bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reciprocal interaction of 5‐hydroxytryptamine and cholecystokinin in the control of feeding patterns in rats
Authors: Grignaschi Giuliano , Mantelli Barbara , Fracasso Claudia , Anelli Marina , Caccia Silvio , Samanin Rosario 
Published: July 2012

The effect of the CCKA receptor antagonist, devazepide (100 mg kg−1) on meal parameters during the initial phase of the dark period was studied in free‐feeding rats by use of a procedure for continuously monitoring feeding patterns.
In a second experiment, the effect of devazepide on the reduction in meal parameters induced by the 5‐hydroxytryptamine (5‐HT) releaser and uptake inhibitor, (+)‐fenfluramine (1.5 mg kg−1) in 4 h food‐deprived rats was examined.
The hypophagic effect of an intraperitoneal injection of cholecystokinin (CCK‐8, 4 μg kg−1) was studied in rats treated with the 5‐HT receptor antagonist, metergoline (1 and 2 mg kg−1).
Devazepide increased the size of the first meal in free‐feeding, but not in 4 h food‐deprived rats and partially antagonized the effect of (+)‐fenfluramine on the size and duration of the first meal. The reduction in eating rate induced by (+)‐fenfluramine was not modified by devazepide. No changes in (+)‐fenfluramine or (+)‐norfenfluramine levels were found in the brain of rats treated with devazepide.
The effect of CCK‐8 on meal size was completely antagonized by 2 mg kg−1 metergoline. A significant interaction was also found between 2 mg kg−1 metergoline and CCK‐8 as regards their effect on the inter‐meal interval.
The results suggest a reciprocal interaction between 5‐HT and CCK‐8 in enhancing the satiating effect of food in rats.
Action of α‐dendrotoxin on K+ currents in nerve terminal regions of axons in rat olfactory cortex
Authors: McGivern J. , Scholfield C.N. , Dolly J.O. 
Published: July 2012

In the rat olfactory cortex, unmyelinated axons give rise to synapses en passant. This tissue was used to study the pharmacology of axonal K+‐currents. Responses were measured from a group of these axons as unclamped field currents, with a polarizable suction electrode.
A single stimulus to the axons elicited a tetrodotoxin‐sensitive Na+‐dependent transient. K+‐currents were revealed by positive polarization of the suction electrode and were manifest as a negative current following the Na+‐component.
In the presence of tetraethylammonium (TEA, 5 mm) and Cd2+ (100 μm), the K+‐component was depressed by 3,4‐diaminopyridine (3,4‐DAP; 1 to 20 μm; IC50 2.0 ± 0.4 μm). α‐Dendrotoxin (DTX; 15–1500 nm) also attenuated the aminopyridine‐sensitive component (IC50 93 ± 4 nm). At the highest DTX concentration, depression of the K+‐current was incomplete, the residual K+ current being reduced by 3,4‐DAP (0.1 to 5 μm).
These results indicate the presence of two aminopyridine‐sensitive K+ currents in this preparation distinguished by their susceptibility to DTX.
Activation by Phoneutria nigriventer (armed spider) venom of tissue kallikrein‐kininogen‐kinin system in rabbit skin in vivo
Authors: Marangoni Rossana A. , Antunes Edson , Brain Susan D. , de Nucci Gilberto 
Published: July 2012

