bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of cannabinoid binding sites in guinea‐pig forebrain and small intestine
Authors: Ross Ruth A , Brockie Heather C , Fernando Susanthi R , Saha Bijali , Razdan Raj K , Pertwee Roger G 
Published: January 2005

We have investigated the nature of cannabinoid receptors in guinea‐pig small intestine by establishing whether this tissue contains cannabinoid receptors with similar binding properties to those of brain CB1 receptors. The cannabinoids used were the CB1‐selective antagonist SR141716A, the CB2‐selective antagonist SR144528, the novel cannabinoid receptor ligand, 6′‐azidohex‐2′‐yne‐Δ8‐tetrahydrocannabinol (O‐1184), and the agonists CP55940, which binds equally well to CB1 and CB2 receptors, and WIN55212‐2, which shows marginal CB2 selectivity.
[3H]‐CP55940 (1 nm) underwent extensive specific binding both to forebrain membranes (76.3%) and to membranes obtained by sucrose density gradient fractionation of homogenates of myenteric plexus‐longitudinal muscle of guinea‐pig small intestine (65.2%).
Its binding capacity (Bmax) was higher in forebrain (4281 fmol mg−1) than in intestinal membranes (2092 fmol mg−1). However, the corresponding KD values were not significantly different from each other (2.29 and 1.75 nm respectively). Nor did the Ki values for its displacement by CP55940, WIN55212‐2, O‐1184, SR141716A and SR144528 from forebrain membranes (0.87, 4.15, 2.85, 5.32 and 371.9 respectively) differ significantly from the corresponding Ki values determined in experiments with intestinal membranes (0.99, 5.03, 3.16, 4.95 and 361.5 nm respectively).
The Bmax values of [3H]‐CP55940 and [3H]‐SR141716A in forebrain membranes did not differ significantly from each other (4281 and 5658 fmol mg−1) but were both greater than the Bmax of [3H]‐WIN55212‐2 (2032 fmol mg−1).
O‐1184 (10 or 100 nm) produced parallel dextral shifts in the log concentration‐response curves of WIN55212‐2 and CP55940 for inhibition of electrically‐evoked contractions of the myenteric plexus‐longitudinal muscle preparation, its KD values being 0.20 nm (against WIN55212‐2) and 0.89 nm (against CP55940).
We conclude that cannabinoid binding sites in guinea‐pig small intestine closely resemble CB1 binding sites of guinea‐pig brain and that O‐1184 behaves as a cannabinoid receptor antagonist in the guinea‐pig myenteric plexus‐longitudinal muscle preparation.

British Journal of Pharmacology (1998) 125, 1345–1351; doi:10.1038/sj.bjp.0702204
Identification and characterization of an endogenous P2X7 (P2Z) receptor in CHO‐K1 cells
Authors: Michel A D , Chessell I P , Hibell A D , Simon J , Humphrey P P A 
Published: January 2005

CHO‐K1 cells were examined for their cellular responses to the P2 receptor agonist, 2′‐ and 3′‐O‐(4‐benzoylbenzoyl)‐ATP (DbATP), and for the presence of mRNA for P2X receptors.
Reverse transcriptase‐polymerase chain reactions, using primers directed against the rat P2X subunits, detected the presence of P2X7 but not P2X1‐P2X6 subunits.
DbATP (EC50∼100 μm) evoked non‐desensitizing inward currents which reversed at ∼0mV, suggesting activation of a non‐selective cation channel. ATP also evoked inward currents but was less potent than DbATP.
DbATP also stimulated the accumulation of 45calcium (45Ca2+) and the DNA binding dye, YO‐PRO‐1, in CHO‐K1 cells. Both responses were inhibited by NaCl and MgCl2. In 280 mm sucrose buffer, 45Ca2+ accumulation was measurable within 10–20 s of agonist addition, whereas YO‐PRO‐1 accumulation was only detectable after 8 min. ATP and ATPγS were also agonists but were less potent than DbATP, while UTP, 2‐methylthio ATP, ADP and αβmethylene ATP were inactive at concentrations up to 100 μm.
DbATP increased lactate dehydrogenase release from CHO‐K1 cells, suggesting cell lysis, although this effect was only pronounced after 60–90 min.
These data suggest that CHO‐K1 cells express an endogenous P2X7 receptor which can be activated by DbATP to cause a rapid inward current and accumulation of 45Ca2+. Prolonged receptor activation results in a delayed, increased permeability to larger molecules such as YO‐PRO‐1 and ultimately leads to cell lysis. Importantly, the presence of an endogenous P2X7 receptor should be considered when these cells are used to study recombinant P2X receptors.

