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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 47 (1994), S. 377-378 
    ISSN: 1432-1041
    Keywords: Metoclopramide ; Aldosterone ; Serotonin (5-HT4)-receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 335 (1987), S. 629-635 
    ISSN: 1432-1912
    Keywords: GABAA agonists ; Substance P ; Cholinergic neurons ; Guinea-pig ileum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The possible involvement of substance P (SP) in cholinergic contractions induced by GABAA agonists in the guinea-pig ileum was further investigated. 2. Responses evoked by 3-aminopropane sulphonic acid (3-APS) or muscimol consisted of a rapid phasic contraction followed in 70% of preparations by a tonic contraction, usually smaller in amplitude but considerably longer in duration. Phasic and tonic components were sensitive to bicuculline, neurogenic (cholinergic) in nature and susceptible to desensitization. 3. Capsaicin (0.2 μM) pretreatment and SP receptor desensitization caused by 3 different priming SP concentrations (10 nM, 30 nM, 100 nM), depressed both components of the 3-APS-induced response, the magnitude of antagonism being greater for tonic contractions. Similar findings were obtained by using 10 μM (d-Pro4, d-Trp7,9)SP-(4–11), even though the degree of antagonism caused by this SP antagonist was consistently lower. 4. These results indicate that depression of SP receptor function achieved by three different procedures decreases cholinergic contractile responses to GABAA agonists in the guinea-pig ileum. This provides further support for the hypothesis that GABAA receptor activation evokes both direct and indirect stimulation of enteric cholinergic neurons and that SP and/or a related peptide play an important role in mediating the indirect component of the cholinergic response.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1912
    Keywords: BIMU 1 ; Cisapride ; Ondansetron ; DAU 6285 ; 5-HT3 receptors ; 5-HT4 receptors ; Heidenhain pouch model ; Gastric motility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have investigated the in vivo motor stimulating and gastroprokinetic properties of the azabicycloalkyl benzimidazolone derivative BIMU 1 (3-ethyl-2,3dihydro-N-(8-methyl-8-azabicyclo [3.2.1] oct-3-yl)-2-oxo 1H-benzimidazole-1-carboxamide hydrochloride) and its binding profile at 5-hydroxytryptamine3 and 5-hydroxytryptamine4 receptors, in an attempt to assess the serotonergic mechanism underlying its prokinetic action. BIMU 1 dose-dependently (0.01–0.3 mg/kg iv.) increased the motility of a denervated pouch of canine stomach. This excitatory action was sensitive to muscarinic blockade. A similar stimulatory effect was exerted by the benzamidic prokinetic agent cisapride (0.03–0.3 mg/kg i.v.) but not by the 5-HT3 receptor antagonist ondansetron (up to 1 mg/kg i.v ). The significance for propulsive efficacy of the motor stimulating activity of BIMU 1 was evaluated in a model of gastric emptying of liquids in the conscious dog. The emptying rate of a non-caloric liquid meal instilled through a gastric fistula was accelerated by both BIMU 1 (0.01–1 mg/kg i.v. and 0.1–3 mg/kg p.o.) and cisapride (0.03–1 mg/kgiv.and0.3–10 mg/kgp.o.).Ondansetron (1 mg/kg i.v.) did not show any effect. The activity of the 5-HT4 receptor antagonist DAU 6285 was evaluated in the gastric emptying model per se and in interaction experiments on the accelerating action of BIMU 1 (0.3 mg/kg L v.). At 1 mg/kg iv., DAU 6285 was ineffective on its own and failed to antagonize BIMU 1-induced prokinetic action;at the dose of 3 mg/kg i.v., it depressed the gastric emptying rate per se by 15% and totally abolished the accelerating effect of BIMU 1. In the binding assay, BIMU 1 exhibited an appreciable affinity for 5-HT3 receptors in NG 108-15 cells (KD: 0.8 nmol/l) and for 5-HT4 receptors in pig striatum (KD: 26.5 nmol/l). Compared to BIMU 1, cisapride bound with a similar affinity to 5-HT4 (KD: 35.2 mnol/l) and a much lower affinity to 5-HT3 receptors (KD: 155 nmol/l). By contrast, ondansetron was highly selective for 5-HT3 sites (KD: 4.7 nmol/l), being ineffective in the assay for 5-HT4 receptors (KD 〉 10000). Our results show that BIMU 1, like cisapride and unlike ondansetron, is an effective stimulant of gastric motility and propulsion. The action of BIMU 1 appears to depend on 5-HT4 receptor stimulation and to involve the activation of cholinergic nerve pathways.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 351 (1995), S. 229-236 
    ISSN: 1432-1912