The purpose of the present study was to investigate the mechanisms by which venom from Phoneutria nigriventer spider induces increases in vascular permeability in rabbit skin.
Local oedema formation, in response to intradermally‐injected agents, was measured in male New Zealand white rabbits as the local accumulation of i.v. injected 125I‐labelled human serum albumin into skin sites.
Phoneutria nigriventer venom (10–30 μg/site) increased vascular permeability, which was inhibited by trasylol (10 μg/site) and the bradykinin B2 receptor antagonists d‐Arg,[Hyp3,Thi5,8,d‐Phe7]‐BK (3 nmol/site) and Hoe 140 (0.3 nmol/site). In addition, the oedema induced by the venom was potentiated by the kinase II inhibitor, captopril (1 nmol/site). The lipoxygenase inhibitor, BWA4C (10 nmol/site) and the PAF antagonist, WEB 2086 (100 nmol/site) had no effect on the venom‐induced increase in vascular permeability.
Incubation of rabbit plasma with Phoneutria nigriventer venom in vitro did not cause bradykinin formation. Further, the plasma kallikrein inhibitor, soybean trypsin inhibitor (10 μg/site), had no effect on the venom‐induced increase in vascular permeability in rabbit skin.
These results indicate that the oedema produced by Phoneutria nigriventer venom is dependent on the activation of the tissue kallikrein‐kinin system.
Differential localization of endothelin ETa and ETB binding sites in human placenta
Authors: Rutherford Richard A.D. , Wharton John , McCarthy Andrew , Gordon Lee , Sullivan Mark H.F. , Elder Murdoch G. , Polak Julia M. 
Published: July 2012

The localization and differential distribution of endothelin (ET) receptor subtypes (ETA and ETB) was investigated in sections of human placenta by use of quantitative in vitro autoradiography and receptor selective ligands.
Specific, high density [125I]‐ET‐1 binding sites were localized to the decidua and foetal membranes as well as to arteries and veins in the chorionic plate and throughout the villous tree. Moderate to low density binding was found in the extravillous and villous trophoblast respectively.
[125I]‐ET‐1 binding sites exhibited a rank order of inhibition by unlabelled peptide sequences (ET‐1 > ET‐3 >[Ala3,11,18Nle7]‐ET‐1 > BQ123 ≥ sarafotoxin 6c). However, in contrast to the monophasic inhibition curve of ET‐1, the other sequences produced a significantly better fit to a two component inhibition curve suggesting the presence of a heterogeneous population of ET binding sites.
ETA and ETB receptors were distinguished by competitive inhibition of [125I]‐ET‐1 binding with increasing concentrations of unlabelled ET‐3, [Ala3,11,18Nle7]‐ET‐1, sarafotoxin 6c and BQ123 and by incubating sections with the ETB agonist, [125I]‐BQ3020. ET receptor subtypes exhibited a differential distribution in the placenta. ETA type binding sites predominated (∼ 80% of the total) on veins and arteries in the chorionic plate. Veins in stem villi, blood vessels in distal regions of the villous tree and decidual cells displayed a high density (∼ 60–70% of the total) of the ETB receptor subtype.
No difference was detected in either the relative density of [125I]‐ET‐1 binding sites or the proportion of ETA to ETB sites in placentae from pregnancies complicated by pre‐eclampsia compared with normal term controls.
ET may have a local autocrine or paracrine role in the placenta, acting via specific receptors to influence foetoplacental blood flow and other aspects of placental function.
Kinetic study of the tubular dopamine outward transporter in the rat and dog kidney
Authors: Soares‐da‐Silva P. 
Published: July 2012

