bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of pH on the inhibition of fatty acid amidohydrolase by ibuprofen
Authors: Holt Sandra , Nilsson Jonas , Omeir Romelda , Tiger Gunnar , Fowler Christopher J
Published: January 2005

The pharmacological properties of fatty acid amidohydrolase (FAAH) at different assay pH values were investigated using [3H]‐anandamide ([3H]‐AEA) as substrate in rat brain homogenates and in COS‐7 cells transfected with wild type and mutant FAAH.

Rat brain hydrolysis of [3H]‐AEA showed pH dependency with an optimum around pH 8‐9. Between pH 6.3 and 8.2, the difference in activity was due to differences in the Vmax, rather than the KM values.

For inhibition of rat brain [3H]‐AEA metabolism by a series of known FAAH inhibitors, the potencies of the enantiomers of ibuprofen and phenylmethylsulphonyl fluoride (PMSF) were higher at pH 5.28 than at pH 8.37, whereas the reverse was true for oleyl trifluoromethylketone (OTMK) and arachidonoylserotonin. At both pH values, (−)ibuprofen was a mixed‐type inhibitor of FAAH. The Ki(slope) and Ki(intercept) values for (−)ibuprofen at pH 5.28 were 11 and 143 μM, respectively. At pH 8.37, the corresponding values were 185 and 3950 μM, respectively.

The pH dependency for the inhibition by OTMK and (−)ibuprofen was also seen in COS‐7 cells transiently transfected with either wild type, S152A or C249A FAAH. No differences in potencies between the wild type and mutant enzymes were seen.

It is concluded that the pharmacological properties of FAAH are highly pH‐dependent. The higher potency of ibuprofen at lower pH values raises the possibility that in certain types of inflamed tissue, the concentration of this compound following oral administration may be sufficient to inhibit FAAH.

British Journal of Pharmacology (2001) 133, 513–520; doi:10.1038/sj.bjp.0704113
Effects of YM471, a nonpeptide AVP V1A and V2 receptor antagonist, on human AVP receptor subtypes expressed in CHO cells and oxytocin receptors in human uterine smooth muscle cells
Authors: Tsukada Junko , Tahara Atsuo , Tomura Yuichi , Wada Koh‐ichi , Kusayama Toshiyuki , Ishii Noe , Yatsu Takeyuki , Uchida Wataru , Taniguchi Nobuaki , Tanaka Akihiro
Published: January 2005

YM471, (Z)‐4′‐{4,4‐difluoro‐5‐[2‐(4‐dimethylaminopiperidino)‐2‐oxoethylidene]‐2,3,4,5‐tetrahydro‐1H‐1‐benzoazepine‐1‐carbonyl}‐2‐phenylbenzanilide monohydrochloride, is a newly synthesized potent vasopressin (AVP) receptor antagonist. Its effects on binding to and signal transduction by cloned human AVP receptors (V1A, V1B and V2) stably expressed in Chinese hamster ovary (CHO) cells, and oxytocin receptors in human uterine smooth muscle cells (USMC) were studied.

YM471 potently inhibited specific [3H]‐AVP binding to V1A and V2 receptors with Ki values of 0.62 nM and 1.19 nM, respectively. In contrast, YM471 exhibited much lower affinity for V1B and oxytocin receptors with Ki values of 16.4 μM and 31.6 nM, respectively.

In CHO cells expressing V1A receptors, YM471 potently inhibited AVP‐induced intracellular Ca2+ concentration ([Ca2+]i) increase, exhibiting an IC50 value of 0.56 nM. However, in human USMC expressing oxytocin receptors, YM471 exhibited much lower potency in inhibiting oxytocin‐induced [Ca2+]i increase (IC50=193 nM), and did not affect AVP‐induced [Ca2+]i increase in CHO cells expressing V1B receptors. Furthermore, in CHO cells expressing V2 receptors, YM471 potently inhibited the production of cyclic AMP stimulated by AVP with an IC50 value of 1.88 nM. In all assays, YM471 showed no agonistic activity.

These results demonstrate that YM471 is a potent, nonpeptide human V1A and V2 receptor antagonist which will be a valuable tool in defining the physiologic and pharmacologic actions of AVP.

British Journal of Pharmacology (2001) 133, 746–754; doi:10.1038/sj.bjp.0704117
Effects of GABAA receptor partial agonists in primary cultures of cerebellar granule neurons and cerebral cortical neurons reflect different receptor subunit compositions
Authors: Hansen Suzanne L , Ebert Bjarke , Fjalland Bjarne , Kristiansen Uffe
Published: January 2005

Based on an unexpected high maximum response to piperidine‐4‐sulphonic acid (P4S) at human α1α6β2γ2 GABAA receptors expressed in Xenopus oocytes attempts to correlate this finding with the pharmacological profile of P4S and other GABAA receptor ligands in neuronal cultures from rat cerebellar granule cells and rat cerebral cortex were carried out.

GABA and isoguvacine acted as full and piperidine‐4‐sulphonic acid (P4S) as partial agonists, respectively, at α1β2γ2, α6β2γ2 and α1α6β2γ2 GABA receptors expressed in Xenopus oocytes with differences in potency.

Whole‐cell patch‐clamp recordings were used to investigate the pharmacological profile of the partial GABAA receptor agonists 4,5,6,7‐tetrahydroisoxazolo‐(5,4‐c)pyridin‐3‐ol (THIP), P4S, 5‐(4‐piperidyl)isoxazol‐3‐ol (4‐PIOL), and 3‐(4‐piperidyl)isoxazol‐5‐ol (iso‐4‐PIOL), and the competitive GABAA receptor antagonists Bicuculline Methbromide (BMB) and 2‐(3‐carboxypropyl)‐3‐amino‐6‐methoxyphenyl‐pyridazinium bromide (SR95531) on cerebral cortical and cerebellar granule neurons. In agreement with findings in oocytes, GABA, isoguvacine and P4S showed similar pharmacological profiles in cultured cortical and cerebellar neurones, which are known to express mainly α1, α2, α3, and α5 containing receptors and α1, α6 and α1α6 containing receptors, respectively.

4‐PIOL and iso‐4‐PIOL, which at GABAA receptors expressed in oocytes were weak antagonists, showed cell type dependent potency as inhibitors of GABA mediated responses. Thus, 4‐PIOL was slightly more potent at cortical neurones than at granule neurones and iso‐4‐PIOL was more potent in inhibiting isoguvacine‐evoked currents at cortical than at granule neurons. Furthermore the maximum response to 4‐PIOL corresponded to that of a partial agonist, whereas that of iso‐4‐PIOL gave a maximum response close to zero.

