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[Effect of mazindol on insulin and glucagon secretion in ventromedial hypothalamic obese rats].

The effect of mazindol on insulin and glucagon secretion was studied in ventromedial hypothalamic lesioned (VMH) obese rats with hyperinsulinemia and VMH sham rats. Three weeks after the VMH or sham operation, VMH and sham rats were divided into two groups: one was fed diet containing mazindol (50 mg/kg) and the other was fed diet without mazindol. They were housed three more weeks before the experiment. Mazindol reduced significantly body weight increase and calorie intake in VMH rats, but not in sham rats. In addition, the fasting plasma insulin level and the arginine-induced insulin secretion in VMH rats treated with mazindol were significantly lower than those in the VMH rats without treatment of mazindol. On the other hand, in both in vivo and in vitro experiments, mazindol produced no significant change in the insulin secretion of sham-operated rats. These results suggest that mazindol suppresses hypersecretion of insulin in VMH rats probably through an anorectic effect and/or suppression of vagal hyperactivity.

Animals↗

Endocrine studies with mazindol in obese patients.

Detailed endocrine studies were carried out in 95 hospitalized obese patients during their treatment with diet and the tricyclic anoretic mazindol. The results obtained after 1 week or more of mazindol (2 mg or occasionally 4 mg/day) administration were compared with the results after placebo and with the initial pre-treatment values. There were no significant changes in the following parameters: FSH, LH, testosterone, renin, angiotensin II, growth hormone (GH) levels during insulin tolerance tests (ITT), 131I uptake, basal metabolic rate, Achilles tendon reflexes, T3 RIA, rT3 RIA, 17-ketosteroids and 17-ketogenic steroids in urine, both basal and after stimulation with ACTH and metyrapone. Blood glucose and plasma immunoreactive insulin (IRI) levels during oral glucose tolerance tests decreased during mazindol administration, IRI levels were significantly lower during ITTs after mazindol. T4 RIA serum levels increased significantly after mazindol. When mazindol was administered, GH levels increased somewhat in some obese patients during ITTs, while T3 RIA and rT3 RIA decreased in some patients. Mazindol has not only hunger (appetite) suppressing properties, but it probably affects the metabolism of energy substrates as well. The drug was well tolerated and there were no pathological findings in routine laboratory examinations during a long-term study with mazindol (non-stop treatment for 6 months).

Adolescent↗

Radiolabeling of dopamine uptake sites in mouse striatum: comparison of binding sites for cocaine, mazindol, and GBR 12935.

This study addressed the possibility of a unique binding interaction between cocaine and the dopamine transporter as compared with other blockers of dopamine uptake. Cocaine binding sites in a fresh P2 fraction of mouse striatum were labeled with [3H]CFT, a phenyltropane analog of cocaine also known as WIN 35,428, and compared with sites labeled with [3H]mazindol or [3H]GBR 12935. Under the conditions used, homogeneous binding was observed that was inhibited monophasically by cocaine, CFT, and mazindol; the same potencies were observed with the three radioligands. Saturation analysis in the presence and in the absence of unlabeled inhibitor (CFT, mazindol, cocaine) indicated a change in the Kd but not the Bmax, consonant with a competitive mechanisms. Tris-HCl reduced the affinity of each radioligand and unlabeled inhibitor without changing the Bmax. N-Ethylmaleimide reduced the binding of all radioligands equally and cocaine offered protection. The dissociation rate of [3H]CFT and [3H]mazindol binding was not affected by the presence of mazindol and CFT, respectively. The Bmax of [3H]CFT and [3H]mazindol binding was the same; the relatively higher value for [3H]GBR 12935 binding in analyses involving varying tritiated GBR 12935 only, was due primarily to an underestimation of the specific activity of [3H]GBR 12935. All results are in agreement with a one-site model in which cocaine, CFT, mazindol, and GBR 12935 share a common binding site in mouse striatum.

Animals↗

Mazindol and amphetamine as inhibitors of the uptake and releasers of 3H-dopamine by rat striatal synaptosomes.

