bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bidirectional effects of the neuroactive steroid tetrahydrodeoxycorticosterone on GABA‐activated Cl− currents in cultured rat hypothalamic neurons
Authors: Wetzel C H R , Vedder H , Holsboer F , Zieglgänsberger W , Deisz R A 
Published: January 2005

The nongenomic effects of tetrahydrodeoxycorticosterone (THDOC; 5‐alpha‐pregnane‐3‐alpha, 21‐diol‐20‐one) were studied in cultured hypothalamic neurons of the rat.
The effects of THDOC (10 nM–1 μM) on responses to different concentrations of exogenously applied GABA and on spontaneous inhibitory postsynaptic currents (IPSCs) were measured with whole‐cell voltage clamp recordings.
Application of GABA induced inward currents with dose‐dependently increasing amplitudes (up to 3.9 nA at a holding potential of −20 mV). High doses of THDOC (100 nM–1 μM) induced small inward currents on its own (14±3 and 24±3 pA, respectively).
Simultaneous application of 10 μM GABA with 100 nM or 1 μM THDOC increased current amplitudes by 125 and 128%, respectively. At 10 nM THDOC exerted no consistent effects on GABA currents.
Responses to 1 μM of GABA were modulated in a bidirectional manner by different doses of THDOC: 10 nM THDOC reduced the amplitude of GABA responses to 80% (P=0.018, n=15), whereas 100 nM and 1 μM THDOC enhanced the GABA response to 115 and 180% (P=0.0007, n=15), respectively.
The time constant of decay of spontaneous inhibitory postsynaptic currents (IPSCs) was reversibly increased from 91±10 to 314±34 ms (n=3) by the application of THDOC (1 μM). The amplitudes of the IPSCs were not affected by THDOC.
These data indicate that THDOC modulates GABA responses of hypothalamic neurons in a bidirectional manner, resulting in a complex tuning of neuronal excitability in the hypothalamus.

British Journal of Pharmacology (1999) 127, 863–868; doi:10.1038/sj.bjp.0702597
The effect of deep pore mutations on the action of phenylalkylamines on the Kv1.3 potassium channel
Authors: Rauer Heiko , Grissmer Stephan 
Published: January 2005

We investigated the action of the phenylalkylamines verapamil and N‐methyl‐verapamil on the Kv1.3 potassium channel using the whole‐cell configuration of the patch‐clamp technique. Our goal was to identify their binding as a prerequisite for using the phenylalkylamines as small, well‐defined molecular probes, not only to expand the structural findings made with peptide toxins or by crystallization, but also to use them as lead compounds for the generation of more potent and therefore more specific K+ channel modulators.
Competition experiments with charybdotoxin, known to interact with external residues of Kv1.3, showed no interaction with verapamil. The internal application of quarternary N‐methyl‐verapamil in combination with verapamil suggested competition for the same internal binding site.
Verapamil affinity was decreased 6 fold by a mutation (M395V) in a region of the internal pore which forms part of the internal tetraethylammonium (TEA+) binding site, although mutations at neighbouring residues (T396 and T397) were without effect.
Modification of C‐type inactivation by mutations in the internal pore suggest that this region participates in the inactivation process.
The action of phenylalkylamines and local anaesthetics on L‐type Ca2+ channels and Na+ channels, respectively, and verapamil on Kv1.3 indicate very similar blocking mechanisms. This might allow the use of these compounds as molecular probes to map the internal vestibule of all three channel types.

British Journal of Pharmacology (1999) 127, 1065–1074; doi:10.1038/sj.bjp.0702599
Halothane enhances exocytosis of [3H]‐acetylcholine without increasing calcium influx in rat brain cortical slices
Authors: Gomez R S , Prado M A M , Carazza F , Gomez M V 
Published: January 2005

