bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of excitatory amino acid responses by tachykinins and selective tachykinin receptor agonists in the rat spinal cord
Authors: Cumberbatch Michael J. , Chizh Boris A. , MaxHeadley P. 
Published: July 2012

The effects of tachykinins and agonists selective for the three subtypes of neurokinin (NK) receptor have been tested on spinal neuronal responses both to the excitatory amino acids (EAAs) NMDA, AMPA and kainate, and to noxious heat stimuli. The agonists were applied by microiontophoresis in in vivo experiments in α‐chloralose‐anaesthetized, spinalized rats.
The NK1selective agonist, GR 73632, enhanced responses to all three EAAs similarly, whilst the NK2‐selective agonist, GR64349, reduced responses to AMPA and kainate without affecting those to NMDA, and the NK3 selective agonist, senktide, enhanced responses to AMPA and kainate.
The endogenous ligands substance P (SP) and neurokinin A (NKA) both enhanced responses to NMDA with little effect on responses to kainate, whereas neurokinin B (NKB) selectively enhanced responses to kainate without affecting those to NMDA.
The effects of GR73632 on EAA responses showed some differences between the dorsal and ventral horn, with more selectivity towards enhancement of NMDA responses in the ventral horn, but a smaller maximum effect.
Background activity was significantly enhanced by GR73632, GR64349, SP and NKA but not by senktide or NKB. GR73632 had the greatest effect on background firing, but this action was variable between cells and was related both to the location within the spinal cord and to the degree of spontaneous activity prior to GR73632 administration.
Responses to noxious heat were enhanced consistently only by NKA.
These data show that selective agonists for the tachykinin receptors are capable of modulating EAA responses differentially. SP, NKA and NKB appear to act via more than one receptor type when modulating EAA responses in vivo. This indicates that NK‐EAA interactions can be more specific than suggested hitherto, with the combined actions at NK1 and NK2 receptors biasing EAA responsiveness towards NMDA receptor mediated functions, whereas NK3 receptor activation would have the opposite effect. The physiological role of such interactions is likely to be complex.
Effects of BRL55834 in rat portal vein and bovine trachea: evidence for the induction of a glibenclamide‐resistant, ATP‐sensitive potassium current
Authors: Edwards G. , Schneider J. , Niederste‐Hollenberg A. , Noack Th. , Weston A.H. 
Published: July 2012

The effects of the benzopyran K‐channel opener, BRL55834, on mechanical activity in bovine trachealis and rat portal vein were studied together with membrane currents in freshly‐isolated single cells derived from these tissues.
BRL55834 (3nM‐l μm) produced a concentration‐dependent relaxation of bovine trachealis precontracted with 100 μm histamine and reduced the spontaneous mechanical activity of rat portal veins, effects which were antagonized by glibenclamide (1–10 μm) but were not reversible on washing. In contrast, charybdotoxin (250 nM) did not modify the spasmolytic effect of BRL55834 in bovine trachealis.
BRL55834 (10 nM‐10 μm) did not relax segments of bovine trachealis precontracted with 80 mM KC1.
In some freshly‐isolated single cells from bovine trachealis held at −10 mV, BRL55834 (3 μm) induced a time‐independent outward K‐current which was partially resistant to inhibition by glibenclamide (10 μm). In other cells, a very noisy, outwardly‐rectifying and charybdotoxin‐sensitive current developed in the presence of BRL55834 (3 μm) and in time‐matched control cells.
In freshly‐isolated single cells from rat portal vein held at −10 mV, BRL55834 (3 μm) induced a time‐and calcium‐independent outward K‐current which was partially resistant (approximately 25% inhibition at +40 mV) to subsequent inhibition by glibenclamide (10 um). In contrast, levcromakalim induced a time‐independent outward K‐current which was completely inhibited by glibenclamide 10 μm.
With the non‐hydrolysable ATP analogue, AMP‐PCP (5 mM), in the pipette, the ability of BRL55834 to induce a time‐independent K‐current in portal vein cells was markedly reduced (approximately 80% inhibition at +40 mV) whereas the effects of 10 um levcromakalim were totally inhibited.
The glibenclamide‐resistant current component induced by BRL55834 was totally inhibited by phentolamine (100 μm), a concentration that had no effect on the peak current (IBK(Ca)) induced by NS1619 (33 μm).
Stationary fluctuation analysis of the noise associated with the glibenclamide‐insensitive K‐current induced by BRL55834 in rat portal vein cells indicated that the unitary current flowing through the underlying channels was 0.26 pA at −10 mV, a value inconsistent with the involvement of BKca.
It is concluded that the relaxations of both bovine trachea and rat portal vein produced by BRL55834 are associated with the opening of K‐channels. These are probably identical to the ATP‐sensitive K‐channel opened by levcromakalim, although the involvement of an additional K‐channel cannot be excluded. The reduced sensitivity of the BRL55834‐induced changes to glibenclamide and to AMP‐PCP may result from avid binding of BRL55834 to its site of action.
The effect of neuropeptide Y on sodium, chloride and potassium transport across the rat distal colon
Authors: Strabel D. , Diener M. 
Published: July 2012

