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Involvement of alpha2-adrenergic mechanisms in experimental analgesic and anti-inflammatory activities of a benzamide derivative.

Several non-steroidal anti-inflammatory drugs of the N-pyridinyl-benzamide series that produce experimental peripheral and central anti-inflammatory effects possess a dopaminomimetic component and inhibit eicosanoid synthesis without acting directly on the enzymes classically involved in this process. We compared the anti-inflammatory and analgesic activities of one of the most active benzamide derivatives with those of clonidine. Rat paw and brain edemas were inhibited by these two agents, whereas different methods showed that yohimbine counteracted this effect and the analgesia it induced. The involvement of an alpha2-adrenergic and/or serotoninergic components in these activities is considered, without excluding the possibility that the mechanism of action is in part due to inhibition of prostaglandin synthesis.

Adrenergic alpha-Agonists↗

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.

Animals↗

Unexpected potentiation by discriminant benzamide derivatives of stereotyped behaviours elicited by dopamine agonists in mice.

Among four stereotyped manifestations that can be simultaneously quantified in mice treated with apomorphine (APO), two of them (climbing and sniffing) emerge at low APO dosages (below 1 mg/kg) whereas licking and sniffing require APO dosages above 6 mg/kg. However, in mice pretreated (either i.p. or i.c.v.) with sulpiride (especially the levo isomer) or (+/-)amisulpride in moderate dosage stereotyped licking and sniffing are elicited by APO in much lower dosage (0.75 mg/kg). As a consequence, in mice pretreated with these benzamide derivatives and receiving 0.75 mg/kg APO, a biphasic effect was observed: licking and gnawing progressively appear at low dosages, whereas they are progressively abolished at higher dosages. This potentiation of the effects of APO by (+/-) amisulpride is even more obvious (maximal scores increased) with larger test-doses of the dopamine agonist (up to 5 mg/kg). Amisulpride also allows the emergence of the two stereotyped behaviours in mice receiving other dopamine agonists in subthreshold dosages (Dipropyl 5,6-ADTN, dexamphetamine or cocaine). The potentiation of APO is still observed after dopamine depletion by reserpine and alpha-methylparatyrosine, whereas that of dexamphetamine is abolished. In contrast with the benzamide derivatives, haloperidol does not potentiate at any dosage the effect of APO but, at 0.15 mg/kg, suppresses licking and gnawing elicited by 0.75 mg/kg APO in mice pretreated with 6.25 mg/kg amisulpride or veralipride.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Differential effects of benzamides and thioxanthenes on dopamine-elicited accumulation of cyclic AMP in isolated rabbit retina.

Benzamides or thioxanthenes were tested as potential antagonists of the cyclic AMP accumulation induced by 10(-4) M dopamine in intact rabbit retinae in vitro in the presence of 5 to 7 mM theophylline. The neuroleptic sulpiride (10(-4) M) was found to be totally inactive whereas a substituted benzamide (clebopride) had small but significant antagonist effect at the same concentration. Among thioxanthenes, isomers of cisconfiguration, which are potent neuroleptics, completely inhibit the cyclic AMP accumulation induced by dopamine, in contrast to trans-isomers which had no inhibitory effects. These data would confirm that retina in vitro is another suitable model for screening antipsychotic activity of classical neuroleptics and that the mechanism of action of sulpiride still needs further investigation.

Animals↗

Trihalogenated benzamides--a new class of artificial sweeteners.

2,4,6-tribromo-3-carboxyalkyl-benzamides and -carboxyalkoxy-benzamides are intensely sweet. With a recognition threshold value of about 1 mumol/l the 3-carboxyethyl compound is one of the sweetest compounds known. The intensity of the sweet taste depends upon the nature of the carboxyalkyl/carboxylalkoxy group. In respect to the acute toxicity to mice the compounds are similar to the sodium salt of saccharin and sodium cyclamate. The compounds are easily obtainable in good yield.

Animals↗

[The benzamides tiapride, sulpiride, and amisulpride in treatment for Tourette's syndrome].

