bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation by intracellular GDP, metabolic inhibition and pinacidil of a glibenclamide‐sensitive K‐channel in smooth muscle cells of rat mesenteric artery
Authors: Zhang H. , Bolton T.B. 
Published: July 2012

Single‐channel recordings were made from cell‐attached and isolated patches, and whole‐cell currents zwere recorded under voltage clamp from single smooth muscle cells obtained by enzymic digestion of a small branch of the rat mesenteric artery.
In single voltage‐clamped cells 1 mm uridine diphosphate (UDP) or guanidine diphosphate (GDP) added to the pipette solution, or pinacidil (100 μm) a K‐channel opener (KCO) applied in the bathing solution, evoked an outward current of up to 100pA which was blocked by glibenclamide (10 μm). In single cells from which recordings were made by the ‘perforated patch’ (nystatin pipette) technique, metabolic inhibition by 1 mm NaCN and 10 mm 2‐deoxy‐glucose also evoked a similar glibenclamide‐sensitive current.
Single K‐channel activity was observed in cell‐attached patches only infrequently unless the metabolism of the cell was inhibited, whereupon channel activity blocked by glibenclamide was seen; pinacidil applied to the cell evoked similar glibenclamide‐sensitive channel activity. If the patch was pulled off the cell to form an isolated inside‐out patch, similar glibenclamide‐sensitive single‐channel currents were observed in the presence of UDP and/or pinacidil to those seen in cell‐attached mode; channel conductance was 20 pS (60:130 K‐gradient) and openings showed no voltage‐dependence and noisy inward currents, typical of the nucleoside diphosphate (NDP) activated K‐channel (KNDP) seen previously in rabbit portal vein.
Formation of an isolated inside‐out patch into an ATP‐free solution did not increase the probability of channel opening which declined with time even when some single‐channel activity had occurred in the cell‐attached mode before detachment. However, application of 1 mm UDP or GDP, but not ATP, to inside‐out patches evoked single‐channel activity. Application of ATP‐free solution to isolated patches, previously exposed to ATP and in which channel activity had been seen, did not evoke channel activity.
It is concluded that small conductance K‐channels (KNDP) open in smooth muscle cells from this small artery in response to UDP or GDP acting from the inside, or pinacidil acting from the outside; the same channels open during inhibition of metabolism presumably mainly due to the rise in nucleoside diphosphates, but a fall in the ATP concentration on the inside of the channel did not by itself evoke channel activity. Failure to respond to a fall in ATP concentration upon formation of an inside‐out patch could not be due to dephosphorylation of the channel because sometimes it had been active previously during cell‐attached recording. NDPs, instead of ATP, are more important regulators of KNDP channels. It is suggested that the KNDP is the main target K‐channel for KCOs.
Involvement of endogenous nitric oxide in the mechanism of bradykinin‐induced peripheral hyperalgesia
Authors: Nakamura Akihiro , Fujita Manabu , Shiomi Hirohito 
Published: July 2012