British Journal of Pharmacology (1998) 125, 1194–1201; doi:10.1038/sj.bjp.0702205
Effect of nimesulide and indomethacin on contractility and the Ca2+ channel current in myometrial smooth muscle from pregnant women
Authors: Sawdy Robert , Knock Gregory A , Bennett Philip R , Poston Lucilla , Aaronson Philip I 
Published: January 2005

The non‐steroidal anti‐inflammatory drug (NSAID) indomethacin inhibits both constitutive and inducible forms of cyclo‐oxygenase (COX‐1 and COX‐2, respectively), while nimesulide is a selective COX‐2 inhibitor. Uterine COX‐2 is upregulated before and during term and pre‐term labour, and prostaglandins play a crucial role in parturition. We therefore evaluated the effects of these drugs on myometrial contractility and the voltage‐gated Ca2+ channel current in tissue strips and isolated human myometrial smooth muscle cells (HMSMC) from myometrial biopsies taken with informed consent from women undergoing caesarean section at term (not in labour).
Nimesulide and indomethacin caused almost complete inhibition of spontaneous myometrial contractions at concentrations of 100 and 300 μm, respectively. The Ca2+ channel current was inhibited in a concentration‐dependent manner by both drugs, with a 40% reduction of the current at 100 μm nimesulide and 300 μm indomethacin. Nimesulide also accelerated the decay of the Ca2+ channel current.
The inhibition of the Ca2+ channel current by 100 μm nimesulide and 300 μm indomethacin was unaffected by the presence of either PGF2α or PGE2 (30 μm), and was of similar magnitude whether 10 mm Ba2+ or 1.5 mm Ca2+ was used as the charge carrier.
The concentrations of indomethacin and nimesulide required to suppress spontaneous contractility in human pregnant myometrium were much higher than those necessary to inhibit prostaglandin production. The results suggest that both nimesulide and indomethacin inhibit myometrial contractility via mechanisms independent of cyclo‐oxygenase inhibition. Blockade of the Ca2+ current may contribute to this effect.

British Journal of Pharmacology (1998) 125, 1212–1217; doi:10.1038/sj.bjp.0702211
Carbon monoxide is a major contributor to the regulation of vascular tone in aortas expressing high levels of haeme oxygenase‐1
Authors: Sammut Ivan A. , Foresti Roberta , Clark James E. , Exon David J. , Vesely Martin J. J. , Sarathchandra Padmini , Green Colin J. , Motterlini Roberto 
Published: January 2005