The treatment of Tourette's syndrome is a challenge. Dopamine receptor antagonists are the drugs of first choice for the treatment of tics. Because large controlled trials are lacking, there is no consensus about which of the different neuroleptic drugs should be preferred. In Germany, tiapride seems to be used most often for the treatment of tics in children - although only one small controlled trial has been performed on it till now. In adults, other dopamine receptor antagonists such as risperidone, pimozide, and sulpiride seem to be more effective than tiapride. Today it is unknown whether new atypical neuroleptic drugs including the benzamide amisulpride are more effective than the older benzamides tiapride and sulpiride.

Amisulpride↗

The effects of benzamide analogues on cocaine self-administration in rhesus monkeys.

RATIONALE: Based on the differential distribution of dopamine (DA) D(3) receptors in mesolimbic regions relative to nigrostriatal regions, the hypothesis was that D(3)-selective antagonists (i.e., higher affinity at D(3)- than D(2)-receptors) would be more potent than D(2)-selective antagonists at decreasing total cocaine intake relative to disrupting rates of responding. OBJECTIVE: To evaluate the effects of acute administration of seven DA antagonists with varying affinities for D(2) and D(3) receptors in monkeys self-administering cocaine. METHODS: Rhesus monkeys were trained to self-administer intravenous cocaine (0.01-0.3 mg/kg per injection) under a fixed-interval (FI) 5-min schedule during daily 4-h sessions. The use of a FI schedule allowed for independent assessment of rate effects and changes in reinforcement frequency as a consequence of drug pretreatments. The compounds examined, in order of D(3) binding affinity, were: 2,3-dimethoxy-N-(9-p-fluorobenzyl)-azabicyclo[3.3. 1]nonan-3beta-yl benzamide (MABN) = eticlopride = 5-bromo- 2, 3-dimethoxy-N-[1-(4-fluorobenzyl)piperidin-4-yl]benz-amide (BBP) > spiperone > fluoroclebopride (FCP) > 2, 3-dimethoxy-N-(p-fluorobenzyl)piperdin-4-yl benzamide (MBP) > haloperidol. RESULTS: In the absence of any pretreatments, cocaine-maintained responding varied as a function of dose and was characterized as an inverted U-shaped function, while cocaine intake increased in a dose-related fashion. When the dose of cocaine that maintained peak rates was available, all DA antagonists decreased response rates and cocaine intake in a dose- dependent manner. Increases in cocaine dose attenuated the effects of the DA antagonists, resulting in rightward shifts of the cocaine dose-response curves. Based on the ratio of behavioral potency at decreasing response rates relative to intake (ED(50) rate/ED(50) intake) when the highest cocaine dose was available, the order of potency and ED(50) ratio values were: MABN (2.5) > eticlopride (1. 63) > BBP = spiperone (1.5) > FCP (1.35) > MBP = haloperidol (0.89). This order parallels each compound's affinity at D(3) receptors (r(2)=0.84) to a greater degree than D(2) receptor affinity (r(2)=0. 34). CONCLUSIONS: These results, using a FI schedule of cocaine self-administration, suggest that D(3) receptor antagonists are more likely to selectively decrease intake relative to response rates than D(2) receptor antagonists.

Animals↗

Synthesis and binding properties of the fluorinated substituted benzamide [3H]NCQ 115, a new selective dopamine D2 receptor ligand.

[3H]NCQ 115 [R)-5-bromo-2,3-dimethoxy-N-[1-([2,5-3H]-4- fluorobenzyl)-2-pyrrolidinyl)methyl)benzamide) was prepared by acylation of (R)-(2-aminomethyl)-1- ([2,5-3H]-4-fluorobenzyl)pyrrolidine, which was obtained in a stereo-conservative synthesis from (R)-prolinamide. Purification by reversed phase high performance liquid chromatography (HPLC) gave [3H]NCQ 115 with a radiochemical purity of greater than 99% and a specific activity of 0.97 GBq/mumol (36 Ci/mmol). Saturation analyses, association and dissociation kinetics as well as binding competition with several compounds of various classes were performed with [3H]NCQ 115 in rat striatal homogenates. Saturation analyses in vitro showed that [3H]NCQ 115 bound to a single binding site with a Kd = 214 pM and Bmax = 35.4 fmol/mg. The binding of [3H]NCQ 115 was dependent upon sodium ions, since the number of binding sites was altered when sodium ions were excluded from the incubation medium. NCQ 115 inhibited the binding of [3H]raclopride to dopamine D2 receptors with high affinity (Ki = 147 pM), having much lower affinity for other receptors. The affinity of this substituted 1-benzyl-2-pyrrolidinylmethyl benzamide was confined to the (R)-enantiomer, which contrasts with that of the corresponding N-ethyl derivatives such as FLB 457, raclopride, eticlopride, sulpiride and NCQ 298, where the pharmacological activity is found in the (S)-enantiomer. It can be concluded that [3H]NCQ 115 binds to dopamine D2 receptors in the rat striatum with high affinity and high selectivity. [3H]NCQ 115 can also be used for in vivo binding studies of the brain. [18F]NCQ 115 may be a suitable ligand for positron emission tomography (PET) studies of the human brain in vivo.