The effect of halothane on the release of [3H]‐acetylcholine ([3H]‐ACh) in rat brain cortical slices was investigated.
Halothane (0.018 mM) did not significantly affect the basal and the electrical field stimulation induced release of [3H]‐ACh. However, halothane (0.063 mM) significantly increased the basal release of [3H]‐ACh and this effect was additive with the electrical field stimulation induced release of [3H]‐ACh.
The release of [3H]‐ACh induced by 0.063 mM halothane was independent of the extracellular sodium and calcium ion concentration and was decreased by tetracaine, an inhibitor of Ca2+‐release from intracellular stores or dantrolene, an inhibitor of Ca2+‐release from ryanodine‐sensitive stores.
Using 2‐(4‐phenylpiperidino)‐cyclohexanol (vesamicol), a drug that blocks the storage of ACh in synaptic vesicles, we investigated whether exocytosis of this neurotransmitter is involved in the effect of halothane. Vesamicol significantly decreased the release of [3H]‐ACh evoked by halothane.
It is suggested that halothane may cause a Ca2+ release from intracellular stores that increases [3H]‐ACh exocytosis in rat brain cortical slices.

British Journal of Pharmacology (1999) 127, 679–684; doi:10.1038/sj.bjp.0702603
Microphysiometric analysis of human α1a‐adrenoceptor expressed in Chinese hamster ovary cells
Authors: Taniguchi Takanobu , Inagaki Rika , Murata Satoshi , Akiba Isamu , Muramatsu Ikunobu 
Published: January 2005

The human recombinant α1a‐adrenoceptor (AR) has been stably expressed in Chinese hamster ovary cells. Four stable clones, aH4, aH5, aH6 and aH7, expressing 30, 370, 940 and 2900 fmol AR mg−1 protein, respectively, have been employed to characterize this AR subtype using radioligand binding and microphysiometry to measure extracellular acidification rates.
Noradrenaline (NA) gave concentration‐dependent responses in microphysiometry with increasing extracellular acidification rates. The potency of NA increased as the receptor density increased; pEC50 values of NA for the clones aH4, aH5, aH6 and aH7 were 6.9, 7.5, 7.8 and 8.1, respectively. This increase of potency according to receptor density indicates the presence of spare receptor for NA. Methoxamine, phenylephrine, oxymetazoline and clonidine also gave concentration‐dependent responses with various intrinsic activities.
Antagonists shifted concentration‐response curves for NA rightward in a concentration‐dependent manner. Schild analysis revealed that the affinity profile of this AR subtype to antagonists in the clone aH7 had a typical pattern for the α1a‐AR; high affinity for prazosin and WB 4101, and low affinity for BMY7378 (pA2=9.5, 9.8 and 7.3, respectively). This profile is similar in the case of the clone aH4. These affinities were in good agreement with those obtained in binding experiments.
These results have demonstrated that (1) classical receptor theory can be applied in microphysiometry, and (2) microphysiometry is a useful tool to investigate the pharmacological characterization of α1a‐AR.

British Journal of Pharmacology (1999) 127, 962–968; doi:10.1038/sj.bjp.0702609
A single amino acid confers barbiturate sensitivity upon the GABA ρ1 receptor
Authors: Belelli Delia , Pau Davide , Cabras Giulia , Peters John A , Lambert Jeremy J 
Published: January 2005

Many structurally diverse general anaesthetics enhance inhibitory neurotransmission in the central nervous system by interacting with the GABAA receptor. By contrast, GABA receptors composed of the ρ1 subunit are anaesthetic‐insensitive. Here, we demonstrate that both δ‐hexachlorocyclohexane (δ‐HCH; 1–100 μM), a positive allosteric modulator of the GABAA receptor, and the anaesthetic pentobarbitone (10–600 μM) have no effect on GABA‐evoked currents mediated by wild‐type ρ1 recombinant receptors (expressed in Xenopus laevis oocytes). By contrast, these agents produce up to a 10 fold enhancement of GABA responses transduced by a ρ1 receptor in which a transmembrane located isoleucine residue is replaced by serine. However, not all general anaesthetics were similarly influenced by this mutation, because propofol and 5β‐pregnan‐3α‐ol‐20‐one (5β3α) remained ineffective. These data are discussed in relation to the specificity of general anaesthetic action.British Journal of Pharmacology (1999) 127, 601–604; doi:10.1038/sj.bjp.0702611
Involvement of serotonin and calcium channels in the intestinal fluid secretion evoked by bile salt and cholera toxin
Authors: Peregrin Attila Timar , Ahlman Håkan , Jodal Mats , Lundgren Ove 
Published: January 2005

