bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antinociceptive and toxic effects of (+)‐epibatidine oxalate attributable to nicotinic agonist activity
Authors: Rupniak N.M.J. , Patel S. , Marwood R. , Webb J. , Traynor J.R. , Elliott J. , Freedman S.B. , Fletcher S.R. , Hill R.G. 
Published: July 2012

Epibatidine is an analgesic substance, isolated from the skin of the poisonous frog Epipedobates tricolor, for which the mechanism of action was previously unknown.
The IC50 of synthetic (+)‐epibatidine oxalate (the naturally occurring isomer) for [3H]‐nicotine binding to rat whole‐brain membranes was 0.1 nm. The (−)−isomer also exhibited high affinity (IC50 = 0.2 nm).
(+)‐ and (−)−Epibatidine exhibited much lower affinity for displacement of the muscarinic ligand [3H]‐N‐methylscopolamine binding to rat cortical membranes (Kapp − 6.9μm and 16.0 μm respectively). The (+)‐enantiomer of epibatidine had an antagonist/agonist (NMS/oxo‐M) binding ratio of 4.2 This is consistent with a muscarinic antagonist profile.
(+)‐Epibatidine oxalate (10 μm) did not cause significant (>30%) displacement of radioligand binding to opioid, excitatory amino acid, benzodiazepine, 5‐HT, dopamine, adrenaline or peptide receptors.
(+)‐ and (−)−Epibatidine (5–20 μg kg−1 s.c.) doubled response latency in the mouse hot‐plate test. Antinociception and behavioural depression induced by (+)‐epibatidine (5 μg kg−1) was fully blocked by the nicotinic antagonists mecamylamine (2 mg kg−1 s.c.) or dihydro‐β‐erythroidine (2 mg kg−1 s.c). The muscarinic antagonist scopolamine (0.4 and 10 mg kg−1 s.c.) caused partial reversal of antinociception induced by (+)‐epibatidine in mice, but not in rats.
These findings demonstrate that (+)‐epibatidine oxalate salt is a highly selective and potent nicotinic analgesic agent.
Ion channel modulation by NS 1619, the putative BKCa channel opener, in vascular smooth muscle
Authors: Edwards G. , Niederste‐Hollenberg A. , Schneider J. , Noack Th. , Weston A.H. 
Published: July 2012

The effects of NS 1619, the putative BKCa channel opener, were investigated on rat intact portal veins and on single smooth muscle cells enzymatically separated from the same tissue.
Under whole‐cell patch clamp conditions with K‐rich pipettes, exposure of single cells held at −10 mV to NS 1619 (10–33 μm) induced a noisy, outward current which reached a maximum (33 μm NS 1619; mean 35.8 ± 17 pA, n = 8) within about 6min.
On stepping to test potentials (range − 50 to + 50 mV) from a holding potential of − 10 mV, the NS 1619‐induced noisy current exhibited time‐dependent activation and marked outward rectification.
The stimulation of outward currents by NS 1619 at − 10 mV was independent of the presence of Ca2+ in the bath or pipette solutions but was antagonized by either charybdotoxin (250 nm) or penitrem A (100 nm) in the bath solution.
Stationary fluctuation analysis of the noisy current induced by NS 1619 at − 10 mV yielded a value of 70 ± 8 pS (n = 4) (under the quasi‐physiological conditions of the experiment) for the unitary conductance of the channel involved.
At − 10 mV, NS 1619 (10–33 μm) rapidly inhibited spontaneous transient outward currents.
With a holding potential of − 90 mV, NS 1619 (10–33 μm) produced a reduction of outward currents evoked by depolarizing steps to + 50 mV, an effect associated with marked inhibition of the delayed rectifier current, IK(V).
NS 1619 (3–100 μm) produced a concentration‐dependent inhibition of spontaneous activity in rat portal vein characterized by a reduction in the amplitude and duration of the tension waves. This inhibition was slightly potentiated in the presence of either charybdotoxin (250 nm) or penitrem A (1 μm). NS 1619 also totally inhibited contractions of rat aorta induced by KC1 (both 20 mm and 80 μm).
Under whole‐cell recording conditions and using Cs‐rich pipettes, Ca‐currents evoked in portal vein cells by stepping from a holding potential of − 90 mV to test potentials in the range − 30 to + 50 mV were totally inhibited in the presence of 33 μm NS 1619.
NS 1619 (33 μm) inhibited the induction of IK(ATP) by levcromakalim (10 μm).
It is concluded that NS 1619 activates the large conductance, Ca2+‐sensitive channel, BKCa and over the same concentration range it inhibits both Kv and L‐type Ca‐channels. The observed NS 1619‐induced mechanical inhibition in rat portal vein and aorta seems most likely to be due to the observed inhibition of Ca‐currents.
Vascular 5‐HT1‐like receptors mediating vasoconstriction and vasodilatation: their characterization and distribution in the intact canine cardiovascular system
Authors: Cambridge D. , Whiting M.V. , Butterfield L.J. , Marston C. 
Published: July 2012