When NG‐nitro‐L‐arginine methyl ester (L‐NAME, 0.1–10 nmol) or NG‐monomethyl‐L‐arginine (L‐NMMA, 10 nmol‐1 μmol) was intradermally administered with bradykinin (BK, 3 nmol) into the instep of rat hind‐paws, a dose‐related suppression of BK‐induced hyperalgesia, assessed by the paw‐pressure test, was produced.
L‐Arginine (1 μmol) but not D‐arginine (1 μmol) reversed the suppressive effects of L‐NAME (10 nmol) and L‐NMMA (1 μmol) on BK‐induced hyperalgesia.
Concomitant intradermal administration of BK (3 nmol) with haemoglobin (1 nmol) significantly suppressed BK‐induced hyperalgesia in the paw‐pressure test. The BK‐induced hyperalgesia was abolished by concomitant intradermal administration of either a guanylate cyclase inhibitor, methylene blue (10 nmol), or LY83583 (1 nmol). In addition, KT5823 (1 nmol) or Rp‐8‐bromoguanosine‐3′:5′‐cyclic monophosphothioate (Rp‐8‐Br‐cGMPS; 1 nmol), an inhibitor of cyclic GMP‐dependent protein kinase, also significantly suppressed BK‐induced hyperalgesia.
The carrageenin‐induced hyperalgesia was significantly attenuated by L‐NAME in a dose‐dependent manner.
L‐Arginine (1 μmol), sodium nitroprusside (1 μmol), dibutyryl cyclic GMP (1 μmol) or 8‐bromo cyclic GMP (1 μmol) all failed to produce any significant relieving effect on the nociceptive threshold of rodent hind‐paws. Concomitant administrations of each agent with a sub‐threshold dose (0.1 nmol) of BK induced significant hyperalgesia.
Rp‐adenosine 3′:5′‐cyclic monophosphothioate (Rp‐cAMPS; 1 nmol), an inhibitor of cyclic AMP‐dependent protein kinase, significantly suppressed BK‐induced mechanical hyperalgesia. Concomitant administration of forskolin (1 nmol) with 8‐bromo cyclic GMP (100 nmol) induced significant hyperalgesia.
In the superfusion experiment of a blister base on the instep of rodent hind‐paws, intradermally administered BK (3 nmol) significantly increased the outflow of both cyclic GMP and cyclic AMP from the blister base. Concomitant administrations of L‐NAME (10 nmol) with BK significantly reduced the BK‐induced outflow of cyclic GMP without affecting the cyclic AMP content.
These results suggest that the NO‐cyclic GMP pathway is involved in the mechanism of BK‐induced hyperalgesia, and an activation of both cyclic GMP‐and cyclic AMP‐second messenger system plays an important role in the production of peripherally induced mechanical hyperalgesia.
Otilonium: a potent blocker of neuronal nicotinic ACh receptors in bovine chromaffin cells
Authors: Gandía Luis , Villarroya Mercedes , Lara Baldomero , Olmos Virginia , Gilabert Juan‐Antonio , LÓPEZ Manuela G. , Martínez‐Sierra Rafael , Borges Ricardo , García Antonio G. 
Published: July 2012

Otilonium, a clinically useful spasmolytic, behaves as a potent blocker of neuronal nicotinic acetylcholine receptors (AChR) as well as a mild wide‐spectrum Ca2+ channel blocker in bovine adrenal chromaffin cells.
45Ca2+ uptake into chromaffin cells stimulated with high K+ (70 mM, 1 min) was blocked by otilonium with an IC50 of 7.6 μm. The drug inhibited the 45Ca2+ uptake stimulated by the nicotinic AChR agonist, dimethylphenylpiperazinium (DMPP) with a 79 fold higher potency (IC50 = 0.096 μm).
Whole‐cell Ba2+ currents (IBa) through Ca2+ channels of voltage‐clamped chromaffin cells were blocked by otilonium with an IC50 of 6.4 μm, very close to that of K+‐evoked 45Ca2+ uptake. Blockade developed in 10–20 s, almost as a single step and was rapidly and almost fully reversible.
Whole‐cell nicotinic AChR‐mediated currents (250 ms pulses of 100 μm DMPP) applied at 30 s intervals were blocked by otilonium in a concentration‐dependent manner, showing an IC50 of 0.36 μm. Blockade was induced in a step‐wise manner. Wash out of otilonium allowed a slow recovery of the current, also in discrete steps.
In experiments with recordings in the same cells of whole‐cell IDMPP, Na+ currents (INa) and Ca2+ currents (ICa), 1 μm otilonium blocked 87% IDMPP, 7% INa and 13% ICa.
Otilonium inhibited the K+‐evoked catecholamine secretory response of superfused bovine chromaffin cells with an IC50 of 10 μm, very close to the IC50 for blockade of K+‐induced 45Ca2+ uptake and IBa.
Otilonium inhibited the secretory responses induced by 10 s pulses of 50 μm DMPP with an IC50 of 7.4 nM. Hexamethonium blocked the DMPP‐evoked responses with an IC50 of 29.8 μm, 4,000 fold higher than that of otilonium.
In conclusion, otilonium is a potent blocker of nicotinic AChR‐mediated responses. The drugs also blocked various subtypes of neuronal voltage‐dependent Ca2+ channels at a considerably lower potency. Na+ channels were unaffected by otilonium. This extraordinary potency of otilonium in blocking nicotinic AChR, unrecognised until now, might account in part for its well known spasmolytic effects.
Antagonism by SR 48692 of mechanical responses to neurotensin in rat intestine
Authors: Mulè F. , Serio R. , Postorino A. , Vetri T. , Bonvissuto F. 
Published: July 2012

