Novel benzamides as selective and potent gastrokinetic agents. 2. Synthesis and structure-activity relationships of 4-amino-5-chloro-2-ethoxy-N-[[4-(4-fluorobenzyl)-2- morpholinyl]methyl] benzamide citrate (AS-4370) and related compounds

The title compounds (19-55) with a 4-substituted 2-(aminomethyl)morpholine group were prepared and evaluated for the gastrokinetic activity by determining their effect on gastric emptying of phenol red semisolid meal in rats. Introduction of chloro, fluoro, and trifluoromethyl groups to the benzyl group of the parent compounds 1a and 1b enhanced the activity. Among compounds tested, 4-amino-5-chloro-2-ethoxy-N-[[4-(4-fluorobenzyl)-2-morpholinyl] methyl] benzamide (23b) showed the most potent gastric emptying activity (effects on phenol red semisolid meal in rats and mice, and on resin pellets solid meal in rats). The gastrokinetic activity of 23b citrate (AS-4370) compared very favorably with that of cisapride and was higher than that of metoclopramide. In contrast to metoclopramide and cisapride, AS-4370 was free from dopamine D2 receptor antagonistic activity in both in vitro ([3H]spiperone binding) and in vivo (apomorphine-induced emesis in dogs) tests.     

Effects of SK-951, a benzofuran derivative, as a prokinetic agent in rats and dogs

The gastrokinetic activity of SK-951 ((-)4-amino-N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-5-chloro-2,3-dihy dro-2-methylbenzo[b]furan-7-carboxamide hemifumarate), a benzofuran derivative with 5-hydroxytryptamine (5-HT)4-receptor agonist activity, was studied in rats and dogs. The effects of SK-951 were also investigated in a model of vagotomy-induced gastroparesis in comparison with cisapride. In rats, both SK-951 and cisapride enhanced gastric emptying of liquids (phenol red) at a dose of 1-100 mg/kg, p.o. Gastric emptying of liquid (acetaminophen) in fasted beagle dogs was enhanced significantly by SK-951 (1.0 mg/kg, i.v.), whereas the effect of cisapride (0.2-1.0 mg/kg, i.v.) was not statically significant. Similar results were found when radiopaque markers were given with standard meal to dogs with vagotomy-induced gastroparesis. The delayed gastric emptying of radiopaque markers by vagotomy was reversed by SK-951 (1.0 mg/kg, i.v.), whereas cisapride showed no effect at doses from 0.1 to 1.0 mg/kg, i.v. These results indicated that oral and intravenous administration of SK-951 accelerates gastric emptying of both liquids and solids in animal models. Thus, SK-951 may be a highly potent and useful prokinetic agent in comparison to cisapride.     

Substituted benzamides with conformationally restricted side chains. 1. Quinolizidine derivatives as selective gastric prokinetic agents

The gastric prokinetic action of metoclopramide may not be primarily due to its dopamine antagonist activity. The present aim was to obtain a selective gastric prokinetic agent lacking dopamine antagonist activity by conformationally restricting the side chain of metoclopramide. In a series of quinolizidinylbenzamides, only compounds with the benzamide moiety at position 2 of the quinolizidine ring retain gastric activity. Of these 2-substituted compounds, the 2 alpha, 9a alpha isomer has potent selective gastric prokinetic activity with only weak dopamine antagonist properties. Spectroscopic data show that the quinolizidine ring preferentially adopts a trans chair-chair conformation with an axial benzamide moiety. However, energy calculations indicate that, at nondopaminergic receptors controlling gastric motility, an alternative cis chair-chair conformation with an equatorial benzamide moiety cannot be ruled out.     

Synthesis and neuroleptic activity of benzamides. Cis-N-(1-benzyl-2-methylpyrrolidin-3-yl)-5-chloro-2-methoxy-4-(methylamino)benzamide and related compounds