The effects of mazindol, amphetamine and fenfluramine on uptake and release of 3H-DA by synaptosomes were studied in different systems. In in vitro incubations of 3H-DA with synaptosomes isolated from the caudate nucleus of the rat, mazindol inhibited the uptake of the radioactivity more potently than did amphetamine. When the synaptosomes were isolated from the caudate nuclei of rats treated in vivo with either mazindol or amphetamine, the uptake of 3H-DA during in vitro incuation was lower with synaptosomes of amphetamine-treated rats than with those of mazindol-treated rats. When synaptosomes of untreated rats were prelabelled with 3H-DA and incubated in the presence of amphetamine or of mazindol, amphetamine caused a greater release of radioactivity than did mazindol. Fenfluramine was without activity in all these systems. In spite of the quantitative differences, both amphetamine and mazindol appear to have similar effects on uptake and release of dopamine, and this may account for their analogous pharmacological profile.

Animals↗

Comparison of characteristics of dopamine uptake and mazindol binding in mouse striatum.

Biochemical and pharmacological studies suggest that the binding of [3H]mazindol is functionally related to the dopamine uptake carrier complex in rodent striatum. In order to study further the relationship between the substrate recognition site for dopamine uptake and the high-affinity binding site for mazindol the uptake of [3H]dopamine and the binding of [3H]mazindol was studied in BALB/cBy mouse striatum in various buffers (Tris, HEPES, bicarbonate-phosphate). Kinetic analysis showed that the Kd of the binding of [3H]mazindol and the Km of the uptake of [3H]dopamine was changed by different sodium concentrations and/or by the presence of Tris, while the Bmax and the Vmax remained essentially the same. However, the shape of the Na+ dependency curves was not the same for mazindol binding and dopamine uptake in the various buffers. The inhibitory effect of other cations such as K+ and Tris was also different on binding and uptake under similar experimental circumstances. Dopamine did not slow down the dissociation of mazindol from its site and this effect was not sodium-sensitive. These complexities can be accommodated by a model that involves overlapping sites for mazindol and dopamine on the dopamine uptake carrier complex, and translocation-reorientation steps.

Animals↗

Some effects of mazindol, an anorectic drug, on rat brain monoaminergic systems.

Mazindol was devoid of effect both on rat brain steady state levels of 5-HT, 5-HIAA and tryptophan and on the rate of synthesis of 5-HT in the rat brain. Mazindol had no effect on rat brain 5-HT uptake in vivo as determined by the effect of drug pretreatment on the ability of p-chloroamphetamine to lower central 5-HT levels. A large dose of mazindol caused a slight transient decrease in rat brain levels of NA and DA. Blockade of rat brain catecholamine uptake was quantified by studying drug effects on the ability of intraventricularly administered 6-hydroxydopamine to lower brain NA and DA content. Mazindol was an extremely potent inhibitor of rat brain NA uptake in vivo, being 4-5 times more potent than desipramine. Mazindol also blocked rat brain DA uptake. Doses of mazindol needed to release alpha-methyl-m-tyramine from the rat striatum were appreciably greater than the corresponding doses of d-amphetamine. The neurochemical profile of mazindol bears a much closer resemblance to that of d-amphetamine than to that of fenfluramine.

Animals↗

Assessment of mazindane, a pro-drug form of mazindol, in assays used to define cocaine treatment agents.

