bluuebunny/crossref_metadata_2025 huggingface dataset:
Psoriatic skin lesions contain a novel lipid neutrophil chemokinetic compound which is distinct from known chemoattractant eicosanoids
Authors: Camp R.D.R. , Cunningham F.M. , Fincham N.J. , Greaves M.W. , Black A. Kobza , Mallet A.I. , Woollard P.M.
Published: July 2012

Lipid extracts of scale from the lesions of the skin disease psoriasis were purified by high performance liquid chromatography (h.p.l.c.). Assay of fractions by an agarose microdroplet method showed the presence of a novel neutrophil chemokinetic compound which possessed the chromatographic properties of a monohydroxy fatty acid, yet was distinct from the chemoattractant eicosanoid, 12‐hydroxyeicosatetraenoic acid, previously isolated in psoriasis.

The novel material, termed compound X, was also detected in fractions collected on h.p.l.c. of extracts of chamber fluid samples obtained from abraded psoriatic lesions, but was not detectable in samples from clinically normal skin.

Comparison of the straight and reversed phase h.p.l.c. retention times of compound X with those of a range of standard monohydroxy fatty acids, together with further analysis by gas chromatography — mass spectrometry and assay of selected standards for neutrophil chemokinetic activity, failed to reveal the structural identity of compound X.

The finding of a further compound in psoriatic lesions, which stimulates neutrophil movement, highlights the complexity of inflammatory mediator production in this disease.
Identification of two taurine receptor subtypes on the primary afferent terminal of frog spinal cord
Authors: Kudo Yoshihisa , Akiyoshi Eri , Akagi Hiroyuki
Published: July 2012

Effects of taurine on primary afferent terminals in the frog spinal cord were examined by a sucrose‐gap method applied to a dorsal root (9th or 10th segment).

In a normal Ringer solution, taurine (1 mM, applied for 5 s at a rate of 0.04 ml s−1, 0.2 μmol) caused a hyperpolarization, but a higher concentration (10 mM, applied at the same rate, 2.0 μmol) caused a biphasic response consisting of a hyperpolarization followed by a slow onset depolarization. A similar biphasic response could also be observed in tetrodotoxin‐treated preparations.

When the concentration of extracellular Mg2+ was increased up to 9.0 mM, the depolarizing response to taurine was augmented. The rate of the augmentation was dependent upon the extracellular Mg2+ concentration.

The depolarizing effect was selectively antagonized by bicuculline in concentrations (10–30 μm) that had no significant antagonizing action on γ‐aminobutyric acid (GABA)‐induced depolarization. On the other hand the hyperpolarizing effect of taurine was selectively reduced by strychnine (0.1 μm) which had no antagonizing effect on responses to glycine.

These results suggest that in the frog spinal cord there are at least two subtypes of taurine receptor whose pharmacological profiles resemble GABA and glycine receptors in the mammalian central nervous system, and whose sensitivity may be modulated by extracellular Mg2+.
GR43175, a selective agonist for the 5‐HT1‐like receptor in dog isolated saphenous vein
Authors: Humphrey P.P.A. , Feniuk W. , Perren M.J. , Connor H.E. , Oxford A.W. , Coates I.H. , Butina D.
Published: July 2012

We describe the actions of a novel and selective 5‐HT1‐like receptor agonist, GR43175, in a range of isolated tissue preparations containing different 5‐hydroxytryptamine (5‐HT) receptor types.

GR43175 was a potent agonist at 5‐HT1‐like receptors mediating contraction of the dog isolated saphenous vein and also at those inhibiting neuronally mediated contractions in the same preparations. For both actions, GR43175 was approximately four times weaker than 5‐HT.

GR43175 was devoid of agonist properties at 5‐HT1‐like receptors mediating relaxation of the cat isolated saphenous vein.

GR43175 was devoid of agonist properties at 5‐HT2 receptors mediating contraction of the rabbit isolated aorta, pig coronary artery, greyhound coronary artery and beagle femoral artery.

GR43175 was devoid of agonist properties at 5‐HT3 receptors mediating depolarization of the rat isolated vagus nerve.

The contractile response to GR43175 in the dog isolated saphenous vein was selectively antagonized by methiothepin but was resistant to antagonism by the 5‐HT2 receptor blocking drug ketanserin and the 5‐HT3 receptor blocking drug MDL 72222. Methiothepin antagonized the contractile action of 5‐HT and GR43175 to an equal extent suggesting that both agonists act at the same receptor.

The results demonstrate that GR43175 is a highly selective agonist for the 5‐HT1‐like receptors found in the dog saphenous vein. The absence of an action of GR43175 at 5‐HT1‐like receptors mediating relaxation of the cat isolated saphenous vein provides further evidence that 5‐HT1‐like receptors are heterogeneous.
Evidence that neutrophil accumulation induced by interleukin‐1 requires both local protein biosynthesis and neutrophil CD18 antigen expression in vivo
Authors: Rampart M. , Williams T.J.
Published: July 2012

Mechanisms involved in neutrophil accumulation induced by intradermal injection of interleukin‐1 (IL‐1) in the rabbit were investigated using intravenously‐injected 111In‐labelled neutrophils. C5a des Arg, N‐formyl‐methionyl‐leucyl‐phenylalanine (FMLP) and leukotriene B4 (LTB4) were included for comparison.

Local inhibition of protein biosynthesis in the skin using actinomycin‐D or cycloheximide blocked 111In‐neutrophil accumulation induced by IL‐1, but not that induced by the other mediators.

Actinomycin‐D and cycloheximide had no effect on local plasma protein leakage induced by intradermally‐injected C5a des Arg, or that induced by zymosan. 111In‐neutrophil accumulation induced by zymosan was, however, partially suppressed.

A monoclonal antibody, MoAb 60.3, recognising neutrophil surface CD18 antigen, was preincubated with 111In‐neutrophils before intravenous injection. This pretreatment did not affect circulating numbers of radiolabelled cells, but it inhibited their accumulation in response to IL‐1, C5a des Arg and the other mediators.