The contribution of haeme oxygenase‐derived carbon monoxide (CO) to the regulation of vascular tone in thoracic aorta was investigated following induction of the inducible isoform of haeme oxygenase (HO‐1).
Isometric smooth muscle contractions were recorded in isolated rat aortic ring preparations. Rings were incubated in the presence of the nitric oxide (NO) donor S‐nitroso‐N‐acetyl penicillamine (SNAP, 500 μm) for 1 h, then repetitively washed and maintained for a further 4 h prior to producing a concentration‐response curve to phenylephrine (PE, 1–3000 nm).
Treatment with SNAP resulted in increased mRNA and protein expression of aortic HO‐1 and was associated with a significant suppression of the contractile response to PE (P<0.05 vs control). Immunohistochemical staining procedures revealed marked HO‐1 expression in the endothelial layer and, to a lesser extent, in smooth muscle cells.
Induction of HO‐1 in SNAP‐treated rings was associated with a higher 14CO release compared to control, as measured by scintillation counting after incubation of aortas with [2‐14C]‐L‐glycine, the precursor of haeme. Guanosine 3′,5′‐monophosphate (cyclic GMP) content was also greatly enhanced in aortas expressing high levels of HO‐1.
Incubation of aortic rings with the NO synthase inhibitor, NG‐monomethyl‐L‐arginine (100 μm), significantly (P<0.05) increased the contractile response to PE in controls but failed to restore PE‐mediated contractility in SNAP‐treated rings. In contrast, the selective inhibitor of haeme oxygenase, tin protoporphyrin IX (SnPP‐IX, 10 μm), restored the pressor response to PE in SNAP‐treated rings whilst markedly reducing CO and cyclic GMP production.
We conclude that up‐regulation of the HO‐1/CO pathway significantly contributes to the suppression of aortic contractility to PE. This effect appears to be mediated by the elevation of cyclic GMP levels and can be reversed by inhibition of the haeme oxygenase pathway.

British Journal of Pharmacology (1998) 125, 1437–1444; doi:10.1038/sj.bjp.0702212
Evidence for two different types of P2 receptors stimulating insulin secretion from pancreatic B cell
Authors: Petit P , Hillaire‐Buys D , Manteghetti M , Debrus S , Chapal J , Loubatières‐Mariani M M 
Published: January 2005

Adenine nucleotides have been shown to stimulate insulin secretion by acting on P2 receptors of the P2Y type. Since there have been some discrepancies in the insulin response of different analogues of ATP and ADP, we investigated whether two different types of P2 receptors exist on pancreatic B cells. The effects of α,β‐methylene ATP, which is more specific for the P2X subtype, were studied in vitro in pancreatic islets and isolated perfused pancreas from rats, in comparison with the potent P2Y receptor agonist ADPβS.
In isolated islets, incubated with a slightly stimulating glucose concentration (8.3 mm), α,β‐me ATP (200 μm) and ADPβS (50 μm) similarly stimulated insulin secretion; by contrast, under a non stimulating glucose concentration (3 mm), α,β‐me ATP was still effective whereas ADPβS was not. In the same way, in islets perifused with 3 mm glucose, α,β‐me ATP but not ADPβS induced a partial but significant reduction in the peak 86Rb efflux induced by the ATP‐dependent potassium channel opener diazoxide.
In the isolated pancreas, perfused with a non stimulating glucose concentration (4.2 mm), ADPβS and α,β‐me ATP (5–50 μm), administered for 10 min, induced an immediate, transient and concentration‐dependent increase in the insulin secretion; their relative potency was not significantly different. In contrast, with a slightly stimulating glucose concentration (8.3 mm), ADPβS was previously shown to be 100 fold more potent than α,β‐me ATP. Furthermore, at 4.2 mm glucose a second administration of α,β‐me ATP was ineffective. In the same way, ADPβS was also able to desensitize its own insulin response. At 3 mm glucose, α,β‐me ATP as well as ADPβS (50 μm) induced a transient stimulation of insulin secretion and down regulated the action of each other.
These results give evidence that pancreatic B cells, in addition to P2Y receptors, which potentiate glucose‐induced insulin secretion, are provided with P2X receptors, which transiently stimulate insulin release at low non‐stimulating glucose concentration and slightly affect the potassium conductance of the membrane.