Animals↗

Effect of a novel benzamide, YM-09151-2, on rat serum prolactin levels.

YM-09151-2(cis-N-(1-benzyl-2-methylpyrrolidin-3-yl) -5-chloro-2-methoxy-4-methylaminobenzamide) is a new benzamide which has been reported to be an antagonist of dopamine (DA) at D1-type DA receptors. In the present study, we have examined the extent of the interaction of YM-09151-2 with D2-type DA receptors in the anterior pituitary gland of the rat. YM-09151-2 was found to be a potent antagonist of these receptors as extremely low doses of this compound produced a marked, dose-dependent elevation of serum prolactin concentrations. This benzamide was also a potent blocker of DA-induced inhibition of prolactin release in vitro and was very effective in displacing 3H-spiperone from bovine pituitary membranes: IC50, 1.04nM. These results are consistent with recent evidence that YM-09151-2 is also a potent antagonist of the D2-type receptors in the intermediate lobe of the rat pituitary gland.

Animals↗

[125]I-spectramide: a novel benzamide displaying potent and selective effects at the D2 dopamine receptor.

The new substituted benzamide Spectramide, (N-[2-[4-iodobenzyl-N-methylamino]-2-methoxy-4-ethyl]-5-chloro- methylamine] benzamide) labelled with 125I was used as a potent and highly selective dopamine-D2 receptor antagonist in rat striatal homogenates for in vitro receptor binding. Kinetic experiments demonstrated the reversibility of the binding and the estimated Kd from saturation analysis was 25 pM, with a Bmax of 20 pmol/g of tissue. Competition studies showed that spectramide did not interact potently with the D1 or dopamine-uptake site. Drugs known to interact with other receptor systems were weak competitors of the binding, while binding was potently inhibited by other D2 antagonists, such as spiperone and eticlopride. These data indicate that Spectramide binds selectively and with high affinity to the dopamine D2 receptors, and may prove to be a useful tool for the study of these receptors in vivo using PET or SPECT.

Animals↗

Methamphetamine (METH) causes reactive gliosis in vitro: attenuation by the ADP-ribosylation (ADPR) inhibitor, benzamide.

We examined the effects of methamphetamine (METH) in an in vitro model of rat fetal mesencephalic cells. METH causes loss of dopamine (DA) cells and neuronal process degeneration. In addition, the drug causes an increase in reactive gliosis as shown by the number of cells that stain for and by the intensity of staining with a glial fibrillary acidic protein (GFAP) antibody. Co-incubation of METH-treated cells with benzamide, which is a known inhibitor of ADP-ribosylation (ADPR), attenuated METH effects on both DA and glial cells. However, the effects of benzamide were somewhat more prominent on the glial cells. These results suggest that ADP-ribosylation may play a very important role in the development of reactive gliosis after the administration of neurotoxic agents.

Adenosine Diphosphate Ribose↗

The discriminant dopamine antagonist property of benzamides is observed at various times after their systemic or intracerebroventricular administration.