The results suggest that neutrophil accumulation induced by IL‐1, but not the other mediators, requires local protein biosynthesis, probably in the microvascular endothelium. Neutrophil accumulation to IL‐1 and the other mediators appears to require neutrophil surface antigen, CD18. The inflammatory response to zymosan may be mediated by both endogenous C5a des Arg and IL‐1.
Alteration of fate of vasoactive autacoids in pulmonary circulation following monocrotaline‐induced lung vascular injury in rats
Authors: Ito Katsuaki , Hayashi Katsuya , Nakashima Teruyuki , Murakami Takayuki
Published: July 2012

To learn how pulmonary vascular injury alters the ability of the lung to metabolize vasoactive autacoids, lung vascular lesions were produced in rats by a single subcutaneous injection of monocrotaline (90 mg kg−1), and the blood pressure responses to angiotensin I (AI), angiotensin II (AII), bradykinin, prostaglandin E2 (PGE2) and substance P were examined. Vasoactive agents were given intravenously or intra‐arterially.

On histological examination of the lung at 3 weeks after monocrotaline treatment, degeneration or necrotization of endothelial cells was evident.

The conversion of AI to AII was only slightly depressed by monocrotaline treatment. On the other hand, the depressor response to intravenously injected bradykinin was enhanced in monocrotaline‐treated rats. When the rats were pretreated with indomethacin the depressor response to intravenous bradykinin was the same for both control and monocrotaline‐treated groups which suggests that endogenous prostaglandins are involved in the enhancement of the response to bradykinin.

In monocrotaline‐treated rats the depressor response to intravenous PGE2 was significantly enhanced depending on the period following the treatment, while that to the intra‐arterial injection did not differ from control.

The data suggest that monocrotaline‐induced lung injury impairs the metabolism of PGE2 during pulmonary circulation but has little effect on the conversion of AI to AII and the degradation of bradykinin in rats.
Comparison of the cardiovascular effects of trans‐diclofurime with different types of calcium antagonists in conscious spontaneously hypertensive rats
Authors: Petty Margaret A. , Mir Anis K.
Published: July 2012

Trans‐diclofurime has been shown to be a potent group II calcium antagonist in in vitro and in vivo test systems. In contrast to the dihydropyridines, group II calcium antagonists have a reduced propensity to cause reflex tachycardia due to well‐balanced inhibitory effects in smooth muscle and heart. Since effects on autonomic reflexes are more reliably assessed in conscious animals, the cardiovascular effects of trans‐diclofurime have been examined and compared to those of nifedipine, verapamil and diltiazem in the conscious spontaneously hypertensive rat (SHR).

Each SHR had an indwelling catheter in the femoral artery to record mean arterial pressure (MAP) and heart rate (HR) and a cannula in the femoral vein for drug infusion over 1 min.

Nifedipine (0.1–3.0 μmol kg−1 i.v.) caused dose‐related falls in MAP accompanied by dose‐related increases in HR. Trans‐diclofurime and verapamil (0.3–3.0 μmol kg−1 i.v.) also caused dose‐related decreases in MAP, but significant tachycardia was only seen at 1.0 and 3.0 μmol kg−1, Trans‐diclofurime (0.3 μmol kg−1) induced a significant fall in HR. Diltiazem (1.0–10.0 μmol kg−1 i.v.) induced dose‐related falls in MAP, significant bradycardia was evident with 1.0 μmol kg−1 and tachycardia with 10 μmol kg−1. Trans‐diclofurime and diltiazem induced less tachycardia than nifedipine and verapamil for equivalent falls in MAP.

These results suggest that trans‐diclofurime is a potent antihypertensive agent in conscious SHR and, like diltiazem, the hypotensive effects are associated with less tachycardia than is usually apparent with calcium antagonists such as nifedipine or verapamil.

The cardiovascular effects of trans‐diclofurime in conscious SHR are those expected of a class II calcium antagonist and are consistent with its proposed mode of interaction with the diltiazem site in the calcium channel.
Modulation of the GABAA receptor by depressant barbiturates and pregnane steroids
Authors: Peters John A. , Kirkness Ewen F. , Callachan Helen , Lambert Jeremy J. , Turner Anthony J.
Published: July 2012

The modulation of the γ‐aminobutyric acidA (GABAA) receptor by reduced metabolites of progesterone and deoxycorticosterone has been compared with that produced by depressant barbiturates in: (a) voltage‐clamp recordings from bovine enzymatically isolated chromaffin cells in cell culture, and (b) an assay of the specific binding of [3H]‐muscimol to a preparation of porcine brain membranes.

The progesterone metabolites 5α‐ and 5β‐pregnan‐3α‐ol‐20‐one (≥30 nm) reversibly and dosedependently enhanced the amplitude of membrane currents elicited by locally applied GABA (100 μm), and over the concentration range 30 nM‐100 μm stimulated the binding of [3H]‐muscimol. In contrast, 5α‐ and 5β‐pregnan‐3β‐ol‐20‐one (30 nM‐100 μm) had little effect in either assay, indicating a marked stereoselectivity of steroid action.

Scatchard analysis of the ligand binding data suggested an apparent increase in the number, rather than the affinity, of detectable [3H]‐muscimol binding sites as the principle action of the active steroid isomers.

GABA‐evoked currents were also potentiated by androsterone (1 μm) and the deoxycorticosterone metabolite 5α‐pregnane‐3α,21‐diol‐20‐one (100 nm).

Secobarbitone (10–100 μm), pentobarbitone (10–300 μm) and phenobarbitone (100–500 μm) reversibly and dose‐dependently potentiated the amplitude of GABA‐evoked currents in the absence of any change in their reversal potential.

At relatively high concentrations (≥ 30 μm) secobarbitone and pentobarbitone directly elicited a membrane current. It is concluded that such currents result from GABAA receptor‐channel activation since they share a common reversal potential with GABA‐evoked responses (≥0mV), are reversibly antagonized by bicuculline (3 μm), and potentiated by either diazepam (1 μm) or 5β‐pregnan‐3α‐ol‐20‐one (500 nm).

