bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mediation of endothelin‐1‐induced inhibition of platelet aggregation via the ETB receptor
Authors: McMurdo Lorraine , Lidbury Paul S. , Thiemermann Christoph , Vane John R. 
Published: July 2012

The effects of FR139317 (ETA antagonist) or PD145065 (non‐selective ETA/ETB antagonist) on endothelin‐1 (ET‐1)‐induced changes in blood pressure and inhibition of ex vivo platelet aggregation were investigated in the anaesthetized rabbit.
ET‐1 (1 nmol kg−1, i.a. bolus) caused a sustained increase in mean arterial pressure (MAP) (peak increase 47 ± 5 mmHg, n = 8). Intravenous infusion of FR139317 at 0.2 (n = 4) or 0.6 mg kg−1 min−1 (n = 4) inhibited the ET‐1 pressor response by 83 or 89%, respectively. Infusion of PD 145065 at 0.2 (n = 4) or 0.6 mg kg−1 min−1 (n = 4) inhibited the ET‐1‐induced increase in MAP by 79 or 75%, respectively.
The transient depressor response (−16 ± 3 mmHg) which preceded the rise in blood pressure induced by ET‐1 (1 nmol kg−1, i.a., n = 8) was enhanced by an intravenous infusion of FR139317 (0.6 mg kg−1 min−1) to −35 ± 5 mmHg (P < 0.05, n = 4). This enhancement was abolished by indomethacin (5 mg kg−1, i.v.) pretreatment (−17 ± 1 mmHg, n = 4). PD145065 (0.2 mg kg−1 min−1, i.v.) attenuated the ET‐1‐induced fall in blood pressure to −9 ± 1 mmHg (n = 4), while a higher dose of this antagonist (0.6 mg kg−1 min−1, i.v.) completely abolished the ET‐1‐mediated depressor response.
ET‐1 (1 nmol kg−1, n = 8) inhibited ex vivo platelet aggregation by 96% at 5 min after injection of the peptide. FR139317 (0.2 or 0.6 mg kg−1 min−1, i.v.) or PD145065 (0.2 mg kg−1 min−1, i.v.) did not affect the inhibition of ex vivo platelet aggregation in response to ET‐1. In contrast, intravenous infusion of PD145065 (0.6 mg kg−1 min−1) abolished the anti‐aggregatory effects of ET‐1.
Thus, FR139317 inhibits the pressor, but not the depressor actions of ET‐1 and has no effect on the ET‐1‐induced inhibition of ex vivo platelet aggregation. In contrast, PD145065 antagonizes the pressor and depressor responses to ET‐1 and abolishes the anti‐aggregatory effects of the peptide.
These results strongly suggest that ET‐1‐induced vasoconstriction in the anaesthetized rabbit is primarily mediated via the ETA receptor while the depressor and antiaggregatory actions of ET‐1 are due to activation of the ETB receptor.
Oestradiol inhibits smooth muscle cell proliferation of pig coronary artery
Authors: Vargas Roberto , Wroblewska Barbara , Rego Alfredo , Hatch Joshua , Ramwell Peter W. 
Published: July 2012

The effect of oestradiol 17β on vascular smooth muscle proliferation was examined in segments of the pig left anterior descending coronary artery (LAD). It was established by cytochemical techniques that out‐growth from the segments was composed of vascular smooth muscle cells.
[3H]‐thymidine uptake by pig LAD segments was used as an index of vascular smooth muscle cell proliferation. Nitroprusside and forskolin significantly inhibited [3H]‐thymidine uptake and were used as positive controls.
Oestradiol 17β (180–360 nm) inhibited thymidine uptake by pig LAD segments (P < 0.05). The inhibition was observed only in the absence of phenol red, which is a weak oestrogen receptor agonist. The anti‐oestrogens tamoxifen and its more potent metabolite 4‐hydroxytamoxifen, both of which are partial oestrogen receptor agonists, also significantly inhibited thymidine uptake. However, pretreatment with either tamoxifen or 4‐hydroxytamoxifen did not signficantly block oestradiol 17β‐induced inhibition of thymidine uptake.
The LAD segments bound [3H]‐oestradiol 17β in a time‐dependent manner and about 20 to 30% was displaced by an excess of unlabelled oestradiol 17β. Autoradiography showed [3H]‐oestradiol 17β was evenly distributed in the cytosol and nuclei of cells in the three layers of the vessel wall.
The data suggest that oestradiol 17β inhibits smooth muscle cell proliferation in porcine LAD segments, possibly through an oestrogen receptor mechanism. This in vitro effect suggests an in vivo role for oestradiol 17β in directly protecting coronary arteries against myointimal proliferation in premenopausal women.
[3H]‐idazoxan binding to rabbit cerebral cortex recognises multiple imidazoline I2‐type receptors: pharmacological characterization and relationship to monoamine oxidase
Authors: Renouard Anne , Widdowson Peter S. , Cordi Alex 
Published: July 2012