The current studies compared mazindane (5-(4-chlorophenyl)-2,3-dihydro-5H-imidazo [2,1a] isoindole) hydrogen sulfate, a water soluble pro-drug of mazindol (5-(4-chlorophenyl-2,3-dihydro-5H-imidazo [2,1-a] isoindol-5-ol), with mazindol in assays used to define cocaine treatment agents. Both compounds enhanced motor activity (LMA) in Swiss Webster mice with ED(50) values of 2.5 mg/kg i.p. for mazindane and 3.9 mg/kg i.p. for mazindol. At 25 mg/kg mazindane displayed toxic effects and death while mazindol was effect/death free at 50 mg/kg. In Sprague-Dawley rats trained to discriminate cocaine from saline both compounds fully substituted for cocaine with mazindane being fourfold more potent in the total session (0.33 vs. 1.3 mg/kg i.p.) and first reinforcer (0.29 vs. 1.2 mg/kg i.p). Complete substitution was observed in rhesus monkeys trained to discriminate cocaine from saline with ED(50) values for mazindane (0.134 mg/kg i.m.) and mazindol (0.119 mg/kg i.m.). Mazindol exhibited little or no activity at 10(-5) M in inhibiting radioligand binding at 14 neurotransmitter sites while mazindane gave weak activity at the histamine H(1) and 5-hydroxytryptamine 5-HT(3) sites. These results demonstrate that mazindane could be a useful alternative to mazindol as a pharmacological tool because of its similar profile of activity and enhanced water solubility.

Analysis of Variance↗

Anorexic and behavioural effects of a new imidazo-isoindole derivative (mazindol) in comparison with d-amphetamine in the rat.

The effect of an imidazo-isoindole derivative (mazindol) upon motor and feeding activity and two different avoidance behaviours have been compared with those of d-amphetamine in rats. It was found that both drugs depress feeding activity in a dose-related manner and increase the motor activity of the animals. However, the ratio of the lowest motility-increasing dose and the lowest appetite suppressant dose is 0.5 for d-amphetamine and 2 for mazindol. Mazindol, like d-amphetamine, caused a stereotyped behaviour in rats when given in very high doses, but the range between the anorexic and the stereotyped behaviour dose is much higher for mazindol than for d-amphetamine. The shuttle-box avoidance behaviour suppressed by tetrabenazine is completely restored by d-amphetamine and partially by mazindol. Lever-pressing avoidance suppressed by tetrabenazine is restored by d-amphetamine while mazindol at the doses used is ineffective. It is concluded that mazindol could be an anorexic agent better suited than d-amphetamine for clinical use.

Animals↗

Mechanisms of action of mazindol in preventing onset and development of obesity induced by gold thioglucose injection.

Biochemical and morphological studies were made on the role of mazindol in treatment of obesity in mice induced by gold thioglucose (GTG) injection. Mazindol was added to the diet at a level of 10 mg/kg body weight and then all animals were fed on a constantly restricted diet of 60 percent of the level of ad lib, food intake for 10 weeks. The following results were obtained: (1) The body weight and Lee's index were significantly increased by GTG injection and these increases in the GTG-obese group were reduced by oral mazindol. (2) The levels of triglyceride and cholesterol in the liver were much higher in the GTG-obese group than in the lean group, and were significantly less in the mazindol-treated group than in the GTG-obese group. (3) The levels of serum triglyceride and immunoreactive insulin were significantly higher in the GTG group than in the lean group and the increase in the GTG-treated animals was reduced by oral mazindol. (4) The size of fat cells and basal lipolytic activity in parametrial adipose tissue were greater in the GTG-obese group than in the lean group and were significantly reduced by mazindol treatment. (5) Disaccharidase activities in the small intestinal mucosa and the absorptive surface area of the mucosa were significantly greater in the GTG-obese group than in the lean group and were increased significantly less in the mazindol-treated group.

Adipose Tissue↗

Mazindol: anorectic and behavioral effects in female rats.

