bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional haemodynamic effects of endothelin‐1 and endothelin‐3 in conscious Long Evans and Brattleboro rats
Authors: Gardiner S.M. , Compton A.M. , Bennett T.
Published: July 2012

The regional haemodynamic effects of bolus doses (4 and 40 pmol) and infusions (12 and 120 pmol h−1) of endothelin‐1 and endothelin‐3 were assessed in conscious, Long Evans and Brattleboro (i.e. vasopressin‐deficient) rats, chronically‐instrumented with pulsed Doppler flow probes.

In both strains of rat the lower bolus dose of endothelin‐1 caused only a slight pressor effect, but there were marked renal and mesenteric vasoconstrictions and hindquarters vasodilatation.

The lower bolus dose of endothelin‐3 did not affect blood pressure significantly, although the changes in regional haemodynamics were qualitatively similar to those seen following endothelin‐1 in Long Evans and Brattleboro rats.

The higher dose of endothelin‐1 caused an initial hypotension accompanied by substantial hindquarters vasodilatations in Long Evans and Brattleboro rats. Subsequently, in both strains, there was a rise in blood pressure accompanied by renal, mesenteric and hindquarters vasoconstrictions.

The higher bolus dose of endothelin‐3 caused initial hypotension and hindquarters vasodilatation similar to those seen with endothelin‐1. However, the subsequent pressor effect was less with endothelin‐3, as was the renal vasoconstriction, and it did not cause any increase in hindquarters vascular resistance.

Infusion of endothelin‐1 at the lower rate (12 pmol h−1) caused renal and mesenteric vasoconstrictions in both strains of rat, whereas endothelin‐3 at this rate caused only mesenteric vasoconstriction.

Infusion of endothelin‐1 at the higher rate (120 pmol h−1) caused progressive hypertension and vasoconstrictions in all three vascular beds studied; these were similar in both strains of rat. Endothelin‐3 had a smaller pressor effect and a lesser constrictor action on the renal and mesenteric vascular beds; it did not constrict the hindquarters vascular bed.

These results show, that in conscious Long Evans and Brattleboro rats, the initial depressor effects of the higher bolus doses of endothelin‐1 and −3 were similar, and, hence, not influenced by the absence of endogenous vasopressin. Endothelin‐1 and −3 appear equipotent in their initial hyperaemic vasodilator effects in the hindquarters vasculature in both strains, making it unlikely that this effect is dependent on the release of atrial natriuretic peptide (ANP), since ANP does not cause significant increases in hindquarters blood flow in Brattleboro rats. The greater delayed pressor effect of endothelin‐1 is associated with its more marked vasoconstrictor effects on renal and mesenteric vascular beds and is accentuated, relative to endothelin‐3, by the lack of a constrictor effect of endothelin‐3 in the hindquarters vasculature.
In vitro cardiac models of dog Purkinje fibre triggered and spontaneous electrical activity: effects of nicorandil
Authors: Lathrop David A. , Nànàsi Pèter P. , Varrò Andràs
Published: July 2012

The effects of nicorandil (30 μm and 100 μm) on two models of triggered activity [early afterdepolarizations (EADs) and delayed afterdepolarizations (DADs)] and on spontaneous automaticity occurring from both normal and depolarized levels of membrane potential were examined in isolated cardiac Purkinje fibres of the dog. Standard intracellular microelectrode techniques were used.

Nicorandil (30 μm) abolished EADs provoked by superfusion with Tyrode solution containing 2.7 mm K+ and 3 mm Cs.

DADs were induced by 0.2 μm acetylstrophanthidin in Tyrode solution containing 5.4 mm K+. Nicorandil (30 μm) significantly reduced the amplitude of these DADs from 12.5 ± 2.5 mV to 5.5 ± 0.2 mV (P > 0.02, n = 6), while DADs were fully abolished by 100 μm nicorandil.

In unstimulated Purkinje strands, superfused with 2.7 mm K+ containing Tyrode solution having a pH of either 7.4 or 6.8, spontaneous depolarizations developed with a mean maximum diastolic potential (MDP) of −84.6 ± 1.6 mV (n = 9) or −54.0 ± 1.2 mV (n = 9), respectively. Nicorandil significantly reduced the frequency of this automatic activity and caused its cessation, at either level of MDP. Nicorandil, however, produced significant hyperpolarization only when automaticity occurred from the depolarized level of potential.

These results suggest that nicorandil may exert significant antiarrhythmic actions in vivo by abolishing both spontaneous and triggered electrical activity.
β1‐Adrenoceptors mediate smooth muscle relaxation in mouse isolated trachea
Authors: Henry Peter J. , Goldie Roy G.
Published: July 2012

The relaxant effects to the β‐adrenoceptor agonists isoprenaline, adrenaline, noradrenaline, RO363, procaterol and fenoterol were investigated in carbachol‐contracted mouse isolated tracheal preparations.

The order of potencies for those β‐adrenoceptor agonists that induced full relaxation of carbachol‐contracted mouse tracheal preparations was isoprenaline > RO363 > noradrenaline = adrenaline > fenoterol. The EC50 value of isoprenaline for relaxation was 46 nm. The β1‐adrenoceptor‐selective agonist, RO363, was ten times more potent than the β2‐adrenoceptor‐selective agonist, fenoterol. The highly β2‐adrenoceptor‐selective agonist procaterol was a partial relaxant and induced only 28 ± 4% relaxation.

Relaxations induced by noradrenaline and isoprenaline were not significantly affected by the neuronal uptake inhibitor, cocaine (10 μm) or by the extraneuronal uptake inhibitor, deoxycorticosterone acetate (25 μm) respectively. The α‐adrenoceptor agonist methoxamine induced no observable elevation of mouse tracheal smooth muscle tone.

Schild plots for the β‐adrenoceptor antagonists, atenolol and betaxolol (β1‐adrenoceptor‐selective) and ICI 118,551 (β2‐adrenoceptor‐selective) were linear, with slope values approaching unity. Mean pA2 values derived for atenolol, betaxolol and ICI 118,551 for antagonism of β‐adrenoceptor‐mediated relaxation were 7.1, 8.4 and 7.2, respectively. These data were independent of the use of isoprenaline or noradrenaline as the agonist.