The present study has determined the kinetic characteristics of the outflow of dopamine of renal origin in slices of rat and dog renal cortex loaded with exogenous l‐dihydroxyphenylalanine (l‐DOPA 5 to 5000 μm).
In both dog and rat renal tissues the production of dopamine was found to be dependent on the concentration of l‐DOPA used and reached its maximum at 2500 μm l‐DOPA. The decarboxylation of l‐DOPA in rat cortical slices (16.4 ± 2.6 to 1479.2 ± 85.2 nmol g−1) was 6 fold that in the dog (2.2 ± 0.4 to 252.1 ± 21.2 nmol g−1). In the rat kidney a large amount (approximately 50%) of the dopamine (5.2 ± 0.6 to 743.4 ± 58.3 nmol g−1) was found to escape into the incubation medium, whereas in dog renal slices the amount of newly‐formed dopamine escaping into the incubation medium (0.7 ± 0.2 to 46.5 ± 9.3 nmol g−1) was less than 25% of the total amount of the amine formed.
The application of the Michaelis‐Menten equation to the net transport of newly‐formed dopamine has allowed the identification of a saturable (carrier‐mediated transfer) and a non‐saturable component (diffusion). The Vmax (nmol g−1 15 min−1) and Km (nm) values for the saturable component were, respectively, 340 ± 41 and 396 ± 45 in the rat kidney and 112 ± 16 and 319 ± 35 in the dog kidney. In both rat and dog renal tissues, the magnitude of the non‐saturable component was found to be of minor importance up to a concentration of 250 nmol g−1 of dopamine to be transported. At high concentrations of the amine (greater then 250 nmol g−1), only attainable in rat kidney slices, most of the dopamine was found to leave the compartment where the synthesis did occur through a non‐saturable transport system.
In conclusion, the results presented here show that the outflow of newly‐formed dopamine in both dog and rat kidney slices loaded with exogenous l‐DOPA follows Michaelis‐Menten kinetics with a saturable component and a non‐saturable one, the latter assuming particular importance only at higher concentrations of the amine.
Impairment of pulmonary‐artery endothelium‐dependent relaxation in chronic obstructive lung disease is not due to dysfunction of endothelial cell membrane receptors nor to l‐arginine deficiency
Authors: Dinh‐Xuan A.T. , Pepke‐Zaba J. , Butt A.Y. , Cremona G. , Higenbottam T.W. 
Published: July 2012

Endothelium‐dependent relaxation mediated by endothelium‐derived relaxing factor (EDRF) or nitric oxide (NO), is impaired in pulmonary arteries (PA) of hypoxic patients with chronic obstructive lung disease (COLD). To determine the mechanisms responsible for this impairment, we compared the response of rings of isolated PA from 12 COLD patients and 8 controls to the endothelium‐dependent vasodilators acetylcholine (ACh), adenosine diphosphate (ADP), and the calcium ionophore, A23187. The response of PA rings to the endothelium‐independent nitro‐vasodilator sodium nitroprusside (SNP) was also studied in both groups. The PA rings had been pre‐contracted by the α‐adrenoceptor agonist phenylephrine (PE).
Endothelium‐dependent relaxation was significantly reduced in PA rings from COLD patients as compared with controls when tested with ACh (37.8 ± 8.8% vs 73.4 ± 7.9%), ADP (38.4 ± 6.7% vs 80 ± 5.6%), and the calcium ionophore, A23187 (35.8 ± 6.1% vs 87 ± 6.6%). Relaxation with SNP was, however, significantly greater in PA rings from COLD patients (99.4 ± 0.6% vs 90.3 ± 3.1%), as was the contractile response to PE (1.91 ± 0.21 g vs 1.33 ± 0.15 g). Pretreatment with the specific inhibitor of NO formation, NG‐monomethyl‐l‐arginine (l‐NMMA; 10−4 m) significantly reduced the relaxation to ACh in all PA rings. This inhibition could be reversed by l‐arginine (10−3 m), the substrate for NO synthesis. Pretreatment with l‐arginine alone, however, did not restore the impaired endothelium‐dependent relaxation of PA rings from COLD patients.
We conclude that EDRF (NO) production is impaired in PA rings from COLD patients and that this impairment is neither due to endothelial receptors dysfunction nor a defect of l‐arginine availability and/or transport. Our hypothesis is that the abnormality must lie within the biosynthesis pathway of NO from l‐arginine, possibly involving the endothelial enzyme cell, NO synthase, the normal function of which might be altered by chronic hypoxia.
Differential properties of type I and type II benzodiazepine receptors in mammalian CNS neurones
Authors: Yakushiji Takashi , Shirasaki Tetsuya , Munakata Mitsutoshi , Hirata Akira , Akaike Norio 
Published: July 2012