The anorectic and behavioral effects of mazindol (2.5, 5 and 10 mg/kg) were determined. The experiments comprized acute and chronic administration to female rats, and the effects were compared with those produced by 2.5 mg/kg of methamphetamine. The following evaluation parameters were considered: food intake, body weight, motor activity, and stereotyped behavior. Acute administration of the three doses of mazindol, as well as of the methamphetamine dose, decreased food intake. Administered chronically to female rats, mazindol (5 and 10 mg/kg) and methamphetamine induced loss of body weight during the first fifteen days. However, weight was subsequently regained by the animals, indicating development of tolerance. Mazindol (10 mg/kg) and methamphetamine produced an increase in motor activity. This increase was, however, not observed after chronic treatment, suggesting development of tolerance. Additionally, mazindol induced noticeable dose-dependent effects, involving stereotyped behavior (sniffing, continuous licking, false bites), similar to those produced by methamphetamine. Verticalization, however, was only observed after administration of 2.5 and 5 mg/kg of mazindol, and was absent after administration of the higher dose of mazindol as well as of methamphetamine. Finally, it should be stressed that features of stereotyped behavior induced by both drugs, such as licking, false bites, sniffing and verticalization, were very similar.

Analysis of Variance↗

Mazindol enhances glucose uptake by rat skeletal muscle.

The pharmacological action of mazindol (5-hydroxy-5-p-chlorophenyl-2,3-dihydro-5-imidazo[2,1-a]isoindo l) was examined by studying its effect on glucose uptake by rat tissues using radiolabelled 2-deoxy-D-glucose. The following results were obtained. (1) The rate constant (Ki) of net tissue 2-deoxy-D-glucose uptake increased in the cerebral cortex (4.7-fold, P < 0.05), the hypothalamus (4.6-fold, P < 0.05), heart (4.0 fold, P < 0.05) and skeletal muscles (gastrocnemius, 5.7-fold, P < 0.01; soleus, 4.7-fold, P < 0.05), but not in epididymal adipose tissue in vivo 90 min after intragastric administration of mazindol (20 mg/kg). (2) This increase in Ki values of net tissue 2-deoxy-D-glucose uptake was not observed after addition of mazindol to the diet (40 mg/100 g of diet) for 4 days. (3) Mazindol (16.7 ng/ml to 16.7 micrograms/ml) stimulated 2-deoxy-D-glucose transport into sarcolemmal vesicles of the gastrocnemius muscle in vitro (1.6-1.8-fold, P < 0.05) and this stimulation was blocked by cytochalasin B (10 microM). These findings suggest that mazindol stimulates glucose transport into skeletal muscles by acting on glucose transporters in the sarcolemmal membrane, and suggest that mazindol may stimulate glucose transport into the brain and heart by a similar mechanism.

Animals↗

Suppression of prolactin and growth hormone responses to 2-deoxy-D-glucose-induced glucoprivation by mazindol in humans.

Glucoprivation induced by 2-deoxy-D-glucose (2DG) 20 min infusions (50 mg/kg) increases growth hormone (GH) and prolactin (PRL) levels in humans. To determine if mazindol, a potent dopamine (DA) and norepinephrine (NE) reuptake blocking agent, might affect basal and stimulated GH and PRL levels in healthy male and female volunteers, mazindol (1 mg, TID,po) or placebo were administered for one week before 2DG infusions. Plasma samples for glucose, epinephrine (E), NE, PRL, and GH were collected before and after 2DG infusions. During placebo and mazindol therapy, basal values (ng/ml) did not differ for either PRL (8.8 +/- 1.6 versus 8.9 +/- 1.5 in females and 8.3 +/- 0.9 versus 7.7 +/- 0.6 in males) or GH (1.6 versus 1.7 +/- 0.1 in males and 6.6 +/- 3.3 versus 7.0 +/- 2.6 in females). Peak stimulated PRL levels were greater in females than in males (97.1 +/- 26.2 versus 21.4 +/- 5.3 ng/ml, p less than 0.05) while peak stimulated GH levels were greater in males than in females (28.2 +/- 1.7 versus 7.0 +/- 2.0 ng/ml, p less than 0.05). Mazindol therapy reduced 2DG-stimulated PRL responses (ng/ml) from 97.1 +/- 26.2 to 44.4 +/- 25.3 (p less than 0.0125) and from 21.4 +/- 5.3 to 13.6 +/- 3.4 (p less than 0.025) in females and males respectively, and GH responses (ng/ml) from 28.2 +/- 1.7 to 13.1 +/- 3.8 (p less than 0.05) and from 10.2 +/- 2.0 to 3.4 +/- 0.1 (p less than 0.05) in males and females respectively, but baseline PRL and GH levels were unaffected. A 50%-60% overall suppression of stimulated GH and PRL levels by mazindol was not significantly different between sexes and not consistently related to elevations in plasma glucose or E although stimulated plasma NE levels were higher during mazindol therapy.