Neuropeptide Y (NPY; 10−10–10−7 mol l−1) reduced basal short‐circuit current (Isc.) in a concentration‐dependent manner in the rat distal colon but was ineffective in the proximal colon.
The action of NPY was dependent upon the presence of CI− and HC03‐ anions and was blocked by prior treatment of the tissue with a Cl− channel blocker. The decrease in Isc was associated with an increase in mucosa‐to‐serosa fluxes of Na+, Rb+ (K+) and Cl−, whereas the serosa‐to‐muc osa flux of Cl− was decreased.
The size of the inhibitory NPY effect was linearly correlated with the height of the basal Isc i.e. it inhibited 55% of basal secretory Isc.
The action of NPY was unaffected by indomethacin and tetrodotoxin, when given alone, but was abolished, when the basal Isc was decreased to values near zero by a combination of both inhibitors. This inhibition could be overcome by restoring basal Isc with prostaglandin E2, indicating that the effect of NPY is not mediated by nerves or prostaglandins, but that NPY is only effective, when anion secretion is stimulated by the spontaneous release of neurotransmitters and prostaglandins.
NPY inhibited the increase in Isc induced by veratridine and prostaglandin E2, but it had no effect on the Isc induced by direct stimulation of the adenylate cyclase with forskolin, or on Isc induced by stimulation of the Ca2+–pathway with carbachol. Inhibition of the response to veratridine or prostaglandin E2 by NPY showed the same dependence on the height of the Isc just prior to addition of NPY as seen in control conditions, i.e. NPY inhibited 55% of cyclic AMP‐mediated secretion.
These results suggest that the effect of NPY is mediated by an inhibition of cyclic AMP‐stimulated secretion, which is stimulated in the rat distal colon by a continuous release of prostaglandins and neurotransmitters.
Potassium currents in human freshly isolated bronchial smooth muscle cells
Authors: Snetkov V.A. , Hirst S.J. , Twort C.H.C. , Ward J.P.T. 
Published: July 2012

K+ currents were studied in smooth muscle cells enzymatically dissociated from human bronchi, by use of the patch‐clamp technique.
In whole‐cell recordings a depolarization‐induced, 4‐aminopyridine (4‐AP)‐sensitive current was observed in only 26 of 155 cells, and in 20 of these 26 cells its amplitude at a test potential of 0 mV was less than 100 pA.
In the majority of cells depolarization to −40 mV or more positive potentials induced a noisy outward current which activated within milliseconds and showed almost no inactivation even during a 5 s depolarizing voltage step. This current was insensitive to 4‐AP (up to 5 mM) but was strongly inhibited in the presence of tetraethylammonium (TEA, 1 mM), charybdotoxin (ChTX, 100 nM) or iberiotoxin (IbTX, 50 nM) in the bath. The same current was also recorded by the nystatin‐perforated patch technique.
Single channels with a conductance of about 210 pS were recorded in cell‐attached patch, inside‐out patch, outside‐out patch and whole‐cell recording configurations. Channel open state probability in inside‐out patches was 0.5 at a membrane potential of 4±14 mV (mean±s.d., n= 13) mV even with a free Ca2+ concentration on the cytosolic side of the patch of less than 0.1 nM. Open state probability increased with depolarization and internal Ca2+ concentration. Single channels could be reversibly blocked by externally applied TEA, ChTX and IbTX.
In current‐clamp recordings with 100 nM free Ca2+ in the intracellular solution both TEA and ChTX caused substantial concentration‐dependent depolarization.
These results suggest that in human bronchial smooth muscle cells, in marked contrast to other species, the majority of the outward current induced by depolarization is not due to a delayed rectifier, but to the activity of a large conductance, ChTX‐sensitive K+ channel. The Ca2+– and voltage‐dependency of this channel may well allow a sufficiently high open state probability for it to play a part in the regulation of the resting membrane potential.
Modulation by prednisolone of calcium handling in skeletal muscle cells
Authors: Metzinger Laurent , Passaquin Anne‐Catherine , Leijendekker Wim J. , Poindron Philippe , Rüegg Urs T. 
Published: July 2012