In rabbit cerebral cortical homogenates, saturation analysis of [3H]‐idazoxan, an α2‐adrenoceptor antagonist, revealed high affinity binding to a single site with high density. Competition experiments demonstrated that the [3H]‐idazoxan recognition site was insensitive to the catecholamines, adrenaline and noradrenaline and possessed a low affinity for the α2‐ and α1‐adrenoceptor antagonists, rauwolscine, yohimbine and prazosin, suggesting that the site was not an adrenoceptor. Mapping [3H]‐idazoxan binding sites in the forebrain of rabbits by autoradiography, showed high densities of I2 sites in the medial preoptic area and in the stria terminalis. Moderate binding was found in caudate nucleus, putamen, cerebral cortex and hippocampus.
The imidazolines cirazoline, naphazoline, guanabenz and BRL44408 along with amiloride, which is structurally related to the imidazolines, all had high affinity for the [3H]‐idazoxan site, suggesting that the site was related to the I2 imidazoline‐recognition site described by other groups. However, the imidazolines, clonidine and UK‐14,304 and the structurally related rilmenidine all had a low affinity for the binding site, showing that [3H]‐idazoxan was not binding to the I1 imidazoline‐recognition site found in rat, bovine and human medulla oblongata.
Naphazoline, guanabenz, clonidine and amiloride competition studies had Hill slopes which were significantly different from unity (P < 0.01) and computer analysis showed that the [3H]‐idazoxan binding data could be best fitted to a model which considers binding to two sites (P < 0.01). One site has a high affinity for idazoxan, cirazoline, naphazoline, guanabenz and amiloride and a moderate affinity for BRL44408 and clonidine (70% of binding) and the second site (30% of binding) has a high affinity for idazoxan and cirazoline, but a lower affinity for naphazoline, guanabenz, amiloride, BRL44408 and clonidine.
Experiments using [3H]‐RX821002, in contrast to [3H]‐idazoxan, clearly demonstrated the presence of a single type of α2‐adrenoceptor in rabbit cortex with a pharmacological profile which is similar to the α2A‐adrenoceptor possessing a high affinity for yohimbine, rauwolscine, BRL44408 and oxymetazoline, but a lower affinity for prazosin.
The monoamine oxidase inhibitors, clorgyline, pargyline and deprenyl had at least a ten fold lower affinity at the rabbirt cortex I2 site as compared to their known affinity at monoamine oxidase suggesting that the I2 site is not related to the active site of the enzyme, monoamine oxidase. In addition, the peripheral benzodiazepine ligands, PK‐11195 or Ro 5–4864 both had very low affinities at the I2 site in rabbit cortex suggesting that the [3H]‐idazoxan binding was not to the peripheral benzodiazepine binding site.
Dual effects of chlorobutanol on secretory response and intracellular Ca2+ dynamics in isolated pancreatic acini of the rat
Authors: Habara Y. , Kanno T. 
Published: July 2012

