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A phase 1 clinical trial in healthy male volunteers was conducted with a somatostatin-dopamine chimera (BIM23B065), from which information could be obtained on the concentration-effect relationship of the inhibition of pulsatile endogenous growth hormone and prolactin secretion. Endogenous growth hormone profiles were analyzed using a two-step deconvolution-analysis-informed population pharmacodynamic modeling approach, which was developed for the analyses of pulsatile profiles. Prolactin concentrations were modelled using a population pool model with a circadian component on the prolactin release. During treatment with BIM23B065, growth hormone secretion was significantly reduced (maximal effect [EMAX] = − 64.8%) with significant reductions in the pulse frequency in two out of three multiple ascending dose cohorts. A circadian component in prolactin secretion was identified, modelled using a combination of two cosine functions with 24 h and 12 h periods. Dosing of BIM23B065 strongly inhibited (EMAX = − 91%) the prolactin release and demonstrated further reduction of prolactin secretion after multiple days of dosing. This study quantified the concentration-effect relationship of BIM23B065 on the release of two pituitary hormones, providing proof of pharmacology of the chimeric actions of BIM23B065. Electronic supplementary material The online version of this article (10.1007/s10928-020-09683-3) contains supplementary material, which is available to authorized users.

Background: Glioblastoma multiforme (GBM) is a common and lethal cancer of the central nervous system. This cancer is difficult to treat because most anticancer therapeutics do not readily penetrate into the brain due to the tight control at the cerebrovascular barrier. Numerous studies have suggested that dopamine D2 receptor (D2R) antagonists, such as first generation antipsychotics, may have anticancer efficacy in vivo and in vitro. The role of the D2R itself in the anticancer effects is unclear, but there is evidence suggesting that D2R activation promotes stem-like and spheroid forming behaviors in GBM. Objectives: We aimed to observe the role of the dopamine D2R and its modulators (at selective concentrations) in spheroid formation and stemness of GBM cell line, U87MG, to clarify the validity of the D2R as a therapeutic target for cancer therapy. Methods: Spheroid formation assays and Western blotting of the glioblastoma cell line, U87MG, were used to observe responses to treatment with the D2R agonists sumanirole, ropinirole, and 4-propyl-9-hydroxynaphthoxazine (PHNO); and the D2R antagonists thioridazine, pimozide, haloperidol, and remoxipride. Extreme limiting dilution analysis was done to determine the impact of sumanirole and remoxipride treatment on sphere-forming cell frequency. Proliferation was also measured by crystal violet staining. Stable lentiviral transduction of DRD2 or shDRD2 was used to validate the role of the D2R in assay behaviors. Results: D2R antagonists thioridazine, pimozide, haloperidol, and remoxipride decrease spheroid formation behaviors at a selective 100 nmol/L concentration, while D2R agonists PHNO, sumanirole, and ropinirole increase the formation of spheroids. Similarly, 100 nmol/L remoxipride decreased sphere-forming cell frequency. These results were recapitulated with genetic overexpression and knockdown of the D2R, and combination experiments indicate that the D2R is required for the effects of the pharmacological modulators. Furthermore, spheroid proliferation and invasive capacity increased under treatment with 100 nmol/L sumanirole and decreased under treatment with 100 nmol/L thioridazine. Expression levels of the stemness markers Nestin and Sox2, as well as those of differentiation marker glial fibrillary acidic protein, were not altered by 100 nmol/L thioridazine or sumanirole for 72 h or continuous treatment with these compounds for 7 days during a spheroid formation assay. Conclusions: Signaling activity of the dopamine D2R may be involved in the spheroid formation phenotype in the context of the U87MG cell line. However, this modulation may not be due to alterations in stemness marker expression, but due to other factors that may contribute to spheroid formation, such as cell-cell adhesion or EGFR signaling.

The recent publication in Nature Communications by Sykes et al.1 made the interesting observation that forward binding rate constants (kon) at the dopamine D2 receptor (D2R) differ widely between antipsychotics, and moreover, that kon rather than koff (dissociation rate constant) values correlate with their liabilities to produce extrapyramidal symptoms (EPS). A high kon is postulated to cause a high degree of rebinding of the antipsychotic to D2R, conferring increased competition with endogenous dopamine, and thereby more EPS. As pointed out by the authors, their results are largely in agreement with our previous findings from a potassium channel (G protein-activated inward rectifier potassium; GIRK) activation assay2. However, there are some discrepancies between their work and ours which may have important consequences for the interpretation of the correlation between kon and EPS, and which we would like to point out below. Remoxipride, a clinically effective antipsychotic which was withdrawn due to the occurrence of aplastic anemia as a rare side-effect, has a very low rate of EPS compared to the typical antipsychotic, haloperidol3 (odds ratio for rigidity, 0.30; 95% CI, 0.22 to 0.41; n = 1104; P

We provide the reader with relevant data related to our recently published paper, comparing two mathematical models to describe prolactin turnover in rats following one or two doses of the dopamine D2 receptor antagonists risperidone, paliperidone and remoxipride, “A comparison of two semi-mechanistic models for prolactin release and prediction of receptor occupancy following administration of dopamine D2 receptor antagonists in rats” (Taneja et al., 2016) [1]. All information is tabulated. Summary level data on the in vitro potencies and the physicochemical properties is presented in Table 1. Model parameters required to explore the precursor pool model are presented in Table 2. In Table 3, estimated parameter comparisons for both models are presented, when separate potencies are estimated for risperidone and paliperidone, as compared to a common potency for both drugs. In Table 4, parameter estimates are compared when the drug effect is parameterized in terms of drug concentration or receptor occupancy.

Different studies have shown the role of neurotransmitters (e.g., dopamine) in the progression of cancers via their various types of receptors. The aim of this study was to determine the pattern of dopamine receptors gene expression on MCF-7 cells and to evaluate the selective dopamine receptors agonist and antagonist effects on them. In addition, some other discoveries which are patented for the treatment of breast cancer are reviewed in this article. To determine the pattern of dopamine receptors gene expression in human breast cancer cells (MCF-7), RT-PCR was performed. Then, MCF-7 cells were treated by different doses of bromocriptine and remoxipride for 48 hours. Cell viability was evaluated by MTT assay. Thus, nuclear morphology of cells was analyzed by mixed dye florescent staining. Real time PCR technique was performed to determine the decreasing rate of proliferating cell nuclear antigen (PCNA) gene expression in treated MCF-7 cells. Finally, quantification of apoptosis and its difference with necrosis at the single cell level were assessed by Flowcytometery technique. This study revealed that, unlike remoxipride, bromocriptine suppressed proliferation of the MCF-7 cells (54.3% at 12.5 µM bromocriptine concentration), but remoxipride could suppress the effect of bromocriptine. Bromocriptine has inhibitory effects on MCF- 7 cells by induction of apoptosis via D2-like receptors. Therefore, in future studies, bromocriptine can be used as a new choice for the treatment of tumoral breast cancer cells.

Prolactin release is a side effect of antipsychotic therapy with dopamine antagonists, observed in rats as well as humans. We examined whether two semimechanistic models could describe prolactin response in rats and subsequently be translated to predict pituitary dopamine D2 receptor occupancy and plasma prolactin concentrations in humans following administration of paliperidone or remoxipride. Data on male Wistar rats receiving single or multiple doses of risperidone, paliperidone, or remoxipride was described by two semimechanistic models, the precursor pool model and the agonist–antagonist interaction model. Using interspecies scaling approaches, human D2 receptor occupancy and plasma prolactin concentrations were predicted for a range of clinical paliperidone and remoxipride doses. The predictions were compared with corresponding observations described in literature as well as with predictions from published models developed on human data. The pool model could predict D2 receptor occupancy and prolactin response in humans following single doses of paliperidone and remoxipride. Tolerance of prolactin release was predicted following multiple doses. The interaction model underpredicted both D2 receptor occupancy and prolactin response. Prolactin elevation may be deployed as a suitable biomarker for interspecies translation and can inform the clinical safe and effective dose range of antipsychotic drugs. While the pool model was more predictive than the interaction model, it overpredicted tolerance on multiple dosing. Shortcomings of the translations reflect the need for better mechanistic models.