Increased calcium (Ca2+) influx has been incriminated as a potential pathological mechanism in the chronic skeletal muscle degeneration exhibited by Duchenne muscular dystrophy (DMD) patients. We have studied the influence of the glucocorticoid α‐methylprednisolone (PDN), the only drug known to have a beneficial effect on the degenerative course of DMD, on Ca2+ handling in the C2 skeletal muscle cell line.
PDN, when added 3 days (when myoblasts start to fuse into myotubes) after cell seeding, led to a 2 to 4 fold decrease in cellular Ca2+ uptake. This decrease was independent of the extracellular Ca2+ concentration applied to cells. The effect took at least 24 h in order to become established (PDN of 10−5 m) and took longer for lower PDN concentrations (EC50 of ca. 10−6 m at day 5, 10−6 5 m at day 7 and 10−7 5 m at day 9 in culture).
Cellular calcium accumulation was also decreased in PDN‐treated myotubes exposed to 45Ca2+‐containing medium for 1 to 6 days.
No effect of PDN was seen on 45Ca2+ efflux; a decrease in the amount of 45Ca2+released was observed due to the reduction of cellular 45Ca2+ loading.
PDN treatment led to an approximately 2 fold decrease in basal cytosolic Ca2+ concentration. 6 Three antioxidant drugs (lazaroids), previously shown to enhance in vitro skeletal muscle cell differentiation to the same extent as PDN, induced a similar decrease in Ca2+ influx. 7 Our results suggest that long‐term incubation of C2 cells with PDN leads to a decrease of the size of the cellular Ca2+ pools and to reduced resting cytosolic Ca2+ levels. Part of the beneficial effect of PDN in DMD patients could be attributed to a reduction of Ca2+ influx and of the size of Ca2+ pools in dystrophic muscle fibres.
Activation of nicotinic acetylcholine receptors expressed in quail fibroblasts: effects on intracellular calcium
Authors: Cross M.L. , Jane S.D. , Wild A.E. , Foreman R.C. , Chad J.E. 
Published: July 2012

The aim of these experiments was to determine the ability of the muscle‐type nicotinic acetylcholine receptor (AChR) stably expressed in quail fibroblasts (QF18 cells) to elevate intracellular calcium ([Ca2+]i) upon activation. Ratiometric confocal microscopy, with the calcium‐sensitive fluorescent dye Indo‐1 was used.
Application of the nicotinic agonist, suberyldicholine (SDC), to the transfected QF18 cells caused an increase in [Ca2+]i. Control [Ca2+]i levels in QF18 cells were found to be 164 ± 22 nM (mean ± s.e.mean; n = 40 cells) rising to 600 ± 81 nM on addition of SDC (10 μm; n=15 cells), whereas no increase in [Ca2+]i was seen in non‐transfected control QT6 fibroblasts (before: 128 ± 9 nM, n = 40; after: 113±13 nM, n= 15).
The increase in [Ca2+]i caused by application of SDC was dose‐dependent, with an EC50 value of 12.7 ± 5.9 μm (n=14).
The responses to SDC in QF18 cells were blocked by prior application of α‐bungarotoxin (200 nM), by the addition of Ca2+ (100 μm), by removal of Na+ ions from the extracellular solution, or by the voltage‐sensitive calcium channel blockers nifedipine and ω‐conotoxin, which act with IC50 values of 100 nM and 100 pM respectively.
We conclude that activation of the nicotinic AChRs leads to a Na+‐dependent depolarization and hence activation of endogenous voltage‐sensitive Ca2+ channels in the plasma membrane and an increase in [Ca2+]i. There is no significant entry of Ca2+ through the nicotinic receptor itself.
Distribution and effects of pituitary adenylate cyclase activating peptide in cat and human lower oesophageal sphincter
Authors: Ny L. , Larsson B. , Alm P. , Ekström P. , Fahrenkrug J. , Hannibal J. , Anderssno K.‐E. 
Published: July 2012