It is concluded that the pharmacological profile of partial agonists is highly dependent on the receptor composition, and that small structural changes of a ligand can alter the selectivity towards different subunit compositions. Moreover, this study shows that pharmacological actions determined in oocytes are generally in agreement with data obtained from cultured neurons.

British Journal of Pharmacology (2001) 133, 539–549; doi:10.1038/sj.bjp.0704121
Antioxidant activity of amiodarone on human lipoprotein oxidation
Authors: Lapenna Domenico , Ciofani Giuliano , Bruno Cristiana , Pierdomenico Sante D , Cuccurullo Franco
Published: January 2005

Lipoprotein oxidation is crucial in atherogenic processes. Amiodarone is a lipophilic antiarrhythmic/antianginal drug which is able to influence the physicochemical status of biological lipid components. Since oxidation of lipids is affected by their physicochemical state and amiodarone binds to lipoproteins, we hypothesized that the drug may exert an antioxidant activity on human lipoprotein oxidation.

Dose‐dependent effects of therapeutically achievable amiodarone concentrations (1.5, 3, 5, 7 and 10 μM) were studied on copper‐catalysed oxidation of the non‐HDL fraction in vitro. Amiodarone inhibited oxidation as judged by generation of thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (LOOH) and fluorescent products of lipoperoxidation (FPL) as well as from the kinetics of conjugated diene formation. This antioxidant activity was significant at 1.5 μM with total inhibition at 10 μM and an IC50 of 4 μM. The primary in vivo metabolite of amiodarone, namely desethylamiodarone, also exhibited specific antioxidant properties although it was less effective than amiodarone with an IC50 of 7 μM.

In further in vivo experiments, susceptibility to copper‐mediated oxidation of the non‐HDL fraction was investigated before and 4 weeks after oral amiodarone administration to humans. Following treatment, significant inhibition of TBARS, LOOH and FPL generation was observed in comparison with baseline levels and a placebo‐treated control group, highlighting an effective antioxidant capacity of amiodarone in vivo.

Amiodarone did not change lipoprotein vitamin E and phospholipid content in vivo and did not show scavenging effects on oxidizing species involved in lipoprotein oxidation, such as peroxyl radicals, nor metal‐binding/inactivating properties, suggesting that physicochemical modifications of lipoprotein lipids induced by the lipophilic drug may be involved in its antioxidant activity.

In conclusion, amiodarone, and its primary metabolite desethylamiodarone, show previously unrecognized antioxidant activity on human lipoprotein oxidation. This effect is also evident in vivo and at therapeutically achievable drug concentrations. Thus, amiodarone may act as an antioxidant/antiatherosclerotic agent in humans, although this issue warrants further clinical study.

British Journal of Pharmacology (2001) 133, 739–745; doi:10.1038/sj.bjp.0704126
Relaxation to authentic nitric oxide and SIN‐1 in rat isolated mesenteric arteries: variable role for smooth muscle hyperpolarization
Authors: Plane Frances , Sampson Laura J , Smith Jennifer J , Garland Christopher J
Published: January 2005

Authentic nitric oxide (NO; 0.1–10 μmoles) caused transient, dose‐dependent relaxation of phenylephrine‐induced tone without changing membrane potential in mesenteric arteries. Larger doses, above 10 μmoles, did not evoke more relaxation (maximal relaxation to 150 μmoles NO in denuded arteries, 69±7%, n=8) but stimulated muscle hyperpolarization (maximum 19±3 mV, n=5).

The soluble guanylyl cyclase inhibitor, 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ; 10 μM), abolished relaxation to low doses of NO (n=4), but did not modify hyperpolarization with higher doses of NO (n=4). The potassium channel blocker charybdotoxin (ChTX; 50 nM) abolished hyperpolarization to high doses of NO and significantly reduced the maximal relaxation (to 43±6%, n=4; P<0.01). ODQ and ChTX together abolished tension and membrane potential change to all doses of NO (n=4).

All relaxations to 3‐morpholino‐sydnonimine (SIN‐1; 0.01–10 μM) were associated with hyperpolarization. When the endothelium was intact, ChTX inhibited hyperpolarization and relaxation to SIN‐1 (n=5), while iberiotoxin (IbTX; 50 nM) or 4‐aminopyridine (4‐AP; 500 μM) reduced relaxation by 40% and 20%, respectively and by 80% in combination (n=6 in each case).

In denuded arteries, relaxation to SIN‐1 was unaffected by either ChTX or ODQ alone, but abolished by the inhibitors together (n=6). Alone, 4‐AP did not alter relaxation, but in the presence of ODQ it reduced the maximal response by around 45% (n=6; P<0.01). 4‐AP, ODQ and IbTX together inhibited relaxation to SIN‐1 by 75% (n=6; P<0.01).

Therefore, cyclic guanosine 3′,5′‐monophosphate (cyclic GMP)‐independent smooth muscle hyperpolarization, possibly involving direct activation of calcium‐activated and voltage‐sensitive potassium channels, contributes to relaxation evoked by authentic NO and SIN‐1. However, the importance of each pathway depends on the source of NO and with SIN‐1 the relative contribution from each pathway is modified by the endothelium.

British Journal of Pharmacology (2001) 133, 665–672; doi:10.1038/sj.bjp.0704127
Nipecotic acid directly activates GABAA‐like ion channels
Authors: Barrett‐Jolley R
Published: January 2005

The GABA‐related compound nipecotic acid is commonly used to inhibit GABA uptake. This report shows that nipecotic acid can also directly activate GABAA‐like chloride channels.

When applied to outside‐out patches of paraventricular neurones, nipecotic acid (1 mM) activated inward unitary currents (approximately 3 pA at a holding potential of −60 mV, ECl+44 mV).

The EC50 for ion channel activation was approximately 300 μM, 3 fold greater than that found for GABA itself in this preparation.

The nipecotic acid activated channels had similar conductance and kinetic properties to those of GABA activated channels in the same patches, reversed near ECl and were inhibited by bicuculline (3 μM).

This study indicates that for experiments in which relatively high concentrations of nipecotic acid are used, possible direct GABAA receptor agonist properties should be considered.

