bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potentiation of the hyporeactivity induced by in vivo endothelial injury in the rat carotid artery by chronic treatment with fish oil
Authors: Joly Ghislaine A. , Schini Valerie B. , Hughes Helen , Vanhoutte Paul M. 
Published: July 2012

The present study investigates whether or not chronic feeding of rats with a diet enriched in fish oil affects the reactivity of balloon‐injured carotid arteries. The left carotid arteries were injured in vivo by the repeated passage of a balloon catheter. Both the right (control artery) and the left carotid arteries were excised 24 h after the injury, and suspended in organ chambers for the measurement of changes in isometric tension in the presence of indomethacin.
Phenylephrine evoked similar concentration‐contraction curves in the right (control) carotid arteries without endothelium from control and fish oil‐fed rats. Balloon injury decreased the contractility of carotid arteries to phenylephrine in both types of rats and the pEC50 for phenylephrine was significantly decreased in balloon‐injured arteries from control rats compared to those obtained in arteries from fish oil‐fed rats (pEC50 7.59 ± 0.1 and 7.28 ± 0.06, respectively) while maximal contractions were similar (1.93 ± 0.15 g and 1.79 ± 0.12 g, respectively).
The treatment of control right carotid arteries without endothelium with either NG‐nitro‐l‐arginine (an inhibitor of nitric oxide synthase) or superoxide dismutase (which protects nitric oxide from degradation) did not affect significantly the contractions to phenylephrine in either group. In these preparations, methylene blue (an inhibitor of soluble guanylate cyclase) decreased slightly but significantly maximal contractions to phenylephrine in both groups. The treatment of balloon‐injured carotid arteries with NG‐nitro‐l‐arginine or methylene blue partly restored contractions to phenylephrine in arteries from both types of rat. Superoxide dismutase further depressed the contractility to the α1‐adrenoceptor agonist in balloon‐injured arteries from control diet‐fed rats but had no effect in balloon‐injured preparations from fish oil‐fed rats.
3‐Morpholino‐sydnonimine (SIN‐1, a donor of nitric oxide) evoked similar concentration‐dependent relaxations in control and balloon‐injured carotid arteries from both types of rat.
Balloon injury caused an increase in the tissue content of cyclic GMP in carotid arteries from control diet‐fed rats. This production of cyclic GMP was abolished by NG‐nitro‐l‐arginine. Superoxide dismutase potentiated significantly the production of cyclic GMP caused by balloon injury in control but not in fish oil‐fed rats.
These observations confirm that in vivo balloon injury causes the production of nitric oxide in the injured blood vessel wall. This production of nitric oxide from l‐arginine accounts for the decreased contractility to phenylephrine and the accumulation of cyclic GMP in balloon‐injured arteries. They further indicate that chronic feeding of rats with fish oil potentiates the l‐arginine‐nitric oxide pathway in the injured vessel leading to an enhanced hyporeactivity to phenylephrine.
Autoradiography of P2X ATP receptors in the rat brain
Authors: Balcar Vladimir J. , Li Yi , Killinger Suzanne , Bennett Maxwell R. 
Published: July 2012

Binding of a P2, receptor specific radioligand, [3H]‐α,β‐methylene adenosine triphosphate ([3H]‐m43‐MeATP) to sections of rat brain was reversible and association/dissociation parameters indicated that it consisted of two saturable components. Non‐specific binding was very low (<7% at 10 nM ligand concentration).
The binding was completely inhibited by suramin (IC50∼ 14–26 μm) but none of the ligands specific for P2y receptors such as 2‐methylthio‐adenosine triphosphate (2‐methyl‐S‐ATP) and 2‐chloro‐adenosine triphosphate (2‐C1‐ATP) nor 2‐methylthio‐adenosine diphosphate (2‐methyl‐S‐ADP) a ligand for the P2 receptor on blood platelets (′P2T′ type) produced strong inhibitions except for P1, P4‐di(adenosine‐5′)tetraphosphate (Ap4A).
Inhibitors of Na+, K+‐dependent adenosine triphosphatase (ATPase) ouabain, P1‐ligand adenosine and an inhibitor of transport of, respectively, adenosine and cyclic nucleotides, dilazep, had no effect.
The highest density of P2x binding sites was found to be in the cerebellar cortex but the binding sites were present in all major brain regions, especially in areas known to receive strong excitatory innervation.
Activation of the micturition reflex by NK2 receptor stimulation in the anaesthetized guinea‐pig
Authors: Bushfield Mark , Metcalfe Maria , Naylor Alasdair M. 
Published: July 2012