Three series of benzamides of N,N-disubstituted ethylenediamines (linear alkane-1,2-diamines), 1-substituted 2-(aminomethyl)pyrrolidines, and 1-substituted 3-aminopyrrolidines (cyclic alkane-1,2-diamines) were designed and synthesized as potential neuroleptics. All target compounds were evaluated for their inhibitory effects on apomorphine-induced stereotyped behavior in rats, and a good correlation between structure and activity was found throughout the series. In the linear series (analogues of metoclopramide), introduction of a benzyl group on the terminal nitrogen, rather than an ethyl group, and a methyl group on the p-amino group of metoclopramide both enhanced the activity. The resulting N-[2-(N-benzyl-N-methylamino)ethyl]-5-chloro-2-methoxy-4-(methylamino) benzamide(23) was about 15 times more active than metoclopramide. In the cyclic series, particularly among the benzamides of 1-benzyl-3-aminopyrrolidine, most of the compounds tested were more active than the corresponding linear benzamides. cis-N-(1-Benzyl-2-methylpyrrolidin-3-yl)-5-chloro-2-methoxy-4-(methylamino) benzamide (YM-09151-2, 55) was the most active among all of the compounds tested, being 13 and 408 times more potent than haloperidol and metoclopramide, respectively. Moreover, compound 55 exhibited a fairly high ratio of antistereotypic activity to cataleptogenicity compared with haloperidol and metoclopramide. It is expected that compound 55 may be used as a potent drug with few side effects in the treatment of psychosis.     

Prokinetic benzamides stimulate peristaltic activity in the isolated guinea pig ileum by activation of 5-HT4 receptors.

Substituted benzamides such as metoclopramide, cisapride, zacopride, renzapride or BRL 20627, stimulate intestinal motility in various species. As they are antagonists at 5-HT3 and agonists at 5-HT4 receptors and as both mechanisms could potentially contribute to their gastrointestinal prokinetic effect, the underlying mechanism is unclear. To clarify this, the effect of some substituted benzamides on gut motility was investigated in the isolated guinea pig ileum using the Trendelenburg technique, in which pressure-induced peristaltic contractions are measured. All benzamides stimulated the peristaltic reflex with the rank order of potency: renzapride greater than cisapride greater than BRL 20627 greater than (+/-)-zacopride greater than metoclopramide. ICS 205-930, granisetron and 2-methyl-5-HT did not change the peristaltic response. 5-HT and 5-methoxytryptamine potently mimicked the effect of the benzamides. The effect of 5-HT was not blocked by ICS 205-930 (10(-7) M). These results indicate that the Trendelenburg preparation is suitable for the investigation of intestinal prokinetic effects of the substituted benzamides. Furthermore, the results suggest that the intestinal effect of benzamides results from activation of 5-HT4 receptors rather than from blockade of 5-HT3 receptors.     

Gastroprokinetic activity of nizatidine during the digestive state in the dog and rat.

The present study was undertaken to clarify a prokinetic activity of nizatidine (CAS 76963-41-2) during the digestive state as well as gastric emptying of a solid test meal in comparison with cimetidine (CAS 51481-61-9), famotidine (CAS 76842-35-6) and cisapride (CAS 81098-60-4). Intravenous administration of nizatidine (0.3-3 mg/kg) enhanced the motility of the gastric antrum and duodenum during the digestive state. With cimetidine (1-10 mg/kg) and famotidine (0.1-1 mg/kg) enhancement of gastric motility was observed only with the highest dose of cimetidine, and famotidine had no effect. Marked enhancement of gastric motility was observed with cisapride (0.1-0.5 mg/kg). After intraduodenal administration of nizatidine (10 and 20 mg/kg) and cisapride (0.25 and 0.5 mg/kg), they also amplified the contractile activity of the gastric antrum. Gastric emptying of a solid test meal was accelerated by intraperitoneal administration of nizatidine (1-10 mg/kg) to the same extent as cisapride (0.1-1 mg/kg). In addition, even in a model of delayed gastric emptying induced by clonidine, nizatidine, like cisapride, improved the rate of gastric emptying. Neither cimetidine (3-30 mg/kg) nor famotidine (0.3-3 mg/kg) affected the gastric emptying of a solid meal or delayed gastric emptying. These results suggest that nizatidine enhanced gastric motility even during the digestive state, and accelerated gastric emptying of a solid meal, similar to cisapride. Furthermore, nizatidine improved clonidine-induced delayed gastric emptying. These prokinetic activities of nizatidine may by useful for the treatment of abdominal symptoms due to dysmotility and delayed gastric emptying in patients with gastritis and non-ulcer dyspepsia (NUD). In comparison with famotidine and cimetidine, nizatidine may be different from other histamine H2-receptor antagonists and has unique properties other than its gastric antisecretory activity.     

