bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of nitric oxide (NO) in ocular inflammation
Authors: Wang Zun‐Yi , Håkanson Rolf 
Published: July 2012

The actions of nitric oxide (NO) have been investigated in the rabbit eye, with particular emphasis on the relationship between NO and C‐fibres and on those effects of NO that may be of importance in the inflammatory response to C‐fibre stimulation.
The NO synthase inhibitor, NG‐nitro‐L‐arginine (L‐NAME; 10–200 mg kg−1), but not the inactive analogue D‐NAME (200 mg kg−1), was found to block the inflammatory response induced by infrared irradiation of the iris in a dose‐dependent manner. The inhibitory effects of L‐NAME (200 mg kg−1) were partially reversed by L‐arginine (500 mg kg−1), but not by D‐arginine (500 mg kg−1).
L‐NAME (200 mg kg−1) virtually abolished the ocular effects of intravitreal injection of calcitonin gene‐related peptide (CGRP) (0.3 nmol).
The concentration of CGRP in aqueous humour from untreated rabbit eyes was 0.1 +0.001 nmol 1−1. Irradiation of the iris raised the CGRP concentration to 8.9±1.5 nmol 1−1. L‐NAME (200 mg kg−1) greatly suppressed the irradiation‐evoked release of CGRP, the concentration in the aqueous humour being 1.2 ± 0.2 nmol 1−1 (P<0.001). L‐Arginine reversed the L‐NAME‐induced inhibition of release of CGRP, the concentration of CGRP in the aqueous humour being 9.7 ± 0.6 nmol 1−1.
In addition, a NO donor, sodium nitroprusside (0.9 μmol), was found to raise the concentration of CGRP in the aqueous humour (14.8 ± 0.8 nmol 1−1) and to induce symptoms of ocular inflammation. The elevation in concentration of CGRP induced by sodium nitroprusside was not affected by L‐NAME (200 mg kg−1) (14.5 ± 1.2 nmol 1−1). Ocular responses were not inhibited by L‐NAME. 6 Our findings suggest that NO plays an important role in ocular inflammation by activating C‐fibres (directly or indirectly) and by mediating CGRP‐induced responses.
Effects of besipirdine at the voltage‐dependent sodium channel
Authors: Tang L. , Smith C.P. , Huger F.P. , Kongsamut S. 
Published: July 2012

Besipirdine (HP 749) is a compound undergoing clinical trials for efficacy in treating Alzheimer's disease. Among other pharmacological effects, besipirdine inhibits voltage‐dependent sodium and potassium channels. This paper presents a pharmacological study of the interaction of besipirdine with voltage‐dependent sodium channels.
Besipirdine inhibited [3H]‐batrachotoxin binding (IC50 = 5.5±0.2 μm) in a rat brain vesicular preparation and concentration‐dependently inhibited veratridine (25 μm)‐stimulated increases in intracellular free sodium ([Na+]i) and calcium ([Ca2+]i) in primary cultured cortical neurones of rat.
Besipirdine (30–100 μm) concentration‐dependently inhibited (up to 100%) veratridine‐stimulated release of [3H]‐noradrenaline (NA) from rat cortical slices.
When examined in greater detail, besipirdine was found to inhibit [3H]‐batrachotoxin binding in vesicular membranes competitively. However, when examined in rat brain synaptosomes, we found that the antagonism by besipirdine was not competitive; that is, the maximal stimulation of [Ca2+]i induced by veratridine decreased with increasing concentrations of besipirdine.
These results show that besipirdine is an inhibitor of voltage‐sensitive sodium channels and appears to bind to a site close to the batrachotoxin/veratridine binding site.
Intraneuronal accumulation and persistence of radiolabel in rat brain following in vivo administration of [3H]‐chlorisondamine
Authors: El‐Bizri H. , Rigdon M.G. , Clarke P.B.S. 
Published: July 2012