The mechanisms underlying stimulation of bladder contractions and bronchoconstriction by the selective NK2 receptor agonist, [β‐Ala8]NKA(4–10), were examined in the anaesthetized guinea‐pig.
Atropine, α,β‐methylene‐ATP and ganglion blocking agents were used to examine the contribution of reflex arc activation and/or potentiation of efferent mechanisms to the NK2 receptor‐mediated responses seen in these two tissues.
[β‐Ala8]NKA(4‐ 10)‐induced bronchoconstriction was immediate, dose‐dependent and was unaffected by pretreatment with ganglion blockers (hexamethonium or chlorisondamine), blockade of muscarinic receptors by atropine, or desensitization of P2 purinoceptors by α,β‐methylene‐ATP.
At doses of 5 μg kg−1 and above, [β‐Ala8]NKA(4–10) induced bladder contractions that appeared to be of an ‘all‐or‐nothing’ nature. These contractions occurred after a delay of 10 to 30 s and were often biphasic, comprised of an initial rapid component followed by a slower tonic component.
Pretreatment of the animals with either atropine or the desensitizing purinoceptor agonist α,β‐methylene‐ATP, resulted in partial inhibition of bladder contractile responses to [β‐Ala8]NKA(4–10). The combination of atropine and α,β‐methylene‐ATP pretreatment resulted in additive inhibition leading to complete blockade of the response.
The bladder responses to [β‐Ala8]NKA(4–10) (5 μg kg−1) were inhibited by pretreatment with the ganglion blockers, hexamethonium and chlorisondamine, indicating a preganglionic mechanism of action.
These findings demonstrate the indirect nature of the bladder contractions induced by activation of NK2 receptors in the anaesthetized guinea‐pig. Contractions occur secondary to the release of endogenous cholinergic and NANC transmitters by activation of neuronal NK2 receptors located at a preganglionic site, possibly on capsaicin‐sensitive sensory afferent nerves, where NK2 sites have been demonstrated autoradiographically. In contrast, [β‐Ala8]NKA(4–10)‐induced bronchoconstriction in the anaesthetized guinea‐pig is a direct smooth muscle contractile response that is unaffected by ganglion blockade or blockade of muscarinic receptors.
Inhibition of bronchoconstriction by pituitary adenylate cyclase activating polypeptide (PACAP 1–27) in guinea‐pigs in vivo
Authors: Lindén Anders , Yoshihara Shigemi , Chan Brendan , Nadel Jay A. 
Published: July 2012

We studied the inhibitory effect of pituitary adenylate cyclase activating polypeptide (PACAP 1–27) on the increase in total pulmonary resistance (RL) caused either by allergen or histamine in anaesthetized, ventilated guinea‐pigs.
PACAP 1–27 given via i.v. infusion (0.045‐4.5 nmol kg−1 min−1) dose‐dependently reduced the increase in RL caused by inhaled ovalbumin and histamine. At the highest dose, PACAP 1–27 prevented the increase in RL caused by ovalbumin and histamine completely. Infusion of PACAP 1–27 and the β2‐adrenoceptor agonist, salbutamol (0.045‐4.5 nmol kg‐1 min−1) inhibited the increase in RL similarly, but salbutamol increased the heart rate more than PACAP 1–27.
PACAP 1–27 and salbutamol given via inhaled aerosol (0.1 mM, 20 breaths) significantly reduced the increase in RL caused by histamine infused i.v., whereas aerosolised sterile saline did not. Both PACAP 1–27 and salbutamol caused bronchodilator effects within 1 min of drug inhalation and these effects remained throughout the 20 min of study.
Because PACAP 1–27 produced significant bronchodilatation and rapid onset of sustained action in vivo and without pronounced cardiovascular side effects, we conclude that this peptide may have therapeutic potential as a bronchodilator.
Attenuation of adrenomedullin‐induced renal vasodilatation by NG‐nitro L‐arginine but not glibenclamide
Authors: Miura Katsuyuki , Ebara Tsuneyuki , Okumura Michiaki , Matsuura Takeshi , Kim Shokei , Yukimura Tokihito , Iwao Hiroshi 
Published: July 2012