The effects of SR 48692 on neurotensin (NT)‐induced mechanical responses were investigated in rat duodenum and proximal colon by use of isometric, isovolumic preparations.
SR 48692 inhibited the relaxant responses to NT in duodenal circular and longitudinal muscle. It also antagonized the NT‐induced contractile effects in duodenal circular muscle and in proximal colon (both muscular layers).
From Schild analysis the pA2 value for SR 48692 was 8.2 in tissues where NT induced relaxant effects and 7.5 in tissues where NT induced contractile effects and the slope of the regression line was not significantly different from unity, indicating competitive antagonism.
SR 48692 did not antagonize the duodenal relaxant effect induced by noradrenaline and the contractile response to carbachol or substance P in duodenum and colon.
Our results demonstrate that SR 48692 selectively antagonizes the mechanical actions of NT in rat intestine and confirm the existence of specific NT receptors. Receptors that subserve a relaxant effect seem to be related, but not identical, to those that mediate contractile effects.
Blockade of nitrergic transmission by hydroquinone, hydroxocobalamin and carboxy‐PTIO in bovine retractor penis: role of superoxide anion
Authors: Paisley Karen , Martin William 
Published: July 2012

The effects of inhibiting endogenous Cu/Zn superoxide dismutase (SOD) with diethyldithiocarbamate (DETCA) were examined on the ability of hydroquinone, hydroxocobalamin and carboxy‐PTIO to block nitrergic relaxation in the bovine retractor penis (BRP) muscle.
Incubation of strips of BRP with DETCA (3 mM) for 2 h reduced SOD activity from 73.1 ± 15.7 to 8.2 ± 1.9 units mg‐1 protein.
Hydroquinone (10 μm‐ 1mM) produced weak inhibition of nitrergic (4 Hz, 10 s) relaxation in control strips of BRP, but powerful inhibition in strips treated with DETCA (3 mM, 2 h). Exogenous SOD (250 units ml‐1) produced a partial blockade of the ability of hydroquinone to inhibit nitrergic relaxation in DETCA‐treated strips.
In an assay of SOD‐inhibitable reduction of cytochrome C, hypoxanthine (0.1 mM)/xanthine oxidase (16 munits ml‐1) and pyrogallol (10 μm), led to the rapid generation of superoxide anion. Hydroquinone (10 μm) also led to the generation of the free radical, although the rate of generation was slower.
Two NO‐scavenging agents, hydroxocobalamin (0.1 μm‐1 mM) and carboxy‐PTIO (0.1‐1 mM), produced concentration‐dependent blockade of nitrergic relaxation of the BRP. The magnitude of the blockade induced by these agents was unaffected following treatment with DETCA or SOD.
The findings with hydroquinone support our previous proposal that endogenous Cu/Zn SOD plays a vital role in protecting nitrergic neurotransmission from inactivation by superoxide anion. Results with hydroxocobalamin and carboxy‐PTIO are consistent with the known ability of these agents to scavenge NO. The nitrergic neurotransmitter in the BRP thus appears to have the properties of NO.
Effect of a non‐sulphonylurea hypoglycaemic agent, KAD‐1229 on hormone secretion in the isolated perfused pancreas of the rat
Authors: Kinukawa Mayumi , Ohnota Hideki , Ajisawa Yukiyoshi 
Published: July 2012