British Journal of Pharmacology (2001) 133, 673–678; doi:10.1038/sj.bjp.0704128
Functional characterization of α1‐adrenoceptor subtypes in human skeletal muscle resistance arteries
Authors: Jarajapu Yagna P R , Coats Paul , McGrath John C , Hillier Chris , MacDonald Allan
Published: January 2005

α1‐adrenoceptor subtypes in human skeletal muscle resistance arteries were characterized using agonists noradrenaline (non‐selective) and A61603 (α1A‐selective), the antagonists prazosin (non‐selective), 5‐methyl‐urapidil (α1A‐selective) and BMY7378 (α1D‐selective) and the alkylating agent chloroethylclonidine (preferential for α1B).

Small arteries were obtained from the non‐ischaemic skeletal muscle of limbs amputated for critical limb ischaemia and isometric tension recorded using wire myography.

Prazosin antagonized responses to noradrenaline with a pA2 value of 9.18, consistent with the presence of α1‐adrenoceptors, although the Schild slope (1.32) was significantly different from unity.

5‐Methyl‐urapidil competitively antagonized responses to noradrenaline with a pKB value of 8.48 and a Schild slope of 0.99, consistent with the presence of α1A‐adrenoceptors. In the presence of 300 nM 5‐methyl‐urapidil, noradrenaline exhibited biphasic concentration response curves, indicating the presence of a minor population of a 5‐methyl‐urapidil‐resistant subtype.

Contractile responses to noradrenaline were not affected by 1 μM chloroethylclonidine suggesting the absence of α1B‐adrenoceptors. Maximum responses to noradrenaline and A61603 were reduced to a similar extent by 10 μM chloroethylclonidine, suggesting an effect of chloroethylclonidine at α1A‐adrenoceptors at the higher concentration.

BMY7378 (10 and 100 nM) had no effect on responses to noradrenaline. BMY7378 (1 μM) poorly shifted the potency of noradrenaline giving a pA2 of 6.52. These results rule out the presence of the α1D‐subtype.

These results show that contractile responses to noradrenaline in human skeletal muscle resistance arteries are predominantly mediated by the α1A‐adrenoceptor subtype with a minor population of an unknown α1‐adrenoceptor subtype.

British Journal of Pharmacology (2001) 133, 679–686; doi:10.1038/sj.bjp.0704130
SB‐272183, a selective 5‐HT1A, 5‐HT1B and 5‐HT1D receptor antagonist in native tissue
Authors: Watson J , Roberts C , Scott C , Kendall I , Collin L , Day N C , Harries M H , Soffin E , Davies C H , Randall A D , Heightman T , Gaster L , Wyman P , Parker C , Price G W , Middlemiss D N
Published: January 2005

A novel compound, SB‐272183 (5‐Chloro‐2, 3‐dihydro‐6‐[4‐methylpiperazin‐1‐yl]‐1[4‐pyridin‐4‐yl]napth‐1‐ylaminocarbonyl]‐1H‐indole), has been shown to have high affinity for human 5‐HT1A, 5‐HT1B and 5‐HT1D receptors with pKi values of 8.0, 8.1 and 8.7 respectively and is at least 30 fold selective over a range of other receptors.

[35S]‐GTPγS binding studies showed that SB‐272183 acts as a partial agonist at human recombinant 5‐HT1A, 5‐HT1B and 5‐HT1D receptors with intrinsic activities of 0.4, 0.4 and 0.8 respectively, compared to 5‐HT. SB‐272183 inhibited 5‐HT‐induced stimulation of [35S]‐GTPγS binding at human 5‐HT1A and 5‐HT1B receptors to give pA2 values of 8.2 and 8.5 respectively. However, from [35S]‐GTPγS autoradiographic studies in rat and human dorsal raphe nucleus, SB‐272183 did not display intrinsic activity up to 10 μM but did block 5‐HT‐induced stimulation of [35S]‐GTPγS binding.

From electrophysiological studies in rat raphe slices in vitro, SB‐272183 did not effect cell firing rate up to 1 μM but was able to attenuate (+)8‐OH‐DPAT‐induced inhibition of cell firing to give an apparent pKb of 7.1.

SB‐272183 potentiated electrically‐stimulated [3H]‐5‐HT release from rat and guinea‐pig cortical slices at 100 and 1000 nM, similar to results previously obtained with the 5‐HT1B and 5‐HT1D receptor antagonist, GR127935.

Fast cyclic voltammetry studies in rat dorsal raphe nucleus showed that SB‐272183 could block sumatriptan‐induced inhibition of 5‐HT efflux, with an apparent pKb of 7.2, but did not effect basal efflux up to 1 μM.

These studies show that, in vitro, SB‐272183 acts as an antagonist at native tissue 5‐HT1A, 5‐HT1B and 5‐HT1D receptors.

British Journal of Pharmacology (2001) 133, 797–806; doi:10.1038/sj.bjp.0704133
Augmented acetylcholine‐induced translocation of RhoA in bronchial smooth muscle from antigen‐induced airway hyperresponsive rats
Authors: Chiba Yoshihiko , Sakai Hiroyasu , Misawa Miwa
Published: January 2005

Acetylcholine (ACh)‐induced translocation of RhoA in bronchial smooth muscle of repeatedly antigen‐challenged rats that have a marked airway hyperresponsiveness (AHR) was examined.

ACh induced time‐ and concentration‐dependent translocation of RhoA to the plasma membrane, indicating an activation of RhoA in bronchial smooth muscle.

The level of ACh‐induced RhoA translocation was further increased markedly in the AHR group as compared to that in the control group.

It is suggested that the augmented activation of RhoA observed in the hyperresponsive bronchial smooth muscle might be responsible for the enhanced ACh‐induced Ca2+ sensitization of bronchial smooth muscle contraction associated with AHR.

British Journal of Pharmacology (2001) 133, 886–890; doi:10.1038/sj.bjp.0704137
Endogenous sulphur‐containing amino acids: potent agonists at presynaptic metabotropic glutamate autoreceptors in the rat central nervous system
Authors: Croucher Martin J , Thomas Lisa S , Ahmadi Hootan , Lawrence Victoria , Harris John R
Published: January 2005

We have recently demonstrated that presynaptically located metabotropic glutamate (mGlu) autoreceptors regulate synaptic glutamate release both in vitro and in vivo. We now report a positive modulatory action of the sulphur‐containing amino acids (SCAAs), L‐cysteic acid (CA) and L‐cysteine sulphinic acid (CSA), at presynaptic group I mGlu receptors, specifically of the mGlu5 subtype, acting to enhance synaptic glutamate release from the rat forebrain in vitro.