The present study was conducted in order to elucidate the in vivo contribution of nitric oxide (NO) and the glibenclamide‐sensitive potassium channel in the renal action of adrenomedullin in anaesthetized dogs.
Intrarenal arterial infusion of adrenomedullin (20 ng kg−1 min−1) elicited a pronounced increase in renal blood flow with no changes in systemic blood pressure. The renal vasodilator action of adrenomedullin was markedly attenuated by pretreatment with NG–nitro L‐arginine (L‐NOARG), but this was reversed by continuous infusion of L‐arginine.
Pretreatment with glibenclamide almost completely blocked the renal vasodilatation induced by lemakalim, but had no effect on the renal vasodilator and diuretic action of adrenomedullin.
Intrarenal arterial infusion of adrenomedullin induced diuresis and natriuresis. Diuretic and natriuretic action of adrenomedullin was also attenuated by L‐NOARG. L‐Arginine partly reversed the effect of L‐NOARG and adrenomedullin‐induced diuresis and natriuresis.
These data indicate that the in vivo renal vasodilator action of adrenomedullin is mediated by the release of NO. The glibenclamide‐sensitive potassium channel is not involved in the renal action of adrenomedullin, at least, not in anaesthetized dogs. Since the inhibition of L‐NOARG of adrenomedullin‐induced diuresis occurred concomitantly with the attenuation of the renal vasodilator action of adrenomedullin, direct involvement of NO in adrenomedullin‐induced diuresis remains to be established.
Endogenous modulation of excitatory amino acid responsiveness by tachykinin NK1 and NK2 receptors in the rat spinal cord
Authors: Chizh Boris A. , Cumberbatch Michael J. , Birch Philip J. , MaxHeadley P. 
Published: July 2012

The effects of selective tachykinin (neurokinin, NK) NK1 and NK2 receptor antagonists have been examined on spinal neurones in α‐chloralose anaesthetized, spinalized rats. They were tested for effects on responses both to excitatory amino acids (EAA) and to noxious heat stimuli. They were also tested for their ability to reverse the actions of selective NK agonists.
The NK1selective antagonists GR82334 (peptide) and CP‐99,994 (non‐peptide), when applied by microiontophoresis, both reduced responses to kainate >AMPA> NMDA. Intravenous CP‐99,994 (3 mg kg−1) also reduced responses to kainate but had inconsistent effects on nociceptive responses.
GR82334, applied microiontophoretically, reduced the enhancement by the selective NK1 agonist, GR73632 of both responses to EAAs and background activity. Systemic CP‐99,994 (≤10 mg kg−1) failed to reverse the effects of GR73632.
The selective peptide NK2 antagonist, GR103537, had no consistent effects on responses to EAAs when applied by iontophoresis. In contrast, the non‐peptide NK2 antagonist, GR159897, administered systemically (0.5‐2 mg kg−1, i.v.) enhanced responses to kainate (but not NMDA); responses to noxious heat were enhanced only weakly.
Iontophoretically‐administered GR 103537 attenuated the effects of the NK2 agonist GR64349, which selectively reduced responses to kainate compared to those to NMDA. Systemically administered GR159897 (≤2 mg kg−1, i.v.) caused little antagonism of the effects of GR64349.
The data indicate that under these conditions the non‐peptide antagonists are not reliable at reversing the actions of selective NK agonists.
These results suggest that there is a tonic release of endogenous tachykinins that can modulate glutamatergic neurotransmission in the spinal cord. They provide further support for the hypothesis that release of endogenous NKs acting on NK1 and NK2 receptors can promote NMDA receptor mediated glutamatergic transmission.
[3H]‐lifarizine, a high affinity probe for inactivated sodium channels
Authors: MacKinnon A.C. , Wyatt K.M. , McGivern J.G. , Sheridan R.D. , Brown C.M. 
Published: July 2012