The effects of chlorobutanol, a widely used drug preservative, on exocrine response and intracellular Ca2+ dynamics were examined in isolated pancreatic acini of the rat.
Chlorobutanol (1 mg ml−1) markedly inhibited the secretory response to cholecystokinin octapeptide (CCK‐8), carbamylcholine chloride (carbachol), or sodium fluoride, a direct G‐protein activator. However, chlorobutanol itself induced a maximal release of amylase when the dose was increased to 4 mg ml−1.
An oscillatory fluctuation of cytoplasmic Ca2+ concentration, [Ca2+]c, induced by 5 pm CCK‐8 or 0.3 μm carbachol was totally abolished in the presence of 1 mg ml−1 chlorobutanol.
A biphasic change in [Ca2+]c induced by 100 pm CCK‐8, a rapid rise followed by a gradual decay, was transformed to an oscillatory fluctuation by the preservative.
Chlorobutanol inhibited 13 pm [125I]‐CCK‐8 or 0.5 nm [3H]‐methylscopolamine chloride binding to the acinar cells in a dose‐dependent manner.
These results indicate that chlorobutanol produces discernible pharmacological effects on the secretory response in rat pancreatic acinar cells through changes in the Ca2+ dynamics. Possible sites of action could be at a binding process of secretagogues to their receptors, at an activation process of a G‐protein located in the plasma membrane, or at the processes following G‐protein activation. However, the possibility that the preservative may distort the Ca2+‐transport function of the plasma membrane or the membrane of intracellular organella, especially Ca2+‐sequestering pools, cannot be excluded.
Pharmacological characterization of muscarinic receptor‐activated cation channels in guinea‐pig ileum
Authors: Chen Shan , Inoue Ryuji , Ito Yushi 
Published: July 2012

The pharmacological properties of cationic currents activated by acetylcholine (ACh) (Icat) in guinea‐pig ileal smooth muscle cells were investigated, with conventional single patch electrode or nystatin‐perforated whole‐cell recording. Cs‐aspartate was used as the internal solution to allow selective measurement of Icat.
Well‐known K channel blockers, tetraethylammonium (TEA), 4‐aminopyridine (4‐AP), procaine and quinine as well as a Ca releasing agent, caffeine, all produced concentration‐dependent inhibition of Icat with rapid onset (time constant ∼100 ms), when applied externally. The recovery from the inhibition on washout also occurred rapidly in the order of 100 ms except in the case of quinine. Approximate values of the half inhibitory concentrations (IC50) were 10 mm for TEA and caffeine, 1–5 mm for 4‐AP and procaine, and 1 μm for quinine. The mode of inhibition was voltage‐dependent, i.e., depolarization relieved the inhibition with no change in reversal potential.
Externally applied diphenylamine‐2‐carboxylate (DPC) derivatives, DCDPC and flufenamic acid, produced potent inhibition of Icat at micromolar concentrations (IC50s were < 30 μm for DCDPC and 32 μm for flufenamic acid). The onset of and recovery from inhibition occurred slowly and the degree of inhibition depended on the membrane potential only weakly, without any discernible change in the reversal potential.
All of the above‐tested drugs exhibited comparable inhibitory actions on the voltage‐dependent Ca current in the concentration ranges effective at inhibiting Icat. However, amongst them, quinine and flufenamic acid seemed to have several‐fold better selectivity for the Icat channel than for the voltage‐dependent Ca channel.
Internally dialysed GTPγS (100 μm) induced inward cationic currents. The effects of drugs on these currents were similar to their effects on the Icat current.
These results clearly indicate that many drugs used as pharmacological tools in smooth muscle research exert considerable nonspecific effects on various types of channels. The mechanism of inhibition and the relevance to use of these drugs as blockers for the Icat channel are discussed.
Involvement of nitric oxide synthase in the delayed vasodilator response to ultraviolet light irradiation of rat skin in vivo
Authors: Warren J.B. , Loi R.K. , Coughlan M.L. 
Published: July 2012