We examined the cooperative effect of a newly synthesized oral hypoglycaemic agent, KAD‐1229 with glucose on insulin, glucagon and somatostatin secretion in the isolated perfused pancreas of the rat.
KAD‐1229 stimulated concentration‐dependently the first phase of insulin secretion without the second phase in the presence of 2.8 mM glucose, while it stimulated both the first and the second phase of insulin release in the presence of 5.6 mM glucose. It was confirmed that the first phase of insulin release is depolarization‐induced release with no other additional signal transduction.
KAD‐1229 also enhanced insulin release evoked by 16.7 mM glucose, a concentration known to inhibit the ATP‐sensitive K+ current completely.
A low concentration (2.8 mM) of glucose stimulated somatostatin release transiently, while a higher concentration (16.7 mM) of glucose exerted a sustained stimulation. KAD‐1229 stimulated somatostatin secretion in a concentration‐dependent manner irrespective of glucose concentrations.
When glucagon release was stimulated with 2.8 mM glucose, KAD‐1229 inhibited this hypoglycaemia‐induced glucagon secretion.
When pancreata from rats pretreated with streptozotocin (STZ) 60 mg kg−1 were perfused, the basal secretion of glucagon was markedly elevated, and the glucagon response to the low glucose was abolished. Further, the insulin and somatostatin responses to KAD‐1229 were largely attenuated. KAD‐1229 showed transient enhancement followed by inhibition of the glucagon release from the STZ‐pretreated rat pancreas.
We conclude that KAD‐1229 stimulates insulin and somatostatin release, while it inhibits glucagon release following transient stimulation.
Involvement of secretory phospholipase A2 activity in the zymosan rat air pouch model of inflammation
Authors: Payá Miguel , Terencio M. Carmen , Ferrándiz M. Luisa , Alcaraz M. José 
Published: July 2012

In the zymosan rat air pouch model of inflammation we have assessed the time dependence of phospholipase A2 (PLA2) accumulation in the inflammatory exudates as well as cell migration, myeloperoxidase activity, prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) levels.
A significant increase in PLA2 activity was detected in 1,200 g supernatants of exudates 8 h after injection of zymosan into rat air pouch. This event coincided with peaks in cell accumulation (mainly neutrophils) and myeloperoxidase activity in exudates and was preceded by a rise in eicosanoid levels.
This enzyme (without further purification) behaved as a secretory type II PLA2 with an optimum pH at 7 − 8 units, lack of selectivity for arachidonate release and dependence on mM calcium concentrations for maximal activity.
The PLA2 inhibitors manoalide and scalaradial inhibited this enzyme activity in vitro in a concentration‐dependent manner. Scalaradial also inhibited zymosan stimulated myeloperoxidase release in vitro.
Injection of the marine PLA2 inhibitor scalaradial together with zymosan into the pouch at doses of 0.5, 1 and 5 μmol per pouch resulted in a dose‐dependent inhibition of PLA2 activity in exudates collected 8 h later. Myeloperoxidase levels and cell migration were also decreased, while eicosanoid levels were not modified.
Colchicine administration to rats prevented infiltration and decreased PLA2 levels in the 8 h zymosan‐injected air pouch.
These results indicate that during inflammatory response to zymosan in the rat air pouch a secretory PLA2 activity is released into the exudates. The source of this activity is mainly the neutrophil which migrates into the pouch.
Scalaradial exerts anti‐inflammatory effects in the zymosan air pouch.
An interaction of ondansetron and dexamethasone antagonizing cisplatin‐induced acute and delayed emesis in the ferret
Authors: Rudd J.A. , Naylor R.J. 
Published: July 2012