[3H]‐lifarizine bound saturably and reversibly to an apparently homogeneous class of high affinity sites in rat cerebrocortical membranes (Kd= 10.7 ± 2.9 nM; Bmax = 5.10±1.43 pmol mg−1 protein).
The binding of [3H]‐lifarizine was unaffected by sodium channel toxins binding to site 1 (tetrodotoxin), site 3 (α‐scorpion venom) or site 5 (brevetoxin), Furthermore, lifarizine at concentrations up to 10 μm had no effect on [3H]‐saxitoxin (STX) binding to toxin site 1. Lifarizine displaced [3H]‐batrachotoxinin‐A 20‐α‐benzoate (BTX) binding with moderate affinity (pIC50 7.31±0.24) indicating an interaction with toxin site 2. However, lifarizine accelerated the dissociation of [3H]‐BTX and decreased both the affinity and density of sites labelled by [3H]‐BTX, suggesting an allosteric interaction with toxin site 2.
The binding of [3H]‐lifarizine was voltage‐sensitive, binding to membranes with higher affinity than to synaptosomes (pIC50 for cold lifarizine = 7.99± 0.09 in membranes and 6.68 ± 0.14 in synaptosomes). Depolarization of synaptosomes with 130 mM KC1 increased the affinity of lifarizine almost 10 fold (pIC50 = 7.86± 0.25). This suggests that lifarizine binds selectively to inactivated sodium channels which predominate both in the membrane preparation and in the depolarized synaptosomal preparation.
There was negligible [3H]‐lifarizine and [3H]‐BTX binding to solubilized sodium channels, although [3H]‐STX binding was retained under these conditions.
The potencies of a series of compounds in displacing [3H]‐lifarizine from rat cerebrocortical membranes correlated well with their affinities for inactivated sodium channels estimated from whole‐cell voltage clamp studies in the mouse neuroblastoma cell line, N1E‐115 (r = 0.96).
These results show that [3H]‐lifarizine is a high affinity ligand for neuronal sodium channels which potently and selectively labels a site, allosterically linked to toxin binding site 2, associated with inactivated sodium channels.
Pharmacological profile of the novel P2T‐purinoceptor antagonist, FPL 67085 in vitro and in the anaesthetized rat in vivo
Authors: Humphries R.G. , Tomlinson W. , Clegg J.A. , Ingall A.H. , Kindon N.D. , Leff P. 
Published: July 2012

The role of endogenous ADP in platelet aggregation in vivo remains unclear due to the lack of suitable P2T‐antagonist probes. This paper describes the potency, selectivity and specificity of the novel P2T‐purinoceptor antagonist, FPL 67085 (2‐propylthio‐D‐β,γ‐dichloromethylene ATP) both in vitro and in the anaesthetized rat in vivo.
FPL 67085 (3–30 nM) produced concentration‐dependent rightward displacement of the concentration‐effect (E/[A]) curve for ADP‐induced aggregation of human washed platelets with no effect on ADP‐independent aggregation at ≤ 10 μm.
Logistic fitting of ADP E/[A] data indicated that the antagonist effect of FPL 67085 did not consistently accord with simple competition: in some preparations depression of the asymptote was seen. Schild analysis of data combined from all preparations, regardless of the antagonist profile observed, gave an apparent pKB of 8.9 (slope parameter 0.90).
The potency of FPL 67085 was unaffected by the P1purinoceptor antagonist, 8‐sulphophenyltheo‐phylline, was similar (IC50 0.6‐3.8 nM) in human and rat washed platelets or whole blood and, in rat blood, did not change following 2–30 min incubation at 37°C.
FPL 67085 was a weak (pA50∼4.2) partial agonist in tissues containing P2x‐ or P2y‐purinoceptors, indicating some 30,000 fold selectivity for the P2T‐subtype.
In anaesthetized rats, intravenous infusion of FPL 67085 produced rapidly‐reversible, dose‐related inhibition of ADP‐induced platelet aggregation measured ex vivo (ID50 1.3μg kg−1 min−1) with no significant effect on haemodynamics or circulating cell counts.
Thus, FPL 67085 is a potent, specific and selective inhibitor of ADP‐induced platelet aggregation both in vitro and in vivo. As such, it represents a novel pharmacological tool to define the role of endogenous ADP in thrombosis and the potential of P2T‐purinoceptor antagonists as a novel class of infusible anti‐thrombotic agents for acute use in man.
Blockade of acetylcholine release at the motor endplate by a polypeptide from the venom of Phoneutria nigriventer
Authors: Souccar Caden , Gonçalo Maria do Carmo , Lapa Antonio José , Troncone Lanfranco Ranieri Paolo , Lebrun Ivo , Magnoli Fabio 
Published: July 2012