Blood Glucose↗

High performance liquid chromatographic determination of mazindol in human plasma.

A simple and convenient high performance liquid chromatographic method with UV detection is described for the determination of mazindol [5-(p-chlorophenyl)-2,5-dihydro-3H-imidazo[2,1-a]isoindol-5-ol] and its major metabolite, 2-(2-aminoethyl)-3-(p-chlorophenyl)-3-hydroxyphthalimidine (Met), in human plasma. The analytes were extracted with ethyl acetate from plasma samples and separated on a C18 column using acetonitrile-0.067 mol dm(-3) phosphate buffer (pH 3.5) (24 + 76 v/v) as a mobile phase. The eluates were monitored at 220 nm. Following complete validation and stability studies, the proposed method proved to be sensitive and precise. The limits of detection were 0.07 and 0.08 ng ml(-1) of plasma for mazindol and Met, respectively. The accuracy and recovery were in the ranges 94-102% and 91-102%, respectively, for both compounds. The intra- and inter-assay precisions were less than 7.6 and 9.2%, respectively, for both compounds. The stability of mazindol under different storage conditions, i.e., at room temperature (rt) and 4 degrees C and with freeze-thaw cycles, was also examined. Mazindol was unstable in plasma samples left at rt and 4 degrees C. The method was applied to the determination of mazindol and Met in the plasma of a patient treated for obesity with mazindol.

Adult↗

High affinity recognition of serotonin transporter antagonists defined by species-scanning mutagenesis. An aromatic residue in transmembrane domain I dictates species-selective recognition of citalopram and mazindol.

Human and Drosophila melanogaster serotonin (5-HT) transporters (SERTs) exhibit similar 5-HT transport kinetics and can be distinguished pharmacologically by many, but not all, biogenic amine transporter antagonists. By using human and Drosophila SERT chimeras, major determinants of potencies of two transporter antagonists, mazindol and citalopram, were tracked to the amino-terminal domains encompassing transmembrane domains I and II. Species-scanning mutagenesis, whereby amino acid substitutions are made switching residues from one species to another, was employed on the eight amino acids that differ between human and Drosophila SERTs in this region, and antagonist potencies were reassessed in 5-HT uptake assays. A single mutation in transmembrane domain I of human SERT, Y95F, shifted both citalopram and mazindol to Drosophila SERT-like potencies. Strikingly, these potency changes were in opposite directions suggesting Tyr95 contributes both positive and negative determinants of antagonist potency. To gain insight into how the Y95F mutant might influence mazindol potency, we determined how structural variants of mazindol responded to the mutation. Our studies demonstrate the importance of the hydroxyl group on the heterocyclic nucleus of mazindol for maintaining species-selective recognition of mazindol and suggest that transmembrane domain I participates in the formation of antagonist-binding sites for amine transporters.

Animals↗

Clinical and basic aspects of an anorexiant, mazindol, as an antiobesity agent in Japan.

The Japanese Mazindol study group investigated the action of an anorexiant, mazindol, and found that it reduced food intake by directly suppressing neurons in the lateral hypothalamus, inhibited gastric acid secretion, increased motor activity, decreased glucose absorption, and inhibited insulin secretion. It thus appears that the main effect of mazindol is to decrease food intake through suppressing feeding centers in the hypothalamus. A multicenter open study of mazindol in Japan revealed that loss of body weight and relative body weight in 14 wk were 4.6 kg and 9.2%, respectively, with suppression of appetite in the majority of obese patients. A multicenter double-blind study demonstrated that mazindol was superior to the placebo in the treatment of simple obesity. We also suggest that mazindol is effective in the maintenance of reduced body weight after obesity therapy and in the treatment of obesity-related diseases such as diabetes, hypertension, or hyperlipidemia.