These findings indicate that β‐adrenoceptor‐mediated relaxations of mouse isolated trachea occur predominantly through activation of β1‐adrenoceptors.
Distribution of β1‐ and β2‐adrenoceptors in mouse trachea and lung: a quantitative autoradiographic study
Authors: Henry Peter J. , Rigby Paul J. , Goldie Roy G.
Published: July 2012

Binding and quantitative autoradiography were used to detect [125I]‐iodocyanopindolol (I‐CYP) associated with β1‐ and β2‐adrenoceptors in mouse tracheal epithelium and airway smooth muscle as well as in lung parenchymal tissue.

Specific I‐CYP binding to slide‐mounted tissue sections of both trachea and parenchyma was of high affinity (KD = 49.0 pm, n = 3, trachea; KD = 118.9 pm, n = 3, parenchyma) and saturable, involving single populations of non‐interacting binding sites (Hill coefficient nH = 1.00 ± 0.02, trachea; nH = 0.99 ± 0.03, parenchyma).

Direct measurement of tissue radioactivity also showed that specific I‐CYP binding was competitively inhibited in the presence of the β‐adrenoceptor antagonists (−)‐propranolol (non‐selective), CGP 20712A (β1‐selective) and ICI 118,551 (β2‐selective). Analysis of the competition binding curves for the two selective antagonists revealed mixed populations of β1‐ and β2‐adrenoceptors in the approximate proportions 33% and 67% respectively in mouse trachea and 28% and 72% respectively in mouse lung parenchyma.

Densities of autoradiographic grains derived from specific I‐CYP binding to alveolar wall tissue and to tracheal epithelium and airway smooth muscle were quantified by a computer‐assisted image analysis system, which allowed the construction of competition binding curves in the presence of the selective β‐adrenoceptor antagonists CGP 20712A and ICI 118,551. Analysis of these data demonstrated that in alveolar wall, β1‐ and β2‐adrenoceptors co‐existed in the proportions 18% and 82%, respectively.

Quantitative autoradiographic analyses also showed that β1‐ and β2‐adrenoceptors were differentially distributed in tracheal epithelium and airway smooth muscle. The β2‐adrenoceptor subtype accounted for 71% of all β‐adrenoceptors in epithelium. Conversely, β1‐adrenoceptors which mediate relaxant responses of mouse trachea to β‐adrenoceptor agonists (Henry & Goldie, 1990), accounted for 69% of all β‐adrenoceptors in the airway smooth muscle.
Differential inhibition by two hetrazepine PAF antagonists of acute inflammation in the mouse
Authors: Henriques Maria G.M.O. , Weg Vivian B. , Martins Marco A. , Silva Patricia M.R. , Fernandes Patricia D. , Cordeiro Renato S.B. , Vargaftig B.B.
Published: July 2012

The injection of 100 or 300 μg of carrageenin into the mouse paw or pleural cavity produced a delayed inflammatory reaction at 48 h while platelet activating factor (PAF)‐induced paw oedema and pleurisy were maximal 30 min after its injection.

The PAF antagonist, WEB 2086, failed to inhibit mouse paw oedema and pleurisy induced by PAF, but reduced the first phase of oedema (1–4 h) induced by carrageenin without interfering with the second one (48–72 h). In contrast, another structurally‐related PAF antagonist, WEB 2170, inhibited dose‐dependently both oedema and pleurisy induced by PAF and by carrageenin (48 h).

Repeated injections of PAF into the mouse paw or pleural cavity led to significant auto‐desensitization. The animals desensitized to PAF and injected with carrageenin also displayed a significantly reduced oedema.

Our results suggest that PAF may be involved in the inflammatory response to carrageenin in mice. Furthermore, because the different receptor antagonists displayed distinct effects against PAF itself, different sites for in vivo interaction of PAF are available and are species‐ and drug‐dependent.
Motor response of the human isolated small intestine and urinary bladder to porcine neuromedin U‐8
Authors: Maggi Carlo Alberto , Patacchini Riccardo , Giuliani Sandro , Turini Damiano , Barbanti Gabriele , Rovero Paolo , Meli Alberto
Published: July 2012

Porcine neuromedin U‐8 produced a concentration (0.3 nm−1 μm)‐dependent contraction of the longitudinal muscle of the human isolated ileum, which was unaffected by either atropine (1 μm) or tetrodotoxin (1 μm).

By contrast, neuromedin U‐8 had only a weak effect on the circular muscle of the human isolated ileum.

Neuromedin U‐8 also produced a concentration‐dependent contraction of mucosa‐free muscle strips from the dome of the human isolated urinary bladder, its action being unaffected by either atropine or tetrodotoxin.

These findings indicate that neuromedin U‐8 exerts a direct contractile effect on smooth muscle of the human intestinal and urinary tract.
Developmental changes in β‐adrenoceptors, muscarinic cholinoceptors and Ca2+ channels in rat ventricular muscles
Authors: Kojima Michio , Ishima Tsuyoshi , Taniguchi Norihisa , Kimura Kiyoshi , Sada Hideaki , Sperelakis Nicholas
Published: July 2012

In an attempt to explain the previous electrophysiological data on the ontogeny of β‐adrenergic and muscarinic cholinergic interactions on cardiac Ca2+ current, biochemical studies were performed on the ontogeny of β‐adrenoceptors, muscarinic cholinoceptors and Ca2+ channels in cardiac muscle of developing rats: 16–20 days old foetuses, 0–20 days old neonates, and 2–3 months old adults.

Developmental changes in cardiac β‐adrenoceptors, muscarinic cholinoceptors, and Ca2+ channels were determined with the use of specific radioligands, [3H]‐dihydroalprenolol (DHA), [3H]‐quinuclidinyl benzilate (QNB), and [3H]‐nitrendipine (NTD), respectively.