The cataleptogenic effect or the antagonism of apormorphine-induced behaviour (climbing, sniffing, licking and yawning) shown by haloperidol, (+/-)sulpiride and (+/-)amisulpride were determined at different times after their intraperitoneal or intraventricular administration. After intraperitoneal injection, the ED50 or ID50 of haloperidol was similar for all the behavioural responses. On the other hand, sulpiride and amisulpride were effective on climbing and yawning in smaller doses than on sniffing, licking and catalepsy. The property of amisulpride to antagonize climbing at smaller doses than sniffing was still found whether this benzamide derivative was injected 30, 90, 150 or 240 min before testing. After the intraventricular administration of neuroleptics, a dissociated antagonist efficacy appeared for haloperidol, but that of sulpiride and amisulpride became much more marked than after their intraperitoneal injection. Amisulpride antagonized climbing in smaller doses than sniffing, whether administered intraventricularly 15, 30 or 120 min before testing. These results indicate that the dissociated dopamine antagonist efficacy of benzamides is long lasting and is observed even when the passage across the blood-brain barrier is avoided (i.c.v. route).

Animals↗

An analysis of the hypothalamic sites at which substituted benzamide drugs act to facilitate gastric emptying in the guinea-pig.

An analysis of the hypothalamic sites at which the substituted benzamides, metoclopramide and clebopride, act to facilitate gastric emptying was undertaken in the guinea-pig. Standard stereotaxic techniques for intracerebral injection via chronically indwelling intracerebral guides were combined with measurement of gastric emptying by fluoroscopic following of the passage of barium sulphate spheroids from the stomach. Injections were made at 7 different locations within the hypothalamus at Ant. 8.0, 8.9 and 9.6, Lat. +/- 1.0, +/- 1.6, +/- 2.2 (relative to the stereotaxic frame) and at 7.0, 8.0 and 9.0 mm below guide tips in the cortex. The most sensitive sites for gastric facilitation by the substituted benzamides were located at Ant. 8.9, Lat. +/- 1.6, Vert. -8.0, -9.0, the "perifornical area". As the distance of the injection site from the area of the fornix increased, so the facilitatory gastric action diminished, with marked delays or loss in response occurring when injection sites were moved 1 mm above, 0.6 mm lateral, 0.4 mm medial, 0.9 mm posterior or 0.7 mm anterior. The facilitatory gastric actions of metoclopramide and clebopride in the perifornical area of the hypothalamus were not mimicked by haloperidol, domperidone or sulpiride. Atropine, injected into the hypothalamus, markedly reduced gastric emptying; hexamethonium was less effective, and phentolamine, propranolol and methysergide were inactive. Atropine (but not hexamethonium, phentolamine, propranolol or methysergide), injected into the hypothalamus, dose-dependently antagonised the facilitatory gastric action of metoclopramide injected at the same site. Carbachol (but not serotonin, noradrenaline, dopamine or apomorphine), injected into the perifornical area, caused marked facilitation of gastric emptying.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Comparison of low dose nicotinamide versus benzamide, administered per os, as radiosensitizers in a C3H mammary carcinoma.

We have evaluated if any differences in tumor radiosensitization exist between the two adenosine diphosphate ribosyl transferase (ADPRT) inhibitors nicotinamide and benzamide at fractionated low doses. A significant radiosensitizing effect with nicotinamide at a 10 mg/kg per day dose was found in the tumor model used. We found, however, no radiosensitizing effect with benzamide given according to this schedule.

Administration, Oral↗

Benzamide derivatives provide evidence for the involvement of a 5-HT4 receptor type in the mechanism of action of serotonin in frog adrenocortical cells.

We have previously shown that serotonin (5-HT) is a potent stimulator of corticosterone and aldosterone secretion by frog adrenocortical cells and we have demonstrated that the action of 5-HT is not mediated by the classical 5-HT receptor subtypes i.e. 5-HT1, 5-HT2 and 5-HT3. Recently, a non-classical 5-HT receptor (termed 5-HT4) has been characterized using 4-amino-5-chloro-2-methoxy-benzamide derivatives as serotonergic agonists. In the present report, we have investigated the possible involvement of the 5-HT4 receptor subtype in the mechanism of action of 5-HT on steroid secretion. Increasing concentrations of benzamide derivatives (zacopride, cisapride and BRL 24924) gave rise to a dose-related stimulation of corticosteroid production, zacopride being the most potent compound of this series to enhance steroidogenesis. Prolonged administration (230 min) of zacopride induced a rapid increase in corticosterone and aldosterone output followed by a gradual decline of corticosteroid secretion. During prolonged exposure of adrenal tissue to zacopride (10(-5) M), the corticotropic activity of 5-HT (10(-6) M) was totally abolished. The stimulatory effects of 5-HT and zacopride were abolished by the non-selective 5-HT3 antagonist ICS 205 930. In contrast methysergide, a 5-HT1 receptor antagonist, and MDL 72222, a selective 5-HT3 antagonist did not block zacopride-induced corticosteroid secretion. Both 5-HT and zacopride induced a dose-related increase in cAMP production by frog adrenal slices. Taken together, these results indicate that the stimulatory effect of 5-HT on frog adrenocortical tissue is mediated by activation of a 5-HT4 receptor subtype positively coupled to adenylate cyclase.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