Background:Breast cancer is one of the common causes of mortality for women in Iran and other parts of the world. The substantial increasing rate of breast cancer in both developed and developing countries warns the scientists to provide more preventive steps and therapeutic measures. This study is conducted to investigate the impact of neurotransmitters (e.g., Dopamine) through their receptors and the importance of cancers via damaging immune system. It also evaluates dopamine receptors gene expression in the women with breast cancer at stages II or III and dopamine receptor D2 (DRD2) related agonist and antagonist drug effects on human breast cancer cells, including MCF-7 and SKBR-3.Methods:The patients were categorized into two groups: 30 native patients who were diagnosed with breast cancer at stages II and III, with the mean age of 44.6 years and they were reported to have the experience of a chronic stress or unpleasant life event. The second group included 30 individuals with the mean age of 39 years as the control group. In order to determine the RNA concentration in all samples, the RNA samples were extracted and cDNA was synthesized. The MCF-7 cells and SKBR-3 cells were treated with dopamine receptors agonists and antagonists. The MTT test was conducted to identify oxidative and reductive enzymes and to specify appropriate dosage at four concentrations of dopamine and Cabergoline on MCF-7 and SKBR-3 cells. Immunofluorescence staining was done by the use of a mixed dye containing acridine orange and ethidiume bromide on account of differentiating between apoptotic and necrotic cells. Flow cytometry assay was an applied method to differentiate necrotic from apoptotic cells.Results:Sixty seven and thirty three percent of the patients were related to stages II and III, respectively. About sixty three percent of the patients expressed ER, while fifty seven percent expressed PR. Thirty seven percent of the patients were identified as HER-2 positive. All types of D2-receptors were expressed in PBMC of patients with breast cancer and healthy individuals. The expression of the whole dopamine receptor subtypes (DRD2-DRD4) was carried out on MCF-7 cell line. The results of RT-PCR confirmed the expression of DRD2 on SKBR-3 cells, whereas the other types of D2- receptors did not have an expression. The remarkable differences in gene expression rates between patients and healthy individuals were revealed in the result of the Real-time PCR analysis. The over expression in DRD2 and DRD4 genes of PBMCs was observed in the patients with breast cancer at stages II and III. The great amount of apoptosis and necrosis occurred after the treatment of MCF-7 cells by Cabergoline from 25 to 100 µmolL-1 concentrations.Conclusion:This study revealed the features of dopamine receptors associated with apoptosis induction in breast cancer cells. Moreover, the use of D2-agonist based on dopamine receptors expression in various breast tumoral cells could be promising as a new insight of complementary therapy in breast cancer.

To reveal unknown and potentially important mechanisms of drug action, multi-biomarker discovery approaches are increasingly used. Time-course relationships between drug action and multi-biomarker profiles, however, are typically missing, while such relationships will provide increased insight in the underlying body processes. The aim of this study was to investigate the effect of the dopamine D2 antagonist remoxipride on the neuroendocrine system. Different doses of remoxipride (0, 0.7, 5.2, or 14 mg/kg) were administered to rats by intravenous infusion. Serial brain extracellular fluid (brainECF) and plasma samples were collected and analyzed for remoxipride pharmacokinetics (PK). Plasma samples were analyzed for concentrations of the eight pituitary-related hormones as a function of time. A Mann–Whitney test was used to identify the responding hormones, which were further analyzed by pharmacokinetic/pharmacodynamic (PK/PD) modeling. A three-compartment PK model adequately described remoxipride PK in plasma and brainECF. Not only plasma PRL, but also adrenocorticotrophic hormone (ACTH) concentrations were increased, the latter especially at higher concentrations of remoxipride. Brain-derived neurotropic factor (BDNF), follicle stimulating hormone (FSH), growth hormone (GH), luteinizing hormone (LH), and thyroid stimulating hormones (TSH) did not respond to remoxipride at the tested doses, while oxytocin (OXT) measurements were below limit of quantification. Precursor pool models were linked to brainECF remoxipride PK by Emax drug effect models, which could accurately describe the PRL and ACTH responses. To conclude, this study shows how a multi-biomarker identification approach combined with PK/PD modeling can reveal and quantify a neuroendocrine multi-biomarker response for single drug action.

SummaryNeuroleptics: preclinical and clinical differencesIn this review we propose that the clinical and preclinical effects of neuroleptic drugs justify a distinction between classical and atypical neuroleptic drugs. Binding, biochemical, electrophysiological and behavioural studies have revealed clearcut differences between classical neuroleptics (like haloperidol and fluphenazine) and atypical neuroleptics (such as clozapine, thioridazine and remoxipride). These large differences are likely due to differences in the workingmechanisms. In view of the clinical relevance of these findings it is therefore both justified and essential to subdivide the neuroleptics in two distinct groups: the classical neuroleptics and the atypical neuroleptics.

We compared the model performance of two semi-mechanistic pharmacokinetic-pharmacodynamic models, the precursor pool model and the agonist-antagonist interaction model, to describe prolactin response following the administration of the dopamine D-2 receptor antagonists risperidone, paliperidone or remoxipride in rats. The time course of pituitary dopamine D-2 receptor occupancy was also predicted.Male Wistar rats received a single dose (risperidone, paliperidone, remoxipride) or two consecutive doses (remoxipride). Population modeling was applied to fit the pool and interaction models to the prolactin data. The pool model was modified to predict the time course of pituitary D-2 receptor occupancy. Unbound plasma concentrations of the D-2 receptor antagonists were considered the drivers of the prolactin response. Both models were used to predict prolactin release following multiple doses of paliperidone.Both models described the data well and model performance was comparable. Estimated unbound EC50 for risperidone and paliperidone was 35.1 nM (relative standard error 51%) and for remoxipride it was 94.8 nM (31%). KI values for these compounds were 11.1 nM (21%) and 113 nM (27%), respectively. Estimated pituitary D-2 receptor occupancies for risperidone and remoxipride were comparable to literature findings. The interaction model better predicted prolactin profiles following multiple paliperidone doses, while the pool model predicted tolerance better.The performance of both models in describing the prolactin profiles was comparable. The pool model could additionally describe the time course of pituitary D-2 receptor occupancy. Prolactin response following multiple paliperidone doses was better predicted by the interaction model. (C) 2016 Elsevier B.V. All rights reserved.

Intranasal (IN) administration could be an attractive mode of delivery for drugs targeting the central nervous system, potentially providing a high bioavailability because of avoidance of a hepatic first-pass effect and rapid onset of action. However, controversy remains whether a direct transport route from the nasal cavity into the brain exists. Pharmacokinetic modeling is proposed to identify the existence of direct nose-to-brain transport in a quantitative manner. The selective dopamine-D2 receptor antagonist remoxipride was administered at different dosages, in freely moving rats, by the IN and intravenous (IV) route. Plasma and brain extracellular fluid (ECF) concentration-time profiles were obtained and simultaneously analyzed using nonlinear mixed-effects modeling. Brain ECF/plasma area under the curve ratios were 0.28 and 0.19 after IN and IV administration, respectively. A multicompartment pharmacokinetic model with two absorption compartments (nose-to-systemic and nose-to-brain) was found to best describe the observed pharmacokinetic data. Absorption was described in terms of bioavailability and rate. Total bioavailability after IN administration was 89%, of which 75% was attributed to direct nose-to brain transport. Direct nose-to-brain absorption rate was slow, explaining prolonged brain ECF exposure after IN compared with IV administration. These studies explicitly provide separation and quantitation of systemic and direct nose-to-brain transport after IN administration of remoxipride in the rat. Describing remoxipride pharmacokinetics at the target site (brain ECF) in a semiphysiology-based manner would allow for better prediction of pharmacodynamic effects.