The Bmax value (fmol mg−1 tissue) for [3H]‐DHA binding started to increase on post‐gestation day 20, reached almost its maximum level on neonatal day 6, kept almost the same level until neonatal day 20, and then decreased slightly to its adult level.

The Bmax value (fmol mg−1 tissue) for [3H]‐QNB binding started to increase on post‐gestation day 16, reached almost its maximum level on neonatal day 0, remained almost constant until neonatal day 15, and then decreased to its adult level.

The Bmax value (fmol mg−1 tissue) for [3H]‐NTD binding increased with age between post‐gestation day 18 and neonatal day 15, stayed almost constant until neonatal day 20, and then decreased to its adult level.

The Kd values for [3H]‐DHA, [3H]‐QNB, and [3H]‐NTD bindings remained almost constant during the developmental period examined.

Isoprenaline (Iso) increased the of slow action potentials (APs) from post‐gestation day 18, and the adult level was reached at about 2 weeks after birth; this developmental time course is similar to that of Ca2+ channels. The number of β‐adrenoceptors also started to increase a few days before birth, but attained its peak about one week earlier than did the of slow APs or the number of Ca2+ channels.

Acetylcholine (ACh) almost completely abolished the Iso‐induced increase in observed from post‐gestation day 18 to neonatal day 20; this developmental time course for the ACh effect is consistent with the finding that the number of muscarinic cholinoceptors started to increase on post‐gestation day 16 and reached a peak on the day of birth.

Previous electrophysiological and the present biochemical findings strongly suggest that the functional coupling between muscarinic cholinoceptors and Ca2+ current is already established when the coupling between β‐adrenoceptors and Ca2+ current starts to operate in developing rat hearts.
Cyclic GMP release and vasodilatation induced by EDRF and atrial natriuretic factor in the isolated perfused kidney of the rat
Authors: Burton G.A. , MacNeil S. , DE Jonge A. , Haylor J.
Published: July 2012

Guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) release and vascular tone was measured in the isolated kidney of the rat perfused at constant flow with Krebs‐Henseleit solution. The effects of 3 vasodilators, acetylcholine (ACh), atrial natriuretic factor (ANF) and sodium nitroprusside (SNP) on the renal release of cyclic GMP and vascular tone were examined. The ability of the endothelial‐derived relaxing factor (EDRF) inhibitors, haemoglobin and gossypol, to modify vasodilatation and vasodilator‐induced changes in cyclic GMP releases from the kidney was also investigated.

Renal cyclic GMP release was elevated 8 fold by ANF (0.01 μm), 5 fold by SNP (1 μm) and 3 fold by ACh (0.3 μm).

For ACh, both the increase in renal cyclic GMP release and the vasodilatation were reduced by the EDRF inhibitors, haemoglobin (1 μm) and gossypol (15 μm). For SNP, neither the increase in renal cyclic GMP release nor vasodilatation were inhibited by gossypol (15 μm).

For ANF, neither the increase in cyclic GMP release from the kidney nor its vasodilator activity were affected by haemoglobin (1 μm).

EDRF inhibitors reduced the basal release of cyclic GMP from 0.32 ± 0.06 pmol min−1 to 0.18 ± 0.03 pmol min−1, gossypol being more effective than haemoglobin.

The results are consistent with the ability of ACh to induce EDRF‐mediated vasodilatation in the isolated perfused kidney of the rat. Basal EDRF release appears to contribute approximately 50% to the basal release of cyclic GMP from this preparation. The renal vasodilator action of ANF however, is independent of EDRF, although the renal vascular endothelium cannot be discounted as a site at which ANF stimulates cyclic GMP production.
Inhibition of elevated arginine vasopressin secretion in response to osmotic stimulation and acute haemorrhage by U‐62066E, a κ‐opioid receptor agonist
Authors: Yamada K. , Nakano M. , Yoshida S.
Published: July 2012

The effect of kappa (κ) opioid receptor activation on the increase in arginine vasopressin (AVP) secretion evoked by two acute and quite different stimuli (i.e., haemorrhage and osmotic stimulus due to hypertonic saline infusion) were evaluated in conscious Long‐Evans rats, by use of U‐62066E, a highly selective κ‐opioid receptor agonist, and MR2266, an opioid receptor antagonist with some selectivity for κ‐receptors.

An acute haemorrhage, which reduced the mean blood pressure by approximately 50%, resulted in a large increase in the plasma AVP (pAVP) levels of control rats. However, the administration of U‐62066E (0.2 mg kg−1 or 2.0 mg kg−1) reduced the increase due to haemorrhage in a dose‐dependent manner. In contrast, concomitant administration of 2.0 mg kg−1 of MR2266 with U‐62066E significantly attenuated the inhibition of pAVP levels produced by U‐62066E 2.0 mg kg−1.

Hypertonic saline infusion (5% hypertonic saline solution at a rate of 0.24 ml kg−1 min−1 for 10 min) caused the elevation of plasma osmolality (pOsm) from 294.0 ± 1.6 mosmol kg−1 to 304.4 ± 1.9 mosmol kg−1, simultaneously resulting in a significant increase in pAVP levels from 2.34 ± 0.28 pg ml−1 to 4.54 ± 0.51 pg ml−1. However, the administration of U‐62066E (0.05 mg kg−1 or 0.2 mg kg−1) reduced the osmotically induced increase in pAVP in a dose‐dependent manner although pOsm showed the same degree of increase as in controls. In contrast, concomitant administration of 0.2 mg kg−1 of MR2266 with U‐62066E significantly attenuated the inhibition of pAVP levels produced by U‐62066E 0.2 mg kg−1, whereas pOsm showed the same degree of increase as in controls. No significant changes in the mean blood pressure of the respective groups were observed during this experiment.