The effects of benzodiazepine receptor (BZR) partial agonists, Y‐23684 and CL218,872, were compared with its full agonist, diazepam, on γ‐aminobutyric acid (GABA)‐induced Cl− current (ICl) in acutely dissociated rat cerebral cortex (CTX), cerebellar Purkinje (CPJ) and spinal ventral horn (SVH) neurones, by the whole‐cell mode patch‐clamp technique.
The GABA‐induced responses were essentially the same in both SVH and CPJ neurones, but the KD value of the GABA response in CTX neurone was lower than those in the other two brain regions.
Enhancement of the GABA response by the two partial agonists was about one‐third of that by diazepam in the SVH neurones (where type II subtype of BZR, BZ2, is predominant), whereas these partial agonists potentiated the GABA response as much as diazepam in CPJ neurones (where the type I subtype of BZR, BZ1, is predominant). In CTX neurones where both type I and II variants are expressed, the augmentation ratio of the GABA response by diazepam was between the values in CPJ and SVH neurones.
In concentration‐response relationships of BZR partial agonists, the threshold concentrations, KD values and maximal augmentation ratio of the GABA response were similar in all CTX, CPJ and SVH neurones. Also, in all preparations, the threshold concentration and KD values of diazepam action were 10 fold less than those induced by partial agonists.
All BZR agonists shifted the concentration‐response relationship for GABA to the left without changing the maximum current amplitude, indicating that activation of both BZ1 and BZ2 increase the affinity of the GABAA receptor for GABA.
The results are important in clarifying the mechanism of anxiety and might explain the anxioselectivity of BZR partial agonists.
Bronchodilatation of guinea‐pig perfused bronchioles induced by the H3‐receptor for histamine: role of epithelium
Authors: Burgaud J.L. , Oudart N. 
Published: July 2012

The influence of epithelium on the effects of H3‐histamine receptor agonist (R)α‐methylhistamine [(R)α‐MeHist] on airways was investigated on the guinea‐pig perfused bronchioles.
In preparations under resting tone, removal of the bronchiolar epithelium or treatment with the cyclo‐oxygenase inhibitor indomethacin (10−5 m) increased the constriction induced by histamine and acetylcholine in a concentration‐dependent manner without an alteration of the K+‐induced contraction.
In this preparation (R)α‐MeHist induced a concentration‐dependent bronchodilatation which was antagonized in a competitive manner by thioperamide (an H3‐antagonist) with a pA2 value of 8.6.
This bronchodilatation was reversed to a low concentration‐dependent constriction after either removal of the epithelium or treatment with indomethacin (10−5 m) but was unaffected by both 10−5 m tranylcypromine (an inhibitor of PGI2 synthesis) and 5 × 10−5 m NG‐nitro‐l‐arginine methyl ester (an inhibitor of NO synthesis).
It is suggested that, in guinea‐pig perfused bronchioles (R)α‐MeHist induces an epithelium‐dependent relaxation via the release of metabolite(s) of arachidonic acid.
Demonstration of the suitability of CGP 12177 for in vivo studies of β‐adrenoceptors
Authors: Law Marilyn P. 
Published: July 2012