AIMS The tolerance to the prolactin response following administration of antipsychotic drugs has been modelled as a depletion of a prolactin pool (pool model) and a model where the tolerance is explained by a feedback loop including the dopamine interaction of prolactin release (agonist-antagonist interaction model, (AAI model)). The AAI model was superior to the pool model when analyzing data from clinical trials of risperidone and paliperidone. Here we evaluated the two models using the remoxipride data, designed to challenge the short-term prolactin response, from which the original pool model was built. METHODS The remoxipride data were collected from a study where eight healthy male subjects received two remoxipride infusions on five occasions. The intervals between the first and second dose on each occasion were 2, 8, 12, 24 and 48 h, respectively. The pool and AAI models were fitted using NONMEM. RESULTS According to the objective function values the pool model with a circadian rhythm function fitted the data slightly better, while the AAI model was better in describing the circadian rhythm of prolactin. Visual predictive checks revealed that the models predicted the prolactin profiles equally well. CONCLUSIONS According to the analysis performed here, a previous analysis of several clinical studies and literature reports on prolactin concentrations, it appears that the dopamine feedback mechanism included in the AAI model is better than the storage depletion mechanism in the pool model to estimate the bio-rhythm of prolactin time-course and the tolerance development across different populations, drugs, treatment schedules and time.

Angiotensin IV (Ang IV) and des-Phe(6)Ang IV are naturally occurring neuroactive peptides of the renin-angiotensin system (RAS) involved in memory processing. However, the relevant mechanisms are poorly understood. In this review it is proposed that the pro-cognitive effects of these peptides are, at least partly, mediated by dopamine (DA). Recent studies demonstrated that the improvement of several memory aspects; recall of appetitively and aversively motivated behaviors and learning of spatial tasks by Ang IV and des-Phe(6)Ang IV was abolished, or significantly diminished by behaviorally inactive per se doses of the D(1) and D(2) receptor blockers SCH 23390 (R-[+]-7-chloro-8-hydroxy-3 methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine) and remoxipride, respectively. The D(3) receptor inhibition with nafadotride was almost ineffective but again, the D(4) receptor blockade by L745,870 hydrochloride (3-{[4-(4-chlorophenyl)piperazin-1-yl]methyl}-1H-pyrrolo[2,3-b]pyridine hydrochloride) diminished all, except for spatial memory, improving actions of the peptides. These results suggest that Ang IV and des-Phe(6)Ang IV enhance memory in a brain region-specific manner, dependent on local DA receptor subpopulations and the memory aspects controlled by them. The data reviewed here, demonstrating DA-Ang IV and des-Phe(6)Ang IV interactions in brain, strongly suggest probability of clinically relevant effects of concomitant use of antipsychotic and RAS affecting drugs.

Typical antipsychotics such as haloperidol exert their therapeutic effects via blockade of dopamine (DA) D 2 receptors, leading to extrapyramidal symptoms (EPS) in humans and catalepsy in rodents. In contrast, atypical antipsychotics and new generation D 2 /5-HT 1A antipsychotics have low cataleptogenic potential. However, there has been no systematic comparative study on the effects of these different classes of antipsychotics in non-human primates, a species displaying a more sophisticated repertoire of behavioural/motor activity than rats. Once weekly, six young adult female non-haloperidol-sensitised cynomolgus monkeys were treated i.m. with a test compound and videotaped to score catalepsy-associated behaviour (CAB: static postures, unusual positions and crouching). Haloperidol, risperidone, olanzapine, nemonapride and remoxipride induced, to different extents, an increase in unusual positions (a response akin to dystonia), some crouching and static postures. In contrast, clozapine, quetiapine, ziprasidone and aripiprazole produced much lower or no unusual positions; clozapine also produced marked increases in static postures and crouching. Among novel D 2 /5-HT 1A antipsychotics, SLV313 and F15063 augmented the number of unusual positions, albeit at doses 16–63 times higher than those of haloperidol for approximately the same score. SSR181507 and bifeprunox produced moderate static postures, little crouching and negligible unusual positions. These data provide the first comparative analysis in cynomolgus monkeys of EPS liability of conventional, atypical and novel D 2 /5-HT 1A antipsychotics. They indicate that the latter are less prone than haloperidol to produce CAB, and provide a basis for comparison with rodent catalepsy studies.

The antidopaminergic potencies of some new substituted benzamides related to remoxipride have been studied in the rat using in vitro (3H-spiperone binding) and in vivo techniques (antagonism of apomorphine induced stereotypies). The lipophilicities of the different benzamides were calculated by the addition of the lipophilic contribution (pi value) of the added substituent. It was found that the in vivo potencies of the compounds were not direct proportional to the in vitro potencies. The discrepancies in the potencies in vitro and in vivo (expressed as the ratio) are correlated to the calculated lipophilicities. Certain substituents in the benzene nucleus affect this in vitro--in vivo ratio more than could be expected from the change in lipophilicity caused by the substituent. The type of side chain is also of great importance. The reasons for the discrepancies between in vitro and in vivo antidopaminergic potencies of the studied substituted benzamides are discussed.

A number of potential neuroleptic drugs of the substituted benzamide type have been compared with some reference neuroleptic drugs regarding their affinities for rat brain receptors using in vitro receptor binding techniques. The effects on dopamine-stimulated adenylate cyclase were also investigated. All 6-methoxysalicylamides were very potent inhibitors of the dopamine-D2 receptor and possessed much less affinity for other receptors as well as for the dopamine-stimulated adenylate cyclase. In contrast, the classical neuroleptic drugs were not selective dopamine-D2 receptor blockers. Several of these neuroleptics were thus potent inhibitors of alpha 1-receptors, 5-HT2 receptors, muscarinic receptors and histamine-H1 receptors. Sulpiride was the most selective dopamine-D2 receptor blocker of the reference compounds with a selectivity ratio of 65. The 6-methoxysalicylamides had selectivity ratios ranging from 18 to 167.

The potent anticonvulsant properties of neuropeptide Y (NPY) are generally attributed to a Y2 receptor-mediated inhibition of glutamatergic synaptic transmission. Independent studies have shown that NPY increases brain dopamine content, possibly via interaction with sigma 1 receptors. Recently, we showed that increased extracellular hippocampal dopamine attenuates pilocarpine-induced limbic seizures via activation of hippocampal D2 receptors. Our aim in this study was to elucidate the role of increased hippocampal dopamine in the mechanism of the anticonvulsant action of NPY and to investigate the involvement of Y2 and sigma 1 receptors in this process. Limbic seizures were evoked in freely moving rats by intrahippocampal administration of pilocarpine via a microdialysis probe. NPY was administered intracerebroventricularly, intrahippocampally via the microdialysis probe, or coadministered intrahippocampally with the D2 receptor antagonist remoxipride, the Y2 receptor antagonist BIIE0246 or the sigma 1 receptor antagonist BD1047. Changes in hippocampal extracellular dopamine were monitored, and behavioural changes indicative of seizure activity were scored. Intracerebroventricular (10 nmol/3 microL) and intrahippocampal (20-50 microm) NPY administration increased hippocampal dopamine and attenuated pilocarpine-induced seizures. Hippocampal D2 receptor blockade (4 microm remoxipride) reversed the anticonvulsant effect of NPY. Y2 receptor blockade (1 microm BIIE0246) reversed the anticonvulsant effect of NPY but did not prevent NPY-induced increases in hippocampal dopamine. Sigma 1 receptor blockade (10 microm BD1047) abolished NPY-induced increases in hippocampal dopamine and reversed the anticonvulsant effect of NPY. Our results indicate that NPY-induced increases in hippocampal dopamine are mediated via sigma 1 receptors and contribute to the anticonvulsant effect of NPY via increased activation of hippocampal D2 receptors. This novel mechanism of anticonvulsant action of NPY is separate from, and may be complementary to, the well established Y2 receptor-mediated inhibition of hippocampal excitability.

The present study investigated the effects of N-methyl-D-aspartic acid.H2O (NMDA) on the dopamine, glutamate and GABA release in the subthalamic nucleus (STN) by using in vivo microdialysis in rats. NMDA (100 micromol/L) perfused through the microdialysis probe evoked an increase in extracellular dopamine in the STN of the intact rat of about 170%. This coincided with significant increases in both extracellular glutamate (350%) and GABA (250%). The effect of NMDA perfusion on neurotransmitter release at the level of the STN was completely abolished by co-perfusion of the selective NMDA-receptor antagonist MK-801 (10 micromol/L), whereas subthalamic perfusion of MK-801 alone had no effect on extracellular neurotransmitter concentrations. Furthermore, NMDA induced increases in glutamate were abolished by both SCH23390 (8 micromol/L), a selective D1 antagonist, and remoxipride (4 micromol/L), a selective D2 antagonist. The NMDA induced increase in GABA was abolished by remoxipride but not by SCH23390. Perfusion of the STN with SCH23390 or remoxipride alone had no effect on extracellular neurotransmitter concentrations. The observed effects in intact animals depend on the nigral dopaminergic innervation, as dopamine denervation, by means of 6-hydroxydopamine lesioning of the substantia nigra, clearly abolished the effects of NMDA on neurotransmitter release at the level of the STN. Our work points to a complex interaction between dopamine, glutamate and GABA with a crucial role for dopamine at the level of the STN.