The enteric nervous system (ENS) is activated when exposing the intestinal mucosa to cholera toxin or certain bile salts. Cholera toxin stimulates ENS, at least in part, by the release of 5‐hydroxytryptamine (5‐HT) from the enterochromaffin cells. Calcium channel blockers of the L‐type markedly attenuate the fluid secretion and the luminal release of 5‐HT caused by cholera toxin.
The objective of the present study was to elucidate if sodium deoxycholate activated ENS in a similar manner as cholera toxin. Furthermore, the effect of several calcium channel blockers was tested on the fluid secretion caused by cholera toxin or bile salt.
Sodium deoxycholate (4 mM) caused a release of 5‐HT into the intestinal lumen, which was inhibited by calcium channel blockade. Granisetron, a 5‐HT3 receptor blocker, partly inhibited the fluid secretion caused by bile salt.
The effects of nifedipine, felodipine, R‐felodipine, H186/86 (t‐butyl analogue of felodipine) on the fluid secretion caused by cholera toxin or sodium deoxycholate were studied. Both secretory states were markedly attenuated in a dose dependent manner by all calcium channel blockers tested regardless of their effects on arterial pressure.
It is concluded that both cholera toxin and bile salt activate ENS, at least in part, via a release of 5‐HT from the enterochromaffin cells. The antisecretory effect calcium channel blockers is partly explained by an inhibition of this release of 5‐HT.

British Journal of Pharmacology (1999) 127, 887–894; doi:10.1038/sj.bjp.0702615
Interactions between cholecystokinin and opioids in the isolated guinea‐pig ileum
Authors: Romanelli Luca , Amico Maria Carmela , Mattioli Francesca , Morrone Luigi Antonio , Valeri Pacifico 
Published: January 2005

Although cholecystokinin octapeptide sulphate (CCK‐8) activates the opioid system of isolated guinea‐pig ileum (GPI) whether it activates the μ‐ or κ‐system, or both, remains unclear. Neither is it known whether CCK‐8 influences the withdrawal responses in GPI preparations briefly exposed to opioid agonists. This study was designed to clarify whether CCK‐8 activates μ‐ or κ‐opioid systems or both; and to investigate its effect on the withdrawal contractures in GPI exposed to μ‐ or κ‐agonists and on the development of tolerance to the withdrawal response.
In GPI exposed to CCK‐8, the selective κ‐antagonist nor‐binaltorphimine elicited contractile responses that were concentration‐related to CCK‐8 whereas the selective μ‐antagonist cyprodime did not.
In GPI preparations briefly exposed to the selective μ‐agonist, dermorphin, or the selective κ‐agonist, U‐50, 488H, and then challenged with naloxone, CCK‐8 strongly enhanced the withdrawal contractures.
During repeated opioid agonist/CCK‐8/opioid antagonist tests tolerance to opioid‐induced withdrawal responses did not develop.
These results show that CCK‐8 preferentially activates the GPI κ‐opioid system and antagonizes the mechanism(s) that control the expression of acute dependence in the GPI.

British Journal of Pharmacology (1999) 127, 909–918; doi:10.1038/sj.bjp.0702621
Role of superoxide dismutase in in vivo and in vitro nitrate tolerance
Authors: Münzel Thomas , Hink Ulrich , Yigit Hussein , Macharzina Roland , Harrison David G , Mülsch Alexander 
Published: January 2005