Secobarbitone (1 μm‐1 mm) dose‐dependently enhanced the binding of [3H]‐muscimol. In common with the active steroids, an increase in the apparent number of binding sites was responsible for this effect.

A saturating concentration (1 mm) of secobarbitone in the ligand binding assay did not suppress the degree of enhancement of control binding produced by 5β‐pregnan‐3α‐ol‐20‐one (30 nM‐100 μm). Similarly the steroid, at a concentration of 100 μm, did not influence the enhancement of [3H]‐muscimol binding by secobarbitone (1 μm‐1 mm). In all combinations of concentrations tested, the effects of secobarbitone and 5β‐pregnan‐3α‐ol‐20‐one on [3H]‐muscimol binding were additive.

In conjunction with previously published observations, the present data indicate close similarities in the GABA‐mimetic and potentiating actions of barbiturates and steroids. However, the results obtained with combinations of steroids and barbiturates in the ligand binding assay appear inconsistent with the two classes of compound interacting with a common site to modulate the GABAA receptor activity.
Neurotransmission in pig renal artery: the actions of angiotensin II and dopamine
Authors: Ferguson D.R. , Randall M.D.
Published: July 2012

Electrical stimulation of pig renal arteries causes contractions which are potentiated in the presence of angiotensin II (5 × 10−8 m).

The potentiation is followed by a long‐lasting inhibitory phase which is mimicked by dopamine and 2‐amino‐6,7,dihydroxy‐1,2,3,4,‐tetrahydronaphthalene (ADTN), but blocked by sulpiride (5 × 10−8 m).

Release of noradrenaline from renal artery rings by 25 mM K+ was measured by h.p.l.c. and found to be increased by 5 × 10−8m angiotensin II. As this was done in the presence of 1 × 10−6 m desmethylimipramine it was concluded that the increase was due to increased neuronal release of noradrenaline, not inhibition of neuronal uptake.

The experiments indicate that dopamine is present in the artery wall and produces its effects through DA2‐receptors.
The classification of prostaglandin DP‐receptors in platelets and vasculature using BW A868C, a novel, selective and potent competitive antagonist
Authors: Giles Heather , Leff P. , Bolofo Mary L. , Kelly M.G. , Robertson A.D.
Published: July 2012

BW A868C, a novel compound, behaved as a simple competitive antagonist in a human washed platelet aggregation assay. Anti‐aggregatory concentration‐effect curves to BW 245C were displaced in a parallel manner. The shifts accorded with a Schild plot slope of unity and a pKB of 9.26.

Inhibition of platelet aggregation by prostaglandin D2 (PGD2) was antagonized with a similar potency, as were the relaxation effects of BW 245C and PGD2 in the rabbit jugular vein. BW A868C can, therefore, be classified as a DP‐receptor antagonist.

Actions of BW A868C at other prostaglandin receptors (IP, EP1, EP2, TP and FP) were excluded at concentrations up to 1,000 times higher than the DP‐receptor affinity.

Analyses of BW 245C‐ and PGD2‐mediated effects were complicated by additional agonist receptor interactions which were revealed by BW A868C. In rabbit jugular vein a resistant phase of agonism was detectable, indicating that both agonists exerted effects through another receptor (possibly EP2). Also, PGD2, in addition to its anti‐aggregatory effect on platelets, demonstrated a pro‐aggregatory action in the presence of BW A868C.

The contractile effects of PGD2 in guinea‐pig tracheal strips were resistant to 10 μm BW A868C indicating that they were not mediated through DP‐receptors.

To our knowledge this is the first account of a well‐classified competitive antagonist at the DP‐receptor. Its potency and selectivity make it an important new tool in prostanoid receptor classification and identification.
The antagonism by BW A868C of PGD2 and BW245C activation of human platelet adenylate cyclase
Authors: Trist D.G. , Collins B.A. , Wood J. , Kelly M.G. , Robertson A.D.
Published: July 2012

In glycerol‐lysed human platelets, prostaglandin D2 (PGD2) and the hydantoin BW245C both activate adenylate cyclase in a biphasic manner. These activations are qualitatively different from those of carbacyclin, iloprost and prostaglandin E2 (PGE2) whose E/[A] curves can be adequately described by rectangular hyperbolae.

Prostaglandin E1 (PGE1) had E/[A] curves of slope significantly lower than that expected for a rectangular hyperbola.

The selective PGD2 antagonist BW A868C shifts the first phase of the PGD2 and BW245C E/[A] curves but has no effect on the second phase.

Applying a two‐receptor model enables a pKB to be derived for BW A868C of 9.11.

BW A868C has no effect on carbacyclin, iloprost, prostacyclin, PGE1 and PGE2 at a concentration 1,000 fold that of its KB against PGD2 and BW245C.

These results indicate that PGD2 and BW245C are capable of activating adenylate cyclase in human platelets through the DP‐receptor and by another mechanism as yet uncharacterized.
Binding of [3H]‐muscimol to GABAA sites in the guinea‐pig urinary bladder: biochemical assay and autoradiography
Authors: Erdö S.L. , Mione M.C. , Amenta F. , Wolff J.R.
Published: July 2012

The specific binding of [3H]‐muscimol, a γ‐aminobutyric acidA receptor (GABAA) agonist, to whole membranes of the guinea‐pig urinary bladder was examined. In addition, the distribution of specific muscimol binding sites within the bladder was visualized by autoradiography.

It was demonstrated that in a frozen‐thawed whole membrane preparation of the organ the specific binding of [3H]‐muscimol is reproducible, reversible and saturable.

Saturable binding was of a single component with an equilibrium dissociation constant (Kd) of 12 nM and a maximal density (Bmax) of about 80 fmol mg−1 protein.

In displacement experiments with several model compounds, [3H]‐muscimol binding sites showed the characteristics of a GABAA receptor site.

Autoradiographic experiments revealed uneven distribution of specifically bound [3H]‐muscimol in the bladder. The density of binding sites was high in clusters within the smooth muscle layers of the bladder fundus and of the urethra, while the apex and the neck were not specifically labelled.