Neuronal glutamate release was monitored using electrically‐evoked efflux of preloaded [3H]‐D‐aspartate from rat forebrain hemisections.

Both CA (3 – 100 μM) and CSA (1 – 100 μM), in addition to the selective group I mGlu receptor agonist, (S)‐3,5‐dihydroxyphenylglycine ((S)‐DHPG), concentration‐dependently enhanced electrically‐stimulated efflux of [3H]‐D‐aspartate from the rat forebrain slices. Basal efflux of label remained unchanged.

The inhibitory activity of the broad spectrum mGlu receptor antagonist, (±)‐α‐methyl‐4‐carboxyphenylglycine ((±)‐MCPG; 200 μM), coupled with the inactivity of the selective mGlu1 receptor antagonists, (R,S)‐1‐aminoindan‐1,5‐dicarboxylic acid ((R,S)‐AIDA; 100 – 500 μM) and the more potent (+)‐2‐methyl‐4‐carboxyphenylglycine (LY367385; 10 μM) against these responses, indicates an action of the SCAAs at the mGlu5 receptor subtype. This proposal is supported by the potent inhibition of these responses by the selective, non‐competitive mGlu5 receptor antagonist, 2‐methyl‐6‐(phenylethynyl)pyridine (MPEP; 10 μM). The observed enhancement of the responses to high concentrations of CA by the selective mGlu5 receptor desensitization inhibitor, cyclothiazide (CYZ; 10 μM), is also consistent with this concept.

Administration of the agonists in the presence of bovine serum albumin (BSA; 5 – 15 mg ml−1) markedly attenuated the positive modulatory responses observed, strongly supporting a role for arachidonic acid in the expression of these mGlu5 receptor‐mediated responses.

The regulatory actions of SCAAs on synaptic glutamate release demonstrated in the present study may provide a physiological function for these putative neurotransmitter amino acids in the mammalian brain. These central actions of the SCAAs may have wide‐ranging implications for a range of neurological and neuropsychiatric disease states and their treatment.

British Journal of Pharmacology (2001) 133, 815–824; doi:10.1038/sj.bjp.0704138
Identification of two distinct vasodilator pathways activated by ATP in the mesenteric bed of the rat
Authors: Stanford Salome J , Gitlin Jonathan M , Mitchell Jane A
Published: January 2005

Adenosine 5′‐triphosphate (ATP) has important roles in the cardiovascular system, modulating vascular tone by acting as both a vasoconstrictor and a vasodilator.

The dilator function of ATP is traditionally thought to be monophasic and mediated primarily by nitric oxide (NO).

Here we have identified the endothelium‐dependent biphasic nature of ATP‐induced vasodilatation of the rat isolated mesenteric bed and investigated the two distinct pathways involved.

ATP, at doses of 1×10−11 to 1×10−8 moles, induced transient relaxations that were inhibited by the NO synthase (NOS) inhibitor, NG‐nitro‐L‐arginine methyl ester (L‐NAME: 1×10−4 M), the soluble guanylyl cyclase inhibitor, 1H‐[1,2,4]Oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ: 3×10−6 M) and KCl (6×10−2 – 1.2×10−1 M).

At doses upwards of 1×10−8 moles (1×10−8 – 3×10−7 moles), ATP also induced prolonged vasodilatations which were unaltered by L‐NAME, L‐NAME (1×10−3 M) and indomethacin (1×10−5 M), or by ODQ, but were abolished in the presence of KCl.

In addition, the cannabinoid CB1 receptor antagonist SR141716A (1×10−5 M) was found to inhibit the second prolonged phase of vasodilatation. However, at the concentration used SR141716A is reported to be non‐selective. A second CB1 receptor antagonist, AM251 (1×10−6 M), had a small but significant inhibitory effect on the second phase of ATP‐induced vasodilatation. SR141716A, AM251 and KCl (6×10−2 – 1.2×10−1 M) all inhibited anandamide‐induced relaxation of the isolated mesenteric bed.

These observations demonstrate that ATP stimulates vasodilatation of the mesenteric bed by two distinct mechanisms involving the release of NO and an EDHF. In the absence of better pharmacological tools we can only speculate as to the involvement of an endogenous CB1 receptor ligand in these responses.

British Journal of Pharmacology (2001) 133, 825–832; doi:10.1038/sj.bjp.0704139
Endothelium‐derived hyperpolarizing factor and potassium use different mechanisms to induce relaxation of human subcutaneous resistance arteries
Authors: McIntyre C‐A , Buckley C H , Jones G C , Sandeep T C , Andrews R C , Elliott A I , Gray G A , Williams B C , McKnight J A , Walker B R , Hadoke P W F
Published: January 2005

This investigation examined the hypothesis that release of K+ accounts for EDHF activity by comparing relaxant responses produced by ACh and KCl in human subcutaneous resistance arteries.

Resistance arteries (internal diameter 244±12 μm, n=48) from human subcutaneous fat biopsies were suspended in a wire myograph. Cumulative concentration‐response curves were obtained for ACh (10−9 – 3×10−5 M) and KCl (2.5 – 25 mM) following contraction with noradrenaline (NA; 0.1 – 3 μM).

ACh (Emax 99.07±9.61%; −LogIC50 7.03±0.22; n=9) and KCl (Emax 74.14±5.61%; −LogIC50 2.12±0.07; n=10)‐induced relaxations were attenuated (P<0.0001) by removal of the endothelium (Emax 8.21±5.39% and 11.56±8.49%, respectively; n=6 – 7).

Indomethacin (10 μM) did not alter ACh‐induced relaxation whereas L‐NOARG (100 μM) reduced this response (Emax 61.7±3.4%, P<0.0001; n=6). The combination of ChTx (50 nM) and apamin (30 nM) attenuated the L‐NOARG‐insensitive component of ACh‐induced relaxation (Emax: 15.2±10.5%, P<0.002, n=6) although these arteries retained the ability to relax in response to 100 μM SIN‐1 (Emax 127.6±13.0%, n=3). Exposure to BaCl2 (30 μM) and Ouabain (1 mM) did not attenuate the L‐NOARG resistant component of ACh‐mediated relaxation (Emax, 76.09±8.92, P=0.16; n=5).