We assessed whether pharmacological inhibition of CuZn‐superoxide dismutase (SOD) mimics the molecular mechanism of either in vitro or in vivo nitrovasodilator tolerance.
In endothelium‐intact aortic rings from in vivo tolerant rabbits the GTN‐ and acetylcholine (ACh)‐induced maximal relaxation was attenuated by 36 and 23%, respectively. In vitro treatment of control rings with GTN (1 h 10 μM) similarly attenuated the vasorelaxant response to GTN, but not to ACh.
Formation of superoxide radicals (•O2−) in endothelium‐intact rings (lucigenin‐chemiluminescence) increased 2.5 fold in in vivo tolerance, but significantly decreased in in vitro tolerance. The membrane associated NADH oxidase activity was increased 2.5 fold in homogenates of in vivo tolerant aortae, but was not changed in in vitro tolerant aorta.
Conversely, SOD activity and protein expression was halved in in vivo tolerance, but SOD activity was not altered by in vitro tolerance. The •O2− scavenger tiron (10 mM) effectively restored the vasorelaxant response to GTN in in vivo tolerant aortic rings, but not the reduced response to GTN in in vitro tolerant rings.
Pretreatment (1 h) of vessels with diethyldithiocarbamate (DETC; 10 mM) attenuated vasorelaxant responses to GTN and ACh, increased vascular •O2− production, and inhibited SOD activity in vessel homogenates to a similar degree as observed in in vivo tolerance. DETC‐treatment of in vivo‐tolerant vessels induced an additional increase in •O2− production.
Increased •O2− production in in vivo nitrate tolerant aorta is associated with activation of vascular NADH oxidase and inactivation of CuZnSOD. Therefore, in vivo tolerance can be mimicked by in vitro inhibition of CuZnSOD, but not by in vitro exposure to GTN, which does not affect vascular •O2− production, NADH oxidase and CuZnSOD.

British Journal of Pharmacology (1999) 127, 1224–1230; doi:10.1038/sj.bjp.0702622
Effects of endothelial impairment by saponin on the responses to vasodilators and nitrergic nerve stimulation in isolated canine corpus cavernosum
Authors: Okamura Tomio , Ayajiki Kazuhide , Fujioka Hideyuki , Toda Megumi , Fujimiya Mineko , Toda Noboru 
Published: January 2005

Responsiveness to EDRF‐releasing substances and inhibitory nerve stimulation of canine isolated penile corpus cavernosum with and without saponin treatment were investigated.
Histological studies demonstrated that saponin did not detach endothelial cells from underlying tissues, but induced degenerative changes in the endothelial cells selectively.
In the cavernous strips contracted with phenylephrine, addition of acetylcholine, sodium nitroprusside, ATP and Ca2+ ionophore A23187 induced relaxations, but substance P and bradykinin did not change the muscle tone.
Acetylcholine‐induced relaxation was significantly attenuated but not abolished by NG‐nitro‐L‐arginine (L‐NOARG). L‐arginine restored the response inhibited by L‐NOARG. The L‐NOARG resistant relaxation was not influenced by 1H[1,2,4]oxadiazole[4,3‐a]quinoxalin‐1‐one (ODQ) but was suppressed in the strips contracted with K+. Treatment with saponin abolished the relaxation elicited by acetylcholine and A23187 but did not influence the response to nitroprusside and ATP. The ATP‐induced relaxation was attenuated by aminophylline.
Transmural electrical stimulation at 2–20 Hz produced endothelium‐independent relaxations which were abolished by tetrodotoxin and L‐NOARG but unaffected by treatment with saponin. In saponin‐treated cavernous strips, the neurogenic relaxation was not affected by acetylcholine, physostigmine, atropine and vasoactive intestinal peptide (VIP) but was abolished by ODQ.
It is concluded that acetylcholine‐induced relaxations are endothelium‐dependent and mediated partly by NO and also by other substances from the endothelium. The endothelium‐independent relaxation to ATP is likely to be mediated by P1 purinoceptors. The function of nitrergic nerve does not seem to be prejunctionally modulated by acetylcholine and VIP.