The role of nitric oxide synthase and cyclo‐oxygenase in the skin blood flow response to ultraviolet light B (u.v.B) irradiation was investigated in the rat in vivo.
Local skin blood flow changes were measured in the shaved dorsal skin of anaesthetized male Sprague‐Dawley rats with a laser Doppler flow probe.
u.v.B irradiation caused delayed onset vasodilatation and by 18 h basal blood flow increased by 125 ± 25% (P < 0.05, n = 12 rats, mean ± s.e.mean).
Indomethacin, 3 nmol per site, NG‐nitro‐l‐arginine methyl ester (l‐NAME) 100 nmol per site, but not d‐NAME 100 nmol per site, injected locally 17.5 h after u.v.B irradiation abolished the 18 h increase in blood flow.
The nitric oxide synthase inhibitor l‐NAME, NG‐monomethyl‐l‐arginine (l‐NMMA) and canavanine, 10 and 100 nmol per site injected at 17.5 h, suppressed significantly the u.v.B 18 h response in a dose‐dependent manner. The order of potency was l‐NAME > canavanine = l‐NMMA. The effect of l‐NAME was reversed partially by the co‐injection of an excess of l‐arginine.
Topical application of the corticosteroid, clobetasol 17‐propionate, immediately after irradiation inhibited the 18 h u.v.B response in a dose‐dependent manner.
The delayed onset microcirculatory vasodilatation induced by u.v.B involves both nitric oxide synthase and cyclo‐oxygenase in this in vivo model. Topical corticosteroids may attenuate the response by inhibiting both prostaglandin and nitric oxide synthesis pathways.
Effects of intracerebroventricular injection of histamine and related compounds on corticosterone release in rats
Authors: Tsujimoto Susumu , Okumura Yasushi , Kamei Chiaki , Tasaka Kenji 
Published: July 2012

The effects of intracerebroventricular (i.e.v.) injection of histamine and related compounds on plasma adrenocorticotrophic hormone (ACTH) and corticosterone concentrations were studied in conscious rats.
Histamine at doses of 5–20 μg kg−1 rapidly increased plasma ACTH and corticosterone concentrations almost simultaneously, and subsequent courses were also similar to each other. However, in the case of CRF‐41 (i.v.), the plasma ACTH concentration first increased followed by an increase in plasma corticosterone concentration. Even in hypophysectomized rats, a significant increase in plasma corticosterone concentration was induced by histamine at doses of 20 and 50 μg kg−1.
Histamine at doses of 10 and 20 μg kg−1 elicited an increase in the amplitude of adrenal nerve activity, and electrical stimulation to the adrenal nerves resulted in an increase in plasma corticosterone concentration.
Both H1‐agonist (2‐methylhistamine) and H2‐agonists (4‐methylhistamine and impromidine) also induced similar effects to those of histamine. Pretreatment with pyrilamine caused an inhibition of histamine‐induced increase in plasma ACTH and corticosterone concentrations, while both cimetidine and ranitidine failed to inhibit this effect. However, both H2‐blockers were effective in inhibiting the 4‐methylhistamine‐induced elevation of plasma ACTH and corticosterone concentrations.
Neither (R)‐α‐methylhistamine nor thioperamide had a significant effect, indicating that the H3‐receptor is not involved in the histamine‐induced increase in plasma ACTH and corticosterone concentrations.
From these findings, it was concluded that (1) electrical signals transmitted from the brain to the adrenal gland through the neurones may be involved in the rapid corticosterone release induced by histamine, and (2) not only H1‐ but also H2‐receptors are implicated in histamine‐induced hormone secretions in rats, though the contribution of the H2‐receptor is less important than that of the H1‐receptor.
Antiarrhythmic drugs, clofilium and cibenzoline are potent inhibitors of glibenclamide‐sensitive K+ currents in Xenopus oocytes
Authors: Sakuta Hidenari , Okamoto Koichi , Watanabe Yasuhiro 
Published: July 2012