Positron emission tomography (PET) with appropriate radioligands offers the possibility of studying receptors non‐invasively in man. The suitability of CGP 12177, a hydrophilic non‐selective β‐adrenoceptor antagonist which can be labelled with the positron emitter 11C, as a ligand for in vivo studies of β‐adrenoceptors was assessed in rats.
[3H]‐CGP 12177 was injected into the tail veins of restrained conscious rats. Serial blood samples were taken from tail arteries to determine clearance from plasma. Rats were killed and tissues removed to determine tissue uptake. Radioactivity was assessed by liquid scintillation counting.
The uptake of (−)‐[3H]‐CGP 12177 in various tissues was compared to that of (±)‐[3H]‐CGP 12177. Maximum tissue:plasma ratios obtained for the (−)‐enantiomer in lung, heart and liver were 170, 42 and 13 compared with 60, 15 and 12 for the racemate. Prior injection of excess unlabelled (±)‐CGP 12177 blocked the uptake of both (−)‐ and (±)‐[3H]‐CGP 12177 in lung and heart but not liver, tissue:plasma ratios for both tracers being reduced to 7, 3 and 7 respectively.
Clearance of (−)‐[3H]‐CGP 12177 from plasma was rapid during the first 5 min but showed only small changes during 5 to 90 min. Uptake in lung and heart reached a maximum at 1 to 5 min and showed a slow decrease during 5–90 min. Prior injection of unlabelled (±)‐CGP 12177 reduced uptake in lung and heart to 10% and 20% respectively. Injection of unlabelled (±)‐CGP 12177 at 15 min displaced ∼75% of the radioactivity by 90 min.
(±)‐Propranolol had a similar effect to that of unlabelled (±)‐CGP 12177. Prior injection reduced uptake of radioactivity in lung and heart to 15% and 20% respectively. Injection of (±)‐propranolol at 15 min displaced ∼60% of the radioactivity by 90 min indicating that the tracer binds to β‐adrenoceptor sites in vivo.
In vivo saturation curves, obtained by injection of (−)‐[3H]‐CGP 12177 with increasing amounts of unlabelled (−)‐CGP 12177, gave values of Bmax for lung of ∼45 pmol per g wet weight of tissue and for heart of ∼ 6 pmol per g wet weight of tissue. KD could only be expressed as nmol injected per kg body weight, that for lung (2.5 nmol kg−1) being greater than that for heart (1.3 nmol kg−1).
Competition studies carried out by co‐injecting (−)‐[3H]‐CGP 12177 with unlabelled (±)‐CGP 12177 or (−)‐propranolol gave similar values for Bmax (lung 44 pmol g−1, heart 6 pmol g−1,). Values of KD for (±)‐CGP 12177 (lung 4.7 pmol kg−1, heart 2.6 pmol kg−1) were approximately twice those for (−)‐CGP 12177. Values of KD for (−)‐propranolol (lung 38 nmol kg−1, heart 104 nmol kg−1) were greater.
The results show that (−)‐[3H]‐CGP 12177 is a suitable ligand for assessing β‐adrenoceptors in vivo.
Pharmacological characterization of acetylcholine‐stimulated [35S]‐GTPγS binding mediated by human muscarinic m1–m4 receptors: antagonist studies
Authors: Lazareno S. , Birdsall N.J.M. 
Published: July 2012

We have used dose‐ratio analysis to estimate functionally the affinity constants (pKb) and Schild slope factors of a range of selective or atypical antagonists at human muscarinic m1–m4 receptors.
The functional response was the stimulation by acetylcholine of [35S]‐GTPγS binding to membranes from Chinese hamster ovary (CHO) cells stably expressing individual receptor subtypes.
A novel experimental design and analysis was used which allowed the estimation of affinity and Schild slope factor from a single antagonist inhibition curve, and the results were compared with other methods of analysis, both theoretically valid and invalid.
In general, the affinity estimates were very similar to previously reported values obtained in binding studies with animal tissues and cloned human receptors and the Schild slope factors were close to unity.
These results demonstrate the validity of the assay and provide no evidence for species differences in antagonist affinity for muscarinic receptor subtypes.
The results confirm both the utility of himbacine in distinguishing between m1 and m4 receptors and a previously reported modest m4‐selectivity for tropicamide and secoverine.
The cholinesterase inhibitor, tacrine (THA), had a potency profile similar to that of gallamine but with less selectivity. Its affinity could not be determined since it had Schild slope factors of about 2 at all subtypes.
o‐Methoxy‐sila‐hexocyclium had only a modest selectivity for the ml subtype.
β‐Adrenoceptor subtypes and the opening of plasmalemmal K+‐channels in bovine trachealis muscle: studies of mechanical activity and ion fluxes
Authors: Chiu P. , Cook S.J. , Small R.C. , Berry J.L. , Carpenter J.R. , Downing S.J. , Foster R.W. , Miller A.J. , Small A.M. 
Published: July 2012