Chlorisondamine (CHL), a bisquaternary amine, produces a remarkably long‐lasting blockade of central responses to nicotine. The mechanism underlying this blockade is not known. The main aim of this study was to test for possible accumulation of [3H]‐CHL in rat brain during the period of chronic blockade.
Rats received CHL, either systemically (10mg kg−1) or centrally (10 μg i.c.v.). Seven days later, striatal synaptosomes prepared from these animals were tested for nicotine‐induced [3H]‐dopamine release. This experiment showed that i.c.v. administration of CHL was as effective as systemic administration in producing ex vivo blockade of central nicotinic receptors.
Rats received bilateral i.c.v. infusions of [3H]‐CHL (10 μg) and radioactivity was subsequently quantified in dissected cerebral cortex, striatum, hippocampus, midbrain and cerebellum. Radiolabel was detected at all three survival times (1, 7, and 21 days). Regional heterogeneity was apparent at 7 and 21 days survival. Radiolabel was almost exclusively confined to the insoluble subcellular fraction in all areas sampled.
The anatomical distribution of radiolabel was also visualized in brain sections. Rats received bilateral i.c.v. infusions of [3H]‐CHL (10 μg) and were killed at 1, 7, 21 or 84 days. Immediately before they were killed, all rats were tested behaviourally, and central nicotinic blockade was demonstrated at 1, 7 and 21 days; partial recovery was observed at 84 days. Particularly at longer survival times, tritium was found to be heavily concentrated in the substantia nigra pars compacta, ventral tegmental area, dorsal raphe nucleus, and the granular layer of the cerebellum.
The possibility of retrograde axonal transport of radiolabel was then examined. Rats received a unilateral intrastriatal infusion of [3H]‐CHL (0.34 or 0.034 μg) one week before they were killed. Autoradiographic labelling was largely confined to the site of infusion and to the ipsilateral substantia nigra pars compacta and dorsal raphe nucleus.
Thus, after i.c.v. administration, CHL (and/or centrally‐formed derivatives) is initially widely distributed within the brain and is then selectively retained within a few brain areas. A persistent accumulation occurs within putative dopaminergic and 5‐hydroxytryptaminergic neurones, at least partly through uptake by terminals and/or axons followed by retrograde transport. This persistent and anatomically‐selective intraneuronal accumulation possibly underlies the long‐term central nicotinic blockade associated with chlorisondamine.
Application of intracerebral microdialysis to study regional distribution kinetics of drugs in rat brain
Authors: de Lange Elizabeth C.M. , Bouw M. Rene , Mandema Jaap W. , Danhof Meindert , de Boer Albertus G. , Breimer Douwe D. 
Published: July 2012

The purpose of the present study was to determine whether intracerebral microdialysis can be used for the assessment of local differences in drug concentrations within the brain.
Two transversal microdialysis probes were implanted in parallel into the frontal cortex of male Wistar rats, and used as a local infusion and detection device respectively. Within one rat, three different concentrations of atenolol or acetaminophen were infused in randomized order. By means of the detection probe, concentration‐time profiles of the drug in the brain were measured at interprobe distances between 1 and 2 mm.
Drug concentrations were found to be dependent on the drug as well as on the interprobe distance. It was found that the outflow concentration from the detection probe decreased with increasing lateral spacing between the probes and this decay was much steeper for acetaminophen than for atenolol. A model was developed which allows estimation of kbp/Deff (transfer coefficient from brain to blood/ effective diffusion coefficient in brain extracellular fluid), which was considerably larger for the more lipohilic drug, acetaminophen. In addition, in vivo recovery values for both drugs were determined.
The results show that intracerebral microdialysis is able to detect local differences in drug concentrations following infusion into the brain. Furthermore, the potential use of intracerebral microdialysis to obtain pharmacokinetic parameters of drug distribution in brain by means of monitoring local concentrations of drugs in time is demonstrated.
Characterization of U‐97775 as a GABAA receptor ligand of dual functionality in cloned rat GABAA receptor subtypes
Authors: Im Haesook K. , Im Wha Bin , Pregenzer Jeff F. , Carter Donald B. , Jacobsen E. Jon , Hamilton Beverly J. 
Published: July 2012