KCl‐mediated relaxation was unaffected by L‐NOARG+indomethacin (Emax; 68.1±5.6%, P=0.33; n=5) or the combination of L‐NOARG/indomethacin/ChTx/apamin (Emax; 86.61±14.02%, P=0.35; n=6). In contrast, the combination of L‐NOARG, indomethacin, ouabain and BaCl2 abolished this response (Emax, 5.67±2.59%, P<0.0001, n=6).

The characteristics of KCl‐mediated relaxation differed from those of the nitric oxide/prostaglandin‐independent component of the response to ACh, and were endothelium‐dependent, indicating that K+ does not act as an EDHF in human subcutaneous resistance arteries.

British Journal of Pharmacology (2001) 133, 902–908; doi:10.1038/sj.bjp.0704143
Modulation of haem oxygenase‐1 expression by nitric oxide and leukotrienes in zymosan‐activated macrophages
Authors: Vicente Ana María , Guillén María Isabel , Alcaraz María José
Published: January 2005

Phagocytosis of unopsonized zymosan by RAW 264.7 macrophages upregulated protein expression of haem oxygenase‐1 (HO‐1), inducible nitric oxide synthase (iNOS) and cyclo‐oxygenase‐2 (COX‐2) in a time‐ and concentration‐dependent manner.

In the presence of zymosan, exogenous prostaglandin E2 (PGE2) did not exert significant effects on the expression of these three enzymes. In contrast, exogenous leukotriene B4 (LTB4) and LTC4 in the nanomolar range inhibited HO‐1 and iNOS expression, as well as nitrite accumulation.

The COX inhibitors indomethacin and NS398 weakly inhibited HO‐1 expression but had no effect on iNOS and COX‐2 expression or nitrite. In contrast, the 5‐lipoxygenase (5‐LO) inhibitor ZM 230,487 significantly decreased HO‐1, iNOS and nitrite, which were not affected by zileuton. Dexamethasone showed an inhibitory effect on HO‐1 expression induced by zymosan.

ZM 230,487 but not zileuton, inhibited the shift due to nuclear factor‐κB (NF‐κB), whereas they did not modify activator protein‐1 (AP‐1) binding. Our results suggest that inhibition of NF‐κB binding could mediate the effects of ZM 230,487 on the modulation of HO‐1 and iNOS protein expression.

NOS inhibition by L‐NG‐nitroarginine methyl ester (L‐NAME) or 1400 W abolished nitrite production and strongly reduced HO‐1 expression. These results show an induction of HO‐1 protein expression by zymosan phagocytosis in macrophages, with a positive modulatory role for endogenous NO and a negative regulation by exogenous LTs, likely dependent on the reduction of iNOS expression and NO production.

British Journal of Pharmacology (2001) 133, 920–926; doi:10.1038/sj.bjp.0704145
Ibudilast attenuates astrocyte apoptosis via cyclic GMP signalling pathway in an in vitro reperfusion model
Authors: Takuma K , Lee E , Enomoto R , Mori K , Baba A , Matsuda T
Published: January 2005

We examined the effect of 3‐isobutyryl‐2‐isopropylpyrazolo[1,5‐a]pyridine (ibudilast), which has been clinically used for bronchial asthma and cerebrovascular disorders, on cell viability induced in a model of reperfusion injury.

Ibudilast at 10 – 100 μM significantly attenuated the H2O2‐induced decrease in cell viability.

Ibudilast inhibited the H2O2‐induced cytochrome c release, caspase‐3 activation, DNA ladder formation and nuclear condensation, suggesting its anti‐apoptotic effect.

Phosphodiesterase inhibitors such as theophylline, pentoxyfylline, vinpocetine, dipyridamole and zaprinast, which increased the guanosine‐3′,5′‐cyclic monophosphate (cyclic GMP) level, and dibutyryl cyclic GMP attenuated the H2O2‐induced injury in astrocytes.

Ibudilast increased the cyclic GMP level in astrocytes.

The cyclic GMP‐dependent protein kinase inhibitor KT5823 blocked the protective effects of ibudilast and dipyridamole on the H2O2‐induced decrease in cell viability, while the cyclic AMP‐dependent protein kinase inhibitor KT5720, the cyclic AMP antagonist Rp‐cyclic AMPS, the mitogen‐activated protein/extracellular signal‐regulated kinase inhibitor PD98059 and the leukotriene D4 antagonist LY 171883 did not.

KT5823 also blocked the effect of ibudilast on the H2O2‐induced cytochrome c release and caspase‐3‐like protease activation.

These findings suggest that ibudilast prevents the H2O2‐induced delayed apoptosis of astrocytes via a cyclic GMP, but not cyclic AMP, signalling pathway.

British Journal of Pharmacology (2001) 133, 841–848; doi:10.1038/sj.bjp.0704146
Effects of sufentanil and NMDA antagonists on a C‐fibre reflex in the rat
Authors: Adam Frédéric , Gairard Anne Cécile , Chauvin Marcel , Bars Daniel Le , Guirimand Frédéric
Published: January 2005

The effects of intravenous sufentanil and pre‐administration of N‐methyl‐D‐aspartate (NMDA) receptor antagonists were tested on a reflex triggered by C‐fibre activation. The reflex was elicited by electrical stimulation of the sural nerve and recorded from the ipsilateral biceps femoris muscle in halothane anaesthetized rats either (1) with an intact neuraxis or (2) in which the brain had previously been transected at the level of the obex.

All four doses of sufentanil (0.33, 0.6, 1 and 2 μg kg−1) elicited a depression of the reflex in a dose‐dependent manner. However, following the expected depression, all doses of sufentanil elicited both facilitation of the reflex and tonic inter‐stimulus discharges.

The C‐fibre reflex was not modified following intravenous ketamine (1 mg kg−1) or (+)‐HA966 (5 or 10 mg kg−1) but, when administered 5 min before sufentanil, these drugs enhanced both the extent and the duration of the depression and strongly reduced the facilitations.

In the obex‐transected rats, the depressive effect of 1 μg kg−1 sufentanil increased, while the facilitation of the C‐fibre reflex and the tonic inter‐stimulus discharges disappeared. Pre‐administration of 10 mg kg−1 (+)‐HA966 reinforced and prolonged the depressive effect of sufentanil.

These results extend previous studies suggesting the involvement of NMDA receptors in the spinal transmission of nociceptive signals. They illustrate the potential of spinal NMDA receptor blockade to both enhance the analgesic, and prevent the pro‐nociceptive, effects of sufentanil.