Cisplatin, 5 mg kg−1, i.p., administered as a single treatment, induced an acute (day 1) and delayed (days 2 and 3) emetic response in the ferret that was used to investigate the potential anti‐emetic activity of ondansetron and dexamethasone and their interaction over a three day period.
Ondansetron, 1 mg kg−1, i.p., administered three times per day in two experiments, antagonized significantly the retching and vomiting that occurred on days 1 and 2 by 60–76 and 73–84%. On the third day of treatment there was a trend for a 38% reduction in one experiment and a 74% reduction in the other.
There was a trend for dexamethasone, 1 mg kg−1, i.p., administered as a single daily injection for three days, to reduce by 37% the retching and vomiting response that occurred on day 1, the reduction of 77% on day 2 achieved significance and dexamethasone non‐significantly increased the retching and vomiting response by 46% on day 3. However, dexamethasone 1 mg kg−1 i.p. administered three times per day for three days significantly reduced the retching+vomiting reponse by 85, 97 and 86% on days 1, 2 and 3 respectively.
The combination of dexamethasone, 1 mg kg−1, i.p., as single daily injections with ondansetron, 1 mg kg−1, i.p., administered three times per day improved the control of the retching and vomiting response, significantly reducing the total numbers of retches and vomits by more than 70% over a three day period. The combination of dexamethasone (1.0 mg kg−1) and ondansetron (1.0 mg kg−1), both administered three times daily, abolished cisplatin‐induced emesis over the three day period.
The three times per day administration of ondansetron, 1 mg kg−1, i.p., plus dexamethasone, 1 mg kg−1, i.p., administered only on day 1 prevented day 1 emesis but did not modify the retching and vomiting that occurred on days 2 and 3.
The present results indicate that ondansetron and dexamethasone significantly reduce cisplatininduced emesis in the ferret during both the acute and delayed phase; drug/co‐treatment can exert an additive action to abolish cisplatin‐induced emesis. The ferret model may be useful to detect anti‐emetic drug action for treatment of chemotherapy‐induced acute and delayed emesis in man.
Improvement by dynorphin A (1–13) of galanin‐induced impairment of memory accompanied by blockade of reductions in acetylcholine release in rats
Authors: Hiramatsu M. , Mori H. , Murasawa H. , Kameyama T. 
Published: July 2012

Human galanin (0.32 nmol per rat, i.c.v.), an endogenous neuropeptide, administered 30 min before acquisition or retention trials, significantly impaired the acquisition of learning and recall of memory in a step‐through type passive avoidance performance.
The role of dynorphin A (1–13) in learning and memory is controversial. Dynorphin A (1–13) (0.5 nmol per rat, i.c.v.) administered 5 min before galanin injection, completely antagonized these impairments.
Galanin significantly decreased acetylcholine release in the hippocampus 40 to 120 min after injection as determined by in vivo brain microdialysis. This peptide also decreased acetylcholine release, albeit to a lesser extent, from the frontal cortex.
Dynorphin A (1–13) (0.5 nmol per rat, i.c.v.) 5 min before galanin injection, completely blocked the decrease in extracellular acetylcholine concentration induced by galanin.
These antagonistic effects of dynorphin A (1–13) were abolished by treatment with nor‐binaltorphimine (5.44 nmol per rat, i.c.v.), a selective κ‐opioid receptor antagonist, 5 min before dynorphin A (1–13).
Dynorphin A (1–13) (0.5 nmol) itself had no effect on learning and memory and on the acetylcholine concentration in the hippocampus or the frontal cortex in normal rats.
These results suggest that the neuropeptide dynorphin A (1–13) ameliorates the galanin‐induced impairment of learning and memory accompanied by abolition of reductions in acetylcholine release via κ‐opioid receptors.
Role of protein kinase C in mesenteric pressor responses of rats with portal hypertension
Authors: Atucha Noemí M. , Ortíz M. Clara , Martínez Concepción , Quesada Tomás , García‐Estañ Joaquín 
Published: July 2012