The aim of this study was to develop a simple experimental methodology and to develop a mechanistic model to characterize the release mechanism from pellets developing cracks during the release process with special focus on osmotic effects. The release of remoxipride from pellets coated with an ethyl cellulose film was chosen as a case study. Dose release experiments at different bulk osmotic pressures revealed that the release process was mainly osmotically driven. The model was used to calculate the solvent permeability of the coating, 1.1 x 10(-10)m(2)h(-1)MPa(-1). The model was validated by release experiments using similar pellets having different coating thicknesses. The effective diffusion coefficient of remoxipride in the coating was also calculated and found to be 1.7 x 10(-10)m(2)h(-1). A series of experiments was performed in which the osmotic pressure of the receiving solution was changed during the experiment. From the results of these experiments, the area of the cracks in the film, formed by the hydrostatic pressure built up inside the pellets, was estimated to be 3.5 x 10(-5)m(2)/m(2) coating. It could also be deduced that the solvent permeability of the coating film was affected by swelling in the same way at different osmotic pressures.

1 In anaesthetised male rats an intravenous (i.v.) injection of p-chloroamphetamine (PCA) produced a specific patterned bursting response in the sympathetic vas deferens nerve (VDN) that corresponds to ejaculation. In the present, study selective dopamine agonists and antagonists were used to investigate whether dopaminergic mechanisms influence the generation of this ejaculatory-related response. 2 Administration of a mixed D1/2 receptor agonist (0.1–1.0 mg kg−1 apomorphine i.v.) also evoked the characteristic bursting pattern responses in the VDN. Similar, but fewer, burst pattern responses could also be evoked by a selective D2/3 receptor agonist (0.1–2.0 mg kg−1 piribedil). Responses to 1.0 mg kg−1 apomorphine were blocked by pretreatments with either 0.5 mg kg−1 remoxipride (D2 receptor antagonist) or 0.5 mg kg−1 nafadotride (D3 receptor antagonist), suggesting that D2-like receptors were involved. 3 Responses could not be evoked by i.v. injections of apomorphine (1.0 mg kg−1) in anaesthetised male rats with a midthoracic spinal section, indicating that activation of D2-like receptors at supraspinal sites leads to an increase in the excitability of the lumbosacral pattern generator for ejaculation. 4 In anaesthetised female rats a similar patterned bursting response occurred in the uterine nerve (UN) in response to apomorphine (0.5–2.0 mg kg−1 i.v.). Thus a common neural mechanism may regulate sexual climactic reflexes in both sexes. British Journal of Pharmacology (2006) 148, 510–516. doi:10.1038/sj.bjp.0706763

Contains fulltext : 51762.pdf (Publisher’s version ) (Closed access) BACKGROUND: Amphetamine is often used to mimic certain aspects of schizophrenia in laboratory animals, such as a decreased prepulse inhibition. MATERIALS AND METHODS: Apomorphine-susceptible and apomorphine-unsusceptible rats represent a well-characterized animal model for individual differences in the sensitivity to dopaminergic drugs. Moreover, apomorphine-susceptible rats show a wide variety of schizophrenia-like abnormalities. The differential response to administration of amphetamine (1-4 mg/kg, i.p.) was investigated in these two rat lines using the prepulse inhibition paradigm. Because amphetamine promotes dopamine release, the cellular mechanism underlying the line-specific effects of amphetamine was investigated by administration of alpha-methyl-para-tyrosine (aMpT) and reserpine, substances that are known to deplete the cytosolic dopamine pool and the vesicular dopamine pool, respectively, the former being primarily implicated in mediating the effects of amphetamine. RESULTS: All doses of amphetamine decreased prepulse inhibition in apomorphine-susceptible rats, whereas only the highest doses (2 and 4 mg/kg, i.p.) of amphetamine decreased prepulse inhibition in apomorphine-unsusceptible rats. Alpha-methyl-para-tyrosine, but not reserpine, blocked the amphetamine-induced disruption in prepulse inhibition in apomorphine-unsusceptible rats, whereas both substances alone had no effect in apomorphine-susceptible rats. However, the combination of alpha-methyl-para-tyrosine and reserpine did block the amphetamine-induced effects in the latter rat line. DISCUSSION: The present study suggests that apomorphine-susceptible rats are more sensitive to systemic administration of amphetamine than apomorphine-unsusceptible rats. In addition, the data show that the cellular mechanism underlying the effects of amphetamine differs between apomorphine-susceptible and apomorphine-unsusceptible rats. Whereas the effects of amphetamine on prepulse inhibition in apomorphine-unsusceptible rats just require the alpha-methyl-para-tyrosine sensitive dopamine pool, the effects in apomorphine-susceptible rats require both the alpha-methyl-para-tyrosine sensitive and the reserpine sensitive dopamine pool. Because apomorphine-susceptible rats share many features with schizophrenic patients, these data open the perspective that in these patients amphetamine may induce dopamine release from both types of dopamine pool. This might provide an explanation for the increased dopamine release after this psychostimulant drug in patients vs controls.

Considerable interest has arisen in identifying antipsychotic agents with improved efficacy against negative symptoms, such as social withdrawal. In rats, a social interaction deficit can be induced by the NMDA antagonist phencyclidine (PCP). Here, we examined the effects of antipsychotics, reported to exert dual 5-HT(1A)/D(2) actions, on PCP-induced social interaction deficits. Drugs were administered daily for 3 days in combination with either vehicle or PCP (2.5mg/kg, SC) and social interaction was measured on the last day of drug treatment. Pairs of unfamiliar rats receiving the same treatment were placed in a large open field for 10 min and the number of social behaviors were scored. The results indicate that: (1) PCP significantly reduced social interaction by over 50% compared with vehicle-treated controls; (2) haloperidol (0.0025-0.16 mg/kg, SC) and clozapine (0.04-10mg/kg, IP) did not reverse PCP-induced social interaction deficits; (3) the substituted benzamide remoxipride reversed PCP-induced deficits at 0.63 and 2.5mg/kg (4) the 5-HT(1A) agonist 8-OH-DPAT was inactive (at 0.01-0.63 mg/kg, SC); (5) among compounds reported to exert dual 5-HT(1A)/D(2) actions, SSR181507 (at 0.16 mg/kg, SC) and aripiprazole (at 0.04 and 0.16 mg/kg, IP), but not ziprasidone (0.04-2.5mg/kg, IP), SLV313 (0.0025-0.16 mg/kg, SC) or bifeprunox (0.01-0.63 mg/kg, IP), significantly reversed PCP-induced social interaction deficits; and (6) the 5-HT(1A) receptor antagonist WAY100635 blocked the effects of SSR181507 and aripiprazole. These findings indicate that the balance of activity at 5-HT(1A) and D(2) receptors profoundly influences the activity of antipsychotics in this model of social withdrawal, and their potential benefit on at least some of the negative symptoms of schizophrenia.