It is suggested that the κ‐opioid receptor activation reduces the increase in AVP secretion evoked by these two different stimuli and that the inhibitory involvement occurs in the neural lobe in the process of AVP secretion.
Prevention of non‐specific airway hyperreactivity after allergen challenge in guinea‐pigs by the PAF receptor antagonist SDZ 64–412
Authors: Havill Andrew M. , van Valen Ronald G. , Handley Dean A.
Published: July 2012

Allergen challenge by aerosol in sensitized guinea‐pigs elicited non‐specific airway hyperreactivity assessed by reactivity to i.v. histamine or acetylcholine. Airway hyperreactivity to histamine persisted for at least 48 h and was accompanied by pulmonary eosinophilia as determined by bronchoalveolar lavage cell analysis.

Airway hyperreactivity was independent of vagal reflex mechanisms since it was not abrogated by bilateral vagotomy.

The novel platelet‐activating factor (PAF) receptor antagonist SDZ 64–412 inhibited the development of airway hyperreactivity, as measured 24 h after aerosol allergen challenge, when given as a single treatment orally 2 h before allergen challenge. The PAF receptor antagonist WEB 2086 as well as methylprednisolone and ketotifen also showed efficacy in preventing development of airway hyperreactivity.

Neither the two PAF antagonists nor ketotifen had any effect on bronchoalveolar lavage (BAL) eosinophil numbers. Methylprednisolone was the only substance which readily prevented eosinophil recruitment in addition to airway hyperreactivity.

We conclude that allergen‐induced airway hyperreactivity in guinea‐pigs is inhibited by prophylactic anti‐asthma drugs and specific PAF receptor antagonists, thus demonstrating a pivotal role of PAF in this response. There was a lack of correlation between airway hyperreactivity and the presence of BAL eosinophils.
Muscarinic receptor stimulation and cyclic AMP‐dependent effects in guinea‐pig ventricular myocardium
Authors: Schmied Robert , Korth Michael
Published: July 2012

The effect of carbachol on force of contraction, contraction duration, intracellular Na+ activity and cyclic AMP content was studied in papillary muscles of the guinea‐pig exposed to isoprenaline or the phosphodiesterase inhibitor 3‐isobutyl, 1‐methyl xanthine (IBMX). The preparations were obtained from reserpine‐pretreated animals and were electrically driven at a frequency of 0.2 Hz.

Isoprenaline (10 nm) and IBMX (100 μm) produced comparable positive inotropic effects of 9.8 and 9.7 mN, respectively. Carbachol (3 μm) attenuated the inotropic effects by 82% (isoprenaline) and by 79% (IBMX). The shortening of contraction duration which accompanied the positive inotropic effect of isoprenaline (by 14.9%) and of IBMX (by 22.4%) was not significantly affected by 3 μm carbachol.

The positive inotropic effect of 10 nm isoprenaline and of 100 μm IBMX was accompanied by an increase in cellular cyclic AMP content of 58 and 114%, respectively. Carbachol (3 μm) failed to reduce significantly the elevated cyclic AMP content of muscles exposed to either isoprenaline or IBMX.

In the quiescent papillary muscle, isoprenaline (10 nm) and IBMX (100 μm) reduced the intracellular Na+ activity by 28 and 17%, respectively. This decline was not influenced by the additional application of 3 μm carbachol.

The results demonstrate that muscarinic antagonism in guinea‐pig ventricular myocardium exposed to cyclic AMP‐elevating drugs is restricted to force of contraction. The underlying mechanism does not apparently involve the cytosolic signal molecule cyclic AMP.
Antagonism of GABAB‐receptor‐mediated responses in the guinea‐pig isolated ileum and vas deferens by phosphono‐analogues of GABA
Authors: Kerr David I.B. , Ong Jennifer , Prager Rolf H.
Published: July 2012

The phosphono‐analogues of γ‐aminobutyric acid (GABA), 4‐amino‐butylphosphonic acid (4‐ABPA), 3‐amino‐2‐(4‐chlorophenyl)‐propylphosphonic acid (phaclofen) and 3‐amino‐2‐cyclohexylpropylphosphonic acid, each antagonized the GABA‐ and baclofen‐induced GABAB‐receptor‐mediated depression of twitch responses to transmural stimulation in the guinea‐pig isolated ileum, in a concentration‐dependent, reversible and surmountable manner (apparent pA2 = 4.0 ± 0.1, 4 ± 0.2 and 3.7 ± 0.2 respectively, compared with 3.9 ±0.1 for δ‐aminovaleric acid). No such activity was found in a variety of related analogues.

By contrast, 3‐amino‐propylphosphonic acid (3‐APPA) behaved as a partial agonist, itself partly depressing ileal twitch contractions in a manner sensitive to 4‐ABPA and phaclofen, as well as antagonizing the depression of the ileal twitch by GABA and baclofen (apparent pA2 = 4.0 ± 0.2).

Both 4‐ABPA and phaclofen also antagonized the baclofen‐induced depression of the twitch in the guinea‐pig isolated vas deferens (apparent pA2 = 4.0 ± 0.1 for each), whilst 3‐APPA behaved as a partial agonist, slightly depressing the vas twitch, and antagonised the baclofen‐induced depression of the twitch (apparent pA2 = 3.9 ±0.1).

None of these phosphono‐analogues exhibited any action at ileal GABAA‐receptors, nor influenced the ileal twitch depression with morphine, adenosine or noradrenaline, suggesting their selectivity as antagonists at GABAB‐receptors.
Simultaneous perfusion of rat isolated superior mesenteric arterial and venous beds: comparison of their vasoconstrictor and vasodilator responses to agonists
Authors: Warner Timothy D.
Published: July 2012

A new isolated perfused preparation is described that allows a direct comparison to be made of the responses of the perfused arterial and retrogradely perfused venous circulations of the rat superior mesenteric vascular bed.

In experiments comparing the responses of the intact arterially perfused mesentery and small intestine to those of the same preparation following removal of the intestine and division of the circulations, the increases in perfusion pressure produced by arginine‐vasopressin (30 pmol) and noradrenaline (1 nmol) were retained by the arterial circulation and those induced by angiotensin II (30pmol) by the venous circulation. Endothelin‐1 (30pmol) constricted both portions of the vasculature but the prolonged nature of its response was associated with only the venous vessels.