British Journal of Pharmacology (2001) 133, 1013–1022; doi:10.1038/sj.bjp.0704148
Role of the extracellular signal‐regulated kinase (Erk) signal transduction cascade in α2 adrenoceptor‐mediated vasoconstriction in porcine palmar lateral vein
Authors: Roberts R E
Published: January 2005

The mechanism of α2 adrenoceptor‐mediated vasoconstriction is unknown, but may involve activation of voltage‐sensitive calcium channels, and/or a protein tyrosine kinase. Recently the extracellular signal‐regulated kinase (Erk) cascade, often an event downstream of tyrosine kinase activation, has been shown to mediate vasoconstriction to a variety of agents. The aim of this present study was to determine the involvement of the Erk signal transduction cascade in α2 adrenoceptor‐mediated vasoconstriction, and to confirm the involvement of activation of voltage‐sensitive calcium channels, and protein tyrosine kinase.

Contractions to the α2 adrenoceptor agonist UK14304 in the porcine palmar lateral vein in vitro were reduced 70 – 80% by the MEK inhibitors PD98059 (10 – 50 μM) and U0126 (10 – 50 μM), indicating the involvement of the Erk signal transduction cascade. Immunoblots also demonstrated an increase in the phosphorylated (activated) form of Erk in palmar lateral vein segments after contraction with UK14304, which was inhibited by PD98059 and U0126.

The calcium channel blockers nifedipine and verapamil, or removal of extracellular calcium inhibited UK14304‐induced contractions and phosphorylation of Erk, demonstrating the importance of an influx of extracellular calcium. UK14304‐induced contractions were inhibited by PP2 (1 – 10 μM), a selective inhibitor of Src tyrosine kinases, but not by PP3, an inactive analogue. PP2 also prevented the phosphorylation of Erk by UK14304.

These data demonstrate that α2 adrenoceptor‐mediated vasoconstriction in the porcine palmar lateral vein is dependent upon activation of the Erk signal transduction cascade, which is downstream of an influx of extracellular calcium, and activation of Src tyrosine kinases.

British Journal of Pharmacology (2001) 133, 859–866; doi:10.1038/sj.bjp.0704149
Inhibition of DNA synthesis in cultured hepatocytes by endotoxin‐conditioned medium of activated stellate cells is transforming growth factor‐β and nitric oxide‐independent
Authors: Uemura Tadahiro , Gandhi Chandrashekhar R
Published: January 2005

Activated hepatic stellate cells play a major role in the pathophysiology of chronic liver disease. They can influence the metabolism of hepatocytes by producing a variety of cytokines and growth factors. Upon stimulation with endotoxin, stellate cells also synthesize nitric oxide (NO), a potent mediator of growth of several cell types including hepatocytes.

We investigated the effect of serum‐free medium conditioned by activated stellate cells in the absence and presence of endotoxin on NO and DNA synthesis in hepatocytes. Stellate cells and hepatocytes were isolated by enzymatic digestion of the liver. Stellate cells were cultured for 10 days after which the majority exhibited α‐smooth muscle actin (a marker for activated cells); hepatocytes were used after overnight culture.

While the medium conditioned by stellate cells in the absence of endotoxin stimulated DNA synthesis in hepatocytes, medium conditioned in its presence inhibited this process in an endotoxin concentration‐dependent manner (10–1000 ng ml−1). Endotoxin‐conditioned stellate cell medium also stimulated NO synthesis in hepatocytes; the effect was consistent with increased protein and mRNA expression of inducible NO synthase (iNOS). However, inhibition of DNA synthesis in hepatocytes caused by endotoxin‐conditioned stellate cell medium was unaffected by the NOS inhibitor, L‐NG‐monomethylarginine (L‐NMMA), guanylyl cyclase inhibitor 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ), and neutralizing antibodies for TGF‐β, IL‐1β, IL‐6 and TNF‐α.

These results indicate that factors other than these cytokines produced by activated stellate cells upon stimulation with endotoxin or by hepatocytes challenged with endotoxin‐conditioned stellate cell medium inhibit DNA synthesis in hepatocytes.

British Journal of Pharmacology (2001) 133, 1125–1133; doi:10.1038/sj.bjp.0704151
Agonists of proteinase‐activated receptor 1 induce plasma extravasation by a neurogenic mechanism
Authors: Garavilla Lawrence de , Vergnolle Nathalie , Young Steven H , Ennes Helena , Steinhoff Martin , Ossovskaya Valeria S , D'Andrea Michael R , Mayer Emeran A , Wallace John L , Hollenberg Morley D , Andrade‐Gordon Patricia , Bunnett Nigel W
Published: January 2005

Thrombin, generated in the circulation during injury, cleaves proteinase‐activated receptor 1 (PAR1) to stimulate plasma extravasation and granulocyte infiltration. However, the mechanism of thrombin‐induced inflammation in intact tissues is unknown. We hypothesized that thrombin cleaves PAR1 on sensory nerves to release substance P (SP), which interacts with the neurokinin 1 receptor (NK1R) on endothelial cells to cause plasma extravasation.

PAR1 was detected in small diameter neurons known to contain SP in rat dorsal root ganglia by immunohistochemistry and in situ hybridization.

Thrombin and the PAR1 agonist TFLLR‐NH2 (TF‐NH2) increased [Ca2+]i >50% of cultured neurons (EC50s 24 mu ml−1 and 1.9 μM, respectively), assessed using Fura‐2 AM. The PAR1 agonist completely desensitized responses to thrombin, indicating that thrombin stimulates neurons through PAR1.

Injection of TF‐NH2 into the rat paw stimulated a marked and sustained oedema. An NK1R antagonist and ablation of sensory nerves with capsaicin inhibited oedema by 44% at 1 h and completely by 5 h.

In wild‐type but not PAR1−/− mice, TF‐NH2 stimulated Evans blue extravasation in the bladder, oesophagus, stomach, intestine and pancreas by 2–8 fold. Extravasation in the bladder, oesophagus and stomach was abolished by an NK1R antagonist.

Thus, thrombin cleaves PAR1 on primary spinal afferent neurons to release SP, which activates the NK1R on endothelial cells to stimulate gap formation, extravasation of plasma proteins, and oedema. In intact tissues, neurogenic mechanisms are predominantly responsible for PAR1‐induced oedema.