U‐97775 (tert‐butyl 7‐chloro‐4,5‐dihydro‐5‐[(1‐(3,4,5‐trimethyl)piperazino)carbonyl]‐imidazo[1,5‐a])quinoxaline‐3‐carboxylate) is a novel GABAA receptor ligand of dual functionality and was characterized for its interactions with cloned rat GABAA receptors expressed in human embryonic kidney cells.
The drug produced a bell‐shaped dose‐response profile in the α1β2γ2 receptor subtype as monitored with GABA‐induced C1− currents in the whole cell patch‐clamp technique. At low concentrations (<0.5 μM), U‐97775 enhanced the currents with a maximal increase of 120% as normalized to 5 μM GABA response (control). An agonist interaction of U‐97775 with the benzodiazepine site is suggested, because Ro 15–1788 (an antagonist at the benzodiazepine site) abolished the current increase and [3H]‐flunitrazepam binding was inhibited by U‐97775 with a Ki of 1.2 nM.
The enhancement of GABA currents progressively disappeared as the U‐97775 concentration was raised above 1 μM, and the current amplitude was reduced to 40% below the control at 10 μM U‐97775. The current inhibition by U‐97775 (10 μM) was not affected by Ro 15–1788. It appears that U‐97775 interacts with a second site on GABA receptors, distinct from the benzodiazepine site, to reverse its agonistic activity on the benzodiazepine site and also to inhibit GABA currents.
U‐97775 at low concentrations reduced and at high concentrations enhanced [35S]‐TBPS binding. Ro 15–1788 selectively blocked the effect of U‐97775 at low concentrations. Analysis of the binding data in the presence of Ro 15–1788 yielded a single low affinity site with an estimated Kd of 407 nM.
In other αβγ receptor subtypes, U‐97775 at low concentrations enhanced C1− currents in the α3β2γ2 but not in the α6β2γ2 subtype. On the other hand, U‐97775 at high concentrations reduced C1− currents in all the receptor subtypes we examined, including those of two subunits, α1β2, β2γ2 and α1gamma;2 subtypes.
Therapeutically, U‐97775 could be unique among benzodiazepine ligands because of its ability to limit its own agonistic activity such that, at high doses the appearance of agonistic activity would be delayed until occupancy of its second site wanes. This property should make the total agonistic activity of U‐97775 relatively constant over a wide range of drug doses, and may minimize its liability to abuse.
Blockade by ONO‐NT‐012, a unique prostanoid analogue, of prostaglandin E2‐induced allodynia in conscious mice
Authors: Minami Toshiaki , Nishihara Isao , Sakamoto Kazuichi , Ito Seiji , Hyodo Masayoshi , Hayaishi Osamu 
Published: July 2012

Intrathecal (i.t.) administration of prostaglandin E2 (PGE2) to conscious mice was reported to induce allodynia, a state of discomfort and pain evoked by innocuous tactile stimuli through prostaglandin E receptor subtype EP1 and hyperalgesia through prostaglandin E receptor subtypes EP2 and/or EP3. In the present study, we investigated the effects of an EP1 antagonist on these sensory disorders by use of ONO‐NT‐012 or AH6809.
ONO‐NT‐012 dose‐dependently antagonized the PGE2‐induced allodynia but had no effect on the PGE2‐induced hyperalgesia by the hot plate test. On the other hand, AH6809 blocked the PGE2‐induced hyperalgesia at the highest dose examined (50 μ kg−1) but had no effect on the PGE2‐induced allodynia. The i.t. injection of AH6809 or ONO‐NT‐012 alone did not have any effect on the response to noxious or innocuous stimuli.
Increasing doses (5 pg kg−1‐500 ng kg−1) of ONO‐NT‐012 produced parallel shifts to the right of the dose‐response curves to PGE2. The Schild plot regression line was linear and the slope was close to unity. The pA2 value against PGE2 was calculated to be 9.96.
The present study demonstrates that i.t. administration of PGE2 exerts allodynia through EP1 in the mouse spinal cord and that ONO‐NT‐012 is a highly potent, simple competitive antagonist for the PGE2‐induced allodynia.
Caffeine‐evoked, calcium‐sensitive membrane currents in rabbit aortic endothelial cells
Authors: Rusko J. , Van Slooten G. , Adams D.J. 
Published: July 2012