In the simultaneously perfused arterial and venous preparation arginine vasopressin (3–100 pmol) was a selective constrictor of the arterial circulation and angiotensin II (3–100 pmol) of the venous circulation. In addition, noradrenaline (0.3–10 nmol), 5‐hydroxytryptamine (0.3–10 nmol) and KCl (1–60 μmol) were more active as constrictors of the arterial than the venous vessels, and U46619 (10–300 pmol) a more active constrictor of the venous than the arterial vessels. Endothelin‐1 (3–100 pmol) constricted both the arterial and venous portions of the vasculature but was significantly longer acting as a venoconstrictor than an arterioconstrictor.

Angiotensin I (300 pmol) caused constrictions of the venous circulation which were dependent upon the presence of angiotensin converting enzyme for captopril (10 μm) abolished constrictions caused by angiotensin I but not by angiotensin II.

In preparations preconstricted by U46619 (0.3–3 μm), acetylcholine (0.01–100 nmol), bradykinin (0.001–1 nmol), sodium nitroprusside (0.01–10 nmol) or isoprenaline (1–100 pmol) produced dose‐related dilatations of both the arterial and the venous vasculatures, whereas adenosine diphosphate (ADP, 0.01–100 nmol) caused dose‐dependent dilatations of the arterial circulation but principally constrictions of the venous circulation. The dilatations caused by acetylcholine and bradykinin in both portions of the circulation, and by ADP in the arterial circulation, were endothelium‐dependent as they were inhibited by gossypol (3 μm), whereas dilatations to sodium nitroprusside were not.

This preparation allows the responses of the arteries and veins of a single perfused mesenteric bed to be compared. In addition, with this preparation it is possible to demonstrate that veins, as well as arteries, show significant endothelium‐dependent relaxations. It is concluded that the venous portion of the vasculature is significantly involved in the responses of the intact circulation.
Continuous fluorimetric assessment of the changes in cytoplasmic calcium concentration during exposure of rat isolated myocardium to conditions of simulated ischaemia
Authors: Northover B.J.
Published: July 2012

The cytoplasmic calcium concentration ([Ca]c) of rat isolated atrial myocardium was assessed with the dye indo‐1. Dye‐loaded atria were superfused with physiological salt solution and excited with radiation at 360 nm, while epifluorescence emissions were collected simultaneously at 400 nm and 500 nm. The ratio of these emissions was used as a measure of [Ca]c.

Dye‐loaded atria showed a phasic rise and fall in [Ca]c with each applied electrical pacing stimulus. The amplitudes of systolic increments in tension and [Ca]c were augmented by the presence of isoprenaline.

Atria superfused with a solution the composition of which resembled that found extracellularly in regions of ischaemia rapidly lost systolic increments in tension and [Ca]c, while end‐diastolic [Ca]c and tension gradually rose.

The presence of lactate (20 μm) or flufenamate (5 μm) in the superfusate during simulated ischaemia aggravated the rises in both end‐diastolic tension and end‐diastolic [Ca]c. Inclusion in the superfusate of sulphinpyrazone (50 μm) or glucose (20 mm) protected against some of the deleterious effects of lactate seen during simulated ischaemia.
Characterization of the adenosine receptor in porcine coronary arteries
Authors: King A.D. , Milavec‐Krizman M. , Müller‐Schweinitzer E.
Published: July 2012

Relaxant responses of ring preparations from porcine ventricular coronary arteries to adenosine and various stable adenosine analogues were investigated in vitro.

The adenosine analogues did not produce contraction but elicited almost complete relaxation of coronary arteries preconstricted with 3 μm prostaglandin F2α (PGF2α), even after removal of the endothelium.

The order of potency, was 5′‐N‐ethylcarboxamide‐adenosine (NECA) > 2‐(2‐phenylethylamino)5′‐N‐ethylcarboxamide‐adenosine (2‐PEA‐NECA) > 2‐phenylamino‐adenosine (CV‐1808) > N6‐[S(−)−1‐phenyl‐2‐propyl]adenosine (S‐PIA) > N6‐[S(+)‐1‐phenyl‐2‐propyl]adenosine (S‐PIA) > N6‐cyclopentyl‐adenosine (CPA) > adenosine > ATP = ADP which suggested the presence of adenosine A2‐receptor subtypes.

There was an excellent correlation between the calculated pD2 values on coronary arteries and the pKD values at adenosine A2 binding sites, whereas no correlation was obtained when the pD2 values were compared to the pKD values at adenosine A1‐binding sites on membranes from porcine striata.

The relaxant effects of adenosine and its analogues were competitively antagonized by 8‐(P‐sulphophenyl)‐theophylline (8‐SPT), producing pA2 values similar to the respective pKD value of the antagonist at adenosine A2 binding sites.

It is suggested that the porcine coronary artery possesses adenosine A2 receptors which seem to be similar to the adenosine A2 binding site in pig striatum, whereas no evidence was obtained for the presence of adenosine A1 receptors.
Influence of capsaicin‐sensitive afferent neurones on the acid secretory responses of the rat stomach in vivo
Authors: Esplugues J.V. , Ramos E.G. , Gil L. , Esplugues J.
Published: July 2012

The influence of capsaicin‐sensitive afferent neurones in modulating acid‐secretory responses has been investigated in the continuously perfused stomach of the anaesthetized rat.

Ablation of primary afferent neurones, after systemic neonatal pretreatment with high doses of capsaicin, did not modify acid responses to direct stimuli of the oxyntic cell with histamine (5 mg kg_1), pentagastrin (20 μg kg−1) or carbachol (4 μg kg−1).

Acid responses to hypoglycaemia induced by insulin (0.3 iu kg−1) were not influenced by systemic capsaicin pretreatment or by acute coeliac ganglionectomy. Vagotomy abolished this secretory response.

The increase in acid output induced by gastric distension (20 cmH2O) was abolished by systemic neonatal capsaicin pretreatment. Likewise, vagotomy and acute coeliac ganglionectomy eliminated this secretory response.