The present findings show that GABAA type receptor sites in the guinea‐pig urinary bladder may be labelled by [3H]‐muscimol in a specific and reproducible manner. Moreover, the localization of these binding sites is consistent with the presence of GABAA receptors in only a sub‐population of vesical ganglia.
Characterization of 5‐HT receptors mediating contraction of canine and primate basilar artery by use of GR43175, a selective 5‐HT1‐like receptor agonist
Authors: Connor H.E. , Feniuk W. , Humphrey P.P.A.
Published: July 2012

The aim of this study was to characterize the 5‐hydroxytryptamine (5‐HT) receptor which mediates contraction of canine and primate isolated basilar artery by use of a variety of selective 5‐HT agonists and antagonists.

5‐HT, α‐methyl 5‐HT and the selective 5‐HT1‐like receptor agonists, GR43175 and 5‐carboxamidotryptamine (5‐CT), each caused contraction of canine and primate basilar artery with a rank order of agonist potency of 5‐CT ≥ 5‐HT > GR43175 > α‐methyl 5‐HT. The 5‐HT1‐like receptor agonists, GR43175 and 5‐CT, produced maximum effects which were less than that produced by 5‐HT or α‐methyl 5‐HT.

In canine basilar artery, ketanserin (0.1–1 μm) caused some depression of the maximum effect of 5‐HT but produced little or no shift of the concentration‐effect curve. The contractile effects of GR43175 were not modified by ketanserin (1 μm), MDL72222 (1 μm) or cyanopindolol (1 μm). However, the effects of 5‐HT and GR43175 were specifically antagonized by methiothepin (0.1 μm); the mean agonist concentration‐ratios were 33 and 48 respectively.

In primate basilar artery, ketanserin (1 μm) again caused a small depression of the 5‐HT maximum response but had no effect against GR43175‐induced contractions. In contrast, methiothepin (0.1 μm) antagonized both 5‐HT‐ and GR43175‐induced contractions; the mean agonist concentration‐ratios were 35 for both.

These results demonstrate that a large component of the effects of 5‐HT in canine and primate basilar artery is produced by stimulation of a 5‐HT1‐like receptor. This receptor can be characterized by the high potency of the novel, selective agonist, GR43175, and susceptibility to blockade by methiothepin. However, there also appears to be a population of 5‐HT2 receptors in these pre‐pAarations which contribute to the contractile effects of 5‐HT.
Modulation of the GABAA receptor complex by steroids in slices of rat cuneate nucleus
Authors: Turner J.P. , Simmonds M.A.
Published: July 2012

Several derivatives of pregnane and androstane that have hypnotic properties have been investigated for their ability to potentiate responses to the GABAA receptor agonist muscimol and to reduce the effect of the non‐competitive GABAA antagonist picrotoxin.

Depolarizing responses to muscimol in slices of rat cuneate nucleus were potentiated most potently by 3α‐hydroxy, 5α‐pregnane‐11,20‐dione (alphaxalone), which gave half‐maximal potentiation at 0.15 μm. The 5β isomer of alphaxalone had little effect up to 3 μm but in analogues lacking an 11‐keto substituent (pregnanolones), both the 5α‐ and 5β‐isomers potentiated with potencies 20 and 10 times lower, respectively, than that of alphaxalone. The a configuration of the 3‐hydroxy was essential in alphaxalone, the 3β‐hydroxy isomer being inactive. However, there was little difference between the potencies of the 3α‐ and 3β‐hydroxy configurations in the pregnanolones, although the maximal effects of the 30‐hydroxy isomers were rather lower than those of the 3α‐hydroxy isomers.

Reductions in the effect of picrotoxin as an antagonist of muscimol were caused most potently by the 3α‐hydroxy pregnanolones, with a ten fold reduction in picrotoxin potency at 1 μm concentrations of these steroids. Alphaxalone and its 5β‐isomer were about half as potent. Androsterone was about 10 times less potent and the 3β‐hydroxy pregnanolones were ineffective.

This difference in the structure‐activity relationships for steroidal potentiation of muscimol and reduction in picrotoxin antagonism of muscimol is reminiscent of an analogous distinction found with the barbiturates.
5‐HT1‐like receptors mediate 5‐hydroxytryptamine‐induced contraction of human isolated basilar artery
Authors: Parsons Andrew A. , Whalley Eric T. , Feniuk Wasyl , Connor Helen E. , Humphrey Patrick P.A.
Published: July 2012

The 5‐hydroxytryptamine (5‐HT) receptor mediating contraction of endothelium denuded human basilar artery has been characterized in vitro.

5‐HT and a variety of 5‐HT agonists contracted human isolated basilar artery with a rank order of agonist potency, 5‐carboxamidotryptamine (5‐CT) > 5‐HT = methysergide > GR43175 > 8‐OHDPAT > 2‐methyl‐5‐HT. The maximum response produced by these agonists differed.

None of the agonists relaxed human basilar artery when tone was elevated with prostaglandin F2α, indeed further contraction was seen.

The contractile responses of human basilar artery to 5‐HT and the selective 5‐HT1‐like agonist GR43175 were highly reproducible whilst those to 5‐CT were not.

The contractile response to both 5‐HT and GR43175 was resistant to antagonism by ketanserin and GR38032, thus excluding activation of 5‐HT2 and 5‐HT3 receptors. The contractile action of 5‐HT and GR43175 was also not antagonized by (±)‐cyanopindolol, excluding the activation of receptors similar to 5‐HT1A and 5‐HT1B recognition sites identified in ligand binding studies.

In marked contrast, methiothepin was a potent antagonist of the contractile actions of both 5‐HT and GR43175, with a pA2 value of 8.8 against both agonists. Methiothepin (100 nm) had no effect on the contractile response to the thromboxane A2‐mimetic U46619.