In anaesthetized dogs, intra‐left atrial administration of 5‐hydroxytryptamine (5‐HT) and selected tryptamine analogues (5‐carboxamidotryptamine, 5‐CT; 5‐methyl tryptamine, 5‐MT; α‐methyl 5‐hydroxytryptamine, α‐HT; sumatriptan, Sum) in the presence of ketanserin and MDL72222 (5‐HT2 and 5‐HT3 receptor antagonists, respectively), produced dose‐related changes in carotid, coronary and renal vascular conductance mediated by vascular 5‐HT1‐like receptors.
In the carotid vascular bed, 5‐HT, 5‐MT, α‐HT and Sum were vasoconstrictors with a rank order of potency (comparing ED50 values) of 5‐HT = Sum > 5‐MT > α‐HT. By contrast in this vascular bed, 5‐CT was a potent vasodilator.
In the coronary vascular bed, 5‐HT, 5‐CT, 5‐MT and α‐HT were vasodilators with a rank order of potency (comparing ED50 values) of 5‐CT > 5‐HT > 5‐MT > α‐HT. In this vascular bed, Sum was without effect.
In the renal vascular bed, 5‐HT, 5‐CT, 5‐MT, α‐HT and Sum were vasoconstrictors with a rank order of potency (comparing ED50 values) of 5‐CT > 5‐HT > Sum> 5‐MT > α‐HT.
The coronary (and carotid) vasodilator responses to 5‐CT were antagonized by the 5‐HT1‐like receptor antagonists, spiperone (1 mg kg−1) and methiothepin (0.1 mg kg−1), whereas the renal vasoconstrictor responses to this tryptamine analogue were antagonized only by methiothepin.
It is concluded from these studies that agonist finger‐printing in vivo, using tryptamine analogues, identifies and confirms the functional presence of at least two pharmacologically distinct subtypes of the 5‐HT1‐like receptor in the intact canine cardiovascular system. These two subtypes are located on the vascular smooth muscle and mediate direct vasoconstriction and vasodilatation responses in vivo.
In addition, these studies confirm that the distribution of these subtypes within the major vascular beds, shows a marked heterogeneity. The carotid vascular responses to the tryptamine analogues indicate the presence of both the vasodilator and the vasoconstrictor subtypes. The coronary vascular responses to these analogues are, however, consistent with presence of the vasodilator subtype, only. By contrast, the renal vascular responses to these analogues indicates only the presence of the vasoconstrictor subtype.
Haemostatic mechanism in the endometrium: role of cyclo‐oxygenase products and coagulation factors
Authors: Gelety Timothy J. , Chaudhuri Gautam 
Published: July 2012

The primary mechanism of haemostasis in the endometrium of rat was studied and results were compared to that in the mesenteric artery.
The bleeding time of the rat endometrium as assessed by haemoglobin output was significantly decreased after pretreatment of the animals with either indomethacin (5 mg kg−1, i.v.) or meclofenamate (3 mg kg−1, i.v.) whereas the bleeding time was significantly increased in the rat mesenteric artery.
The bleeding time of the rat endometrium was unchanged from control values following treatment with prostacyclin (0.5 μg kg−1 min−1, i.v.) or 1‐benzylimidazole (50 mg kg−1, i.v.) whereas the bleeding times were increased in the rat mesenteric artery.
Administration of heparin (100 units kg−1) increased the bleeding time in the rat mesenteric artery but had no effect on the bleeding time of the endometrium.
Superfusion of the endometrium with 16, 16‐dimethyl PGE2 (1 μg ml−1), a vasodilator, increased the bleeding time of the endometrium but superfusion of PGE2 over the mesenteric artery did not affect the bleeding time from this site.
Histological studies of the mesenteric artery and the endometrium following haemostatis revealed that the haemostatic plug in the mesenteric artery was mainly composed of platelets and fibrin whereas in the endometrium it was mainly composed of fibrin.
These findings suggest that haemostasis in the endometrium may be mediated by the vascular tone and fibrin whereas formation of the platelet plug may be the primary mechanism for haemostasis in the mesenteric artery.
Evidence for lack of modulation of μ‐opioid agonist action by δ‐opioid agonists in the mouse vas deferens and guinea‐pig ileum
Authors: Elliott J. , Traynor J.R. 
Published: July 2012

