megaphylla, was determind in rat isolated thoracic aorta, guinea‐pig isolated trachea and human platelet‐rich plasma.

Dicentrine was found to be a potent α1‐adrenoceptor blocking agent in rat thoracic aorta as revealed by its competitive antagonism of noradrenaline‐ (pA2 = 8.19 ± 0.09) or phenylephrine (pA2 = 9.01 ± 0.10)‐induced vasoconstriction. These effects still persisted in denuded aorta. It was less potent than prazosin (pA2 = 10.60 ± 0.10), but was more potent than phentolamine (pA2 = 7.53 ±0.10) or yohimbine (pA2 = 6.20 ± 0.05).

Inositol monophosphate formation induced by noradrenaline (3 μm) in rat thoracic aorta was suppressed by dicentrine (3–10 μm) and prazosin (3 μm).

A high concentration of dicentrine (30 μm) did not affect the aortic contraction induced by the thromboxane receptor agonist U‐46619 (1 μm), angiotensin II (1 μm), high potassium (60 mm) or carbachol (3 μm).

Contraction of guinea‐pig trachea caused by histamine or carbachol was slightly inhibited by dicentrine (30 μm), while β‐adrenoceptor relaxation to isoprenaline in trachea was not affected.

Aggregation in human platelet‐rich plasma induced by adrenaline (10 μm) was blocked by yohimbine (5 μm). A high concentration of dicentrine (> 30 μm) caused slight inhibition of aggregation, the release reaction and thromboxane formation. Complete blockade was obtained with 150 μm dicentrine.

It is concluded that dicentrine is a potent, selective α1‐adrenoceptor antagonist in vascular smooth muscle.
Direct effects of adenylyl 5′‐(β,γ‐methylene)diphosphonate, a stable ATP analogue, on relaxant P1‐purinoceptors in smooth muscle
Authors: Hourani S.M.O. , Bailey S.J. , Nicholls J. , Kitchen I.
Published: July 2012

Previous results obtained with the rat colon muscularis mucosae, which contracts in response to adenosine and adenosine 5′‐triphosphate (ATP), had suggested that adenylyl 5′‐(β,γ‐methylene)diphosphonate (AMPPCP), a stable ATP analogue, acted on P1‐purinoceptors rather than, as expected, on P2‐purinoceptors. This possibility has been examined in two tissues in which adenosine and ATP both cause relaxation, the guinea‐pig taenia caeci and the rat duodenum.

ATP, 2‐methylthio‐ATP (2‐MeSATP), AMPPCP, adenosine 5′‐(α,β‐methylene)triphosphonate (AMPCPP) and adenosine each relaxed the taenia caeci and the duodenum, and the order of potency of the nucleotides in each tissue was 2‐MeSATP > ATP > AMPCPP > AMPPCP, indicating that these effects were mediated by P2Y‐purinoceptors.

The P1 antagonist 8‐(p‐sulphophenyl)theophylline (8‐SPT) (100 μm) did not affect the responses to ATP, 2‐MeSATP or AMPCPP in either tissue, but inhibited the responses of adenosine and of AMPPCP in both tissues. In the duodenum a lower concentration of 8‐SPT caused a parallel shift to the right of the concentration‐response curve to adenosine and to AMPPCP but to different extents, with AMPPCP being inhibited more powerfully than adenosine. A dose‐ratio of around 5 was observed for adenosine and AMPPCP at concentrations of 8‐SPT of 20 μm and 2 μm respectively, but Schild analysis resulted in plots with slopes greater than unity. In the taenia caeci, however, 8‐SPT inhibited adenosine more powerfully than AMPPCP, and a range of concentrations (10–20 μm) only caused a two fold shift in the concentration‐response curve for AMPPCP, although the concentration‐response curve to adenosine was shifted in a concentration‐dependent manner and Schild analysis gave a pA2 value of 5.13 with a slope of 0.90.

As has been shown in other tissues, including the guinea‐pig taenia caeci, ATP (100 μm) was rapidly dephosphorylated by enzymes present in the rat duodenum, with less than 10% remaining after 20 min incubation, whereas AMPPCP (100 μm) was resistant to degradation, with greater than 90% remaining at the same time point.

AMPPCP therefore has pronounced but variable agonist actions on P1‐purinoceptors, and appears to act entirely via these receptors on the rat duodenum although in the guinea‐pig taenia caeci this action is less important and it acts largely via P2Y‐purinoceptors. These P1‐purinoceptor effects of AMPPCP are direct and are not due to its degradation to adenosine.
Characterization of endothelin receptors on a human neuroblastoma cell line: evidence for the ETA subtype
Authors: Wilkes Lesley C. , Boarder Michael R.
Published: July 2012

Specific binding sites for synthetic endothelin (ET) isoforms were studied on intact cells of the SK‐N‐MC cell line, derived from a human neuroblastoma.