The mechanisms underlying the muscle relaxation effect of a fraction (PF3) isolated from the Phoneutria nigriventer spider venom were assessed on mouse diaphragm and chick biventer cervicis muscle preparations.
PF3 (0.25‐4 μg ml−1) produced a concentration‐dependent blockade of the nerve‐elicited muscle twitch of the mouse diaphragm (IC50=0.8 μg ml−1) without affecting the directly induced muscle twitch. In similar preparations, the crude venom (1–10 μg ml−1) produced muscle contracture and blocked both the direct and indirectly induced muscle twitches.
In the chick biventer cervicis muscle, PF3 (1–5 μg ml−1) blocked the nerve stimulated muscle twitch (IC50=1.26 μg ml−1), but did not alter the postjunctional response to exogenous acetylcholine (ACh, 10 μm‐10mm).
PF3 (2–8 μg ml−1) reduced the frequency of miniature endplate potentials (m.e.p.ps) recorded intracellularly from the mouse diaphragm muscle fibres by 58 to 64%, and diminished the amplitude of m.e.p.ps by 20 to 40% of control. The relationship between log m.e.p.p. frequency and log [Ca2+]o was shifted rightwards in the presence of 4 μg ml−1 PF3.
Raising the frequency of m.e.p.ps with high K+ medium or theophylline (3 mm) did not prevent the toxin‐induced depression of spontaneous ACh release.
The quantal content of e.p.ps (m), determined in cut‐diaphragm muscle fibres, was reduced by 53% and 77% of control by 1 and 4 μg ml−1 PF3, respectively. At 1 μg ml−1 the toxin shifted the relationship between log m and log [Ca2+]o towards higher values without apparent change of the slope.
E.p.p. trains elicited at 10 to 50 Hz in the presence of PF3 (1 μg ml−1) exhibited irregular amplitudes and facilitation related to the frequency of nerve stimulation.
It is concluded that PF3 blocks neuromuscular transmission by acting prejunctionally and reducing the nerve‐evoked transmitter release. The effect was related to a diminished Ca2+ entry into the nerve terminal associated with inhibition of exocytosis.
Selective blockade of M2 and M3 muscarinic receptors by hexahydrobenzyl‐ fourdapine and a comparison with zamifenacin
Authors: Barlow R.B. , Bond Susan M. , Branthwaite A.G. , Jackson O. , McQueen D.S. , Smith Kirsten M. , Smith Paula J. 
Published: July 2012