British Journal of Pharmacology (1999) 127, 802–808; doi:10.1038/sj.bjp.0702623
Differential inhibitory mechanism of cyclic AMP on TNF‐α and IL‐12 synthesis by macrophages exposed to microbial stimuli
Authors: Procópio Daniela O , Teixeira Mauro M , Camargo Maristela M , Travassos Luiz R , Ferguson Michael A J , Almeida Igor C , Gazzinelli Ricardo T 
Published: January 2005

Microbial stimuli such as bacterial lipopolysaccharide (LPS) or glycosylphosphatidylinositol‐mucins derived from Trypanosoma cruzi trypomastigotes (tGPI‐mucins) are effective stimulators of the synthesis of cytokines by macrophages. Here, we evaluated the ability of cyclic AMP mimetic or elevating agents to modulate TNF‐α and IL‐12 synthesis by murine inflammatory macrophages.
Cholera Toxin (ChTx) inhibited tGPI‐mucins (2.5 nM) or LPS (100 ng ml−1) induced TNF‐α and IL‐12(p40) synthesis in a concentration‐dependent manner. Similarly, the cyclic AMP mimetics, 8‐bromo cyclic AMP or dibutyryl cyclic AMP, or prostaglandin (PG) E2 inhibited the synthesis of both cytokines by macrophages exposed to microbial stimuli.
The protein kinase A inhibitor H‐89 partially reversed the inhibitory effects of dibutyryl cyclic AMP and PGE2 on both IL‐12(p40) and TNF‐α synthesis.
Pretreatment of macrophages with dibutyryl cyclic AMP or ChTx augmented the synthesis of IL‐10 triggered by microbial products. Elevation of cyclic AMP inhibited the synthesis of TNF‐α, but not IL‐12(p40), by inflammatory macrophages from IL‐10 knockout mice.
Kinetic studies showed that synthesis of both TNF‐α and IL‐10 peaked at 8 h and IL‐12 at 24 h after stimulation with microbial stimuli.
Together, our findings favour the hypothesis that the cyclic AMP inhibitory activity on IL‐12(p40) but not on TNF‐α synthesis is dependent on de novo protein synthesis, most likely involving IL‐10, by macrophages stimulated with microbial products. Accordingly, dibutyryl cyclic AMP inhibited IL‐12(p40) synthesis only when added before or at the same time of the stimuli. In contrast, the effect of this cyclic AMP analogue on TNF‐α synthesis was protracted and observed even 2 h after the addition of the stimuli.

British Journal of Pharmacology (1999) 127, 1195–1205; doi:10.1038/sj.bjp.0702624
Inhibition of GTPase activity of Gi proteins and decreased agonist affinity at M2 muscarinic acetylcholine receptors by spermine and methoctramine
Authors: Daeffler Laurent , Chahdi Ahmed , Gies Jean‐Pierre , Landry Yves 
Published: January 2005

The effects of spermine and methoctramine, a selective M2 muscarinic receptor antagonist, were studied on the high‐affinity GTPase activity of G proteins, and on ligand binding to M2 muscarinic receptors in pig heart sarcolemma.
The spontaneous GTP hydrolysis by pig heart sarcolemma and its stimulation by mastoparan or carbachol were prevented by pertussis toxin and inhibited by methoctramine (IC50s: 21, 13 and 0.005 μM, respectively), and spermine (IC50s: 967, 278 and 11 μM). Spermine and methoctramine also inhibited spontaneous GTP hydrolysis by rat peritoneal mast cell membranes which do not respond to carbachol.
The neutral muscarinic antagonists, AF‐DX 116 and atropine, did not modify the inhibitory effect of high concentrations of methoctramine, indicating that this effect was not related to the antagonist binding site of muscarinic receptors. We suggest that methoctramine behaves as a receptor antagonist at nanomolar concentrations and interacts with G proteins at micromolar concentrations.
Spermine did not modify the binding of the tritiated muscarinic antagonist [3H]‐NMS, but decreased the binding of the agonist [3H]‐Oxo‐M. Spermine elicited a rightward shift of the carbachol/[3H]‐NMS binding isotherm with a decrease in the proportion of sites with high‐affinity for carbachol, suggesting that polyamines uncouple Gi proteins from receptors.
The inhibition of GTPase activity by polyamines, preventing the re‐association of α and βγ subunits of Gi proteins, might sustain the regulatory effect of Gi subunits on downstream effectors. The level of intracellular polyamines might be important for the control of the transduction of extracellular signals through Gi protein‐coupled receptors.