We conclude that 5‐HT and GR43175 contract the human isolated basilar artery by activating the same receptor type. This receptor appears identical to the 5‐HT1‐like receptor causing contraction of the dog isolated saphenous vein and cerebral blood vessels from the dog and primate.
Involvement of 5‐HT2 receptors in the behaviours produced by intrathecal administration of selected 5‐HT agonists and the TRH analogue (CG 3509) to rats
Authors: Fone K.C.F. , Johnson J.V. , Bennett G.W. , Marsden C.A.
Published: July 2012

The behavioural effects of the intrathecal injection of a thyrotrophin‐releasing hormone (TRH) analogue l‐orotyl‐l‐histidyl‐prolineamide (CG 3509, 0.5 μg), the non‐selective 5‐HT1 and 5‐HT2 receptor agonist 5‐methoxy‐N,N′‐dimethyltryptamine (5‐MeODMT, 2–100 μg) and the selective 5‐HT2 receptor agonist 2,5‐dimethoxy‐α,4‐dimethyl‐benzene ethamine hydrochloride (DOM, 2–25 μg) were compared with the response of systemically administered 5‐MeODMT (2 mg kg−1, i.p.) in rats, to establish whether the agonist‐induced behaviours were mediated by bulbospinal 5‐HT1 or 5‐HT2 receptors.

Intrathecal injection of 5‐MeODMT or DOM produced dose‐related back muscle contractions (a previously undocumented behaviour) and wet‐dog shakes which were both markedly attenuated by ritanserin pretreatment (1 mg kg−1, i.p.) indicating the involvement of 5‐HT2 receptors. In contrast, reciprocal forepaw treading, flat body posture and Straub‐tail were evoked by 5‐MeODMT but not by DOM indicating that these behaviours were not produced by 5‐HT2 receptor activation alone. However, as ritanserin pretreatment reduced the reciprocal forepaw treading induced by intrathecal 5‐MeODMT, this behaviour may be facilitated by 5‐HT2 receptor activation.

Intrathecal 5,7‐dihydroxytryptamine (5,7‐DHT, 2 × 150 μg) treatment decreased thoraco‐lumbar spinal cord 5‐HT (‐95%) and potentiated the back muscle contractions produced by intrathecal DOM injection without altering the wet‐dog shake behaviour. None of the components of the 5‐HT syndrome produced by 5‐MeODMT (2 mg kg−1, i.p.), with the exception of a small increase in wet‐dog shakes, was significantly altered by intrathecal 5,7‐DHT (which reduced thoraco‐lumbar spinal cord 5‐HT by 84%). Taken together these data suggest that the only 5‐HT agonist‐induced behaviour mediated by the activation of 5‐HT2 receptors located postsynaptic to bulbospinal 5‐hydroxytryptaminergic (5‐HTergic) neurones was back muscle contractions.

The wet‐dog shake and forepaw licking behaviors produced by intrathecal CG 3509 (0.5 μg) were attenuated when ritanserin was administered intrathecally 30 min before, but not when it was given at the same time as CG 3509 and neither behaviour was altered by intrathecal 5,7‐DHT. This suggests that bulbospinal 5‐HTergic neurones are not involved in the production of these TRH analogue‐induced behaviours and that the 5‐HT2 receptors which mediate these behaviours are not located in the spinal cord.
Estimation of affinities and efficacies for κ‐receptor agonists in guinea‐pig ileum
Authors: Leff P. , Dougall I.G.
Published: July 2012

Ethylketocyclazocine (EKC) and U50,488H have been employed widely as κ‐receptor agonists in the study of opioid receptor systems. However, the quantification of their agonism in terms of affinities and relative efficacies has not been investigated.

In this study, operational model‐fitting was used to analyse the effects of irreversible receptor alkylation by β‐chlornaltrexamine (β‐CNA) on the /c‐receptor mediated effects of EKC and U50,488H in the isolated, coaxially stimulated ileum of the guinea‐pig.

EKC produced monophasic inhibitory concentration‐effect curves which were readily amenable to analysis. In contrast U50,488H produced biphasic curves characterized by a higher potency phase of agonism that was susceptible to antagonism by 16‐methylcyprenorphine (RX8008M) and a lower potency phase that was apparently non‐opioid in nature.

Analysis of the κ‐receptor‐mediated effects of both agonists indicated that EKC has fifteen fold higher affinity than U50,488H and that the two agonists possess similar intrinsic efficacies.
Effects of tetrodotoxin on relaxation of pig duodenal circular muscle induced by C‐terminal fragments of cholecystokinin
Authors: Kimura Ikuko , Kondoh Takashi , Kimura Masayasu
Published: July 2012

The mechanisms by which cholecystokinin (CCK)‐C‐terminal peptides relax the isolated duodenal circular muscles of pigs were compared with mechanisms involving high potassium and electrical stimulation.

The relaxation (30%) induced by CCK‐8 0.263 nm was completely and non‐competitively blocked by tetrodotoxin (TTX) 0.313 μm, and was enhanced 2–2.5 times by mesaconitine 0.158 μm, tetraethylammonium (TEA) 0.597 mm and ouabain 0.136 μm.

The TTX sensitivity was greater for CCK‐8 and CCK‐6, than for CCK‐5 and CCK‐4.

High potassium (11.8–23.6 mm)‐induced, or electrically stimulated (0.3–30 Hz) relaxation showed similar characteristics except that they were not antagonized by the CCK antagonist P3‐I (168 μm).

Apamin (0.385–3.85 μm) enhanced relaxation induced by 10.6 mm K+, but did not affect relaxation induced by CCK‐8.

These results indicate that: (1) CCK‐8, K+, and transmural electrical stimulation relax duodenal circular muscles by releasing an endogenous inhibitory substance; (2) the latter two do not mediate the release of CCK; and (3) the mechanisms for relaxation by CCK‐4 are different from those of CCK‐8.
Vasoactive intestinal polypeptide and non‐adrenergic, non‐cholinergic inhibition in lower oesophageal sphincter of opossum
Authors: Daniel E.E. , Jager L.P. , Jury J.
Published: July 2012

Field stimulation or vasoactive intestinal polypeptide (VIP) relaxed lower oesophageal sphincter (LOS) from North American opossum. Pretreatment with carbachol in Cl‐ion‐containing or Cl‐ion‐free Krebs solution or with 10−3 m 9‐aminoacridine abolished or markedly reduced relaxation due to VIP applied exogenously but not that elicited by field stimulation of non‐adrenergic, noncholinergic nerves.