Antipsychotic drugs can regulate transcription of some genes, including those involved in regulation of hypothalamic-pituitary-adrenal (HPA) axis, whose activity is frequently disturbed in schizophrenic patients. However, molecular mechanism of antipsychotic drug action on the corticotropin-releasing hormone (CRH) gene activity has not been investigated so far. This study was undertaken to examine the influence of conventional and atypical antipsychotic drugs on the CRH gene promoter activity in differentiated Neuro-2A cell cultures stably transfected with a human CRH promoter fragment linked to the chloramphenicol acetyltransferase (CAT) reporter gene. It has been found that chlorpromazine (0.1-5.0 microM), haloperidol (0.5-5.0 microM), clozapine (1.0-5.0 microM), thioridazine (1.0-5.0 microM), promazine (5.0 and 10 microM), risperidone (5.0 and 10.0 microM), and raclopride (only at the highest used concentrations, ie 30 and 100 microM) present in culture medium for 5 days inhibited the CRH-CAT activity. Sulpiride and remoxipride had no effect. Since CRH gene activity is most potently enhanced by cAMP/protein kinase A pathway, the effect of antipsychotics on the forskolin-induced CRH-CAT activity was determined. Chlorpromazine (1.0-5.0 microM), haloperidol (1.0-5.0 microM), clozapine (1.0-5.0 microM), thioridazine (3.0 and 5.0 microM), and raclopride (30 and 100 microM), but not promazine, sulpiride, risperidone, and remoxipride, inhibited the forskolin-stimulated CRH gene promoter activity. A possible involvement of protein kinases in chlorpromazine and clozapine inhibitory action on CRH activity was also investigated. It was found that wortmannin (0.01 and 0.02 microM), an inhibitor of phosphatidylinositol 3-kinase (PI3-K), significantly attenuated the inhibitory effect of chlorpromazine and clozapine on CRH gene promoter activity. In line with these results, a Western blot study showed that these drugs increased phospho-Ser-473 Akt level, had no effect on total Akt, and decreased glycogen synthase kinase-3beta level. Additionally, we found that clozapine decreased protein kinase C (PKC) level and that its action on CRH activity was attenuated by PKC activator (TPA, 0.1 microM). The obtained results indicate that inhibition of CRH gene promoter activity by some antipsychotic drugs may be a molecular mechanism responsible for their inhibitory action on HPA axis activity. Clozapine and chlorpromazine action on CRH activity operates mainly through activation of the PI3-K/Akt pathway. Moreover, PKC-mediated pathway seems to be involved in clozapine action on CRH gene activity.

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') administration to rats produces hyperthermia if they are housed in normal or warm ambient room temperature (Ta) conditions (>or=20 degrees C), but hypothermia when in cool conditions (Ta

It is well known that the mesolimbocortical dopamine pathway is highly active during periods of stress and fear. However, very little research has directly examined how dopamine receptors in this pathway influence fear-related behaviour. The present study examined the effects of selective antagonism of D(4), D(1) and D(2) dopamine receptors of the medial prefrontal cortex (MPFC) on rats' fear behaviour in the elevated plus-maze and the shock-probe burying tests. The results demonstrated that bilateral intra-MPFC infusions of the highly selective D(4) antagonist, L-745 870 (0.2, 1 or 10 nmol/0.5 microL), increased the percentage of open-arm entries and open-arm time in the elevated plus-maze test (1 nmol/0.5 microL), and decreased the duration of burying in the shock-probe test (0.2 or 1 nmol/0.5 microL). Furthermore, none of the doses of the D(4) antagonist affected measures of general activity or pain sensitivity. Intra-MPFC infusions of the D(1) antagonist, SCH-23390 (0.2 or 1 nmol/0.5 microL), or the D(2) antagonist, remoxipride (0.2, 1 or 10 nmol/0.5 microL), had no significant behavioural effects in either test. Taken together, these findings suggest that MPFC D(4) receptors may play an important role in the mediation of fear-related behaviour.

Triadimefon (TDF) is a triazole fungicide that blocks the re-uptake of dopamine (DA) and leads to increased locomotor activity levels in mice and rats, effects similar to those of indirect DA agonists such as cocaine. We recently found in mice that intermittent TDF administration led to robust locomotor sensitization, a phenomenon reflecting neuronal plasticity, following challenge with the same TDF dose after a 2-week withdrawal period. The current study sought to determine whether antagonists to DA D1-like receptors (SCH 23390; SCH), DA D2-like receptors (remoxipride; Rem), ionotropic glutamate n-methyl-d-aspartate (NMDA) receptors (CPP), or ionotropic glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (NBQX) could prevent the development of TDF behavioral sensitization, therefore indicating their mechanistic involvement in TDF sensitization. Mice were treated with either vehicle, SCH (0.015 mg/kg), remoxipride (Rem, 0.3 mg/kg), CPP (2.5 mg/kg) or NBQX (10.0 mg/kg), followed 30 min later by vehicle or 75 mg/kg TDF (TDF), twice a week for 7 weeks, with locomotor activity measured post-dosing once a week. After a 2-week withdrawal period, mice were challenged with 75 mg/kg TDF or vehicle, to test for the presence of behavioral sensitization. Pretreatment with SCH, CPP, or NBQX, but not Rem, blocked the development of behavioral sensitization to TDF specifically for vertical activity. Antagonists that blocked TDF vertical sensitization also attenuated the increase in extracellular DA turnover (homovanillic acid [HVA]/DA) normally associated with this behavioral response. Therefore, DA D1, NMDA and AMPA receptors appear to be necessary for the development of behavioral sensitization to TDF. As such, TDF may be considered an environmental risk factor for behavioral dysfunctions linked to glutamatergic and dopaminergic systems.

Intracerebroventricular (IVT) administration of adrenomedullin (AM) to conscious male hydrated rats increases urinary volume and sodium excretion. The possible involvement of brain dopamine (DA) system on the renal action of IVT-AM was investigated. AM-induced diuretic and natriuretic action was prevented following selective central dopaminergic denervation with 6-hydroxydopamine (6OHDA) in combination with desmethylimipramine (DMI). Selective D 2 DA receptor antagonism with haloperidol, sulpiride, and remoxipride; or with the D 1 DA receptor antagonist, SCH 23390, blunted the increase in urinary volume and sodium excretion induced by IVT-AM. The present results suggest that AM acts centrally, at least in part, via an interaction with endogenous DA through the activation of both DA D 1 /D 2 receptor subtype.

This review examines the question—Do atypical antipsychotic medications improve psychosocial outcomes?—by examining studies that compared the effects of atypicals to conventional antipsychotics or to other atypical medications. The authors reviewed randomized clinical trials of atypical antipsychotic medication that included psychosocial variables as outcomes. Findings from 31 published studies on more than 12,000 individuals generally showed that atypical medications led to significant improvements in negative symptoms compared to conventional antipsychotics. Effects on global assessment of psychosocial functioning and on the quality of life were mixed with only about half the studies reporting significant improvements. Olanzapine yielded the best results on psychosocial functioning; remoxipride was found to yield few significant changes on these variables. This review provides evidence that some atypical antipsychotics may have direct effects on some of the psychosocial disabilities that result from serious mental illness.

Dopamine receptors are significantly involved in hippocampus-based cognitive processes. Whereas the involvement of D1-like receptors in hippocampal plasticity has been described, the role of D2-like receptors remains to be clarified. Therefore, we investigated the contribution of D2-like receptors to synaptic transmission, long-term potentiation (LTP) and depotentiation in the dentate gyrus of freely moving rats. Male Wistar rats underwent chronic implantation of a recording electrode in the granule cell layer, a stimulating electrode in the medial perforant path and a cannula in the ipsilateral cerebral ventricle (to enable drug administration). The D2-like receptor agonists quinpirole and noraporphine dose-dependently inhibited basal synaptic transmission. Agonist priming of D2-like receptors with a drug concentration which had no effect on synaptic transmission inhibited depotentiation but did not affect LTP. The agonist effects on depotentiation were prevented by the D2-like antagonist remoxipride. Remoxipride itself did not influence basal synaptic transmission or depotentiation. Interestingly, 'weak' LTP (4 h) but not 'strong' LTP (24 h) was inhibited by prior application of remoxipride. These results suggest a specific role for dopamine D2-like receptors in the regulation of both depotentiation and LTP in vivo and offer an important and novel insight as to the involvement of these receptors in processes related to learning and memory.