There is evidence from in vivo studies for an interaction of μ‐ and δ‐opioid ligands. In the present work this concept has been investigated using the mouse vas deferens and guinea‐pig ileum myenteric plexus‐longitudinal preparations.
In field stimulated vasa deferentia of the mouse, co‐administration of sub‐effective concentrations of the δ‐opioid agonist [d‐Pen2,d‐Pen5]enkephalin (DPDPE) and [Met5]‐ or [Leu5]enkephalin had no effect on the dose‐response curves of the μ‐agonists [d‐Ala2, MePhe4, Gly‐ol5]enkephalin (DAMGO) and morphine. Similarly, the δ‐opioid agonists did not alter the potency of morphine and DAMGO when added at different times prior to the μ‐opioid agonists, or when EC50 concentrations of δ‐opioid ligands were co‐administered. Compounds with preferred activity for the putative δ1‐(DPDPE) or δ2‐ ([d‐Ala2,Glu4]deltorphin II (Delt II)) opioid receptors were ineffective in this respect.
The guinea‐pig ileum contains δ‐opioid receptors. No function of these receptors in mediating blockage of field‐stimulated contractions was observed with ligands having affinity for the putative δ1 or δ2 subtypes nor were the agonists able to modulate responses to μ‐opioid ligands in this tissue.
The results demonstrate that modulation of μ‐opioid agonists by δ‐opioid agonists does not occur in the isolated peripheral tissues examined. Thus the findings do not support the concept of a functional coupling of opioid receptors, though the results may be explained by differences between opioid systems in the brain and peripheral tissues examined.
Ca2+ entry activated by emptying of intracellular Ca2+ stores in ileal smooth muscle of the rat
Authors: Ohta Toshio , Kawai Kazue , Ito Shigeo , Nakazato Yoshikazu 
Published: July 2012

1 The effects of depletion of intracellular Ca2+ stores on muscle tension and the intracellular Ca2+ concentration ([Ca2+])i were studied in fura‐2 loaded longitudinal smooth muscle cells of the rat ileum.2 After exposure to a Ca2+‐free solution, application of Ca2+ caused a small contraction and a rise in [Ca2+]i, both of which were potentiated when the muscle was challenged with carbachol or caffeine before the addition of Ca2+.3 Cyclopiazonic acid (CPA), a specific inhibitor of sarcoplasmic reticulum Ca2+‐ATPase, dose‐dependently decreased tension development and the rises in [Ca2+]i induced by carbachol and caffeine in the Ca2+‐free solution, but conversely increased the Ca2+‐induced responses even in the presence of the voltage‐dependent Ca2+ channel blockers, methoxyverapamil and nifedipine.4 The contraction and rise in [Ca2+]i evoked by Ca2+ gradually declined with time after removal of CPA, while the reverse was the case for the responses to carbachol and caffeine.5 The Ca2+‐induced contraction and rise in [Ca2+]i in the presence of CPA were inhibited by the replacement of Na+ with K+ or Cs+, and by the addition of Cd2+, Ba2+, Ni2+ or La3+.6 The influx of Mn2+ was much greater in extent in the presence of CPA than in its absence.7 These results suggest that the emptying of intracellular Ca2+ stores may activate Ca2+ influx not associated with voltage‐dependent Ca2+ channels in the rat ileal smooth muscle.
Regulation of prostaglandin production by nitric oxide; an in vivo analysis
Authors: Salvemini Daniela , Settle Steven. L. , Masferrer Jaime. L. , Seibert Karen , Currie Mark. G. , Needleman Philip 
Published: July 2012