Inhibitory junction potentials (7.5 ± 1.2 mV, n = 5) could be recorded in LOS strips with the sucrose gap technique. They lacked significant after‐depolarizations but were accompanied by decreased membrane resistance (61 ± 6%, n = 3). In these strips, VIP (10−6 m) produced small hyperpolarizations (2.1 ± 1.1 mV, n = 5) sometimes followed by membrane potential oscillations but no change in conductance.

Removal of external chloride depolarized the membranes (7.6 ± 1.7 mV) but did not prevent the hyperpolarization to VIP or the occurrence of inhibitory junction potentials. Restoration of external chloride repolarized the cells. It appears that an appreciable chloride conductance may be present in sphincter muscle cells and this may cause them to be more depolarized than non‐sphincter muscle.

We conclude that it is very unlikely that VIP is the inhibitory NANC neurotransmitter since it does not mimic the inhibitory junction potential.
Cholera and pertussis toxins amplify prostacyclin synthesis in aortic smooth muscle cells
Authors: Demolle D. , Boeynaems J.M.
Published: July 2012

Pretreatment of bovine aortic smooth muscle cells in culture with pertussis toxin (PT) or cholera toxin (CT) potentiated the synthesis of prostacyclin (PGI2) induced by 5‐hydroxytryptamine (5‐HT) and phorbol‐12‐myristate, 13‐acetate (PMA). The production of PGI2 by explants from the bovine aortic media was also synergistically stimulated by 5‐HT and CT, whereas PT was inactive. These data are consistent with the hypothesis that guanosine 5′‐triphosphate binding proteins are directly involved in the control of phospholipases which release free arachidonic acid for prostaglandin synthesis.
Protein kinase C regulates the tonic but not the phasic component of contraction in guinea‐pig ileum
Authors: Sasaguri Toshiyuki , Watson Stephen P.
Published: July 2012

We have investigated the effect of phorbol esters and the down‐regulation of protein kinase C on contraction of guinea‐pig ileum longitudinal smooth muscle to carbachol and high K+.

Phorbol 12,13‐dibutyrate (PDBu) enhanced the phasic component and inhibited or enhanced, respectively, the tonic component of contraction to carbachol and high K+. In contrast, 4α‐phorbol, which does not activate protein kinase C, had no effect on these responses.

Exposure to phorbol 12‐myristate 13‐acetate (PMA; 1 μm) for up to 8 h induced a time‐dependent loss of [3H]‐PDBu binding sites, consistent with the down‐regulation of protein kinase C by this treatment.

The phasic component of contraction to carbachol or high K+ was unaffected following the down‐regulation of protein kinase C. The tonic component of contraction to carbachol was markedly enhanced by this treatment while that to high K+ was partially suppressed.

These data suggest that although the activation of protein kinase C can lead to potentiation of the phasic component of contraction to carbachol or high K+, this appears to have little physiological significance since the response is not altered in tissues in which protein kinase C has been down‐regulated. On the other hand, protein kinase C may limit the tonic contraction to carbachol but potentiate that to high K+.
Relations between structure and nicotine‐like activity: X‐ray crystal structure analysis of (−)−cytisine and (−)−lobeline hydrochloride and a comparison with (−)−nicotine and other nicotine‐like compounds
Authors: Barlow R.B. , Johnson O.
Published: July 2012

Although (−)−cytisine is a rigid structure, it occurs in the crystal in two distinct but very similar conformations in which the pyridone ring is tilted relative to the charged nitrogen atom at much the same angle as the pyridine ring is in (−)−nicotine hydrogen iodide. The carbonyl group in the pyridone ring of (−)−cytisine, however, is on the side of the ring opposite to the pyridine nitrogen in (−)−nicotine.

The pKa of (−)−lobeline HCl at 25°C is 8.6 (approx), indicating that (−)−lobeline is at least 90% in the protonated form at physiological pH (7.6). It is probably the phenyl 2‐keto‐ethyl part of (−)−lobeline, rather than the phenyl 2‐hydroxy‐ethyl part, which interacts with the receptor.

The combination within one molecule of a charged (‘onium’) nitrogen atom lying out of the plane of, and some distance (4.5–6.5 Å) from, an aromatic ring is common to many compounds with nicotine‐like activity (e.g. nicotine, cytisine, choline phenyl ether bromide, dimethyl‐phenyl‐piperazinium (DMPP) iodide, coryneine iodide and m‐hydroxyphenylpropyl trimethyl ammonium iodide). In some molecules the aromatic ring can be replaced by an unsaturated group, such as carbonyl (e.g. acetylcholine) or double‐bonds (e.g. anatoxin).

Activity at nicotinic receptors appears to involve interactions between the positively charged nitrogen atom and a negatively charged group, probably close to cysteine residues 192 and 193 in the receptor. It is suggested that rather than specific groups in the molecule also being involved, activity at nicotinic receptors depends on interactions between a flat part of the drug containing double‐bonds, or systems of double bonds, and a planar area in the receptor, possibly tyrosine or phenylalanine residues.
Properties of the cromakalim‐induced potassium conductance in smooth muscle cells isolated from the rabbit portal vein
Authors: Beech D.J. , Bolton T.B.
Published: July 2012

Single smooth muscle cells were isolated freshly from the rabbit portal vein and membrane currents were recorded by the whole‐cell or excised patch configurations of the patch‐clamp technique at room temperature.

Cromakalim (Ckm, 10 μm) induced a potassium current (ICkm) that showed no pronounced voltage‐dependence and had low current noise.

This current, ICkm, was inhibited by (in order of potency): phencyclidine > quinidine > 4‐aminopyridine > tetraethylammonium ions (TEA). These drugs inhibited the delayed rectifier current, IdK, which is activated by depolarization of the cell, with the same order of potency.

