Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Comparative studies of the benzisoxazole derivative risperidone (R 64 766) were made with ritanserin, a selective centrally acting serotonin-S2 antagonist and with haloperidol, a selective centrally acting dopamine-D2 antagonist. Risperidone like ritanserin shows activity in all tests related to serotonin-S2 antagonism, but at even lower doses (peripheral S2-antagonism at 0.0011 mg/kg, central S2-antagonism at 0.014 mg/kg). Like haloperidol, risperidone shows activity in all tests related to dopamine-D2 antagonism; activity in rats for both compounds starts at 0.016 mg/kg, but some central nervous system controlled functions, including the induction of catalepsy, are relatively much less affected by risperidone. Qualitatively, risperidone is a mixed serotonin-dopamine antagonist. Quantitatively, its study in dogs reveals potent dopamine-D2 antagonistic activity with excellent p.o. bioavailability and a relatively long duration of action. From the obtained pharmacological data, risperidone could be expected to possess the complementary clinical effects of a ritanserin-like serotonin-S2 and an haloperidol-like dopamine-D2 antagonist. Serotonin-S2 antagonism may improve the quality of sleep, reduce negative and affective symptoms in schizophrenic patients and decrease extrapyramidal symptoms induced by classical neuroleptics. Because risperidone is a dopamine-D2 antagonist, antidelusional, antihallucinatory and antimanic actions are expected. The first clinical studies indicate that two additional therapeutic targets, which are not reached with classical neuroleptics, may be obtained with risperidone in the monotherapy of schizophrenia and related disorders: very important contact and mood-elevating properties and extrapyramidal symptoms-free maintenance therapy.
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PMID:Pharmacology of risperidone (R 64 766), a new antipsychotic with serotonin-S2 and dopamine-D2 antagonistic properties. 245 Feb

Clozapine is an antipsychotic without the extra-pyramidal adverse effects associated with currently marketed antipsychotics. In animals, this drug has not been shown to induce catalepsy and only weakly antagonizes the stereotypic movements induced by apomorphine and the amphetamines. Clozapine is rapidly absorbed after both single and repeated oral doses, with steady-state concentrations attained within eight to ten days after beginning therapy. It is metabolized to N-oxideclozapine and N-desmethylclozapine, which have less pharmacological activity than the parent compound and are excreted in the urine and, to a lesser extent, in the feces. Clozapine has overall therapeutic efficacy and/or superiority to currently marketed antipsychotics in the treatment of refractory schizophrenia. Usual doses (25-900 mg/d) of clozapine cause fewer extrapyramidal adverse reactions than available antipsychotics. Hypotension, dizziness, salivation, and sedation are the most frequently reported adverse effects and tend to subside over time. Agranulocytosis is the most serious adverse reaction, and those receiving clozapine should undergo weekly white blood cell count determinations. Clozapine is useful for those treatment-resistant patients who have not responded to adequate trials of other antipsychotics.
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PMID:Clozapine: a novel antipsychotic agent. 265 70

Several clinical papers have reported that beta-adrenoceptor antagonists were useful in the management of schizophrenia and tardive dyskinesia. The present study examined effects of beta-antagonists on haloperidol (HAL)-induced catalepsy using mice in order to study the relationship between beta-antagonists and central dopaminergic functions. Catalepsy was tested by the standard bar test 30 min after intraperitoneal treatment of HAL. Beta-antagonists were administered subcutaneously just after HAL-treatment. Propranolol, alprenolol, oxprenolol and pindolol increased the incidence of catalepsy compared to HAL alone. Atenolol, not penetrating into the brain, and the sedative and hypnotic drug chlordiazepoxide did not potentiate it. These results suggest that the potentiation of HAL-catalepsy by beta-antagonists is based on their central action. Therefore, a central beta-receptor appears to be implicated in the regulation of the central dopaminergic functions.
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PMID:Potentiation of haloperidol-induced catalepsy by beta-adrenoceptor antagonists in mice. 287 54