Remoxipride, a dopamine D 2 antagonist, decreases responding that results in the presentation of small amounts (~0.1 ml) of ethanol in limited-access paradigms. This type of operant response is a combined appetitive/consummatory response that is differentially affected by changing stimulus properties of consumed ethanol (i.e., taste, pharmacology) over the course of the session. In the present experimental design, ethanol-directed appetitive and consummatory responses were procedurally separated to investigate the specific effects of remoxipride on these distinct behaviors. Male Long–Evans rats were trained to make a series of lever-press responses once each day that resulted in access to a sipper tube spout containing 10% ethanol for 20 min. Three doses of remoxipride were tested: 5.0, 10.0, and 15.0 mg/kg (–30 min, i.p.). In Experiment 1, a response requirement of 20 was used, and both reinforced and nonreinforced sessions were examined. In nonreinforced sessions, subjects were permitted to lever press for 20 min, after which the session ended without sipper tube presentation. These sessions were conducted to remove the possibility that limiting responding might obscure a drug effect on the seeking response. In Experiment 2, a low response requirement (4) was used to investigate the effects of remoxipride on ethanol intake. Average baseline ethanol intake (Experiment 1) was 0.69 g/kg, with blood ethanol concentrations at the end of the session at 64 mg%. At all doses tested, remoxipride had no effect on the measures of ethanol consumption (e.g., total intake, lick latency, lick rate) in either experiment. However, remoxipride dose dependently decreased the number of appetitive responses made, while having no effect on response latency or rate, during both reinforced and nonreinforced sessions in Experiment 1. In these experiments, the systemic antagonism of the dopamine D 2 receptor decreased ethanol seeking without causing a general impairment of motor function. The procedural separation of seeking and intake responses revealed that appetitive responding was more sensitive than consummatory responding to remoxipride treatment.

Due to methodological reservations, open clinical trials investigating efficacy and tolerability of antipsychotic agents are often regarded with doubt. However, there are nearly no studies comparing findings of controlled double-blind with those of open trials. The aim of this study was to investigate whether results of open and double-blind approaches differ and thereby gain information about the validity of open trials.After literature research, three atypical antipsychotic agents were identified for which at least three open and double-blind trials existed that met the inclusion criteria and from which either the reduction of the Brief Psychiatric Rating Scale (BPRS)- or Positive and Negative Symptom Scale (PANSS) scores or the response rate could be determined.There were no differences in the reduction of the BPRS- or PANSS scores or in the response rates for all three antipsychotic agents between open and double-blind trials.Although double-blind controlled studies are essential in the investigation of new compounds, results of methodologically well-performed open studies are valid and deserve more attention. Preceding open trials may help in the design of double-blind studies.

Real-time analysis of dopamine:antagonist interactions at the recombinant D2short receptor was performed by measuring time-dependent Ca2+ responses following activation of a chimeric Galphaq/o protein in CHO-K1 cells. Terguride (57%), +-UH 232 (20%) and buspirone (16%) demonstrated dopamine-like intrinsic activity at the presumably unoccupied, dopamine-free receptor; remoxipride, pipamperone and L 741626 being silent at 1 microM. Each of the putative antagonists (1 microM) displayed a transient reversal capacity of the low-magnitude Ca2+ phase in the dopamine-bound receptor state ( E(rev): 68%-92% vs. 1 microM tropapride) with a t1/2 between 8.8 s and 13.9 s upon antagonist addition; this capacity was either almost fully [remoxipride, pipamperone and +-UH 232] or partially [buspirone (31%), terguride (45%) and L 741626 (70%)] lost upon further incubation. The biphasic reversal Ca2+ profile of these dopamine antagonists is different from previously characterised dopamine antagonists which display either full reversal of the low-magnitude Ca2+ response with a fast or slow onset of action, or partial reversal stably present over the entire incubation period. The dynamic Ca2+ data strongly suggest that the dopamine D2short receptor can be blocked via multiple molecular mechanisms.

Dopamine D 3 receptors may be involved in drug addiction and in disorders such as schizophrenia and Parkinson’s disease. To determine the pharmacological properties of dopamine D 3 receptors in the rat caudate-putamen, we have investigated R (+)-[ 3 H ]7-hydroxy- N , N -di- n -propyl-2-aminotetralin ([ 3 H ] R (+)-7-OH-DPAT) binding to membrane preparations from the rat caudate-putamen. Kinetic analyses showed that [ 3 H ] R (+)-7-OH-DPAT binding reached equilibrium in approximately 1 h and that both association and dissociation curves were composed of at least two components. Likewise, saturation curves showed at least two binding components with a combined B max value of about 600 fmol/mg protein, which is three times higher than what is present in the subcortical limbic area. Competition curves were performed with agonists such as R (−)-propylnorapomorphine, dopamine, PD 128907, quinpirole, and bromocriptine, and antagonists such as haloperidol, raclopride, clozapine, GR 218231x, remoxipride, and U99194A. These experiments revealed that [ 3 H ] R (+)-7-OH-DPAT binding could be resolved into three specific binding sites ( R 1 – R 3 ) and one nonspecific binding site, with R 1 – R 2 probably representing D 3 receptor binding and the minor R 3 representing D 2 receptor binding. The low affinities of (±)-8-OH-DPAT and 1,3-di(2-tolyl)guanidine to inhibit [ 3 H ] R (+)-7-OH-DPAT binding indicate negligible involvement of 5-HT 1A or sigma binding sites, respectively. The pharmacological profile of [ 3 H ] R (+)-7-OH-DPAT (2 nM) binding in the caudate-putamen was similar to that of dopamine on [ 125 I ]iodosulpride binding in the cerebellar lobule X, which contain D 3 but not D 2 receptors. Mg 2+ increased and GTP and Na + decreased the binding of [ 3 H ] R (+)-7-OH-DPAT, suggesting a coupling of endogenous D 3 receptors to G proteins. Taken together, these results suggest that dopamine D 3 receptors display multiple agonist binding states, and that D 3 receptors are present in high concentrations in the rat caudate-putamen. These results may have implications for the physiological and pathological roles of dopamine D 3 receptors in the brain.

The hydroquinone and catechol like metabolites, NCQ344 and NCQ436 respectively, of the antipsychotic remoxipride have recently been demonstrated to induce apoptosis in myeloperoxidase (MPO)-rich human bone marrow progenitor and HL-60 cells [S.M. McGuinness, R. Johansson, J. Lundstrom, D. Ross, Induction of apoptosis by remoxipride metabolites in HL-60 and CD34+/CD19− human bone marrow progenitor cells: potential relevance to remoxipride-induced aplastic anemia, Chem. Biol. Interact. 121 (1999) 253–265]. In the present study, we determined the molecular mechanisms of apoptosis induced by these remoxipride metabolites in HL-60 cells. Our results show that apoptosis was accompanied by phosphatidylserine (PS) exposure, activation of caspases-9, -3, -7 and DNA cleavage. In HL-60 cells treated with the hydroquinone NCQ344 and catechol NCQ436, the general caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp.fluoromethyl ketone (Z-VAD.FMK) blocked DNA cleavage and activation of caspases-9, -3/-7. In addition, PS exposure was significantly but not completely inhibited by Z-VAD.FMK. These results demonstrate that although Z-VAD.FMK inhibitable caspases are necessary for maximal apoptosis induced by NCQ344 and NCQ436, additional caspase-independent processes may orchestrate changes leading to PS exposure during apoptosis induced by the remoxipride polyphenolic metabolites.

Rationale: Previous drug discrimination studies with clozapine have not reliably distinguished between atypical and typical antipsychotics. Objectives: The present study was conducted to determine whether low-dose clozapine drug discrimination could distinguish atypical from typical antipsychotics. Methods: Rats were trained to discriminate 1.25 mg/kg clozapine from vehicle in a two-lever drug discrimination procedure. Results: Generalization testing revealed full substitution with the atypical antipsychotics olanzapine (90.3% maximum generalization), sertindole (99.8%), and risperidone (87.1%) and partial substitution for quetiapine (seroquel, 66.4%) and the typical antipsychotics haloperidol (56.8%) and thioridazine (74.3%). Remoxipride (23.1%) and the typical antipsychotics chlorpromazine (27.9%) and fluphenazine (29.5%) did not reliably substitute for clozapine. Conclusions: In contrast to previous clozapine drug discrimination studies with higher training doses, the atypical antipsychotics olanzapine, sertindole, and risperidone reliably substituted for clozapine while typical antipsychotics did not. These results suggest that low-dose clozapine drug discrimination may be a more sensitive assay for distinguishing atypical from typical antipsychotic drugs.