British Journal of Pharmacology (1998) 125, 1368–1374; doi:10.1038/sj.bjp.0702214
Effect of lercanidipine and its (R)‐enantiomer on atherosclerotic lesions induced in hypercholesterolemic rabbits
Authors: Soma Maurizio R. , Natali Malvina , Donetti Elena , Baetta Roberta , Farina Pierluigi , Leonardi Amedeo , Comparato Carmen , Barberi Laura , Catapano Alberico L. 
Published: January 2005

The in vivo antiatherogenic activity of the calcium antagonist lercanidipine and its (R)‐enantiomer was investigated in two different types of atherosclerotic lesions (hyperplastic and fatty‐streak lesions) in rabbits.
Lercanidipine (0.3, 1, and 3 mg kg−1 week−1) as well as its (R)‐enantiomer at 3 mg kg−1 week−1 were given by subcutaneous injection for 10 weeks to White New Zealand rabbits, with cholesterol feeding beginning at week 2. The hyperplastic lesion was obtained by positioning a hollow silastic collar around one carotid artery, while aortic fatty streak lesions were induced by cholesterol feeding. In untreated animals (n=5), 14 days after collar positioning an intimal hyperplasia was clearly detectable: the arteries without collar showed a intima/media (I/M) ratio of 0.03±0.02, whereas in carotids with a collar the ratio was 2±0.42. In lercanidipine‐treated animals a significant and dose‐dependent effect on intimal hyperplasia was observed. I/M ratios were 0.73±0.4, 0.42±0.1, 0.32±0.1 for 0.3, 1, and 3 mg kg−1 week−1, respectively (P<0.05). The lercanidipine enantiomer (3 mg kg−1 week−1) was as effective as the racemate (0.41±0.11). Proliferation of smooth muscle cells, assessed by incorporation of BrdU into DNA, was reduced by about 50%, 70%, 85%, and 80% by lercanidipine (0.3, 1, and 3 mg kg−1 week−1) and its (R)‐enantiomer, respectively.
The area of fatty‐streaks in the aorta (n=11–15) was significantly reduced by lercanidipine (3 mg kg−1 week−1, 16% vs 27%, P<0.05), a trend was observed also with lower doses. When different segments of the aorta were considered (arch, thoracic, abdominal) a significant and dose‐dependent effect in the thoracic and abdominal aorta was observed also at lower doses. The (R)‐enantiomer was as effective as lercanidipine.
These results suggest a direct antiatherosclerotic effect of lercanidipine, independent of modulation of risk factors such as hypercholesterolemia and/or hypertension as demonstrated by the absence of stereoselectivity.

British Journal of Pharmacology (1998) 125, 1471–1476; doi:10.1038/sj.bjp.0702221
Insensitivity of volume‐sensitive chloride currents to chromones in human airway epithelial cells
Authors: Zegarra‐Moran Olga , Lantero Sabina , Sacco Oliviero , Rossi Giovanni A , Galietta Luis J V 
Published: January 2005

Chromones (sodium cromoglycate and sodium nedocromil) block cell swelling‐activated Cl− channels in NIH‐3T3 fibroblasts and endothelial cells. This has led to hypothesize that cell volume regulation might be involved in asthma pathogenesis.
Using whole‐cell patch‐clamp experiments, we studied the effect of chromones on volume‐sensitive Cl− currents in transformed human tracheal epithelial cells (9HTEo‐) and in primary cultures of human bronchial epithelial cells (BE).
Cl− currents activated by hypotonic shock were poorly blocked by extracellular nedocromil or cromoglycate. The block was voltage‐dependent since it was observed only at positive membrane potentials. At the concentration of 5 mm, the current inhibition by both chromones at +80 mV was about 40% for 9HTEo‐ and only 20% for BE.
Intracellular application of chromones elicited a voltage‐independent inhibition in 9HTEo‐ cells. Under this condition, volume‐sensitive Cl− currents were reduced at all membrane potentials (60 and 45% inhibition by 2 mm nedocromil and cromoglycate respectively). In contrast intracellular chromones were ineffective in BE cells.
The relative refractoriness to chromones, in contrast with the high sensitivity shown by other Cl− channels, suggests that the epithelial volume‐sensitive Cl− channel is not involved in asthma.