[125I]‐ET‐1 (2.5 × 10−11 m) specifically bound to a single class of binding sites on these cells (Hill coefficient of 1.06 ± 0.04, n = 3) with an apparent Kd of 1.4 ± 0.3 × 10−9 m and a Bmax of 3.1 ± 1.0 pmol mg−1 protein. [125I]‐ET‐3 (2.5 × 10−11 m), did not specifically bind to SK‐N‐MC cells.

The binding of [125I]‐ET‐1 was competitively inhibited by other ET isoforms, the order of potency being ET‐1 > sarafotoxin S6b > ET‐3.

Association of 1 nm [125I]‐ET‐1 at 37°C reached apparent equilibrium at 60–80 min, with half‐maximal binding being achieved at 12 min.

Dissociation was measured after both 10 min and 60 min of association with 64% and 30% respectively of specifically bound [125I]‐ET‐1 dissociating. The actual amounts of [125I]‐ET‐1 dissociated were similar in both cases.

Incubation of [125I]‐ET‐3 with SK‐N‐MC cells at 37°C for 60 min did not result in significant degradation of this peptide. However, [125I]‐ET‐1 was broken down by incubation with SK‐N‐MC cells, the pattern of degradation of dissociable [125I]‐ET‐1 (and that found in the supernatant) being different from that of non‐dissociable [125I]‐ET‐1.

ET‐1 concentration‐dependently induced an increase in total inositol phosphate accumulation in sub‐confluent (but not in confluent) cultures of SK‐N‐MC cells (EC50 = 6.43 ± 1.9 × 10−10 m). ET‐3 was without effect.

These results show that ET‐1 specifically binds to SK‐N‐MC cells with the characteristics of an ETA receptor. Our earlier finding that adrenal chromaffin cells express an ETB receptor indicates the existence of multiple ET receptor types on neuronal cells.
Access of peripherally administered DuP 753 to rat brain angiotensin II receptors
Authors: Song Keifu , Zhuo Jialong , Mendelsohn Frederick A.O.
Published: July 2012

The in vivo access of the nonpeptide angiotensin II (Ang II) antagonist, DuP 753 (10 mg kg−1, i.v.), to Ang II receptors of rat brain was investigated by in vitro autoradiography with [125I]‐[Sar1, Ile8] Ang II as a ligand. DuP 753 markedly inhibited the binding to sites which contain exclusively AT1 receptors both outside and within the blood brain barrier, such as the circumventricular organs, paraventricular hypothalamic nucleus, median preoptic nucleus and nucleus of the solitary tract. However, binding to other nuclei containing AT2 receptors was not significantly inhibited. These results demonstrate that DuP 753 and/or its active metabolite readily cross the blood brain barrier in vivo and selectively inhibit binding to AT1 receptors in specific brain nuclei.
Evidence for inhibition of sympathetic neurotransmission by endogenously released acetylcholine in the guinea‐pig trachea
Authors: Pendry Yvonne D. , Maclagan Jennifer
Published: July 2012

Interactions between pulmonary cholinergic and noradrenergic nerves were studied in the innervated tracheal tube preparation isolated from guinea‐pigs anaesthetized with urethane. Relaxations of the trachealis smooth muscle in response to postganglionic stimulation of the sympathetic nerve were recorded as decreases in the intraluminal pressure of the tracheal tube after the pressure had been raised with the stable thromboxane‐mimetic, U46619. In contrast, contractions following preganglionic stimulation of the vagal nerve trunk were recorded as increases in intraluminal pressure.

In approximately half of the preparations studied, concurrent stimulation of the vagal nerve trunk inhibited relaxation responses elicited by stimulation of the sympathetic nerves. The vagi were stimulated at parameters which caused no change in intraluminal pressure, excluding the involvement of postjunctional mechanisms.

The effect of simultaneous stimulation of the sympathetic nerve trunk was studied on contractile responses evoked by preganglionic stimulation of the vagus nerve. In 80% of the preparations tested the vagal responses were inhibited. This inhibitory effect of sympathetic nerve stimulation was antagonized by propranolol.

The potassium channel agonist, cromakalim, endothelins 1 and 3 and the neuropeptides, vasoactive intestinal peptide, neurokinin A and substance P, did not significantly modulate sympathetic nerve‐induced relaxations.

The anticholinesterase drug, physostigmine, induced a concentration‐dependent increase in the intraluminal pressure of the tracheal tube and potentiated the postjunctional action of exogenously applied acetylcholine to contract the guinea‐pig trachealis muscle. In the presence of higher concentrations of physostigmine both vagally‐induced contractions and sympathetic nerve‐induced relaxations were reduced. Atropine blocked both the inhibitory effect of physostigmine on sympathetic relaxations and its postjunctional contractile action on the trachealis smooth muscle.

It is concluded that, in the guinea‐pig trachea, acetylcholine released endogenously from pulmonary parasympathetic nerves, either by anticholinesterase drugs or in response to nerve stimulation, can inhibit transmission in the adjacent sympathetic nerves via activation of prejunctional muscarinic heteroreceptors, probably of the M3 subtype.