British Journal of Pharmacology (1999) 127, 1021–1029; doi:10.1038/sj.bjp.0702625
IL‐2 and IL‐4 counteract budesonide inhibition of GM‐CSF and IL‐10, but not of IL‐8, IL‐12 or TNF‐α production by human mononuclear blood cells
Authors: Larsson Susanne , Löfdahl Claes‐Göran , Linden Margareta 
Published: January 2005

The combination of interleukin‐2 (IL‐2) and IL‐4 reduces the inhibitory effects of glucocorticoids on granulocytemacrophage colonystimulating factor (GM‐CSF) production, in agreement with the hypothesis that this combination causes glucocorticoid resistance. Whether a general cytokine resistance to glucocorticoids is induced by IL‐2 and IL‐4 has not been reported.
Mononuclear blood cells from healthy individuals were pretreated with IL‐2, IL‐4, or IL‐2+ IL‐4 (31.3–500 U ml−1) for 48 h, prior to lipopolysaccharide (LPS; 10 ng ml−1; 20 h) and budesonide addition. Cytokine levels in the supernatants were analysed using specific immunoassays. DNA content was analysed to estimate cell numbers.
GM‐CSF production was totally inhibited by budesonide at 10−8 M in vehicle treated cultures, while IL‐10 was inhibited to 33.4±4.3% of control. IL‐2, IL‐4, or IL‐2+IL‐4 reduced the inhibitory effects of budesonide on GM‐CSF to similar levels (23.7±6.7, 31.6±8.5 and 35.1±4.3% of control, respectively). IL‐2, IL‐4, or IL‐2+IL‐4 also reduced the inhibitory effects of budesonide on IL‐10 production (46.5±6.6, 55.9±7.3%, and 68.3±9.9% of control, respectively). In contrast, IL‐8, IL‐12 and TNF‐α production did not become resistant to budesonide.
Thus, glucocorticoid resistance induced by IL‐2 and IL‐4 is not general at the cytokine production level. While the glucocorticoid sensitivity of GM‐CSF and IL‐10 production decreased, the sensitivity of IL‐8, IL‐12 or TNF‐α production was unchanged. Also, the mixture of IL‐2 and IL‐4 is not crucial for induction of glucocorticoid resistance of GM‐CSF production.

British Journal of Pharmacology (1999) 127, 980–986; doi:10.1038/sj.bjp.0702631
Cannabinoid receptor activation inhibits GABAergic neurotransmission in rostral ventromedial medulla neurons in vitro
Authors: Vaughan Christopher W , McGregor Iain S , Christie MacDonald J 
Published: January 2005

The rostral ventromedial medulla (RVM) is thought to play a crucial role in the antinociceptive actions of cannabinoids. This study examined the actions of the cannabinoid receptor agonist, WIN55,212‐2, on membrane properties and GABAergic synaptic transmission in RVM neurons using whole cell patch clamp recordings in brain slices.
WIN55,212‐2 (3 μM) had no effect on membrane K+ conductance of primary or secondary RVM neurons. Primary neurons responded to the κ‐opioid receptor agonist U69,593 (300 nM–1 μM). Secondary neurons responded to the μ,δ‐opioid receptor agonist met‐enkephalin (10 μM).
WIN55,212‐2 reduced the amplitude of electrically evoked (GABAergic) inhibitory postsynaptic currents (IPSCs) in all neurons (58%, pEC50=6.2±0.1). The inhibition was reversed by the CB1 receptor selective antagonist, SR141716 (3 μM). WIN55,212‐2 also produced relative facilitation of the second IPSC to paired evoked IPSCs.
WIN55,212‐2 and met‐enkephalin reduced the rate of spontaneous miniature IPSCs in all cells (44 and 53%), but had no effect on their amplitude distributions or kinetics.
These results suggest that the antinociceptive actions of cannabinoids within RVM are primarily due to presynaptic inhibition of GABAergic neurotransmission. The neuronal substrates of cannabinoid actions in RVM therefore differ from those of opioids, which have both pre‐ and postsynaptic inhibitory actions.

British Journal of Pharmacology (1999) 127, 935–940; doi:10.1038/sj.bjp.0702636