4‐Diphenylacetoxy‐N‐cyclohexylmethyl‐piperidine HC1 (hexahydro‐benz‐4DAP) is more active as an antagonist of carbachol at receptors in guinea‐pig isolated ileum, log K (pA2) = 6.64±0.14 (s.e. 7 results), than at receptors in guinea‐pig isolated atria, log K= 5.43 ±0.14 (7). In the presence of neostigmine bromide (0.2 μm) the value for atria was 5.62 ±0.19 (4), so the lower activity on atria cannot be attributed to hydrolysis of the compound by cholinesterases present in this tissue.
The limit of solubility of the free base in Krebs solution (pH 7.6) is about 50 μm for both hexahydro‐benz‐4DAP and benzyl‐fourdapine (benz‐4DAP).
In experiments on guinea‐pig isolated ileum with hexahydro‐benz‐4DAP given together with 4‐DAMP methobromide, the combined dose‐ratio was consistent with competition: similar results were obtained with benz‐4DAP.
In rats anaesthetized with pentobarbitone, hexahydro‐benz‐4DAP antagonized the effects of bethanechol on blood‐pressure in doses that had little effect on heart rate or airflow. There was a limit to the effect which could be obtained, however, and the slopes of the Schild plots were less than one. The effects on rat blood‐pressure had a half‐life of at least 30 min.
In similar experiments with zamifenacin the slopes of the Schild plots were close to 1 and the compound was 10 to 20 times as active on blood‐pressure at it was on heart‐rate.
The limited solubility of the base probably accounts for the flat Schild plots obtained with hexahydro‐benz‐4DAP, which had about 10 fold selectivity for effects on blood‐pressure and was more active than expected from tests on isolated ileum.
Cellular localization of the inhibitory action of relaxin against uterine spasm
Authors: Hughes Sarah J. , Hollingsworth Michael 
Published: July 2012

The aim of this study was to determine whether the site of action of relaxin as a relaxant of rat myometrium is at the cell membrane or at an intracellular site. Therefore, the potency of relaxin was determined against spasms reliant predominantly upon either extracellular Ca2+ or intracellular Ca2+. Uterine spasms dependent upon extracellular Ca2+ were elicited by (i) oxytocin (0.2 nM) (ii) Bay K 8644 (1 μm) in 10 mM K+‐rich PSS and (iii) KC1 (80 mm). Uterine spasm dependent upon intracellular Ca2+ was elicited by oxytocin (20 nM) in the presence of nifedipine (500 nM). The effects of relaxin against these spasmogens were compared with those of levcromakalim, nifedipine and salbutamol.
Relaxin (0.2–6.3 nM), levcromakalim (25–800 nM), salbutamol (1–63 nM) and nifedipine (1–250 nM) caused concentration‐dependent inhibition of the spasm evoked by oxytocin (0.2 nM) and relaxin was the most potent relaxant.
Relaxin and nifedipine were slightly less potent against the spasm induced by Bay K 8644 (1 μm) than against spasm induced by oxytocin (0.2 nM) (15 fold and 13 fold respectively). Levcromakalim and salbutamol were equipotent against the spasm evoked by Bay K 8644 (1 μm) and that evoked by oxytocin (0.2 nM).
Relaxin induced only 47 ± 7% inhibition of the KC1 (80 mm)‐evoked spasm at a concentration of 0.8 μm. Levcromakalim was much less potent (427 fold) against the spasm evoked by KC1 (80 mm) than against the spasm evoked by oxytocin (0.2 nM). The potency of salbutamol against the spasm evoked by KC1 (80 mm) was modestly reduced (14 fold) compared to that against the spasm evoked by oxytocin (0.2 nM). The potency of nifedipine against the KC1 (80 mm)‐evoked spasm was not different from that against the oxytocin (0.2 nM)‐evoked spasm.
The potencies of relaxin and levcromakalim against the spasm evoked by oxytocin (20 nM) + nifedipine (500 nM) were greatly reduced (74 fold and 234 fold respectively) compared to their potencies against the spasm evoked by oxytocin (0.2 nM). The potency of salbutamol against these two spasmogens was not different.
Relaxin was much less potent against the spasm dependent upon intracellular Ca2+ (that induced by oxytocin (20 nM) + nifedipine (500 nM)) than against the spasms dependent upon extracellular Ca2+, those induced by oxytocin (0.2 nM) and Bay K 8644 (1 μm). In this regard, relaxin resembled levcromakalim and nifedipine rather than salbutamol. Therefore, the major site of action of relaxin appears to be located at the plasma membrane rather than at an intracellular level. The observation that relaxin was less effective against the KC1 (80 mm)‐induced spasm than against the oxytocin (0.2 nM)‐evoked spasm may indicate that relaxin has a minor action involving K+‐channel opening.
High concentrations of relaxin (up to 1 μm) induced significant inhibition of the spasm dependent upon intracellular Ca2+. Thus at high concentrations relaxin also appears to have an additional intracellular action.