Animals↗

[Effect of mazindol on glucose absorption in everted rat small intestine].

Effect of an anorexiant, mazindol, on glucose absorption was investigated. Ten weeks-old female Sprague-Dawley rats were divided into mazindol treated (fed on powder diet containing 100 mg/kg of mazindol) and control groups. Four weeks later, experiments of continuous observation of glucose absorption and glucose transport were performed in each group using the everted sac method. During 180 min of continuous observation of glucose absorption, significantly lowered glucose concentrations of the serosal medium were observed in the mazindol treated group at oral and caudal ends of the upper, caudal end of the middle, and caudal ends of the lower small intestine, whereas no significant differences in glucose concentrations of the mucosal medium were observed between the two groups. After 60 min incubation for monitoring the glucose transport, significantly decreased glucose concentrations of serosal medium were observed in mazindol treated group at oral and caudal ends of the upper, caudal ends of the middle and caudal ends of the lower small intestine, whereas no significant differences in glucose concentrations of mucosal medium were observed. The results suggested that there is little effect on glucose absorption, but the metabolism of glucose or the remaining glucose in the small intestinal wall is increased by mazindol treatment.

Animals↗

The effects of 5-hydroxy-5(4'-chlorophenyl)-2, 3-dihydro-5H-imidazo (2, 1-a) isoindole (mazindol, SaH 42-548) on the metabolism of brain norepinephrine.

Mazindol, 5-hydroxy-5-(4'-chlorophenyl)-i, 3-dihydro-5H-imidazo-(2, 1-a) isoindole, has demonstrated anorexic activity and other pharmacological responses which suggest alterations in brain norepinephrine metabolism. Studies of the effects of mazindol on neuronal uptake and/or release of norepinephrine showed that mazindol, when given before cerebral intraventricular injection of 3-H-norepinephrine by a mechanism that increases 3-H-normetanephrine synthesis via catechol-O-methyl-transferase and provided no significant effect on deamination of the catecholamine. Studies designed to measure norepinephrine release showed that mazindol (in contrast to d-amphetamine) did not cause release of 3-H-norepinephrine from neuronal stores. Furthermore, mazindol did not inhibit norepinephrine synthesis, whereas d-amphetamine did. The effect of d-amphetamine on norepinephrine release and synthesis may be more important than effects on uptake of this catecholamine. In contrast, mazindol appears to produce its primary effect on norepinephrine metabolism by inhibition of neuronal uptake mechanism.

Animals↗

Double blind clinical trial of mazindol on weight loss blood glucose, plasma insulin and serum lipids in overweight diabetic patients.

Mazindol, a drug with tricyclic structure unrelated to amphetamine and other anorectic drugs, has been used as an anorectic agent in a double blind clinical trial at a dose of 2 mg/day for 12 week (mazindol v. s. placebo), associated with a 1000 calorie diet on 46 obese diabetic patients. Thirty seven patients completed the trial with no significant difference between the two groups in the drop-out population; mazindol was well tolerated. In the mazindol-treated group the mean weight loss was 13.5 kg (22.3%) which was significantly greater (p less than 0.001) than in the placebo treated group where the mean weight loss was 4.2 kg (9.8%). Comparing the two groups after the 12 week trial, decrease in fasting blood glucose, serum insulin and triglycerides was not significant. In the mazindol-treated group a significant decrease of serum cholesterol, triglycerides and of the mean area under the curve of insulinemia during the OGTT has been observed. In the placebo treated group only serum triglycerides decreased significantly. The variations of plasma insulin and serum cholesterol were found to be correlated to the magnitude of weight loss. In conclusion mazindol is an effective drug for weight loss on the whole well tolerated but without specific properties on metabolism.

Blood Glucose↗