To clarify the role of dopamine D1 and D2 receptors in the volume-induced micturition reflex, conscious, female rats were investigated cystometrically before and after intravenous administration of SKF 38393 (a selective D1 receptor agonist), SCH 23390 (a selective D1 receptor antagonist), quinpirole (a selective D2 receptor agonist), and remoxipride (a selective D2 receptor antagonist). The effect of quinpirole was also investigated in the presence of remoxipride. Intravenous administration of SKF 38393 (0.01-3.0 mg/kg) did not affect any cystometric parameters investigated. On the other hand, SCH 23390 (0.1-1.0 mg/kg i.v.) reduced bladder capacity and micturition volumes and increased the micturition pressure in a dose-dependent manner. Quinpirole (0.01-0.1 mg/kg) given intravenously, dose-dependently decreased bladder capacity and micturition volumes. Pre-treatment with remoxipride (1.0 mg/kg i.v.) significantly attenuated the effect of quinpirole (0.1 mg/kg i.v.). Remoxipride (0.1-1.0 mg i.v.) itself did not cause any significant changes in the cystometric parameters. These results suggest that in conscious rats, D1 receptors tonically inhibit the micturition reflex and that D2 receptors are involved in facilitation of the micturition reflex. It may be speculated that detrusor hyperreflexia associated with Parkinson's disease results from activation failure of D1 receptors and that administration of D2 receptor agonists might worsen the condition.

Objective: To determine if the inclusion of a placebo control in clinical trials of schizophrenia affects retention rates in the first 35 days of inclusion relative to trials that did not have a placebo control. Method: This was a retrospective study of 8 double-blind clinical trials, 5 of which had a placebo control while 3 did not. Using survival analysis, retention rates between the placebo-controlled trials (PCTs) and the nonplacebo-controlled trials (NPCTs) were compared. Screening and percentage improvement on Brief Psychiatric Rating Scale and Positive and Negative Syndrome Scale scores were compared. Results: Significantly more patients were retained in the 35-day period for NPCTs. Also, the PCT group had significantly more psychopathology at screening than did the NPCT group. Conclusions: Differences in retention rates between PCTs and NPCTs cannot be uniquely attributed to placebo itself.

The antipsychotic agent, remoxipride [(S)-(-)-3-bromo-N-[(1-ethyl-2-pyrrolidinyl)methyl]-2,6-dimethoxybenz amide] has been associated with acquired aplastic anemia. We have examined the ability of remoxipride, three pyrrolidine ring metabolites and five aromatic ring metabolites of the parent compound to induce apoptosis in HL60 cells and human bone marrow progenitor (HBMP) cells. Cells were treated for 0-24 h with each compound (0-200 microM). Apoptosis was assessed by fluorescence microscopy in Hoechst 33342- and propidium iodide stained cell samples. Results were confirmed by determination of internucleosomal DNA fragmentation using gel electrophoresis for HL60 cell samples and terminal deoxynucleotidyl transferase assay in HBMP cells. The catechol and hydroquinone metabolites, NCQ436 and NCQ344, induced apoptosis in HL60 and HBMP cells in a time- and concentration dependent manner, while the phenols, NCR181, FLA873, and FLA797, and the derivatives formed by oxidation of the pyrrolidine ring, FLA838, NCM001, and NCL118, had no effect. No necrosis was observed in cells treated with NCQ436 but NCQ344 had a biphasic effect in both cell types, inducing apoptosis at lower concentrations and necrosis at higher concentrations. These data show that the catechol and hydroquinone metabolites of remoxipride have direct toxic effects in HL60 and HBMP cells, leading to apoptosis, while the phenol metabolites were inactive. Similarly, benzene-derived catechol and hydroquinone, but not phenol, induce apoptosis in HBMP cells [Moran et al., Mol. Pharmacol., 50 (1996) 610-615]. We propose that remoxipride and benzene may induce aplastic anemia via production of similar reactive metabolites and that the ability of NCQ436 and NCQ344 to induce apoptosis in HBMP cells may contribute to the mechanism underlying acquired aplastic anemia that has been associated with remoxipride.

Phenothiazines are widely used in older patients, but little experimental work has been carried out in this age group. Two groups of healthy volunteers, a younger group (Y: six males and six females, aged 20-42 years) and an older group (0: six males and eight females, aged 65-77 years) took part in a randomized double-blind threeperiod crossover study in which they received by mouth single doses of thioridazine (Y: 50mg; 0: 25mg) remoxipride (Y: 100mg; 0: 50mg) or placebo. Measures of central nervous system (CNS) and haemodynamic function were carried out before drug administration and at 1.5-h intervals up to 9h post-dose, and blood samples were collected over a 24-h period. No significant differences in dose-corrected pharmacokinetic variables were found between the two groups. There was evidence of marked CNS depressant effects of thioridazine from both objective and subjective measures. The effects for remoxipride were similar, though generally less marked. After allowance was made for dose, there was little indication of any difference in degree of CNS depression between the two age groups. Haemodynamic measures showed orthostatic reductions in blood pressure with thioridazine which were particularly marked in the older group, who also showed lower compensatory increases in pulse rate. These results indicate potential problems with orthostatic hypotension with thioridazine in older patients. CNS depression may also be a problem, especially in patients with compromised cholinergic function.

This is a review on the recent results of research on sigma-receptor antagonists. NE-100, a selective sigma1-receptor antagonist, shows improvement of abnormal behaviors and cognitive dysfunction induced by phencyclidine (PCP). However, NE-100 does not inhibit dopamine agonist-induced behaviors nor induces catalepsy. The mode of action of NE-100 is estimated to be the indirect modulation of the NMDA/PCP-receptor ion channel complex and the modulation of dopamine release from the dopaminergic nerve terminals. The recently reported MS-355/MS-377, which is also a selective sigma1-receptor antagonist, has a similar pharmacological profiles as NE-100, but in addition, MS-355/MS-377 inhibits methamphetamine-induced formation of reversal tolerance and also inhibits apomorphine-induced climbing behavior like dopamine D2-receptor antagonists. The report on clinical trial targeting schizophrenia shows results on rimcazole, remoxipride, BMY 14802, panamesine (EMD 57445) and SL 82.0715. Rimcazole was effective in the open study, but the double blind trial was discontinued due to seizure induction. Remoxipride showed efficacy different from those of dopamine D2-receptor antagonists (less extrapyramidal adverse effects), but the trial was discontinued due to occurrence of aplastic anemia. Panamesine and SL 82.0714 showed favorable efficacy in the open studies, but BMY 14802 showed no efficacy in clinical trials.

Background This article reviews the published clinical experience with atypical neuroleptics in children and adolescents. Method A computerized literature search was conducted (MEDLINE, 1974-1998) to retrieve all reports on the use of atypical neuroleptics in children and adolescents. A hand search was performed as well. All relevant clinical data were collated by type of drug. Results We found 5 blind placebo-controlled clinical trials (105 patients), 24 open-label clinical trials (387 patients), and 33 case series (115 patients) describing the use of the atypical neuroleptics clozapine, risperidone, olanzapine, sulpiride, tiapride, amisulpride, remoxipride, and clothiapine in children and adolescents. Some of these agents, especially clozapine, risperidone, and olanzapine, were found to be efficacious in the treatment of schizophrenia, bipolar disorders, and pervasive developmental disorders. The role of atypical neuroleptics as augmenters of serotonin reuptake inhibitors in obsessive-compulsive disorder is unclear. Risperidone appears to possess anti-tic properties in patients with Tourette's disorder. Conclusion The most convincing evidence of the efficacy of atypical neuroleptics in children and adolescents concerns clozapine in the treatment of schizophrenia. Data on other atypical neuroleptics in other disorders are still sparse, and further research is needed. Some of the atypical neuroleptics may become the first-line treatment for childhood schizophrenia and pervasive developmental disorders.

An HPLC method for the determination of NCQ-344, a remoxipride metabolite with a hydroquinone structure, in human plasma is described. Special precautions for the sampling were necessary as the compound rapidly decomposes. An efficient clean-up of the plasma samples was necessary to make use of the inherent sensitivity of the electrochemical detector. This was accomplished by a fast and simple liquid–liquid extraction at pH 7.05 combined with further cleaning on-line by using a short cyanopropyl column as the first column in a column switching system. A heart-cut from the cyanopropyl column containing the NCQ-344 fraction was then injected onto the analytical octadecyl silica column and NCQ-344 was detected at an oxidation potential of 0.70 V. The absolute recovery was >95% and concentrations down to 0.10 nM could be determined with acceptable precision. The NCQ-344 levels in a limited number of samples from patients given remoxipride were found to be between 0.10 and 1 nM. The remoxipride concentrations in the same samples were 5 000–20,000 nM. © 1998 John Wiley & Sons, Ltd.