1 Endotoxin E. Coli lipopolysaccharide (LPS)‐treatment in conscious, restrained rats increased plasma and urinary prostaglandin (PG) and nitric oxide (NO) production. Inducible cyclo‐oxygenase (COX‐2) and nitric oxide synthase (iNOS) expression accounted for the LPS‐induced PG and NO release since the glucocorticoid, dexamethasone inhibited both effects. Thus, LPS (4 mg kg−1) increased the plasma levels of nitrite/nitrate from 14 ± 1 to 84 ± 7 μm within 3 h and this rise was inhibited to 35 ± 1 μm by dexamethasone. Levels of 6‐keto PGF1α in the plasma were below the detection limit of the assay (< 0.2 ng ml−1). However, 3 h after the injection of LPS these levels rose to 2.6 ± 0.2 ng ml−1 and to 0.7 ± 0.01 ng ml−1 after LPS in rats that received dexamethasone.2 The induced enzymes were inhibited in vivo with selective COX and NOS inhibitors. Furthermore, NOS inhibitors, that did not affect COX activity in vitro markedly suppressed PG production in the LPS‐treated animals. For instance, the LPS‐induced increased in plasma nitrite/nitrate and 6‐keto PGF1α at 3 h was decreased to 18 ± 2 μm and 0.5 ± 0.02 ng ml−1, 23 ± 1 μm and 0.7 ± 0.01 ng ml−1, 29 ± 2 μm and 1 ± 0.01 ng ml−1 in rats treated with LPS in the presence of the NOS inhibitors NG‐ monomethyl‐l‐arginine, NG‐nitro arginine methyl ester and aminoguanidine, respectively.3 The intravenous infusion of the NO donors sodium nitroprusside (SNP) or glyceryl trinitrate (GTN) increased prostaglandin production in normal animals (for instance urinary PGE2 excretion was increased from 96 ± 10 to 576 ± 12 pg min−1 and 400 ± 24 pg min−1 in the presence of GTN or SNP respectively).4 Proteinuria was measured in order to evaluate the roles of NO and PG in renal damage associated with the in vivo injection of LPS. Interestingly, dexamethasone and the NOS inhibitors attenuated proteinuria in the LPS‐treated rats. The COX inhibitors had no effect. It therefore appears that NO and not PG contributes to the LPS‐induced renal damage; these findings support the potential use of NOS inhibitors in the treatment of renal inflammation.5 This study demonstrates the regulatory contribution of NO on the in vivo production of prostanoids and suggests that in inflammatory diseases that are driven by both NO and the prostaglandins, NOS inhibitors may act to reduce inflammation by the dual inhibition of cytotoxic NO and pro‐inflammatory PG.
Effects of the tachykinin NK1 receptor antagonist, RP 67580, on central cardiovascular and behavioural effects of substance P, neurokinin A and neurokinin B
Authors: Culman Juraj , Wiegand Brigitte , Spitznagel Heidi , Klee Sabine , Unger Thomas 
Published: July 2012

1 We have investigated the effects of the non‐peptide NK1 tachykinin receptor antagonist, RP 67580, and its inactive enantiomer, RP 68651, on the cardiovascular and behavioural responses to substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) injected intracerebroventricularly (i.c.v.) in conscious rats.2 The SP and NKA (25 pmol)‐induced increases in blood pressure (BP) and heart rate (HR) were of the same magnitude. The cardiovascular responses to both peptides were associated with excessive grooming behaviour and wet dog shakes (WDS). Relative to SP, NKA was weaker in inducing hindquarter grooming (HG), but more effective in eliciting WDS. The cardiovascular response to NKB (50 pmol) comprised an increase in BP and HR, while the behavioural response was weak.3 RP 67580 (100 pmol), injected 10 or 30 min prior to SP, effectively inhibited the cardiovascular and behavioural responses to the peptide whereas lower doses were ineffective. Pretreatment with 500 pmol of RP 67580, 10 or 30 min prior to SP, reduced the BP response. Of the behavioural manifestations, only face washing was attenuated when the antagonist was injected 10 min before SP. At 2500 pmol, the antagonist exaggerated the BP response to the peptide without affecting the behavioural response. RP 68651 (100 or 2500 pmol) did not modify the central responses to SP.4 Neither RP 67580 nor RP 68651 (100 pmol), affected the cardiovascular and behavioural responses to NKA or NKB.5 Our results indicate that RP 67580 is a selective and high affinity antagonist at central NK1 tachykinin receptors in the rat.
Influence of chronic treatment with a nitric oxide donor on fatty streak development and reactivity of the rabbit aorta
Authors: Bult Hidde , De Meyer Guido R.Y. , Herman Arnold G. 
Published: July 2012