Hyporesponsiveness to vasoconstrictors is a characteristic abnormality of liver diseases of uncertain origin. In the present study, we have evaluated the involvement of protein kinase C (PKC) in the reduced pressor response to methoxamine (MTX) of a rat model of portal hypertension induced by partial portal vein ligation (PVL). Experiments were performed in the isolated and perfused mesentery.
The pressor response to MTX was reduced in PVL compared to that of control animals (Sham) and pretreatment with NG‐nitro‐L‐arginine (L‐NOARG, 10−4 m) or removal of the endothelium potentiated the response of both groups. However, only removal of the endothelium completely eliminated the reduced pressor response to MTX of the PVL vessels.
Pretreatment of the mesentric vessels with calphostin C (10−6 m), a PKC inhibitor, reduced the response to MTX of Sham to a level similar to that of untreated PVL vessels, but did not change that of PVL animals.
Mesenteric pressor responses to a PKC activator, phorbol 12,13‐dibutyrate (PDBu), were similar in vessels from both PVL and Sham rats and pretreatment with L‐NOARG or removal of the endothelium enhanced those responses while indomethacin (10−5 m) decreased them. In all cases, the responses to PDBU were similar in PVL vessels compared to Sham.
These results indicate that the reduced pressor response to MTX of the mesenteric vascular bed of PVL rats is due to an endothelial alteration, compatible with an enhanced production of nitric oxide. The lack of response to calphostin C in PVL vessels suggests an impairment in agonist‐induced PKC activation. Since direct activation of PKC induces a normal pressor response, it is concluded that the endothelial alteration interacts with the mechanism producing PKC activation, which results in a lower pressor response of the PVL mesenteric vaculature.
Effect of gadolinium on stretch‐induced changes in contraction and intracellularly recorded action‐ and afterpotentials of rat isolated atrium
Authors: Tavi P. , Laine M. , Weckström M. 
Published: July 2012

Atrial arrhythmias, like atrial fibrillation and extrasystoles, are common in clinical situations when atrial pressure is increased. Although cardiac mechanoelectrical feedback has been under intensive study for many years, the mechanisms of stretch‐induced arrhythmias are not known in detail. This is partly due to methodological difficulties in recording intracellular voltage during stretch stimulation. In this study we investigated the effects of gadolinium (Gd3+), a blocker of stretch‐activated (SA) channels, on stretch‐induced changes in rat atrial action potentials and contraction force.
By intracellular voltage recordings from rat isolated atria we studied the effects of Gd3+ (80 μm) on stretch‐induced changes in action potentials. The stretch was induced by increasing pressure inside the atrium (1 mmHg to 7 mmHg). An elastic electrode holder that moved along the atrial tissue was used in the recordings. Thus the mechanical artifacts were eliminated and the cell‐electrode contact was made more stable. To examine the influence of Gd3+ on atrial contraction we stretched the atria at different diastolic pressure levels (1 to 7 mmHg) with Gd3+ application of (80 μm) or diltiazem (5.0 μm). Contraction force was monitored by recording the pressure changes generated by the atrial contractions.
Our results show that: (1) atrial stretch induces delayed afterdepolarizations (DADs), increase in action potential amplitude and increase in relative conduction speed; (ii) Gd3+ blocks stretch‐induced DADs and action potential changes; (iii) Gd3+ inhibits pressure‐stimulated increase in the atrial contraction force, while similar inhibition is not observed with diltiazem, a blocker of L‐type calcium channels.
This study suggests that Gd3+ inhibits stretch‐induced changes in cell electrophysiology and contraction in the rat atrial cells and that the effects of gadolinium are due to rather specific block of stretch‐activated ion channels with only a small effect on voltage‐activated calcium channels.