    Keywords: Key words BIMU 8 ; BIMU 1 ; Renzapride ; 5-HT4 receptors ; Acetylcholine release ; Myenteric plexus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effects of the 5-HT4 receptor agonists BIMU 8, BIMU 1, renzapride and of the 5-HT1p receptor agonist 5-hydroxyindalpine on basal and electrically evoked outflow of tritium were studied in guinea-pig longitudinal muscle myenteric plexus preparations preincubated with [3H]choline. Muscle contractions were recorded simultaneously. BIMU 8 caused a calcium dependent and tetrodotoxin sensitive increase in basal [3H]outflow that was assumed to represent release of [3H]acetylcholine. In addition, BIMU 8 enhanced the release of [3H]acetylcholine and twitch contractions evoked by submaximal electrical stimulation. Ondansetron (1 μmol/l) did not change the effects of BIMU 8, but DAU 6285 and tropisetron (each 1 μmol/l) competitively antagonized the various facilitatory effects of BIMU 8 with pA2 values of 7.0–7.2 (DAU 6285) and 7.0–7.3 (tropisetron). The phosphodiesterase inhibitors IBMX and rolipram did not increase the effects of BIMU 8. BIMU 1 and renzapride also concentration-dependently increased basal release of acetylcholine, and release and contractions caused by submaximal stimulation. The effects of BIMU 1 and renzapride were competitively antagonized by 1 μmol/l tropisetron (pA2 6.6–7.1). The EC50 values for the increase in the evoked [3H]acetylcholine release and contractions were closely similar. 5-Hydroxyindalpine did not change basal release and slightly inhibited the evoked release of [3H]acetylcholine. Release of acetylcholine and contractions elicited by submaximal stimulation were strongly inhibited by (+)-tubocurarine which indicates that nicotinic ganglionic transmission is involved in this kind of release. The results suggest that BIMU 8, BIMU 1 and renzapride stimulate 5-HT4 receptors at cholinergic interneurones and thereby facilitate nicotinic ganglionic transmission in the myenteric plexus. Cyclic AMP is probably not involved in the 5-HT4 receptor mediated facilitation of acetylcholine release.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1912
    Keywords: 5-HT4 receptor antagonist ; 5-HT3 receptor antagonist ; Azabicycloalkyl benzimidazolone derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three chemical classes of serotonin 5-HT4 receptor agonists have been identified so far: 5-substituted indoles (e.g. 5-HT), benzamides (e.g. renzapride) and benzimidazolones (e.g. BIMU 8). In a search for 5-HT4 receptor antagonists, we have discovered that the benzimidazolone derivative DAU 6285 (for structure see text), is 3–5 times more potent than tropisetron in blocking 5-HT, renzapride and BIMU 8 induced stimulation of adenylate cyclase activity in mouse embryo colliculi neurons. Schild plot analysis yielded Ki values of 220, 181 and 255 nmol/l, respectively. In addition, DAU 6285 showed poor activity as a 5-HT3 receptor ligand with respect to tropisetron, as demonstrated by in vitro binding studies (Ki, 322 vs 2.8 nmol/l) and by its antagonistic activity in the Bezold-Jarisch reflex test (ID50, 231 vs 0.5 μg/kg, i.v.). No significant binding (Ki〉10 μmol/l) of DAU 6285 to serotonergic 5-HT1A, 5-HT1B, 5-HT1C, 5-HT1D, and 5-HT2 receptors as well as to adrenergic α1, α2, dopaminergic D1, D2 or muscarinic M1–M3 receptor subtypes was found. The data indicate that DAU 6285 has a somewhat higher affinity than tropisetron for 5-HT4 receptors, a property confirmed in functional tests, and much lower affinity than tropisetron for 5-HT3 receptors. The compound represents a new interesting tool for investigating the pharmacological and physiological properties of 5-HT4 receptors.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 351 (1995), S. 229-236 
    ISSN: 1432-1912
    Keywords: BIMU 8 ; BIMU 1 ; Renzapride ; 5-HT4 receptors ; Acetylcholine release ; Myenteric plexus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of the 5-HT4 receptor agonists BIMU 8, BIMU 1, renzapride and of the 5-HT1p receptor agonist 5-hydroxyindalpine on basal and electrically evoked outflow of tritium were studied in guinea-pig longitudinal muscle myenteric plexus preparations preincubated with [3H]choline. Muscle contractions were recorded simultaneously. BIMU 8 caused a calcium dependent and tetrodotoxin sensitive increase in basal [3H]outflow that was assumed to represent release of [3H]acetylcholine. In addition, BIMU 8 enhanced the release of [3H]acetylcholine and twitch contractions evoked by submaximal electrical stimulation. Ondansetron (1 μmol/l) did not change the effects of BIMU 8, but DAU 6285 and tropisetron (each 1 μmol/l) competitively antagonized the various facilitatory effects of BIMU 8 with pA2 values of 7.0–7.2 (DAU 6285) and 7.0–7.3 (tropisetron). The phosphodiesterase inhibitors IBMX and rolipram did not increase the effects of BIMU 8. BIMU 1 and renzapride also concentration-dependently increased basal release of acetylcholine, and release and contractions caused by submaximal stimulation. The effects of BIMU 1 and renzapride were competitively antagonized by 1 μmol/l tropisetron (pA2 6.6–7.1). The EC50 values for the increase in the evoked [3H]acetylcholine release and contractions were closely similar. 5-Hydroxyindalpine did not change basal release and slightly inhibited the evoked release of [3H]acetylcholine. Release of acetylcholine and contractions elicited by submaximal stimulation were strongly inhibited by ( + )-tubocurarine which indicates that nicotinic ganglionic transmission is involved in this kind of release. The results suggest that BIMU 8, BIMU 1 and renzapride stimulate 5-HT4 receptors at cholinergic interneurones and thereby facilitate nicotinic ganglionic transmission in the myenteric plexus. Cyclic AMP is probably not involved in the 5-HT4 receptor mediated facilitation of acetylcholine release.
    Type of Medium: Electronic Resource
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