Search results for "electric [mass]"
showing 10 items of 1101 documents
Stimulatory effects of DB-c-AMP and adrenaline on myocardial contraction and 45Ca exchange. Experiments at reduced calcium concentration and low freq…
1973
The effects of adrenaline (2.2×10−6 M) and cyclic N6-2′-O-dibutyryl-adenosine-3′,5′-monophosphate (DB-c-AMP; 10−3 M) on mechanical performance, 45Ca uptake and total tissue calcium concentration were investigated in electrically stimulated left auricles isolated from female rats weighing 180–220 g. The experiments were performed at reduced [Ca]e of 0.45 mM and at various frequencies of stimulation (0–120 beats/min). In the first series of experiments 45Ca incubation time was 5 min. Under these conditions DB-c-AMP as well as adrenaline enhanced contractile force to 300–450% of the control values at all frequencies tested (Fig.1). This increase in contractile force was accompanied by a signif…
On the purinergic system in rat duodenum : existence of P1and P2receptors on the smooth muscle
1990
In rat duodenum, in vitro, in the presence of atropine and guanethidine, ATP administration caused a tetrodotoxin-insensitive relaxation followed by a rebound contraction. A similar response was obtained also after electrical field stimulation (EFS) of non-adrenergic, non-cholinergic (NANC) nerves. alpha, beta-methylene-TP and theophylline antagonized the response to ATP, but they failed to affect the noradrenaline- and EFS-induced relaxation. These results suggest that P1 and P2 receptors are present in rat duodenum, but their activation is not responsible for the inhibitor effects due to the NANC nerves.
Effects of Mn2+ on the responses induced by different spasmogens in the oestrogen-primed rat uterus
1997
Abstract We investigated the effect of Mn 2+ on the mechanical responses evoked by high K + (60 mM) or low Na + (25 mM) solutions, oxytocin and neurokinin A in the oestrogen-primed rat uterus. In a Ca 2+ -free, Mn 2+ (0.54 mM)-containing solution, high K + or low Na + solutions produced contractions of smaller amplitude than those observed in a normal Ca 2+ (0.54 mM) solution, which were abolished by nifedipine (1 μM). Oxytocin (1 μM) and neurokinin A (1 μM, in the presence of phosphoramidon 1 μM) evoked nifedipine-insensitive contractile responses similar to (oxytocin) or smaller (neurokinin A) in amplitude than those observed in Ca 2+ (0.54 mM)-containing solution. In strips loaded with C…
Different muscarine receptors mediate the prejunctional inhibition of [3H]-noradrenaline release in rat or guinea-pig iris and the contraction of the…
1989
To investigate the muscarine receptor type mediating inhibition of [3H]-noradrenaline release from the isolated rat and guinea-pig iris we have determined the potency of antimuscarinic drugs to antagonize the methacholine-induced inhibition of [3H]-noradrenaline overflow evoked by field stimulation (3 Hz, 2 min). The prejunctional apparent affinities were compared with those obtained for postjunctional muscarine receptors mediating the methacholine-induced contraction of the isolated rabbit iris sphincter muscle. Prejunctional apparent affinity constants of pirenzepine (6.67), himbacine (8.51), methoctramine (7.92), 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP, 8.00), hexahydro-d…
Five-fold Gastrointestinal Electrical Stimulation With Electromyography-based Activity Analysis: Towards Multilocular Theranostic Intestinal Implants
2019
Background/aims Motility disorders are common and may affect the entire gastrointestinal (GI) tract but current treatment is limited. Multilocular sensing of GI electrical activity and variable electrical stimulation (ES) is a promising option. The aim of our study is to investigate the effects of adjustable ES on poststimulatory spike activities in 5 GI segments. Methods Six acute porcine experiments were performed with direct ES by 4 ES parameter sets (30 seconds, 25 mA, 500 microseconds or 1000 microseconds, 30 Hz or 130 Hz) applied through subserosal electrodes in the stomach, duodenum, ileum, jejunum, and colon. Multi-channel electromyography of baseline and post-stimulatory GI electri…
ERPs to pitch changes: a result of reduced responses to standard tones in rabbits.