British Journal of Pharmacology (2001) 133, 975–987; doi:10.1038/sj.bjp.0704152
Further investigations into the endothelium‐dependent hyperpolarizing effects of bradykinin and substance P in porcine coronary artery
Authors: Edwards G , Félétou M , Gardener M J , Glen C D , Richards G R , Vanhoutte P M , Weston A H
Published: January 2005

In porcine coronary arteries, smooth muscle hyperpolarizations produced by the nitric oxide donor, NOR‐1, and the prostacyclin analogue, iloprost, were compared with those induced by substance P and bradykinin and attributed to the endothelium‐derived hyperpolarizing factor (EDHF).

In the presence of 300 μM L‐nitroarginine and 10 μM indomethacin, iloprost‐induced hyperpolarizations were partially inhibited by 10 μM glibenclamide whereas those to NOR‐1, substance P and bradykinin were unaffected.

Hyperpolarizations produced by maximally‐effective concentrations of NOR‐1 and NS1619 were identical (to −65 mV). They were significantly less than those generated by either substance P or bradykinin (to approximately −80 mV) and were abolished by iberiotoxin 100 nM, a concentration which had essentially no effect on responses to substance P or bradykinin.

Incubation of segments of intact arteries for 16–22 h in bicarbonate‐buffered Krebs solution had little effect on EDHF responses to substance P or bradykinin. In contrast, after incubation for this period of time in HEPES‐buffered Tyrode solution or Krebs containing 10 mM HEPES the EDHF response to substance P was abolished and that to bradykinin was markedly reduced. The residual bradykinin‐induced hyperpolarization following incubation in Tyrode solution was inhibited by iberiotoxin and by 10 μM 17‐octadecynoic acid.

We conclude that substance P activates only the EDHF pathway in the presence of nitric oxide synthase and cyclo‐oxygenase inhibitors. Incubation in HEPES‐buffered Tyrode solution abolishes the EDHF responses to substance P and bradykinin to reveal an additional hyperpolarizing mechanism, associated with the opening of K+ channels, activated only by bradykinin.

British Journal of Pharmacology (2001) 133, 1145–1153; doi:10.1038/sj.bjp.0704157
Phloretin differentially inhibits volume‐sensitive and cyclic AMP‐activated, but not Ca‐activated, Cl− channels
Authors: Fan Hai‐Tian , Morishima Shigeru , Kida Hajime , Okada Yasunobu
Published: January 2005

Some phenol derivatives are known to block volume‐sensitive Cl− channels. However, effects on the channel of the bisphenol phloretin, which is a known blocker of glucose uniport and anion antiport, have not been examined. In the present study, we investigated the effects of phloretin on volume‐sensitive Cl− channels in comparison with cyclic AMP‐activated CFTR Cl− channels and Ca2+‐activated Cl− channels using the whole‐cell patch‐clamp technique.

Extracellular application of phloretin (over 10 μM) voltage‐independently, and in a concentration‐dependent manner (IC50 ∼30 μM), inhibited the Cl− current activated by a hypotonic challenge in human epithelial T84, Intestine 407 cells and mouse mammary C127/CFTR cells.

In contrast, at 30 μM phloretin failed to inhibit cyclic AMP‐activated Cl− currents in T84 and C127/CFTR cells. Higher concentrations (over 100 μM) of phloretin, however, partially inhibited the CFTR Cl− currents in a voltage‐dependent manner.

At 30 and 300 μM, phloretin showed no inhibitory effect on Ca2+‐dependent Cl− currents induced by ionomycin in T84 cells.

It is concluded that phloretin preferentially blocks volume‐sensitive Cl− channels at low concentrations (below 100 μM) and also inhibits cyclic AMP‐activated Cl− channels at higher concentrations, whereas phloretin does not inhibit Ca2+‐activated Cl− channels in epithelial cells.

British Journal of Pharmacology (2001) 133, 1096–1106; doi:10.1038/sj.bjp.0704159
Direct effect of an acyl‐CoA:cholesterol acyltransferase inhibitor, F‐1394, on atherosclerosis in apolipoprotein E and low density lipoprotein receptor double knockout mice
Authors: Chiwata Tsuyoshi , Aragane Katsumi , Fujinami Koji , Kojima Kazuhiro , Ishibashi Shun , Yamada Nobuhiro , Kusunoki Jun
Published: January 2005

The acyl‐CoA:cholesterol acyltransferase (ACAT) enzyme is thought to be responsible for foam cell formation and the subsequent progression of atherosclerosis. The apolipoprotein E and low density lipoprotein receptor double knockout (apoE/LDLr‐DKO) mouse is an animal model that develops severe hyperlipidaemia and atherosclerosis.

Here we have examined the effect of oral administration of an ACAT inhibitor, F‐1394, on atherosclerosis in apoE/LDLr‐DKO mice fed a regular chow diet.

In en face analysis, a dose of 10, 30, or 100 mg kg−1 day−1 F‐1394 for 10 weeks reduced the extent of lesions visible in the aorta by 24, 28 and 38%, respectively, as detected by staining with oil red O, without affecting serum cholesterol level in these mice. At the highest dose 100 mg kg−1 day−1 of F‐1394, the reduction was statistically significant.

For quantitative analysis of the cellular and non‐cellular components comprising the lesions at the aortic sinus, the effects of an oral dose of 100 mg kg−1 day−1 F‐1394 for 15 weeks were studied. There was a significant reduction (31.9%) in the oil‐red O‐stained area in cross‐sections of the aortic sinus. In addition, the neointimal area, as well as levels of ACAT‐1 protein tended to be decreased (15.2 and 25.8%, respectively, not significant). However, the areas containing macrophages, smooth muscle cells, and collagen were not affected by F‐1394.

In vitro, F‐1394 attenuated foam cell formation in mouse peritoneal macrophages.

These results indicate that ACAT may be primarily responsible for lipid accumulation in atherosclerotic lesions, and that its inhibition diminishes the lipid deposition via a direct effect on macrophages in the arterial wall.

British Journal of Pharmacology (2001) 133, 1005–1012; doi:10.1038/sj.bjp.0704160
The anti‐migraine 5‐HT1B/1D agonist rizatriptan inhibits neurogenic dural vasodilation in anaesthetized guinea‐pigs
Authors: Williamson David J , Hill Raymond G , Shepheard Sara L , Hargreaves Richard J
Published: January 2005

These studies investigated the pharmacology of neurogenic dural vasodilation in anaesthetized guinea‐pigs. Following introduction of a closed cranial window the meningeal (dural) blood vessels were visualized using intravital microscopy and the diameter constantly measured using a video dimension analyser.