Acute intragastric infusion with high doses of capsaicin inhibited the acid responses to distension but failed to modify the increase in acid output induced by insulin.

Local application (7–14 days before) of capsaicin to the coeliac ganglion abolished the acid response to gastric distension. This lack of secretory response was not the result of a nonspecific destruction of the ganglion, since changes in intragastric pressure after electrical stimulation of the coeliac ganglion were unaffected by such treatment.

These observations indicate that peripheral capsaicin‐sensitive sensory neurones, located both in the gastric mucosa and in the coeliac ganglion, play a physiological role in the acid secretory responses to gastric distension.
A study of the pyrogenic actions of interleukin‐1α and interleukin‐1β: interactions with a steroidal and a non‐steroidal anti‐inflammatory agent
Authors: Davidson J. , Milton A.S. , Rotondo D.
Published: July 2012

The pyrogenic effects of intravenously administered human recombinant interleukin‐1α (IL‐1α) and IL‐1β were studied in the rabbit.

Both cytokines produced dose‐related increases in body temperature. At all doses studied (100–5000 u kg−1) both cytokines elicited a monophasic increase in body temperature, beginning 15 min and reaching a maximum 45 min after administration.

A comparison of thermal response index (TRI2, the magnitude of febrile responses over 2 h obtained by integrating the change in temperature in °C against time in hours) values indicated that IL‐1β (500 u kg−1, TRI2 = 0.69 ± 0.04, n = 4) was approximately 5 fold more potent than IL‐1α (2500 u kg−1, TRI2 = 0.73 ± 0.07, n = 4, all values are means ± s.e.means) in elevating body temperature. ΔTmax values for the above doses of IL‐1β and IL‐1α were 0.60 ± 0.06 and 0.61 ± 0.03 respectively. When IL‐1α and IL‐1β were heated for 30 min at 60°C prior to administration no biological activity was observed.

A cyclo‐oxygenase inhibitor, ketoprofen (3 mg kg−1) administered 15 min before either cytokine completely abolished the fever induced by both IL‐1α (2500 u kg−1) and IL‐1β (500 u kg−1).

Intravenous administration of the steroidal anti‐inflammatory agent dexamethasone (3 mg kg−1) 1 h before either cytokine attenuated the fever induced by IL‐1α (2500 u kg−1) and IL‐1β (500 u kg−1).

The effects of ketoprofen and dexamethasone on IL‐1 pyrogenicity indicate that prostanoids are almost certainly involved in the responses. The different potencies of IL‐1α and IL‐1β may be related to their relative ability to stimulate prostanoid biosynthesis.
Action of noradrenaline on isolated proximal and distal coronary arteries of rat: selective release of endothelium‐derived relaxing factor in proximal arteries
Authors: Nyborg Niels C. Berg
Published: July 2012

The effect of noradrenaline (NA) on the vascular smooth muscle and endothelial cells in isolated ring segments from the proximal and distal part of the left coronary artery (LCA) in rats was examined.

NA had a weak concentration‐dependent contractile effect on proximal but relaxed distal segments of the LCA. The maximal NA‐induced contraction of the proximal segments was doubled while the relaxation of the distal LCA segments was converted to a contraction after blockade of β‐adrenoceptors with propranolol 3 × 10−6m, thus indicating the presence of both α‐ and β‐adrenoceptors in the arteries, with dominance of α‐adrenoceptors and of β‐adrenoceptors in the proximal and distal segments of the LCA, respectively.

The contractile effect of NA (β‐adrenoceptors blocked) was doubled in the proximal LCA segments after the endothelium was removed. Endothelial denudation had, in contrast, no potentiating effect on the contractile response of the distal arteries to NA. Both proximal and distal segments became more sensitive to the contractile action of NA after removal of the endothelium.

The spontaneous myogenic tone increased in both proximal and distal LCAs after endothelial removal, indicating spontaneous release of a relaxing endothelial factor in the vessels.

Following contraction with prostaglandin F2α (PGF2α), and in the presence of propranolol, 3 × 10−6 m, and prazosin, 10−6 m, NA induced an endothelium‐dependent relaxation of only proximal but not distal segments of the precontracted LCA. The NA‐induced relaxation of the proximal segments of the LCA was not altered by indomethacin 10−5 m but was completely abolished after incubation with methylene blue, 3 × 10−6 m, or following endothelium removal. These results are compatible with NA‐induced release of EDRF in these arteries.

The selective α2‐adrenoceptor agonist, B‐HT 933, only induced a weak relaxation of PGF2α‐precontracted proximal (endothelium intact) LCA segments at a concentration of 10−4m. The NA‐induced relaxation of these vessels was unaffected by incubating the vessels with 10−5 m B‐HT 933. The NA relaxation response curve was shifted ca 1.1 log unit to the right by rauwolscine, 10−6m, giving an estimated pA2‐value of 7.12. The receptor through which NA activates the endothelium appears to be of an atypical α2‐subtype.
Evidence for the involvement of cyclic GMP in adenosine‐induced, age‐dependent vasodilatation
Authors: Moritoki Hideki , Matsugi Takeshi , Takase Hideshi , Ueda Haruyasu , Tanioka Asao
Published: July 2012

Adenosine‐induced dilatation of rat aorta was present in aorta taken from 4 week‐old rats, attenuated with increase in age of rats to 8 weeks, and was virtually absent in the aorta from 12 week‐old rats.

Removal of the endothelium by mechanical rubbing attenuated adenosine‐induced dilatation.

Haemoglobin and methylene blue partly reversed the adenosine‐induced endothelium‐dependent dilatation.

The order of potency of adenosine derivatives was 5′‐(N‐ethylcarboxamido)adenosine (NECA) > 2‐phenylaminoadenosine (CV‐1808) > 2‐chloroadenosine > N6‐([R]‐[‐]‐phenylisopropyl)adenosine (R‐PIA) > adenosine > N6‐cyclohexyladenosine (CHA) > N6‐([S]‐[+]‐phenylisopropyl)adenosine (S‐PIA), indicating that adenosine receptors mediating the dilatation are of the A2 subtype.