Single cell photometry and whole‐cell patch clamp recording were used to study caffeine‐induced intracellular Ca2+ signals and membrane currents, respectively, in endothelial cells freshly dissociated from rabbit aorta.
Caffeine (5 mM) evoked a transient increase in [Ca2+]i in fura‐2‐loaded endothelial cells. Pretreatment of cells with lO μM ryanodine did not alter resting [Ca2+]i but irreversibly inhibited the caffeine‐induced rise in [Ca2+]i. The caffeine‐induced increase in [Ca2+]i was not attenuated by the removal of extracellular Ca2+ and did not stimulate the rate of Mn2+ quench of fura‐2 fluorescence.
Bath application of caffeine evoked a dose‐ and voltage‐dependent outward current. The rate of onset and amplitude of the caffeine‐evoked outward current increased with higher caffeine concentrations and membrane depolarization. The relationship between caffeine‐evoked current amplitude and membrane potential was non linear, suggesting that the channels underlying the current are voltage‐sensitive.
In the absence of extracellular Ca2+, the amplitude of the caffeine‐evoked outward current was reduced by approximately 50% but the duration of the current was prolonged compared to that observed in the presence of external Ca2+. Ca2+‐free external solutions produced an unexpected increase in both the frequency and amplitude of spontaneous transient outward currents (STOCs).
Inclusion of heparin (10 μg ml−1) in the patch pipette abolished the acetylcholine (ACh)‐induced outward current but failed to inhibit either STOCs or the caffeine‐evoked outward current in native endothelial cells. In the absence of extracellular Ca2+, heparin did not affect either STOCs or the caffeine‐induced outward current.
Externally applied tetraethylammonium ions (TEA, 3–10 mM) reversibly inhibited unitary Ca2+‐activated K+ currents and STOCs in endothelial cells but failed to inhibit completely the outward current evoked by 20 mM caffeine.
Bath application of 0.1 mM zinc ion (Zn2+), a chloride channel blocker, did not affect unitary currents or STOCs but reduced the amplitude of the caffeine‐evoked current by >75% compared to control. Replacement of extracellular NaCl with Na gluconate also reduced the amplitude of the caffeine‐induced outward current. Bath application of 0.1 mM Zn2+ and 10 mM TEA completely blocked the caffeine‐evoked outward current in endothelial cells.
Caffeine‐induced Ca2+ release from intracellular stores evokes a transient rise in [Ca2+]i which is correlated with a large, transient outward current. The ionic dependence and inhibition of the caffeine‐sensitive current by TEA and Zn2+ suggests that Ca2+‐activated K+ and Cl− conductances contribute to the caffeine response in rabbit aortic endothelial cells.
Characterization of α1‐adrenoceptor subtypes in tension response of human prostate to electrical field stimulation
Authors: Guh Jih‐Hwa , Chueh Shih‐Chieh , Ko Feng‐Nien , Teng Che‐Ming 
Published: July 2012