Studies of mechanical activity and 86Rb+ efflux have been made in bovine isolated trachealis with the objectives of (a) identifying which of the β‐adrenoceptor subtypes mediates the opening of plasmalemmal K+‐channels, (b) gaining further insight into the properties of the novel, long‐acting β2‐adrenoceptor agonist, salmeterol and (c) clarifying the role of K+‐channel opening in mediating the mechano‐inhibitory actions of agonists at β‐adrenoceptors.
In bovine trachealis muscle strips precontracted with histamine (460 μm), isoprenaline (0.1 nm– 1 μm), procaterol (0.1–10 nm) and salmeterol (0.1–10 nm) each caused concentration‐dependent relaxation.
ICI 118551 (10 nm–1 μm) antagonized isoprenaline, procaterol and salmeterol in suppressing histamine‐induced tone of the isolated trachealis muscle. The antagonism was concentration‐dependent. In contrast, CGP 20712A (10 nm–1 μm) failed to antagonize isoprenaline, procaterol or salmeterol.
Salmeterol (1–10 μm) antagonized isoprenaline in relaxing strips of bovine trachea which had been precontracted with carbachol (1 μm).
Cromakalim (10 μm), isoprenaline (100 nm–10 μm), procaterol (10 nm–1 μm) and salbutamol (100 nm–10 μm) each promoted the efflux of 86Rb+ from strips of bovine trachealis muscle preloaded with the radiotracer. In contrast, salmeterol (100 nm–10 μm) failed to promote 86Rb+ efflux.
CGP 201712A (1 μm), ICI 118551 (100 nm) and salmeterol (1 μm) did not themselves modify 86Rb+ efflux from trachealis muscle strips, nor did they affect the promotion of 86Rb+ efflux induced by cromakalim (10 μm). In contrast, CGP 20712A (1 μm) and ICI 118551 (100 nm) were each able to inhibit the promotion of 86Rb+ efflux induced by isoprenaline (1 μm) or procaterol (100 nm). Furthermore, salmeterol (10 μm) inhibited isoprenaline (1 μm)‐induced promotion of 86Rb+ efflux.
It is concluded that, in bovine trachealis, activation of either β1‐ or β2‐adrenoceptors can promote the opening of 86Rb+‐permeable K+‐channels in the plasmalemma. The failure of salmeterol to promote plasmalemmal K+‐channel opening may reflect, not its selectivity in activating β2‐ as opposed to β1‐adrenoceptors, but rather its low intrinsic efficacy at β2‐adrenoceptors. The opening of plasmalemmal K+‐channels plays a supportive rather than a crucial role in mediating the mechano‐inhibitory effects of agonists at β‐adrenoceptors acting on trachealis muscle.
Transmitter‐mediated local contracture of the endplate region of the focally innervated mouse diaphragm treated with anticholinesterase
Authors: Hong S.J. , Chang C.C. 
Published: July 2012

Local contraction of the endplate region in response to nerve stimulation was studied in isolated mouse diaphragms. In normal preparations, muscle contractions involved the whole length of the muscle fibre with rise and decay times in the order of tens of ms whether evoked with a single or train of pulses.
When acetylcholinesterase was inhibited with neostigmine, tetanic stimulation produced a twitch‐like phasic contraction and a delayed tonic contracture. A brief train of pulse (10 ms, 300 Hz) was enough to trigger a full size tonic contracture which reached an amplitude about one tenth that of control tetanus and had a duration of about 4 s.
Tetanic stimulation evoked a non‐propagating prolonged depolarization at the endplate region lasting for about 1 s following a few muscle action potentials.
μ‐Conotoxin, a specific inhibitor of muscle Na+ channel, selectively abolished the phasic contraction and the muscle action potentials leaving the tonic contracture and the prolonged depolarization unaffected.
Both the tonic contracture and the prolonged depolarization were highly sensitive to blockade by tubocurarine (IC50 0.05–0.1 μm) and vesamicol (1 μm, an inhibitor of packaging acetylcholine into synaptic vesicles), were attenuated by increasing Ca2+ concentration and were prolonged by decreasing Ca2+.
The results suggest that prolonged activation of endplate nicotinic receptors by endogenously released transmitter can produce substantial contractions of the endplate region when acetylcholinesterases are inhibited. The source of Ca2+ for the contraction seems to come mainly from intracellular stores.