British Journal of Pharmacology (1998) 125, 1382–1386; doi:10.1038/sj.bjp.0702225
Expression of cyclic GMP‐inhibited phosphodiesterases 3A and 3B (PDE3A and PDE3B) in rat tissues: Differential subcellular localization and regulated expression by cyclic AMP
Authors: Liu H , Maurice D H 
Published: January 2005

A combination of pharmacological, molecular biological and biochemical approaches were used to investigate the differential expression of two cyclic GMP‐inhibited cyclic nucleotide phosphodiesterase genes (PDE3A and PDE3B) in the rat.
RT–PCR using PDE3A‐ or PDE3B‐specific oligonucleotide primers allowed amplification of products encoding PDE3A (508 bp) or PDE3B (499 bp) sequences from several rat tissues (heart, aorta, liver, kidney and epididymal fat), from primary cultures of aortic vascular smooth muscle cells (VSMC) as well as from an SV40 large T‐antigen immortalized aortic VSMC line.
Immunoblotting experiments with PDE3‐selective antisera allowed the detection of both PDE3A and PDE3B immunoreactive proteins in several rat tissues, including tissues of the cardiovascular system, in primary cultures of aortic VSMC and in an SV40 large T‐antigen immortalized aortic VSMC line. In all cases, PDE3A was expressed as a 120 kDa protein which was only detected in the cytosolic fraction. PDE3B was expressed as a 135 kDa protein and its expression was limited to the particulate fraction of all tissues and cells studied.
Prolonged incubation of cultured aortic VSMC with agents that increase VSMC cyclic AMP (forskolin or 8‐bromo‐cyclic AMP) produced marked time‐dependent increases in PDE3 activity which correlated with increases in PDE3A and PDE3B RT–PCR signals and a marked increase in particulate PDE3 activity and PDE3B protein.
The physiological, pharmacological and biochemical implications of these findings are discussed based on previous reports of the effects of PDE3 inhibitors in the cardiovascular system and the relevance of our findings are presented in the context of the development of PDE3A and/or PDE3B‐selective pharmacological agents.

British Journal of Pharmacology (1998) 125, 1501–1510; doi:10.1038/sj.bjp.0702227
Inhibition of ornithine decarboxylase potentiates nitric oxide production in LPS‐activated J774 cells
Authors: Baydoun Anwar R , Morgan David M L 
Published: January 2005

We have examined whether modulation of the polyamine biosynthetic pathway, through inhibition by α‐difluoromethylornithine (DFMO) of the rate limiting enzyme, ornithine decarboxylase (ODC), modulates NO synthesis in J774 macrophages.
DFMO potentiated LPS‐stimulated nitrite production in both a concentration‐ and time‐dependent manner, increasing nitrite levels by 48±5% at 10 mm. This effect was observed in cells pre‐treated with DFMO for 24 h prior to stimulation with LPS. Addition of DFMO 12 h after LPS failed to potentiate LPS‐induced nitrite production.
Supplementation of the culture medium with horse serum (10%) in place of foetal calf serum (10%) caused no significant change in either LPS‐induced nitrite production or in the ability of DFMO (10 mm) to potentiate LPS‐induced NO synthesis.
Metabolism of L‐[3H]arginine to L‐[3H]citrulline by partially purified inducible nitric oxide synthase (iNOS) was not significantly altered by either DFMO (1–10 mm) or by putrescine (0.001–1 mm), spermidine (0.001–1 mm) or spermine (0.001–1 mm). iNOS activity was also unaffected by 1 mM EGTA but was markedly attenuated (70±0.07%) by L‐NMMA (100 μm).
Pre‐incubation of cells with DFMO (10 mm; 24 h) prior to activation with LPS resulted in enhanced (∼2 fold) iNOS protein expression.
These results show that DFMO potentiates LPS‐induced nitrite production in the murine macrophage cell line J774. Since the only known mechanism of action of DFMO is inhibition of ODC, and thus polyamine biosynthesis, we conclude that expression of iNOS can be critically regulated by endogenous polyamines.