The effects of various α1‐adrenoceptor antagonists and nifedipine on tension responses of human prostate to electrical field stimulation were evaluated in this study.
Prazosin (3 × 10−10 to 10−8M) and 5‐methyl‐urapidil (10−9 to 3 × 10−8 M) blocked concentration‐dependently the tension responses to electrical field stimulation and completely abolished them in the maximal concentrations (10−8 M and 3 × 10−8 M, respectively); in contrast, chloroethylclonidine (CEC), in the maximal concentration of 100 μM, blocked these effects by only 50%.
The contractile responses of rat vas deferens and spleen to exogenously‐applied α1radrenoceptor agonists were competitively inhibited by prazosin and 5‐methyl‐urapidil; in addition, the pA2 values were calculated and the relative potencies with reference to prazosin were obtained. The relative potency of 5‐methyl‐urapidil in human prostate (0.105) was close to that in rat vas deferens (0.257), which contains primarily putative α1A‐adrenoceptors. However, it was much more than that in rat spleen (0.011), which contains primarily putative α1B‐adrenoceptors.
Nifedipine (10−8 to 10−6 M) inhibited concentration‐dependently the contractile responses to electrical field stimulation in human prostate; in addition, the inhibition percentages were similar to those to exogenously‐applied noradrenaline in rat vas deferens. In contrast, CEC (10 μM), which almost flattened the concentration‐response curve of the rat spleen to phenylephrine, only partially inhibited (by 33.1%) the nerve‐mediated contraction of human prostate.
The involvement of prejunctional α2‐adrenoceptors situated on the sympathetic nerve terminals of human prostate was also examined. Clonidine (3 × 10−9 to 3 × 10−7 M) blocked concentration‐dependently the contractile response to electrical field stimulation of human prostate and this inhibitory effect was reversed by yohimbine (10−7 M). Additionally, the inhibitory effect of CEC (3 × 10−6 to 3 × 10−4 M) to the nerve‐mediated contraction was also partially reversed by yohimbine (10−7M).
It is suggested that the putative α1A‐adrenoceptors in human prostate may be functionally confined to the synaptic region whereas only minor populations of the putative α1B‐ and/or αlc‐adrenoceptors exist in this region.
Pharmacological identification of different inhibitory mediators involved in the innervation of the internal anal sphincter
Authors: Tottrup A. , Knudsen M.A. , Sorensen F. Hanberg , Glavind E.B. 
Published: July 2012

Inhibitory non‐adrenergic, non‐cholinergic (NANC) responses were studied in isolated strips from the rabbit internal anal sphincter.
In the presence of atropine and guanethidine, transmural field stimulation induced frequency‐dependent relaxations that reached a plateau at frequencies ≥ 4 Hz.
These relaxations were inhibited by apamin (10−6M) and by Nω‐nitro‐L‐arginine (L‐NOARG, 10−4M). With these two substances in combination, relaxations were still seen in response to field stimulation, but only at frequencies >2Hz.
In the presence of both apamin (10−6 M) and L‐NOARG (10−4 M), responses at high frequencies consisted of a fast relaxation followed by a slow return to prestimulus tension level. α‐Chrymotrypsin hastens the return of tension to prestimulus level after high frequency stimulation.
Zinc‐protoporphyrin IX, an inhibitor of haeme oxygenase, had a significant inhibitory effect on relaxations induced by transmural field stimulation. It was found, however, that responses to sodium nitroprusside and to isoprenaline (both 10−9‐10−4M) were reduced comparably, indicating that the effect of zinc‐protoporphyrin IX was unspecific.
It is concluded that pharmacological analysis allows identification of at least three distinguishable components of the inhibitory NANC innervation of the rabbit internal anal sphincter. The study does not allow conclusions about the role of carbon monoxide, a recently proposed mediator of NANC responses in opossum internal anal sphincter.
Inhibition by zinc protoporphyrin‐IX of receptor‐mediated relaxation of the rat aorta in a manner distinct from inhibition of haem oxygenase
Authors: Ny Lars , Andersson Karl‐Erik , Grundemar Lars 
Published: July 2012