Preparation and biological evaluation of 18F-labeled benzamide analogs as potential dopamine D2 receptor ligands.

Three 18F-labeled benzamide derivatives were prepared and evaluated as potential ligands to study the dopamine D2 receptor phenomenon. The compounds are analogs of iodobenzamide, eticlopride and raclopride and are labeled with an N-2-[18F]fluoroethyl functionality on the pyrrolidine ring. The compounds were tested in vitro for binding affinity and found to exhibit somewhat lower affinity than the non-fluorinated analog. In vivo distribution studies revealed that all compounds were more highly bound to plasma proteins than was raclopride. In addition, compartmentation of radioactivity demonstrated nonspecific binding to be the predominate retention in the brain as reflected by the low caudate to cerebellum ratios for these compounds. These three 18F-labeled benzamide derivatives are inferior to raclopride and iodobenzamide for studies of the D2 receptor system using positron emission tomography.

Animals↗

Preparation and preliminary evaluation of 4-[211At]astato-N-piperidinoethyl benzamide.

The potential therapeutic agent, 4-[211At]astato-N-piperidinoethyl benzamide (4-APAB) was synthesized via a halodestannylation reaction. Radiochemical yields were 69% for a 5 min reaction and reached 74% by 25 min, whereas 82% radiochemical yields were obtained under similar reaction conditions for radioiodination. A simplified procedure was adopted for the purification of the target compound. In vitro binding of 4-APAB to SK-MEL 28 melanoma and D247 glioma cell lines was 20.7 +/- 1.3% and 12.2 +/- 1.3%, respectively. In comparison, binding of 4-[131I]iodo-N-piperidinoethyl benzamide (4-IPAB) to SK-Mel 28 cells was 13.9 +/- 1.9%. Paired label biodistribution studies were performed in normal Balb/c mice using 4-IPAB and 4-APAB. Thyroid uptake at 1, 2, and 6 h was significantly higher for 4-APAB. Differences in liver accumulation between the two compounds were small but statistically significant at most time points. A higher accumulation of 211At compared with 131I was observed in lungs and spleen at all time points studied. These results indicate that 4-APAB is not stable in vivo, suggesting the need for a better sigma receptor ligand for use in 211At.

Animals↗

Synthesis and pharmacological evaluation of benzamide derivatives as selective 5-HT(4) receptor agonists.

It is thought that selective 5-HT(4) receptor agonists-such as 4-amino-5-chloro-2-methoxy-N-[1-(6-oxo-6-phenylhexyl)piperidin-4ylmethyl]benzamide (2)-have the ability to enhance both upper and lower gastrointestinal motility without any significant adverse effects. Modification of 2 was performed. Variation of the piperidin-4ylmethyl moiety of 2 led to a decrease in the binding affinity for the 5-HT(4) receptor. Following conversion of the carbonyl group on the benzoyl part to a hydroxyl or sulfoxide group, the binding affinity for the 5-HT(4) receptor was retained although the effect on defecation was reduced. Many of the 4-amino-5-chloro-2-methoxy-N-(piperidin-4ylmethyl)benzamides that had a ether or sulfide moiety in the side-chain part at the 1-position of the piperidine exhibited high affinity for the 5-HT(4) receptor. Among these, phenylthio 41c and benzylthio derivative 44 were selective 5-HT(4) receptor agonists, and had a similar effect on defecation to compound 2.

Animals↗