The localization, tissue concentrations, and effects of pituitary adenylate cyclase activating peptide (PACAP) 27 and 38 were investigated in cat and human lower oesophageal sphincter (LOS), and compared with those of vasoactive intestinal peptide (VIP) and helospectin.
PACAP‐immunoreactive nerve structures were found in the cat and human LOS, with an abundance in the circular smooth muscle layer. PACAP 27‐immunoreactivity was often co‐localized with VIP‐immunoreactivity.
In cat tissue, PACAP (PACAP 27 plus PACAP 38) concentrations were 50 fold lower than VIP concentrations; in human tissue they were 10 fold lower.
PACAP 27, PACAP 38, helospectin I, and VIP induced concentration‐dependent relaxations in circular smooth muscle preparations from cat and human LOS. The order of potency was: VIP > helospectin I ≤ PACAP 27 > PACAP 38. NG‐nitro‐L‐arginine, scopolamine, or apamin, did not influence the relaxant effects of PACAP 27 or VIP.
In cat preparations, both cyclic AMP and cyclic GMP levels were increased after exposure to PACAP 27 and helospectin I, whereas exposure to VIP was followed by an increase in cyclic AMP levels only. In human preparations, there was an increase in cyclic AMP levels without any change in cyclic GMP levels.
These results suggest that in the cat and human LOS, PACAP 27 and VIP can occur within the same nerve structures. PACAP 27 has a potent relaxant action, but its functional importance has to be established.
Interaction between the μ‐agonist dermorphin and the δ‐agonist [D‐Ala2, Glu4]deltorphin in supraspinal antinociception and δ‐opioid receptor binding
Authors: Negri L. , Improta G. , Lattanzi R. , Potenza R.L. , Luchetti F. , Melchiorri P. 
Published: July 2012

In rats, the interaction between the μ‐opioid agonist dermorphin and the δ‐opioid agonist [D‐Ala2, Glu4]deltorphin was studied in binding experiments to δ‐opioid receptors and in the antinociceptive test to radiant heat.
When injected i.c.v., doses of [D‐Ala2, Glu4]deltorphin higher than 20 nmol produced antinociception in the rat tail‐flick test to radiant heat. Lower doses were inactive. None of the doses tested elicited the maximum achievable response. This partial antinociception was accomplished with an in vivo occupancy of more than 97% of brain δ‐opioid receptors and of 17% of μ‐opioid receptors. Naloxone (0.1 mg kg−1, s.c), and naloxonazine (10 mg kg−1, i.v., 24 h before), but not the selective δ‐opioid antagonist naltrindole, antagonized the antinociception.
In vitro competitive inhibition studies in rat brain membranes showed that [D‐Ala2, Glu4]deltorphin displaced [3H]‐naltrindole from two δ‐binding sites of high and low affinity. The addition of 100 μm Gpp[NH]p produced a three fold increase in the [D‐Ala2, Glu4]deltorphin Ki value for both binding sites. The addition of 10 nM dermorphin increased the Ki value of the δ‐agonist for the high affinity site five times. When Gpp[NH]p was added to the incubation medium together with 10 nM dermorphin, the high affinity Ki of the δ‐agonist increased 15 times.
Co‐administration into the rat brain ventricles of subanalgesic doses of dermorphin and [D‐Ala2, Glu4]deltorphin resulted in synergistic antinociceptive responses.
Pretreatment with naloxone or with the non‐equilibrium μ‐antagonists naloxonazine and β∼ funaltrexamine completely abolished the antinociceptive response of the μ‐δ agonist combinations.
Pretreatment with the δ‐opioid antagonists naltrindole and DALCE reduced the antinociceptive response of the dermorphin‐[D‐Ala2, Glu4]deltorphin combinations to a value near that observed after the μ‐agonist alone. At the dosage used, naltrindole occupied more than 98% of brain δ‐opioid receptors without affecting μ‐opioid‐receptors.
These data suggest that in the rat tail‐flick test to radiant heat, μ‐ and δ‐opioid agonists co‐operate positively in evoking an antinociceptive response. Although interactions between different opioid pathways cannot be excluded, in vitro binding results indicate that this co‐operative antinociception is probably mediated by co‐activation of the δ‐opioid receptors at the cellular level by the μ‐ and δ‐agonist.
Dual mechanisms of GABAa response inhibition by β‐lactam antibiotics in the pyramidal neurones of the rat cerebral cortex
Authors: Fujimoto Mika , Munakata Mitsutoshi , Akaike Norio 
Published: July 2012