Carbon monoxide (CO), produced by haem oxygenase through degradation of haem, has been claimed to be a neuromessenger and a possible regulator of vascular tone. We examined whether the haem oxygenase inhibitor, zinc protoporphyrin‐IX (ZnPP) and other porphyrins affect the relaxation evoked by various agents in the rat isolated aorta.
Pretreatment with ZnPP (0.1 mM) virtually abolished the relaxation evoked by vasoactive intestinal peptide (VIP) and atrial natriuretic peptide (ANP). ZnPP also evoked a rightward shift of the concentration‐response curve for the relaxation induced by acetylcholine.
In contrast, ZnPP did not affect the relaxation evoked by forskolin and 3‐morpholino‐sydnonimine, agents which directly activate adenylate and guanylate cyclase, respectively.
Although, less effective than ZnPP, tin protoporphyrin‐IX (SnPP; 0.1 mM) and protoporphyrin‐IX (PP; 0.1 mM) also attenuated the VIP‐evoked relaxation.
The elevation of cyclic AMP and cyclic GMP levels evoked by VIP and ANP, respectively, were abolished by pretreatment with ZnPP (0.1 mM).
ZnPP, SnPP and PP did not affect the contraction evoked by phenylephrine.
The results show that ZnPP inhibits relaxation induced by VIP, ANP and acetylcholine, probably by interfering with membrane receptor‐coupled signal transduction pathways. This inhibition does not seem to be dependent upon inhibition of haem oxygenase. The lack of specificity of the haem oxygenase inhibiting metalloporphyrins makes them less suitable as pharmacological tools in the investigation of a messenger role for CO.
ETA receptor‐mediated constrictor responses to endothelin peptides in human blood vessels in vitro
Authors: Maguire Janet J. , Davenport Anthony P. 
Published: July 2012

We have characterized the constrictor endothelin receptors present in human isolated blood vessels using ETA and ETB selective agonists and antagonists.
Monophasic dose‐response curves were obtained for ET‐1 with EC50 values of 6.8 nM in coronary artery, 3.9 nM in internal mammary artery, 17.4 nM in pulmonary artery, 14.5 nM in aorta and 3.2 nM in saphenous vein. In coronary artery, ET‐2 was equipotent with ET‐1 with an EC50 value of 5.7 nM. The non‐selective peptide, sarafotoxin 6b, was 2–3 times less potent than ET‐1 but the maximum responses to these two were comparable.
In each vessel ET‐3 was much less active than ET‐1. No response was obtained to ET‐3 in aorta and pulmonary artery or in up to 50% of coronary artery, mammary artery and saphenous vein preparations. In those preparations that did respond, dose‐response curves were incomplete at 300 nM. Variable contractions were also obtained with the ETB‐selective agonist, sarafotoxin 6c (S6c). Where responses were detected, although S6c was more potent than ET‐1 (EC50 values of 0.6‐1.2 nM), the maximum response produced was always less than 20% of that to ET‐1.
The synthetic ETB agonists, BQ3020 and [l,3,11,15Ala]‐ET‐l, were without effect in any of the five blood vessels at concentrations up to 3 μM.
ET‐1‐induced vasoconstriction was blocked by the ETA‐selective antagonists, BQ123 and FR139317. Schild‐derived pA2 values were 7.0, 7.4 and 6.9 for BQ123 and 7.6, 7.9 and 7.3 for FR139317 in coronary artery, mammary artery and saphenous vein, respectively, consistent with antagonism of ETA receptors. Slopes of the Schild regressions were not significantly different from one. Comparable values of pA2 were estimated for 3 μM BQ123 in aorta (7.4 ±0.5) and pulmonary artery (6.9) from the Gaddum‐Schild equation.
In conclusion we have shown that in human isolated blood vessels, ET‐1 is more potent than ET‐3 suggesting the presence of vasoconstrictor ETA receptors. This is supported by the lack of effect of the ETB agonists, BQ3020 and [1,3,11,15Ala]‐ET‐l and the ability of the ETA antagonists, BQ123 and FR 139317 to block ET‐1 responses. Some preparations did contract in response to low concentrations of the ETB‐selective sarafotoxin 6c but responses were variable and the maximum was always much less than that to ET‐1 in the same preparations. Therefore although constrictor ETB receptors were present on the smooth muscle of human blood vessels, vasoconstriction elicited by the endothelin peptides in vitro is via ETA receptor activation.