Large conductance calcium‐activated potassium channels (LKCa) in isolated membrane patches were blocked by (in order of potency) quinidine > TEA ≅ phencyclidine. 4‐Aminopyridine was ineffective. A similar order of potency was found for block of spontaneous transient outward currents thought to represent bursts of openings of LKCa channels.

The low current noise of ICkm at positive potentials, and its susceptibility to inhibitors indicated that it was not carried by LKCa channels, and that it may be carried by channels which underlie IdK. It was observed that when ICkm was activated, IdK was reduced. However, in two experiments, ICkm was much more susceptible to glibenclamide than IdK; possible reasons for this are discussed.
Mediators of burn‐induced neuromuscular changes in mice
Authors: Tomera John F. , Martyn Jeevendra
Published: July 2012

Muscle paresis and aberrant pharmacological responses are two important pathophysiological changes that have been observed at the neuromuscular junction following thermal injury. By use of the mouse model of 20%, 30% and 50% total body surface area (BSA) burn, we examined the significance of intracellular mediators, adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) and prostaglandin E2 (PGE2) in perturbing the physiological function of tension development and the pharmacological response to (+)‐tubocurarine (+)‐Tc at day 21 post‐burn.

Cyclic AMP levels increased with the size of burn. The relationship between mean cyclic AMP levels and burn size was significant (R2 = 0.96, r = 0.98). Significant (P < 0.05) reductions in tension development (g) were observed for the 30% and 50% BSA burn group compared to controls (30.3 ± 8.3 and 34.1 ± 5.9 vs 59.1 ± 1.0, respectively). Tension alterations were associated with increased cyclic AMP levels; the relationship between increased cyclic AMP levels and tension decrease was significant (R2 = 0.82, r = 0.91). The dose of (+)‐Tc required to inhibit twitch tension increased in proportion to burn size and was statistically significant in the 50% BSA burn group compared to controls (0.3320 ± 0.09 vs 0.1093 ± 0.11 mg kg−1, P < 0.05). The alterations in the effective dose of (+)‐Tc were significantly correlated to increases in cyclic AMP levels (R2 = 0.70, r = 0.83). Although PGE2 levels were elevated in the 30% and 50% burn groups, no relation was seen to either tension or (+)‐Tc doses.

These studies, therefore, support the hypothesis that cyclic AMP plays a significant role in physiological and pharmacological responses in skeletal muscle following thermal injury.
Effects of changes in extra‐ and intracellular K+ on the endothelial production of prostacyclin
Authors: Boeynaems J.M. , Ramboer I.
Published: July 2012

Changes in the KCl concentration of the incubation medium, from 0 to 80 mm, had no effect on the basal or ATP‐stimulated release of prostacyclin (PGI2) from bovine aortic endothelial cells.

The monovalent cation ionophores, valinomycin and nigericin (5 μm), enhanced the release of PGI2 from endothelial cells stimulated by ATP or bradykinin.

The action of nigericin, unlike that of valinomycin, was time‐dependent, abolished in a high‐KCl medium and associated with an increased efflux of 86Rb and a time‐dependent depletion of intracellular K+.

Ouabain (1–100 μm) also enhanced the release of PGI2 in response to ATP and induced a significant depletion of intracellular K+ in bovine aortic endothelial cells.

In conclusion, modifications of the endothelial cell membrane potential, resulting from changes in the extracellular K+ concentration, do not modulate the basal or ATP‐stimulated production of PGI2. An acute depletion of intracellular K+ by nigericin or ouabain enhances the production of PGI2 in aortic endothelial cells stimulated by ATP or bradykinin.
Effects of amiloride analogues on the production of prostacyclin by aortic endothelial cells
Authors: Boeynaems J.M. , Demolle D. , Lagneau C. , Cragoe E.J.
Published: July 2012

The release of prostacyclin (PGI2) from bovine aortic endothelial cells stimulated by adenosine 5′‐triphosphate (ATP) was decreased by amiloride analogues bearing alkyl groups on the 5‐amino nitrogen atom, like 5‐(N‐ethyl‐N‐isopropyl)amiloride (EIPA), which are inhibitors of the Na+/H+ exchanger. Analogues substituted on a terminal guanidino nitrogen atom were not inhibitory.

The release of PGI2 induced by ATP was not significantly depressed in a Na+‐poor medium or in a medium acidified to pH 6.9, two conditions known to inhibit the Na+/H+ exchanger.

Cytoplasmic alkalinization by ammonium chloride did not suppress the inhibitory action of EIPA. By itself, ammonium chloride decreased the response of endothelial cells to ionophore A23187 and ATP, whereas sodium acetate had no effect.

EIPA did not decrease the mobilization of free arachidonic acid induced by ATP. It inhibited the conversion of exogenous arachidonate into PGI2 and prostaglandin E2 (PGE2).

Although the intracellular pH was not measured in this study, it seems unlikely that cytoplasmic alkalinization via the activation of the Na+/H+ exchanger plays a significant role in the stimulatory action of ATP on the release of PGI2 from endothelial cells. The inhibition of that release by EIPA and other amiloride analogues might involve a direct effect on cyclo‐oxygenase, although an action on the reacylation of free arachidonic acid cannot be excluded.
δ‐Opioid mediated inhibitions of acute and prolonged noxious‐evoked responses in rat dorsal horn neurones
Authors: Sullivan A.F. , Dickenson A.H. , Roques B.P.
Published: July 2012

The effects of a selective δ‐opioid agonist Tyr‐D‐Ser(Otbu)‐Gly‐Phe‐Leu‐Thr (DSTBULET) were examined on the C‐ and Aβ‐evoked responses of convergent dorsal horn neurones in the halothane anaesthetized, intact rat.

Intrathecal DSTBULET produced selective dose‐dependent inhibitions of electrically‐evoked C fibre responses of both superficial and deep neurones. A near‐complete inhibition of 83 ± 5% followed 100 μg of DSTBULET and the ED50 was 9 μg (13.5 nmol). Inhibitions were antagonised by intrathecal naloxone and ICI 174,864 but were not antagonised by pretreatment with intrathecal β‐funaltrexamine at a dose that blocked μ‐opioid effects. By contrast, DSTBULET produced excitations of electrically‐evoked responses of cells recorded in a zone intermediate between the superficial and deep neurones.