The novel K+ channel opener, Y‐26763 induced outward K+ currents in voltage‐clamped follicle‐enclosed Xenopus oocytes in a concentration‐dependent manner with an EC50 value of 58 μm.
The Y‐26763‐induced K+ current was completely and reversibly blocked by glibenclamide (an ATP‐sensitive K+ channel blocker) in a concentration‐dependent manner (IC50 140 nm). Effects of several antiarrhythmic drugs on Y‐26763‐induced glibenclamide‐sensitive K+ currents were investigated.
(±)‐Cibenzoline, RS‐2135, pirmenol, lorcainide and KW‐3407 (class I antiarrhythmic drugs, Na+ channel blockers) suppressed Y‐26763 responses in a concentration‐dependent manner with IC50 values (in μm) of 6.6, 54, 68, 71 and 370, respectively.
Clofilium, E‐4031, MS‐551 and bretylium (class III antiarrhythmic drugs which increase the action potential duration) also suppressed Y‐26763 responses concentration‐dependently, IC50 values (in μm) were 3.3, 660, 980 and ≥ 2000, respectively. N‐acetylprocainamide (class III antiarrhythmic drug) scarcely suppressed Y‐26763 responses.
The glibenclamide‐sensitive K+ currents elicted by KRN2391 were also suppressed by all these antiarrhythmic drugs.
The antiarrhythmic drugs, clofilium and (±)‐cibenzoline block glibenclamide‐sensitive K+ channels in Xenopus oocytes at concentrations comparable to their therapeutic plasma levels.
Effects of lisinopril on electromechanical properties and membrane currents in guinea‐pig cardiac preparations
Authors: Valenzuela Carmen , Pérez Onésima , Casis Oscar , Duarte Juan , Pérez‐Vizcaino Francisco , Delpón Eva , Tamargo Juan 
Published: July 2012

The effects of the angiotensin‐converting enzyme inhibitor, lisinopril, were studied in guinea‐pig atria and papillary muscles and in single isolated ventricular cells.
In isolated right atria, lisinopril (0.001–10 μm) decreased the amplitude and rate of the spontaneous contractions. In electrically driven left atria this negative inotropic effect was accompanied by a shortening of the time to peak tension and time for total contraction.
Lisinopril did not modify the electrophysiological characteristics of the ventricular action potentials recorded in papillary muscles perfused with normal Tyrode solution or elicited by isoprenaline in papillary muscles perfused with 27 mm K Tyrode solution.
In single ventricular cells, lisinopril (10 μm) had no effect on the inward L‐type Ca2+ (ICa,L), the inward rectifier (IK1) or the delayed rectifier K+ currents (IK). However, it abolished the stimulation‐dependent facilitation of the L‐type Ca2+ current.
These results indicate that the negative inotropic effect of lisinopril cannot be explained by a decrease in Ca2+ entry through L‐type channels and suggest that lisinopril may possibly act at an intracellular site to reduce contractile force.
Inositol 1,4,5‐trisphosphate and inositol 1,3,4,5‐tetrakisphosphate binding sites in smooth muscle
Authors: Zhang Lubo , Bradley Michael E. , Khoyi Mohammad , Westfall David P. , Buxton Iain L.O. 
Published: July 2012

We have previously demonstrated that activation of M3 muscarinic receptors increases inositol 1,4,5‐trisphosphate (InsP3) and inositol 1,3,4,5‐tetrakisphosphate (InsP4) accumulation in colonic smooth muscle.
In the present study, we demonstrate the existence of InsP3 and InsP4 binding sites in colonic circular smooth muscle by use of radioligand binding methods. Both [3H]‐InsP3 and [3H]‐InsP4 bound rapidly and reversibly to a single class of saturable sites in detergent‐solubilized colonic membranes with affinities of 5.04 ± 1.03 nm and 3.41 ± 0.78 nm, respectively. The density of [3H]‐InsP3 binding sites was 335.3 ± 19.3 fmol mg−1 protein which was approximately 2.5 fold greater than that of [3H]‐InsP4 sites (127.3 ± 9.1 fmol mg−1 protein).
The two high affinity inositol phosphate binding sites exhibited markedly different pH optima for binding of each radioligand. At pH 9.0, specific [3H]‐InsP3 binding was maximal, whereas [3H]‐InsP4 binding was only 10% that of [3H]‐InsP3. Conversely, at pH 5.0, [3H]‐InsP4 binding was maximal, while [3H]‐InsP3 binding was reduced to 15% of its binding at pH 9.0.
InsP3 was about 20 fold less potent (K1 = 50.7 ± 8.3 nm) than InsP4 in competing for [3H]‐InsP4 binding sites and could compete for only 60% of [3H]‐InsP4 specific binding. InsP4 was also capable of high affinity competition with [3H]‐InsP3 binding (K1 = 103.5 ± 1.5 nm), and could compete for 100% of [3H]‐InsP3 specific binding.
[3H]‐InsP3 binding in subcellular fractions separated by discontinuous sucrose density gradients followed NADPH‐cytochrome c reductase activity, suggesting an intracellular localization for the majority of InsP3 receptors in this tissue, whereas [3H]‐InsP4 binding appeared to be equally distributed between plasma membrane and intracellular membrane populations.
These results suggest the existence of distinct and specific InsP3 and InsP4 binding sites which may represent the physiological receptors for these second messengers; differences in the subcellular distribution of these receptors may contribute to differences in their putative physiological roles.
Modulation of opioid antinociception by CCK at the supraspinal level: evidence of regulatory mechanisms between CCK and enkephalin systems in the control of pain
Authors: Noble Florence , Derrien Muriel , Roques Bernard P. 
Published: July 2012