The effects of β‐lactam antibiotics on the γ‐aminobutyric acid (GABA)‐induced Cl− current were investigated in pyramidal neurones freshly dissociated from the rat frontal cortex by the use of a nystatin‐perforated patch recording mode under voltage‐clamp conditions.
The GABA‐induced inward current increased in a concentration‐dependent manner with an EC50 of 6.7 × 10−6 m at a holding potential of −40 mV. The GABA response was accompanied by an increase in the membrane conductance and reversed at near the Cl− equilibrium potential.
All β‐lactams (penicillin, imipenem, aztreonam and cefotiam) inhibited the 10−5 m GABA‐induced response in a concentration‐dependent manner with an IC50 and Hill coefficient of 1.3 × 10−3 m and 0.64 for penicillin, 9.6 × 10−4 m and 0.83 for imipenem, 2.5 × 10−3 m and 9.99 for aztreonam, and 2.9 × 10−4 m and 1.03 for cefotiam.
Imipenem inhibited the GABA‐response competitively while penicillin inhibited the same response in a noncompetitive fashion.
The inhibitory action of imipenem showed no voltage‐dependency, whereas the effect of penicillin was voltage‐dependent.
It is thus proposed that some classes of β‐lactams, including imipenem, may have a mechanism that is different from penicillin and competitively affects the GABAA receptor.
Neuromuscular blocking profile of the vecuronium analogue, Org‐9487, in the rat isolated hemidiaphragm preparation
Authors: Prior Chris , Tian Lijun , Mallah Ahmed I. El , Young Louise , Ward Joanna M. 
Published: July 2012

The neuromuscular effects of the short‐acting aminosteroid muscle relaxant Org‐9487 have been studied in the in vitro rat phrenic nerve/hemidiaphragm preparation by use of twitch tension and electrophysiological recording techniques.
Org‐9487 (5–100 μm) produced a concentration‐dependent decrease in the amplitude of twitches (0.1 Hz) and tetanic contractions (50 Hz) evoked by motor nerve stimulation. The compound produced fade of force during both 50 Hz stimulation and train‐of‐four stimulation at 2 Hz, indicating a prejunctional component of action.
Anticholinesterases only partially reversed the effect of Org‐9487 on twitch responses. This was possibly because, at the concentrations required to block twitches in the rat, Org‐9487 itself was found to possess significant anticholinesterase activity.
Org‐9487 (3 μm) increased the rundown of endplate current amplitudes during a 2 s train of 50 Hz nerve stimulation. This was because Org‐9487 increased the quantal content of the first endplate current in the train without affecting acetylcholine release towards the latter part of the train.
Org‐9487 (10 μm) produced a voltage‐dependent decrease in the time constant of decay of endplate currents at 32°;C and 0.5 Hz, indicative of a block of endplate ion channels. The blocking rate constant increased with membrane hyperpolarization.
Antithrombotic effect of a novel recombinant hirudin analogue, CX‐397, in a rat arterial thrombosis model
Authors: Takiguchi Yoshiharu , Asai Fumitoshi , Wada Kouichiro , Hayashi Hideya , Nakashima Mitsuyoshi 
Published: July 2012

The antithrombotic effect of a new specific thrombin inhibitor, CX‐397, was examined in a photochemically‐induced arterial thrombosis model in the rat femoral artery and compared with that of heparin.
Pretreatment with CX‐397 (10, 20 and 40 μg kg−1 min−1, i.v.) from 15 min before the experiment prolonged the time required for thrombotic occlusion of the artery in a dose‐dependent manner. The antithrombotic efficacy of CX‐397 was associated with modest increases in activated partial thromboplastin time (APTT) and template bleeding time.
On the other hand, heparin at a dose of 450 μg kg−1 markedly prolonged APTT and the bleeding time, but did not inhibit thrombo‐occlusion.
CX‐397 selectively inhibited platelet aggregation and concurrent secretion of 5‐hydroxytryptamine (5‐HT) and thromboxane A2 (TXA2) production from platelets in response to thrombin, but not to collagen and ADP, in a dose‐dependent manner (5–100 ng ml−1).
CX‐397 at 10 μg kg−1 combined with vapiprost, a TXA2 receptor antagonist, at O.l mg kg−1 significantly prevented occlusion, whereas, at these doses, neither drug alone had much effect.
These results demonstrate that CX‐397 may prove to be more efficient for preventing platelet‐rich thrombosis than heparin. Thrombin may play an important role in the rat thrombosis model.
The additive antithrombotic effect of the combination of thrombin inhibitor and TXA2 receptor antagonist at low doses suggests that thrombin and TXA2 may work in concert to produce thrombosis.