DSTBULET (50 μg) was also tested on the more prolonged noxious neuronal response produced by subcutaneous formalin (5%, 50 μl) into the receptive field. DSTBULET profoundly inhibited the response to formalin. Pretreatment with ICI 174, 864 before DSTBULET antagonised the effects of the δ‐agonist on the formalin response.

The full peptidase inhibitor kelatorphan, known to protect endogenous enkephalins, was also tested on the formalin response. The intrathecal administration of 50 μg kelatorphan has previously been shown to inhibit electrically‐evoked C fibre resonses of dorsal horn neurones and to be antagonised by ICI 174,864. The same dose of kelatorphan inhibited the formalin response in the present study.

From this study it appears that the δ‐opioid agonist DSTBULET can produce profound inhibitions of the responses of convergent neurones to nociceptive afferent inputs. Furthermore, activation of δ‐opioid receptors either by DSTBULET, or by protection of endogenous enkephalins with kelatorphan, can inhibit a more prolonged chemically‐evoked nociceptive input onto these dorsal horn neurones.
Antagonism of swim‐stress‐induced antinociception by the δ‐opioid receptor antagonist naltrindole in adult and young rats
Authors: Kitchen Ian , Pinker Sally R.
Published: July 2012

The availability of the non‐peptide δ‐opioid receptor antagonist naltrindole has provided the possibility for in vivo studies on the function of δ‐opioid receptors. We have studied the effects of naltrindole on swim‐stress‐induced antinociception in adult and neonatal rats.

Adult, 25 and 20 day old rats were stressed by warm water (20°C) swimming for 3 min periods and antinociception was assessed by the tail immersion test (50°C).

Naltrindole (0.5 and 1 mg kg−1) antagonized swim‐stress‐induced antinociception in adult and 25 day old rats but in 20 day old rats naltrindole (1 mg kg−l) was without effect.

Antinociception induced by the highly μ‐opioid receptor selective agonist alfentanil was completely antagonized by naloxone (1 mg kg−l) but virtually unaffected by naltrindole (1 mg kg−1).

Neither naloxone nor naltrindole (1 mg kg−1) antagonized swim‐stress‐induced rises in plasma corticosterone in adult rats at the time of peak antinociception.

In conclusion, naltrindole shows in vivo antagonism of opioid‐mediated responses. Swim‐stress‐induced antinociception is mediated through the δ‐opioid receptor in 25 day old and adult rats and through the μ‐opioid site in 20 day old animals.
Nicergoline inhibits T‐type Ca2+ channels in rat isolated hippocampal CA1 pyramidal neurones
Authors: Takahashi Kazuyoshi , Akaike Norio
Published: July 2012

The effects of nicergoline on the T‐ and L‐type Ca2+ currents in pyramidal cells freshly isolated from rat hippocampal CA1 region were investigated by use of a ‘concentration‐clamp’ technique. The technique combines a suction‐pipette technique, which allows intracellular perfusion under a single‐electrode voltage‐clamp, and rapid exchange of extracellular solution within 2 ms.

T‐type Ca2+ currents were evoked by step depolarizations from a holding potential of −100 mV to potentials more positive than −70 to −60 mV, and reached a peak at about −30 mV in the current‐voltage relationship. Activation and inactivation of T‐type Ca2+ currents were highly potential‐dependent.

Nicergoline and other Ca2+ antagonists dose‐dependently blocked the T‐type Ca2+ channel with an order of potency nicardipine > nicergoline > diltiazem.

The L‐type Ca2+ channel was also blocked in the order nicardipine > nicergoline > diltiazem, although the T‐type Ca2+ channel was more sensitive to nicergoline.

The inhibitory effects of nicergoline and nicardipine on the T‐type Ca2+ current were voltage‐, time‐, and use‐dependent, and the inhibition increased with a decrease in the external Ca2+ concentration. Diltiazem showed only a use‐dependent block.
The influence of the initial stretch and the agonist‐induced tone on the effect of basal and stimulated release of EDRF
Authors: Dainty I.A. , McGrath J.C. , Spedding M. , Templeton A.G.B.
Published: July 2012

The effects of initial stretch and degree of agonist‐induced tone on acetylcholine‐induced relaxations were examined in rings of rat isolated aorta. The relaxation to acetylcholine was antagonized by atropine and almost completely abolished by haemoglobin. Relaxation to sodium nitroprusside was similar in rings with an intact or disrupted endothelium but that to isoprenaline was greater in intact preparations.

In preparations with either an intact or disrupted endothelium there was a similar length‐dependent increase in the resting tension of the aortic rings. The size of the contractile response to phenylephrine (1 μm) was dependent on the initial length (and hence degree of stretch) of the preparation in both rubbed and unrubbed tissues. The absolute difference in contractile response between rubbed and unrubbed was greatest at 1.8 mm and less at the other lengths tested, including the optimum degree of stretch for contraction i.e. 2.4 mm.

The absolute acetylcholine‐induced relaxation (only seen in rings with an intact endothelium) was dependent on the initial length (and hence degree of stretch) of the preparation and was maximum at 2.4 mm. The proportionate relaxation (i.e. expressed as a percentage of induced tone) was also length‐dependent, being optimal at 1.5 mm.

The sensitivity of the vessels to acetylcholine varied depending on the level of agonist‐induced tone. When tone was low, acetylcholine sensitivity was high (at [NA] 0.03 μm: pIC50 = 7.36 ± 0.07), when the concentration of noradrenaline was increased the tone increased and the acetylcholine sensitivity was low (at [NA] 0.3 μm: pIC50 = 6.57 ± 0.07).

The absolute sensitivities and maximum relaxations induced by acetylcholine are discussed in relation to the initial degree of stretch (and hence length of the preparation) or the degree of agonist‐induced tone.