Much evidence in the literature supports the idea that cholecystokinin (CCK) interacts with opioids in pain mechanisms. In this work, we have investigated the supraspinal interactions between enkephalins and CCK, using the hot plate test in mice.
Intracerebroventricular (i.c.v.) administration of BDNL (a mixed CCKA/CCKB agonist) induced dose‐dependent antinociceptive responses on both paw lick and jump responses. In contrast, using the same test, the i.c.v. injection of BC 264 (a selective CCKB agonist) induced a hyperalgesic effect, which was restricted to paw licking and occurred only at a high dose of 2.5 nmol.
In addition, i.c.v. administration of BDNL potentiated the antinociceptive effects of the mixed inhibitor of enkephalin degrading enzymes, RB 101 and of the μ‐agonist, DAMGO, while BC 264 reduced these effects.
Furthermore, at a dose where it interacts selectively with δ‐opioid receptors, the opioid agonist BUBU reversed the hyperalgesic responses of BC 264 (2.5 nmol) but was unable to modify the effects induced by BDNL.
Taken together, these results suggest the existence of regulatory mechanisms between CCK and enkephalin systems in the control of pain. These regulatory loops could enhance the antinociceptive effects of morphine allowing the opiate doses used to be reduced and thus, possibly, the side‐effects to be minimized.
A novel metabotropic glutamate receptor agonist: marked depression of monosynaptic excitation in the newborn rat isolated spinal cord
Authors: Ishida M. , Saitoh T. , Shimamoto K. , Ohfune Y. , Shinozaki H. 
Published: July 2012

Neuropharmacological actions of a novel metabotropic glutamate receptor agonist, (2S,1′R,2′R,3′R)‐2‐(2,3‐dicarboxycyclopropyl)glycine (DCG‐IV), were examined in the isolated spinal cord of the newborn rat, and compared with those of the established agonists of (2S,1′S,2′S)‐2‐(carboxycyclopropyl)glycine (l‐CCG‐I) or (1S,3R)‐1‐aminocyclopentane‐1,3‐dicarboxylic acid ((1S,3R)‐ACPD).
At concentrations higher than 10 μm, DCG‐IV caused a depolarization which was completely blocked by selective N‐methyl‐d‐aspartate (NMDA) antagonists. The depolarization was pharmacologically quite different from that caused by l‐CCG‐I and (1S,3R)‐ACPD.
DCG‐IV reduced the monosynaptic excitation of motoneurones rather than polysynaptic discharges in the nanomolar range without causing postsynaptic depolarization of motoneurones. DCG‐IV was more effective than l‐CCG‐I, (1S,3R)‐ACPD or l‐2‐amino‐4‐phosphonobutanoic acid (l‐AP4) in reducing the monosynaptic excitation of motoneurones.
DCG‐IV (30 nm–1 μm) did not depress the depolarization induced by known excitatory amino acids in the newborn rat motoneurones, but depressed the baseline fluctuation of the potential derived from ventral roots. Therefore, DCG‐IV seems to reduce preferentially transmitter release from primary afferent nerve terminals.
Depression of monosynaptic excitation caused by DCG‐IV was not affected by any known pharmacological agents, including 2‐amino‐3‐phosphonopropanoic acid (AP3), diazepam, 2‐hydroxysaclofen, picrotoxin and strychnine.
DCG‐IV has the potential of providing further useful information on the physiological function of metabotropic glutamate receptors.