British Journal of Pharmacology (1998) 125, 1511–1516; doi:10.1038/sj.bjp.0702231
The effect of inhibitors of receptor internalization on the desensitization and resensitization of three Gs‐coupled receptor responses
Authors: Mundell Stuart J , Kelly Eamonn 
Published: January 2005

Many G protein‐coupled receptors (GPCRs) are known to internalize following agonist exposure, however the relative importance of this mechanism for the desensitization and resensitization of different GPCRs is unclear. In the present study, we have pretreated NG108‐15 cells with hypertonic sucrose or concanavalin A (con A), to investigate the effects of these inhibitors of internalization on the agonist‐induced desensitization and subsequent resensitization of three Gs‐coupled receptor responses.
Incubation of cells with sucrose or con A did not affect subsequent acute agonist stimulation of the A2A adenosine receptor or the agonist‐induced desensitization of this receptor response. However, the resensitization of the A2A adenosine receptor response following agonist removal was abolished in the presence of sucrose or con A.
Sucrose or con A treatment affected neither the desensitization nor resensitization of IP‐prostanoid receptor responsiveness. On the other hand con A but not sucrose reduced the agonist‐induced desensitization of secretin receptor responsiveness. However, secretin receptor responsiveness did not resensitize within the time period studied whether or not inhibitors of internalization were present.
These results indicate that receptor internalization appears to subserve different functions for different GPCRs.

British Journal of Pharmacology (1998) 125, 1594–1600; doi:10.1038/sj.bjp.0702234
In vivo demonstration of H3‐histaminergic inhibition of cardiac sympathetic stimulation by R‐α‐methyl‐histamine and its prodrug BP 2.94 in the dog
Authors: Mazenot Catherine , Ribuot Christophe , Durand Andrée , Joulin Yves , Demenge Pierre , Godin‐Ribuot Diane 
Published: January 2005

The aim of this study was to investigate whether histamine H3‐receptor agonists could inhibit the effects of cardiac sympathetic nerve stimulation in the dog.
Catecholamine release by the heart and the associated variation of haemodynamic parameters were measured after electrical stimulation of the right cardiac sympathetic nerves (1–4 Hz, 10 V, 10 ms) in the anaesthetized dog treated with R‐α‐methyl‐histamine (R‐HA) and its prodrug BP 2.94 (BP).
Cardiac sympathetic stimulation induced a noradrenaline release into the coronary sinus along with a tachycardia and an increase in left ventricular pressure and contractility without changes in mean arterial pressure. Intravenous administration of H3‐receptor agonists significantly decreased noradrenaline release by the heart (R‐HA at 2 μmol kg−1 h−1: +77±25 vs +405±82; BP 2.94 at 1 mg kg−1: +12±11 vs +330±100 pg ml−1 in control conditions, P0.05), and increases in heart rate (R‐HA at 2 μmol kg−1 h−1: +26±8 vs +65±10 and BP 2.94 at 1 mg kg−1: +30±8 vs 75±6 beats min−1, in control conditions P0.05), left ventricular pressure, and contractility. Treatment with SC 359 (1 mg kg−1) a selective H3‐antagonist, reversed the effects of H3‐receptor agonists. Treatment with R‐HA at 2 μmol kg−1 h−1 and BP 2.94 at 1 mg kg−1 tended to decrease, while that with SC 359 significantly increased basal heart rate (from 111±3 to 130±5 beats min−1, P0.001).
Functional H3‐receptors are present on sympathetic nerve endings in the dog heart. Their stimulation by R‐α‐methyl‐histamine or BP 2.94 can inhibit noradrenaline release by the heart and its associated haemodynamic effects.

British Journal of Pharmacology (1999) 126, 264–268; doi:10.1038/sj.bjp.0702257