[3H]‐NECA bound to preparations of membranes from rats of 4 weeks old; it was displaced more effectively by NECA and the A2 ligand CV‐1808 than by the A1 ligands CHA and S‐PIA. ligands CHA and S‐PIA.

The number but not affinity of specific binding sites for NECA decreased considerably with increase in age of rats to 8 weeks, and binding sites for [3H]‐NECA were hardly detected in membrane preparations from rats of 20 weeks old.

Adenosine caused a marked increase in cyclic GMP production, but did not induce an increase in the cyclic AMP level.

This increase in cyclic GMP production induced by adenosine was abolished by methylene blue or 8‐phenyltheophylline, or by removal of the endothelium.

The age‐associated decrease in adenosine‐induced dilatation was found to be associated with a reduction in the formation of cyclic GMP, but not of cyclic AMP.

These results suggest that adenosine causes dilatation via A2 receptors by inducing production of an endothelium‐derived relaxing factor (EDRF), which in turn stimulates soluble guanylate cyclase, and so increases production of cyclic GMP. It is also suggested that the main reason for the age‐associated decrease in adenosine‐induced dilatation is a decrease in the number of A2‐receptors or the ability of the endothelium to produce EDRF, leading to decreased production of cyclic GMP.
Evidence that A2 purinoceptors are involved in endothelium‐dependent relaxation of the rat thoracic aorta
Authors: Rose'Meyer R.B. , Hope W.
Published: July 2012

The effect of adenosine and some adenosine analogues on the isolated thoracic aorta from rats was compared with the effect of adenosine 5′‐triphosphate (ATP) and adenosine 5′‐diphosphate (ADP).

Both ATP and adenosine analogues caused relaxation of the noradrenaline (30 nm)‐contracted thoracic aorta.

The order of potency for adenosine analogues was 5′‐(N‐ethyl) carboxamidoadenosine (NECA) > l‐N6‐phenylisopropyladenosine (l‐PIA), adenosine 5′‐monophosphate (AMP), adenosine indicating the presence of adenosine A2 receptors.

Removal of the endothelium or prior treatment with haemoglobin (10 μm) attenuated relaxant responses to both ATP and NECA, attenuation being greater for ATP than NECA.

8‐Phenyltheophylline (10 μm) reduced relaxant responses to NECA but not to ATP in the intact tissue.

These results provide evidence that there are two components to relaxation of the rat thoracic aorta induced by purinoceptor agonists. The first is an endothelium‐dependent mechanism involving release of endothelium‐derived relaxant factor (EDRF) and the second is due to a direct effect on smooth muscle.
Competitive antagonists discriminate between NK2 tachykinin receptor subtypes
Authors: Maggi Carlo Alberto , Patacchini Riccardo , Giuliani Sandro , Rovero Paolo , Dion Stephane , Regoli Domenico , Giachetti Antonio , Meli Alberto
Published: July 2012

We have compared the ability of various tachykinins and selective tachykinin receptor agonists to induce contraction of the endothelium‐denuded rabbit pulmonary artery (RPA) and hamster trachea (HT) and have estimated the affinity of some newly developed NK2 selective antagonists in the same tissues.

In confirmation of previous findings, experiments with the agonists indicated that NK2 receptors are the main if not the sole mediators of the response to tachykinins in both RPA and HT. No evidence for significant degradation of neurokinin A (NKA) was found in either tissue when experiments were repeated in the presence of a mixture of peptidase inhibitors (thiorphan, captopril and bestatin, 1 μm each).

The peptide antagonists tested were: Peptide I = [Tyr5, d‐Trp6,8,9, Arg10]‐NKA(4–10); Peptide II = [Tyr5, d‐Trp6,8,9, Arg10]‐NKA(3–10); Peptide III = Ac‐Leu‐Asp‐Gln‐Trp‐Phe‐Gly‐NH2. The three peptides produced a concentration‐dependent rightward shift of the concentration‐response curve to NKA in both RPA and HT with no significant depression of the maximal response attainable. The slopes of the Schild plots were not significantly different from unity, indicating a competitive antagonism. Peptides I and II were about 100 times more potent in the RPA than in the HT, while Peptide III was about 100 times more potent in the HT than RPA.

The pA2 values obtained in these two tissues with the three antagonists were not significantly different when tested in the absence or presence of peptidase inhibitors, or when a selective NK2 receptor agonist, [βAla8]‐NKA(4–10) was used instead of NKA. Similar pA2 values were obtained after 15 or 90 min of incubation with the antagonists. Peptides I, II and III had no inhibitory effect on contractions produced by noradrenaline in the RPA or by carbachol in the HT.

Peptides I, II and III showed weak or no antagonistic activity toward the vasodilatator effect of substance P in the dog carotid artery (NK1 receptor‐mediated) or toward the contractile effect of neurokinin B in the rat portal vein (NK3 receptor‐mediated).

These results provide pharmacological evidence for heterogeneity of NK2 receptors in the RPA and HT. The NK2 receptors present in these tissues are not discriminated by natural tachykinins or selective agonists, but are recognized with very different affinity by NK2 receptor antagonists.
Increase in calcium channel current by β‐adrenoceptor agonists in single smooth muscle cells isolated from porcine coronary artery
Authors: Fukumitsu T. , Hayashi H. , Tokuno H. , Tomita T.
Published: July 2012

The action of catecholamines (isoprenaline and noradrenaline) and forskolin on membrane currents was studied in single cells freshly dispersed from the pig coronary artery by use of the whole‐cell clamp method, usually with electrodes containing CsCl.

In normal Krebs solution, with and without 30 mm tetraethylammonium (TEA) and 0.5 mm 4‐aminopyridine, isoprenaline (1–5 μm) clearly increased the inward currents elicited by membrane depolarization, without affecting the holding current at −80 mV. The same effect was observed when the external Cl− was replaced with isethionate. The outward current recorded with K+‐containing electrodes was not significantly affected by isoprenaline.