1 The influence of chronic treatment with molsidomine, pro‐drug of the nitric oxide (NO) donor, 3‐morphohno‐sydnonimine (SIN‐1), on fatty streak development and release of NO and prostacyclin (PGI2) was studied in the aorta of normal and cholesterol‐fed rabbits.2 Groups of 10 rabbits received standard diet (150 g day−1), or diets with 0.3% cholesterol, with 0.02% molsidomine or with the combination of cholesterol and molsidomine for 16 weeks. Lesion area and thickness, maximum change in isometric force (Emax and sensitivity (‐logEC50 or pD2) to constricting and relaxing agonists were assessed in segments of arch, thoracic and abdominal aorta. Bioassay was used to assess NO release.3 Cholesterol‐induced fatty streaks tapered off towards the abdominal aorta. Area, thickness, weight and cholesterylester content of the lesions were augmented by the NO donor, whereas the hypercholesterolaemia remained unchanged. The exacerbation was attributed to co‐release of superoxide anion from the sydnonimine.4 As fatty streaks progressed, amplitude and pD2 of acetylcholine (ACh)‐induced relaxations decreased, whereas cyclic GMP and cyclic AMP second messenger systems were not influenced, since Emax and sensitivity to SIN‐1 and forskolin remained unchanged. However, extensive lesions apparently trapped some NO, as the pD2 of authentic NO decreased.5 The fatty streaks curtailed the biosynthesis of PGI2 and the overflow of NO from the perfused thoracic aorta. The latter defect was not restored by L‐arginine and appears to be consistent with a functional change of the endothelial muscarinic receptors.6 The NO donor desensitized the aorta to cyclic GMP‐mediated relaxations (ACh, SIN‐1 and NO), without affecting cyclic AMP‐mediated relaxation to forskolin or constrictor responses to phenylephrine and 5‐hydroxytryptamine.7 The drug also suppressed the ACh‐induced overflow of NO, without changing PGI2 release. This selective reduction of endothelial NO release and the desensitization of cyclic GMP‐mediated relaxations occurred independently of fatty streak formation.8 The results indicate that chronic exposure to exogenous NO downregulates endothelial NO release and cyclic GMP‐mediated relaxations, and provide evidence for the existence of negative feedback regulations of the L‐arginine NO pathway under in vivo conditions.
Increase of meningeal blood flow after electrical stimulation of rat dura mater encephali: mediation by calcitonin gene‐related peptide
Authors: Kurosawa Mieko , Messlinger Karl , Pawlak Matthias , Schmidt Robert F. 
Published: July 2012

1 The dura mater encephali of the rat was exposed and the blood flow around branches of the medial meningeal artery was monitored with a laser Doppler flowmeter. Changes in the meningeal blood flow (MBF) following electrical stimulation of the dura mater at a parasagittal site were registered. The effects of human calcitonin gene‐related peptide (h‐αCGRP) and the CGRP antagonist (h‐αCGRP8–37) on the MBF were tested.2 Electrical stimulation with rectangular pulses of 0.5 ms, 10–20 V, 5–10 Hz and a duration of 30 s caused an increase of the MBF in 14 out of 16 rats tested. The increases were dependent on stimulus strength and frequency.3 The increase in MBF was inhibited in a dose‐dependent manner by topical application of 0.1 ml of h‐αCGRP8–37 at concentrations of 10−7‐10−5M. The highest dose abolished the increase in MBF.4 Topical administration of 0.1 ml of h‐αCGRP at a concentration of 10−4 M increased the basal MBF by 15% on average.5 It is suggested that the increase in MBF following electrical stimulation of the dura mater is mediated by the release of CGRP. The contribution of the dural afferent and sympathetic and parasympathetic efferent nerve fibres to this response are discussed.
5‐HT2‐mediated bronchial responses after syngeneic lung transplantation in the rat
Authors: Tavakoli Reza , Frossard Nelly 
Published: July 2012

1 The effect of lung transplantation was assessed on the subsequent bronchial responses to 5hydroxytryptamine (5‐HT) in the rat in vitro.2 Bronchial ring segments from syngeneic lung transplant recipients, from sham‐operated and from non‐operated control animals were studied in organ baths one month after unilateral left lung transplantation.3 Responses of the bronchial smooth muscle to 5‐HT (10−8 to 10−4M) significantly increased after lung transplantation (80.6 ± 7.6% of the maximal contractile response to acetylcholine) compared with the responses of all other controls (ca. 40% of the maximal contractile response to acetylcholine, P<0.01). pD2 values were similar for the left transplanted (5.70 ±0.11) and all other control bronchi (ranging from 5.53 to 5.82).4 Contraction to 5‐HT was blocked by the selective 5‐HT2 antagonist, ketanserin. Responses to the selective 5‐HT2 agonist, α‐methyl‐5‐HT, were similar to those to 5‐HT; pD2 values were similar in all groups (ranging from 5.41 to 5.74).5 The selective 5‐HT3 agonist, 1‐m‐chlorophenyl biguanide, had no contractile effect on rat bronchus, whether transplanted or not.6 Atropine, a muscarinic cholinoceptor blocking agent, had no effect on 5‐HT‐induced bronchial contraction. Hence, acetylcholine released from nerve terminals does not play any role in the observed bronchial hyperresponsiveness to 5‐HT.7 These results show bronchial hyperresponsiveness to 5‐HT in vitro one month after lung transplantation in the rat, mediated through 5‐HT2 receptor activation. This might be caused by upregulation of 5‐HT2 receptors in the lung after transplantation.