Pharmacological effects of the gastroprokinetic agent mosapride citrate]

Mosapride citrate (mosapride) is a novel gastroprokinetic agent that enhances the gastrointestinal motility by stimulating the 5-hydroxytryptamine4 (5-HT4) receptor. Mosapride dose-dependently enhanced the gastric emptying of a liquid or solid meal in rats with a potency equal to that of cisapride and more potent than that of metoclopramide. In rats, mosapride improved the gastric emptying delayed by gastroduodenal surgical intervention. In the conscious dogs with force transducers implanted chronically, mosapride stimulated antral and duodenal motility with a potency equal to those of cisapride. In isolated guinea-pig ileal longitudinal muscle preparations, mosapride enhanced the electrically stimulated contractions, and the enhancing effect of mosapride was antagonized by a high dose of tropisetron, a 5-HT4-receptor antagonist. In addition, mosapride inhibited [3H]-GR-113808 binding to 5-HT4 receptor sites of guinea-pig ileum and striatum. Mosapride had no affinity for dopamine D2 receptor, whereas metoclopramide and cisapride had a high affinity for dopamine D2 receptor. In isolated guinea-pig papillary muscles, mosapride did not prolong the duration of action potentials, whereas cisapride concentration-relatedly prolonged it. In conclusion, mosapride is a selective and potent 5-HT4 receptor agonist and improves gastrointestinal symptoms in patients with non-ulcer dyspepsia without causing the extrapyraminal syndrome associated with dopamine-D2-receptor blockage and adverse cardiovascular effects such as torsadoes de points.     

Effect of metoclopramide, bethanechol and the cholecystokinin receptor antagonist, L-364,718, on gastric emptying in the rat

The prokinetic effects of metoclopramide, bethanechol and L-364,718 on a semisolid meal and solid pellet gastric emptying were evaluated and compared. Each compound increased the rate of meal emptying as measured 90 min post-dose. L-364,718, a non-peptide CCK antagonist, was the most potent of these three agents with statistically significant activity observed at 0.03, 0.1 and 0.3 mg/kg p.o. Only metoclopramide significantly enhanced pellet emptying in a dose-dependent manner (3-30 mg/kg p.o.). The effects of each test agent and the potential physiologic role of cholecystokinin in regulating gastric emptying are discussed.     

Cisapride accelerates gastric emptying and mouth-to-caecum transit of a barium meal

Summary Cisapride (R 51 619) is a newly synthesized compound, which facilitates the release of acetylcholine in the myenteric plexus of the gut. Its effect on gastric emptying of a barium meal was evaluated in 84 patients under randomized, double-blind conditions. Two oral doses (5 mg and 10 mg) of cisapride were compared with a placebo, and two intravenous doses (4 mg and 8 mg) with a placebo and with 10 mg metoclopramide. All doses of cisapride and metoclopramide were significantly superior to placebo in accelerating gastric emptying, intensifying antral contractions and shortening the mouth-to-caecum transit time. The effects of 8 mg cisapride and 10 mg metoclopramide given intravenously were comparable.     

General pharmacology of the four gastrointestinal motility stimulants bethanechol, metoclopramide, trimebutine, and cisapride

The pharmacological profile of bethanechol (CAS 674-38-4), metoclopramide (CAS 364-62-5), trimebutine (CAS 39133-31-8) and cisapride (CAS 81098-60-4) was studied in a series of simple pharmacological tests in rats and dogs. Bethanechol stimulated both gastric emptying and intestinal propulsion but displayed also the well-known behavioral effects of a direct muscarinic acetylcholine receptor agonist. Metoclopramide showed the profile of a centrally active dopamine D2 antagonist. In addition, metoclopramide displayed a stimulant effect on spontaneous gastric emptying in rats, an effect that could not be related to dopamine D2 antagonism. The only effect observed with trimebutine was protection from castor oil diarrhea, probably due to its reported interaction with peripheral opiate receptors. Cisapride was a potent stimulant of gastric emptying in rats, 7 times more potent than metoclopramide. Cisapride was also a very specific gastrokinetic, over a large dose range (specificity ratio: greater than or equal to 20) devoid of effects indicative for direct interaction with dopamine or acetylcholine receptors. The relationship between the differential activity profiles of the compounds in the present study and differences in their mechanism of action and side-effect liability is discussed.     