The pharmacological properties of the novel antipsychotic drugs (APDs) risperidone, sertindole, olanzapine, quetiapine, ziprasidone, remoxipride, and amperozide are reviewed and compared with haloperidol and clozapine. Focus is made on their receptor profiles, their effects in animal models used for evaluation of antipsychotic activity, and extrapyramidal side effects (EPS). In addition, the contrasting actions of these compounds on animal models of cognition, anxiety, and depression are briefly reviewed. The available evidence indicates that novel APDs and clozapine can be differentiated from haloperidol, particularly in models of EPS and cognitive side effects. However, among the group of novel APDs there are many individual differences in models reflecting limbic versus striatal inhibition of dopamine function: clozapine and sertindole show the largest limbic selectivity, followed by quetiapine, ziprasidone, olanzapine and remoxipride, whereas risperidone in many respects has a profile that resembles haloperidol. To date, the results of clinical studies have confirmed the predictions of lower incidence or absence of EPS after administration of novel APDs in doses which demonstrate antipsychotic efficacy.

Antipsychotics have been used for decades to treat individuals exhibiting psychosis. During this time, new antipsychotic agents have been introduced periodically, each with different pharmacological profiles. Some antipsychotics, particularly clozapine and risperidone, have been termed ‘atypical’ with respect to their therapeutic and adverse effect profiles.

The study was designed to optimize the effects of the screened in vitro dissolution variables agitation, temperature, osmolality, and polarity on the release of the neuroleptic compound remoxipride from extended release coated spheres. The variables were varied independently by means of a fractional factorial design. The in vitro tests were performed with the Basket method (USP). The polarity and the osmolality of the medium had significant effects on the dissolution rate of remoxipride. A statistical model was calculated based on the obtained dissolution in vitro. The model was then used to predict the in vitro conditions that most closely correlated with the dissolution rate of remoxipride in vivo, after administration of the formulation to 16 volunteers. The predicted in vitro conditions were experimentally verified, and an excellent association with the in vivo behavior of the formulation was found. Validation of the optimal in vitro conditions was performed on another batch of the formulation. The dissolution profile obtained showed a significant association with the corresponding dissolution profile in vivo. The use of statistically designed experiments in the development of critical dissolution tests for the establishment of in vitro/in vivo correlations seems to be a useful working approach, and supports further application to other oral solid systems.

In order to gain a better understanding of the characteristics of antipsychotic-induced within-session decrements in unconditioned behavioral responses of mice, and whether they are sensitive to novel environmental stimuli, we studied the acute effects of haloperidol and atypical antipsychotic drugs (sulpiride, thioridazine, clozapine, and remoxipride) in familiar and novel open-field conditions in mice. The results show that familiarized controls and antipsychotic-treated groups had a progressive reduction in ambulation and rearing during the 10-minute open-field session. By manipulating the configuration of the open-field situation, familiarized controls as well as mice treated with typical or atypical antipsychotic drugs were able to exhibit an enhanced response to the presentation of novel stimuli. It may be noted that both the maintenance and the initiation of ambulation were affected by antipsychotic treatment. Furthermore, when comparing novel versus familiar groups during the 10-minute session, the increase in ambulation induced by atypical antipsychotic treatment was maintained longer (6-8 minutes) than that induced by haloperidol (4 minutes). In summary, these findings show that an important feature in the reinstatement of both typical and atypical antipsychotic-induced behavioral decrement may be a change in the stimulus conditions.

A stereoselective high-performance liquid chromatographic (HPLC) method is described for the selective and sensitive quantitation in human plasma of R-(+)- and S-(-)-enantiomers of remoxipride. Remoxipride was extracted from basified plasma into hexane-methyl-tert.-butyl ether (20:80, v/v), washed with sodium hydroxide (1.0 M), then back-extracted into phosphoric acid (0.1 M). A structural analog of remoxipride was used as an internal standard. The sample extracts were chromatographed using a silica-based derivatized cellulose chiral column, Chiralcel OD-R, and a reversed-phase eluent containing 30-32% acetonitrile in 0.1 M potassium hexafluorophosphate. Ultraviolet (UV) absorbance detection was performed at 214 nm. Using 0.5-ml plasma aliquots, the method was validated in the concentration range 0.02-2.0 microg/ml and was applied in the investigation of systemic inversion of remoxipride enantiomers in man.

The effects of conventional and novel atypical antipsychotic drugs were compared to clozapine in squirrel monkeys that discriminated I.M. injections of clozapine (1.0 mg/kg) from saline in a two-lever drug discrimination procedure. Clozapine (0.03-3.0 mg/kg) produced dose-related increases in responding on the clozapine-associated lever with full substitution at the training dose in all monkeys. Dose-related increases in responding on the clozapine-associated lever and full substitution also were observed with structural analogues of clozapine including perlapine and fluperlapine (0.1-3.0 mg/kg), seroquel (0.1-5.6 mg/kg), and JL 5, JL 8 and JL 18 (0.1-3.0 mg/kg). Other clozapine analogues, including olanzapine, amoxapine, loxapine and clothiapine, and conventional antipsychotic drugs, including phenothiazines such as chlorpromazine and thioridazine, produced some clozapine-associated responding up to the highest doses that could be studied, but did not substitute for clozapine. Olanzapine did produce full clozapine-lever responding following pretreatment with the dopamine D2-receptor agonist (+)-PHNO (0.003-0.01 mg/kg). Putatively atypical antipsychotics that are structurally unrelated to clozapine including risperidone (0.003-0.1 mg/kg), sertindole (0.03-1.0 mg/kg) and remoxipride (0.1-5.6 mg/kg) similarly failed to substitute for clozapine up to the highest doses. The present results indicate that some, but not all, structural analogs of clozapine have clozapine-like discriminative-stimulus effects and that novel antipsychotic drugs which purportedly have clozapine-like clinical efficacy may not produce its interoceptive stimulus effects.

In a previous study using Sprague-Dawley rats, we showed that in a prepulse inhibition (PPI) procedure with levels of PPI ranging from approximately 10 to 40% (for prepulse intensities 2, 9 and 15 dB above background noise), the antipsychotics clozapine and haloperidol, but also the alpha 1 adrenoceptor antagonist prazosin, robustly and dose-dependently potentiated PPI. In contrast, the antipsychotics risperidone, amisulpride, raclopride and remoxipride did not potentiate PPI. The false positive (prazosin) and the four false negatives led us to conclude that this PPI-enhancing procedure had poor predictive validity as a screening tool for potential antipsychotics. In the present study, we used Wistar rats, which under the same protocol as that used for Sprague-Dawley rats show a very low level of PPI. We examined the ability of six antipsychotics, given intraperitoneally (i.p.), to reverse this PPI deficit. It was found that clozapine (5-20 mg/kg), olanzapine (5-20 mg/kg) and sertindole (1-10 mg/kg) reversed this deficiency of PPI (i.e. potentiated the low level of PPI). In contrast, risperidone (0.1-1 mg/kg), remoxipride (1-10 mg/kg) and haloperidol (0.1-1 mg/kg) were inactive. The negative results with three clinically active antipsychotics (risperidone, remoxipride and haloperidol) indicate that reversal of this PPI deficit in Wistar rats has poor predictive validity to screen for potential antipsychotic activity. In an attempt to investigate the mechanism that might underlie the reversing effect of clozapine, olanzapine and sertindole, we tested the ability of the alpha 1 adrenoceptor antagonist prazosin (3-20 mg/kg), the dopamine D1 receptor antagonist SCH 23390 (0.01-0.1 mg/kg) and the 5-HT2 antagonist ritanserin (0.3-3 mg/kg) to reverse the PPI deficit. Negative results with these three drugs did not allow us to characterize the receptor(s) that might be implicated in the reversal of this type of PPI deficit.