1996
EVENT-RELATED potentials (ERPs) were recorded in rabbits when pitch deviant tones occurred in a series of standard tones (oddball situation). In control recordings, the deviant tones were presented without the standard tones (deviant-alone situation). In the oddball situation, significant difference ERPs (deviant ERPs - standard ERPs) could be found in the hippocampal and cerebellar recordings but not in the visual cortex. All the ERPs to the deviant stimuli observed in the oddball situation were also present in the deviant-alone situation. The difference ERPs were therefore based on reduced responses to the standards. The results are discussed in the context of a mismatch negativity (MMN) …
gamma-Aminobutyric acid and cholinergic transmission in the guinea-pig ileum.
1983
1. The effects of GABA on release of acetylcholine and on contractility of the smooth muscle were studied in the myenteric plexus-longitudinal muscle preparation of the guinea pig. Acetylcholine was determined as radiolabelled transmitter from strips preloaded with 3H-choline. 2. GABA (1–300 μM) caused an increase in resting tension of smooth muscle as well as an increase in release of acetylcholine that was considerably reduced by tetrodotoxin. The facilitation by GABA of acetylcholine release exhibited a marked tachyphylaxis. The increase in muscle tension was clearly related to the increase in acetylcholine release. Muscimol (0.1–10 μM) also enhanced the release of acetylcholine. The eff…
Characterization of prejunctional muscarinic autoreceptors in the guinea-pig trachea
1991
1. The effects of ten muscarinic antagonists on electrically evoked [3H]-acetylcholine release and muscle contraction were compared in an epithelium-free preparation of the guinea-pig trachea that had been preincubated with [3H]-choline. 2. The M3-selective antagonists UH-AH 37, 4-diphenyl-acetoxy-N-piperidine methobromide and para-fluorohexahydrosiladiphenidol were more potent in reducing the contractile response than in facilitating the evoked [3H]-acetylcholine release. Hexahydrosiladiphenidol did not discriminate between pre- and postjunctional effects. The rank order of the postjunctional potencies of the ten antagonists as well as the postjunctional pA2 values obtained for hexahydrosi…
Inhibitory and excitatory muscarinic receptors modulating the release of acetylcholine from the postganglionic parasympathetic neuron of the chicken …
1992
The effects of muscarinic receptor antagonists on ACh release were studied in the absence or presence of cholinesterase (ChE) inhibition using the isolated perfused chicken heart. Presynaptic inhibitory muscarinic autoreceptor were characterized by determining the potency of various antagonists to enhance [3H]-ACh release evoked by field stimulation (3 Hz, 1 min). The order of potencies was: (±)-telenzepine > atropine > 4-DAMP > silahexocyclium > pirenzepine > hexahydro-siladifenidol > AF-DX 116. The comparison with known pA2 values for M1-, M2- and M3-receptors revealed that the presynaptic autoreceptor meets the criteria of an M1-receptor. Basal, not electrically evoked overflow of unlabe…
Increase by NO synthase inhibitors of acetylcholine release from guinea-pig myenteric plexus
1994
The effects of nitric oxide (NO) synthase inhibitors on the electrically evoked release of [3H]acetylcholine were studied in guinea-pig myenteric plexus preparations preincubated with [3H]choline. NG-monomethyl-L-arginine (EC50 5.3 mumol l-1) and NG-nitro-L-arginine (EC50 1.3 mumol l-1) concentration-dependently increased the evoked release of [3H]acetylcholine without affecting the basal outflow. The facilitatory effect of NG-mono-methyl-L-arginine was prevented by L-arginine but not by D-arginine. The results suggest that endogenous NO inhibits the depolarisation-evoked release of acetylcholine.