Substituted benzamides with conformationally restricted side chains. 2. Indolizidine derivatives as central dopamine receptor antagonists

The substituted benzamides metoclopramide (1) and clebopride (3) are stimulants of gastric motility. They are also central dopamine receptor antagonists with 3 being the more potent. This is presumed to be due to an additional interaction of its N-benzyl group with the receptor. The effect of restricting the conformation of this group by replacing the N-benzylpiperidine side chain of 3 by phenyl-substituted quinolizidines and indolizidines has been investigated. Only the indolizidines had significant activity, the nature of which depended upon the orientation of the phenyl substituent. The 2 alpha-phenyl isomers 5d-h were potent central dopamine D2 receptor antagonists with 5h showing selectivity for the limbic system. The 2 beta-phenyl isomer 5c was a gastric motility stimulant devoid of significant central dopamine receptor antagonist activity. Implications on receptor models are discussed.     

Anti-Helicobacter pylori agents. 3. 2-[(Arylalkyl)guanidino]-4-furylthiazoles.

A series of 2-[(arylalkyl)guanidino]-4-[(5-acetamidomethyl)furan-2-yl]thiazole s and some 4-acetamidomethyl positional isomers were synthesized and evaluated for antimicrobial activity against Helicobacter pylori. Among the compounds that had potent antimicrobial activity (MIC < 0. 1 microgram/mL), compounds 31 and 36 additionally possessed H2 antagonist and gastric antisecretory activities. Though compound 51, an analogue incorporating a methyl group onto the furan nucleus of 36, and compound 54, a positional isomer of 51, also showed potent anti-H. pylori activity, the H2 antagonism profile was eliminated from these compounds. Thus, two types of potent anti-H. pylori agents could be derived from the same scaffold.     

The interaction of substituted benzamides with brain benzodiazepine binding sites in vitro.

1. The interaction of substituted benzamides with brain benzodiazepine (BDZ) binding sites was examined by their ability to displace [3H]-flunitrazepam ([3H]-FNM) from specific binding sites in bovine cortical membranes in vitro. 2. Clebopride, Delagrange 2674, Delagrange 2335 and BRL 20627 displayed concentration-dependent displacement of [3H]-FNM with IC50 values of 73 nM, 132 nM, 7.7 microM and 5.9 microM, respectively. Other substituted benzamides including metoclopramide, sulpiride, tiapride, sultopride and cisapride were inactive at 10(-5) M. 3. Inhibition by clebopride and Delagrange 2674 of [3H]-FNM binding was apparently competitive and readily reversible. 4. In the presence of gamma-aminobutyric acid (GABA), the ability of diazepam and Delagrange 2674 to displace [3H]-Ro 15-1788 binding was increased 3.6 and 1.6 fold respectively, compared to the absence of GABA, while ethyl beta-carboline-3-carboxylate (beta CCE) and clebopride were less potent in the presence of GABA. 5. Diazepam was 30 fold less potent at displacing [3H]-Ro 15-1788 in membranes that had been photoaffinity labelled with FNM than in control membranes, whereas the potency of beta CCE did not differ. Clebopride and Delagrange 2674 showed a less than two fold loss of potency in photoaffinity labelled membranes. 6. The pattern of binding of clebopride and Delagrange 2674 in these in vitro tests is similar to that found previously with partial agonists or antagonists at BDZ binding sites. 7. Clebopride and Delagrange 2674 inhibited [3H]-FNM binding with similar potency in rat cerebellar and hippocampal membranes, suggesting they have no selectivity for BDZ1 and BDZ2 binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)     

Domperidone, a novel and safe gastrokinetic anti-nauseant for the treatment of dyspepsia and vomiting

The new potent anti-nauseant 5-chloro-1-(1p[3-(2,3-dihydro-2-oxo-1H-benzimidazol-1-yl)-propyl]-4-piperidinyl)-1.3-dihydro-2H-benzimidazol-2-one (domperidone), which in contrast to available anti-emetics does not provoke extrapyramidal or adrenolytic adverse effects, also enhances gastric emptying motility. Controlled clinical trials have confirmed its prokinetic effects on the stomach and its lack of side-effects, even at high doses. This anti-nauseant appears to be a safe and effective treatment for patients, both adults and children, with dyspepsia or vomiting.     