In the presence of 67 mm Ba2+ and 30 mm TEA, the maximum inward current recorded with CsCl containing electrodes was 119 ± 7pA (the mean ± s.e.mean, n = 90) in cells where the current was larger than 30 pA. The L‐type Ca2+ channel was considered to be responsible for these currents, based on the threshold voltage, the slow time course of decay, the large depolarization necessary to produce inactivation, and the high susceptibility to the Ca2+ channel antagonist, nicardipine.

Isoprenaline and noradrenaline increased the amplitude of inward currents evoked by depolarizing pulses. The maximum inward current was potentiated by 43 ± 7% (n = 12) by isoprenaline and 39 ± 10% by noradrenaline (n = 6) at a concentration of 1 μm. These effects were strongly inhibited by propranolol, but not phentolamine. Forskolin (10 μm) also potentiated the currents to a similar degree.

It is suggested that stimulation of β‐adrenoceptors increases the amplitude of inward currents through L‐type Ca2+ channels in the pig coronary artery and that intracellular cyclic adenosine monophosphate is likely to be inolved in this action.
Evidence for the involvement of imidazoline receptors in the central hypotensive effect of rilmenidine in the rabbit
Authors: Feldman J. , Tibiriça E. , Bricca G. , Dontenwill M. , Belcourt A. , Bousquet P.
Published: July 2012

Rilmenidine has recently been introduced as a new centrally‐acting antihypertensive agent. We examined its cardiovascular effects after intracerebral injection to anaesthetized rabbits. Cumulative doses of rilmenidine injected intracisternally (1 to 300 μg kg−1) led to dose‐dependent decreases in arterial blood pressure and heart rate. The effective doses of rilmenidine were lower when injected centrally than when injected intravenously.

Pretreatment with the same dose of yohimbine or idazoxan shifted the rilmenidine dose‐response curves for its hypotensive and bradycardic effects to the right. Idazoxan, which has an imidazoline structure, proved to be a more active antagonist than yohimbine of rilmenidine centrally‐mediated cardiovascular effects.

The dose‐response curve for the central hypotensive effect of rilmenidine was also shifted to the right after pretreatment with a bovine brain extract. This extract contains the endogenous ligand of the imidazoline‐preferring receptors which is not a catecholamine.

Rilmenidine, like clonidine, proved to be active when micro‐injected into the rabbit nucleus reticularis lateralis region.

In conclusion, rilmenidine exhibited in the rabbit a central hypotensive effect which originated in the same area as where clonidine acts. Specific imidazoline‐preferring receptors appear to be involved in this hypotensive effect.
Modulation of fluoroaluminate‐induced inositol phosphate formation by increases in tissue cyclic AMP content in bovine tracheal smooth muscle
Authors: Hall I.P. , Donaldson J. , Hill S.J.
Published: July 2012

The effect of fluoroaluminate complexes (AlCl3 plus NaF) upon smooth muscle tone, [3H]‐inositol phosphate accumulation and [3H]‐cyclic AMP accumulation has been investigated in slices of bovine tracheal smooth muscle.

Fluoroaluminate (10 μm AlCl3 + various concentrations of NaF) elicited concentration‐dependent contractions of bovine tracheal smooth muscle strips at concentrations of NaF in the range 1–10 mm. The resultant contractile response was reversed by isoprenaline (50 nm) and was preserved in calcium‐free medium.

Fluoroaluminate stimulated [3H]‐inositol phosphate formation at concentrations of NaF over 1 mm. The response to 20 mm NaF + 10 μm AlCl3 was 164 ± 29% of the response to 1 mm histamine. Fluoroaluminate also increased the incorporation of [3H]‐myo‐inositol into membrane phospholipids.

Fluoroaluminate produced a small rise in [3H]‐cyclic AMP levels (2.1 fold increase over basal with 20 mm NaF). The response to forskolin (1 μm, 8.6 fold over basal) was reduced by fluoroaluminate in a concentration‐dependent manner, but still remained significantly (P < 0.05) elevated over the response to fluoroaluminate alone.

The [3H]‐inositol phosphate response to fluoroaluminate was inhibited by salbutamol (maximum inhibition 60%, IC50 = 0.08 μm), forskolin (1 μm, 46% inhibition) and isobutylmethylxanthine (1 mm, 73% inhibition).

These data suggest that inhibition of agonist‐induced inositol phospholipid turnover by cyclic AMP in this tissue can occur at the post‐receptor level.
Bradykinin‐induced depolarization of primary afferent nerve terminals in the neonatal rat spinal cord in vitro
Authors: Dunn P.M. , Rang H.P.
Published: July 2012

Application of bradykinin (BK) to the spinal cord of the neonatal rat evoked depolarizations which could be recorded via either the dorsal or ventral roots. However, responses recorded via the ventral root were abolished by removal of extracellular Ca2+ or the addition of Cd2+, while responses recorded via the dorsal root were unaffected.

The response recorded via the ventral root was inhibited by the substance P antagonist spantide, while responses recorded via the dorsal root were unaffected.

Depolarizations recorded via the dorsal root were concentration‐dependent with an EC50 of 30 nm. These responses were not antagonized by the BK1 selective antagonist Leu8des‐Arg9BK, but were antagonized by d‐Arg0Hyp3Thi5,8D‐Phe7BK with a pA2 of 6.8 ± 0.6, which is similar to the values determined for other BK2‐mediated responses.

Application of phorbol dibutyrate (PDBu) to the spinal cord also evoked a depolarization with respect to the dorsal root. This response to PDBu was enhanced by removal of extracellular Ca2+, while the response to BK was unaffected.

The potent protein kinase inhibitor staurosporine reduced the response to PDBu, but did not affect the response to BK.

These results suggest that BK by acting on BK2 receptors can depolarize the central terminals of primary afferent nerve fibres. This response to BK does not appear to be mediated via the activation of protein kinase C. The depolarization to BK recorded via the ventral root of the spinal cord is indirect and may be secondary to the action of BK on the primary afferent terminals.