Dural blood vessels were constricted with endothelin‐1 (3 μg kg−1, i.v.) prior to dilation of the dural blood vessels with calcitonin gene‐related peptide (CGRP; 1 μg kg−1, i.v.) or local electrical stimulation (up to 300 μA) of the dura mater.

In guinea‐pigs pre‐treated with the CGRP receptor antagonist CGRP(8‐37) (0.3 mg kg−1, i.v.) the dilator response to electrical stimulation was inhibited by 85% indicating an important role of CGRP in neurogenic dural vasodilation in this species.

Neurogenic dural vasodilation was also blocked by the 5‐HT1B/1D agonist rizatriptan (100 μg kg−1) with estimated plasma levels commensurate with concentrations required for anti‐migraine efficacy in patients. Rizatriptan did not reverse the dural dilation evoked by CGRP indicating an action on presynaptic receptors located on trigeminal sensory fibres innervating dural blood vessels.

In addition, neurogenic dural vasodilation was also blocked by the selective 5‐HT1D agonist PNU‐142633 (100 μg kg−1) but not by the 5‐HT1F agonist LY334370 (3 mg kg−1) suggesting that rizatriptan blocks neurogenic vasodilation via an action on 5‐HT1D receptors located on perivascular trigeminal nerves to inhibit CGRP release.

This mechanism may underlie one of the anti‐migraine actions of the triptan class exemplified by rizatriptan and suggests that the guinea‐pig is an appropriate species in which to investigate the pharmacology of neurogenic dural vasodilation.

British Journal of Pharmacology (2001) 133, 1029–1034; doi:10.1038/sj.bjp.0704162
Induction of cyclo‐oxygenase‐2 in human endothelial cells by SIN‐1 in the absence of prostaglandin production
Authors: Eligini Sonia , Habib Aïda , Lebret Marilyne , Créminon Christophe , Lévy‐Toledano Sylviane , Maclouf Jacques
Published: January 2005

Nitric oxide (NO) regulates cyclo‐oxygenase (COX) activity in various cell systems and reports conflict in regard to its stimulatory versus inhibitory role. Incubation of human umbilical vein endothelial cells (HUVEC) with SIN‐1 (3‐morpholinosydnonimine), a donor of NO, resulted in a rapid and dose‐dependent increase in the expression of COX‐2 as analysed by Western and Northern blotting.

Incubation of HUVEC with SIN‐1 and interleukine (IL)‐1α resulted in increased induction of COX‐2 compared with IL‐1α alone and corresponded to an additive effect. The COX‐2 induction was dependent on a de novo synthesis since cycloheximide, an inhibitor of protein synthesis, blocked the enzyme expression. The increase in COX‐2 expression was not accompanied by a corresponding change in prostaglandin (PG) production. However, the COX activity was partially recovered when immunoprecipitated COX‐2 was incubated with arachidonic acid and haematin.

Peroxynitrite, a highly reactive nitrogen molecule derived from the interaction of NO and superoxide anion, significantly increased COX‐2 expression. Under these conditions and within the limit of detection of the antibody, selective antibody for nitrotyrosine failed to detect nitrated COX‐2 in immunoprecipitated COX‐2 when cells where incubated with SIN‐1 or SIN‐1+IL‐1α.

Ro 31‐8220, a specific inhibitor of protein kinase (PK) C, blocked the induction of COX‐2. Also, SB203580, the selective inhibitor of p38 MAP kinase, strongly blocked the induction of COX‐2 by SIN‐1 in the presence or absence of IL‐1α, whereas the MEK‐1 inhibitor, PD 98059, affected it to a lesser extent. These data demonstrate that SIN‐1 induces COX‐2 in HUVEC in the absence of PG formation and suggest a complex regulation of COX‐2 expression and PG formation by NO in endothelial cells.

British Journal of Pharmacology (2001) 133, 1163–1171; doi:10.1038/sj.bjp.0704163
Tachykinin NK2 receptors and enhancement of cholinergic transmission in the inflamed rat colon: an in vivo motility study
Authors: Carini F , Lecci A , Tramontana M , Giuliani S , Maggi C A
Published: January 2005

In the gastrointestinal tract, tachykinin NK2 receptors are localized both on smooth muscle and nerve fibres. NK2 receptor antagonists reduce exaggerated intestinal motility in various diarrhoea models but the site of action contributing to this effect is unknown. In this study we investigated the effects of atropine (1.4 μmol kg−1, i.v.), hexamethonium (13.5 μmol kg−1, i.v.), and nepadutant (0.1 μmol kg−1, i.v.), a selective tachykinin NK2 receptor antagonist, on distension (0.5 and 1 ml)‐, or irritation (acetic acid, 0.5 ml of 7.5% v v−1)‐induced motility in the rat distal colon in vivo. The effects of atropine, hexamethonium or Nω‐nitro‐L‐argininemethylester (L‐NAME, 1.85 μmol kg−1, i.v.) on [βAla8]NKA(4‐10) (10 nmol kg−1, i.v.)‐induced colonic contractions were also investigated.

When the colonic balloon was filled with a subthreshold volume (0.5 ml), the intraluminal instillation of acetic acid triggered a high‐amplitude phasic colonic motility which was partially reduced by nepadutant and suppressed by either hexamethonium or atropine. Filling of the balloon with 1 ml evoked reflex (hexamethonium‐sensitive), atropine‐sensitive phasic colonic motility: nepadutant had no significant effect on the distension‐evoked motility.

Neither hexamethonium nor atropine significantly reduced [βAla8]NKA(4‐10)‐induced colonic contractions, whereas nepadutant suppressed them. Following L‐NAME pretreatment, [βAla8]NKA(4‐10)‐induced colonic contractions were inhibited by both atropine and hexamethonium. In hexamethonium‐pretreated animals, an atropine‐sensitive component of [βAla8]NKA(4‐10)‐induced colonic contractions was also evident.

These results indicate that the application of irritants onto the colonic mucosa induces the release of endogenous tachykinins which enhance excitatory cholinergic mechanisms through the stimulation of NK2 receptors.

British Journal of Pharmacology (2001) 133, 1107–1113; doi:10.1038/sj.bjp.0704164