Effects of 5-Hydroxytryptamine Agonists on Myoelectric Activity of the Forestomach and Antroduodenal Area in Sheep

To increase knowledge of the role of 5-hydroxytryptamine (5-HT) receptors in the regulation of reticuloruminal, omasal and antroduodenal myoelectric activity in sheep, the effects of 5-HT agonists on forestomach and antroduodenal myoelectric activity have been investigated in conscious sheep. 5-Carboxamidotryptamine, methysergide, α-methyl-5-HT, 2-methyl-5-HT, cisapride, zacopride or metoclopramide were infused intravenously for 5 min and myoelectric recordings were obtained from electrodes chronically implanted in the reticulum, rumen (dorsal sac), omasal body, abomasal antrum and duodenal bulb. The integrated activity of the reticular and ruminal spike bursts was modified only by the highest doses of α-methyl-5-HT, 2-methyl-5-HT, metoclopramide and cisapride. A phase III-like activity pattern was recorded in the antroduodenal area with all 5-HT-ergic agents and a dose-dependent inhibition of myoelectric activity was recorded in both reticulorumen and omasum at the same time as the antroduodenal effects. In the forestomach, methysergide alone induced inhibition of ruminal secondary contractions; 5-HT, α-methyl-5-HT, cisapride and metoclopramide, moreover, evoked an initial dose-dependent increase in antral activity. These results suggest that 5-HT₁; 5-HT₂, 5-HT₃ and 5-HT₄ receptors are involved in the regulation of the migrating myoelectric complex in sheep and in the genesis of forestomach hypomotility that is occasionally recorded concomitantly with the spontaneous duodenal phase III in sheep. 5-HT₄ receptors also have a prokinetic action in the antral area.     

Comparative effects of levosulpiride and cisapride on gastric emptying and symptoms in patients with functional dyspepsia and gastroparesis

BACKGROUND: The efficacy of several prokinetic drugs on dyspeptic symptoms and on gastric emptying rates are well-established in patients with functional dyspepsia, but formal studies comparing different prokinetic drugs are lacking. AIM: To compare the effects of chronic oral administration of cisapride and levosulpiride in patients with functional dyspepsia and delayed gastric emptying. METHODS: In a double-blind crossover comparison, the effects of a 4-week administration of levosulpiride (25 mg t.d.s.) and cisapride (10 mg t.d.s.) on the gastric emptying rate and on symptoms were evaluated in 30 dyspeptic patients with functional gastroparesis. At the beginning of the study and after levosulpiride or cisapride treatment, the gastric emptying time of a standard meal was measured by 13C-octanoic acid breath test. Gastrointestinal symptom scores were also evaluated. RESULTS: The efficacy of levosulpiride was similar to that of cisapride in significantly shortening (P < 0.001) the t1/2 of gastric emptying. No significant differences were observed between the two treatments with regards to improvements in total symptom scores. However, levosulpiride was significantly more effective (P < 0.01) than cisapride in improving the impact of symptoms on the patients' every-day activities and in improving individual symptoms such as nausea, vomiting and early postprandial satiety. CONCLUSION: The efficacy of levosulpiride and cisapride in reducing gastric emptying times with no relevant side-effects is similar. The impact of symptoms on patients' everyday activities and the improvement of some symptoms such as nausea, vomiting and early satiety was more evident with levosulpiride than cisapride.     

Pharmacological properties of a novel gastrointestinal prokinetic benzamide selective for human 5-HT4 receptor versus human 5-HT3 receptor.

Binding properties of gastrointestinal prokinetic benzamides for both cloned human 5-hydroxytryptamine (5-HT)3 receptors and cloned human 5-HT4 receptors were examined and pharmacological properties of YM-53389{(+)-(S)-2-chloro-5-methoxy-4-[5-(2-piperidylmethyl)-1,2, 4-oxadiazol-3-yl]aniline monohydrochloride} were characterised in animals. Cisapride, renzapride and zacopride inhibited specific binding of [3H]ramosetron to cloned human 5-HT3 receptors, with Ki values of 684, 7.64 and 0.38 n m, respectively. YM-53389, however, slightly replaced that (Ki>10,000 n m). YM-53389, cisapride, renzapride and zacopride replaced specific binding of [3H]GR 113808 to cloned human 5-HT4 receptors, with Ki values of 54.6, 41.5, 115 and 373 n m, respectively. The potency for inhibitory effect of YM-53389 on 5-HT3 receptor-mediated contraction in the guinea-pig isolated colon was very low with pIC50 of 4.7. YM-53389 exerted 5-HT4 receptor-mediated relaxation in the carbachol-precontracted rat isolated oesophagus with pEC50 of 6.3. In mice, YM-53389 at 10 and 30 mg kg-1, s.c. significantly shortened whole gut transit time, in contrast to cisapride, renzapride and zacopride which were reported to delay that. YM-53389 had no significant effect on upper gastrointestinal propulsion at doses up to 30 mg kg-1, s.c. Based on these results, YM-53389 may surpass existing benzamides in facilitating lower intestinal propulsion and benefit patients with gastrointestinal disorders associated with impair of intestinal propulsion, such as constipation, based on the selective interaction with human 5-HT4 receptors vs human 5-HT3 receptors.     

Gastrointestinal motility stimulating drugs and 5-HT receptors on myenteric neurons

5-HT3 receptor antagonists may have both antiemetic and gastric and intestinal motility stimulating properties, but they differ in their relative potencies and efficacies for these two activities. Since the 5-HT3 receptor is present on enteric neurons, intracellular recordings of myenteric neuronal transmembrane potential were used to assess the actions of four proposed motility stimulating drugs, metoclopramide, BRL 24924, ICS 205-930 and cisapride. BRL 24924 (10(-6) M), ICS 205-930 (10(-7) M) and cisapride (5 x 10(-6) M) each antagonized the 5-HT3-mediated fast depolarization of myenteric neurons. Metoclopramide (10(-5) M) was less consistent in its ability to antagonize this response, and the response often returned in the continued presence of metoclopramide. In the present study, BRL 24924 (10(-6) M) and, as previously shown, cisapride (5 x 10(-6) M) antagonized the slow depolarization of myenteric neurons induced by 5-HT. Metoclopramide (10(-5) M), BRL 24924 (10(-6) M) and cisapride (5 x 10(-6) M), but not ICS 205-930 (10(-7) M) depolarized myenteric neurons within the first 2 min of contact with myenteric neurons. These data support the view that there are separate receptors that may be responsible for the prokinetic actions of these drugs and a series of 5-HT3-mediated actions which include antiemesis.     

Gastroprokinetic properties of the benzimidazolone derivative BIMU 1, an agonist at 5-hydroxytryptamine4 and antagonist at 5-hydroxytryptamine3 receptors

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 (K_D: 0.8 nmol/l) and for 5-HT₄ receptors in pig striatum (K_D: 26.5 nmol/l). Compared to BIMU 1, cisapride bound with a similar affinity to 5-HT₄ (K_D: 35.2 mnol/l) and a much lower affinity to 5-HT₃ receptors (K_D: 155 nmol/l). By contrast, ondansetron was highly selective for 5-HT₃ sites (K_D: 4.7 nmol/l), being ineffective in the assay for 5-HT₄ receptors (K_D > 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. Correspondence to: C. A. Rizzi at the above address     

Conformationally restrained analogues of pravadoline: nanomolar potent, enantioselective, (aminoalkyl)indole agonists of the cannabinoid receptor.

Pravadoline (1) is an (aminoalkyl)indole analgesic agent which is an inhibitor of cyclooxygenase and, in contrast to other NSAIDs, inhibits neuronally stimulated contractions in mouse vas deferens (MVD) preparations (IC50 = 0.45 microM). A number of conformationally restrained heterocyclic analogues of pravadoline were synthesized in which the morpholinoethyl side chain was tethered to the indole nucleus. Restraining the morpholine diminished the ability of these pravadoline analogues to inhibit prostaglandin synthesis in vitro. In contrast, mouse vas deferens inhibitory activity was enhanced in [2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl] pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-(4-methoxyphenyl)methano ne (20). Only the R enantiomer of 20 was active (IC50 = 0.044 microM). An optimal orientation of the morpholine nitrogen for MVD inhibitory activity within the analogues studied was in the lower right quadrant, below the plane defined by the indole ring. A subseries of analogues of 20 and a radioligand of the most potent analogue, (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo [1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthalenyl)methanone (21) were prepared. Inhibition of radioligand binding in rat cerebellar membranes was observed to correlate with functional activity in mouse vas deferens preparations. Binding studies with this ligand (Win 55212-2) have helped demonstrate that the (aminoalkyl)indole binding site is functionally equivalent with the CP-55,940 cannabinoid binding site. These compounds represent a new class of cannabinoid receptor agonists.