The principal finding of this manuscript is that the incidence of catalepsy observed in the rat after a single administration of low, clinically relevant doses of the dopamine receptor antagonists and antipsychotic agents, haloperidol and fluphenazine hydrochloride, grows over time such that one re-exposure to the same compound up to 8 weeks later results in a marked enhancement (i.e. sensitization) of this response. This phenomenon appears to be independent of pharmacokinetic or conditioning factors as well as alterations in dopamine or dihydroxyphenylacetic acid. It suggests that the antidopaminergic influence of acute exposure to a neuroleptic not only persists but continues to sensitize for extraordinary periods of time even after the drug is no longer detectable in the system. Our findings may hold the key to understanding the apparent paradox that although neuroleptics presumably induce their therapeutic actions in disorders such as Tourette syndrome and schizophrenia as well as their parkinsonian effects by blocking dopamine receptors, this antagonism occurs immediately while behavioral changes often require weeks for maximal development.
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PMID:Behavioral effects of a single neuroleptic treatment grow with the passage of time. 376 22

A new experimental brain syndrome involving localized periventricular damage induced by intracerebroventricular injections of lysophosphatidyl choline has been developed in adult rats. The acute periventricular injury syndrome is characterized by transient weight loss, decreased emotionality, extreme postural indifference (catalepsy), inappropriate aggressive responses, impaired grooming, cerebral ventricular enlargement, and periventricular damage to both cells and fiber sheaths. This syndrome appears to simulate several features of schizophrenia, and it may prove useful in the study of psychotic disorders in man.
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PMID:The acute periventricular injury syndrome: a possible animal model for psychotic disease. 393 84

Neuroleptic activity in laboratory animals is characterized by a decrease in locomotor activity, ptosis, catalepsy, antagonism of certain amphetamine-induced responses, and inhibition of a conditioned avoidance response. Neuroleptics have also been shown to be potent antagonists of dopamine (DA), cis-5,6-Dimethoxy-2-methyl-3-[2-(4-phenyl-1-piperazinyl)-ethyl]indoline (DHO) has been shown to possess the above described pharmacological profile. However, in contrast to known neuroleptics, DHO has no effect on DA levels, DA turnover rate or DA-stimulated cyclase; nor did it have an effect on tyrosine hydroxylase activity. In addition, DHO did not antagonize apomorphine-induced gnawing or amphetamine-induced stereotyped behavior, both of which have been reported to be DA-dependent. However, the agent decreased the level of norepinephrine in the forebrain. An attempt is made to demonstrate that the "DA-hypothesis" of schizophrenia may not be valid in all cases, and that the biochemistry of the disease state is very complex.
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PMID:Is dopamine antagonism a requisite of neuroleptic activity? 611 Dec 98

Neuroleptic drugs are believed to control schizophrenia by blocking brain dopamine receptors, although most act also on a number of other neuronal systems in brain. Substituted benzamide drugs in general, are more specific for the dopamine system. Brain dopamine receptors, however, are not a single entity. They can be divided on the basis of their linkage to adenylate cyclase. Substituted benzamide drugs are selective antagonists of the adenylate cyclase independent dopamine receptor population. They may be selective antagonists of one sub-population of these adenylate cyclase independent receptors, for unlike typical neuroleptics the receptor interaction of substituted benzamide drugs with brain dopamine receptors depends upon the presence of sodium ions. The specificity of substituted benzamide drugs for brain dopamine receptors is reflected in their behavioural profile. Typical substituted benzamide drugs do not cause catalepsy and, in general, only weakly inhibit motor phenomena. This inability to act in vivo cannot be entirely explained by the poor penetration of these drugs into brain. The unique properties of the substituted benzamide drugs might explain their clinical value in the treatment of schizophrenia and in the treatment of dyskinesias.
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PMID:Multiple dopamine receptors in brain and the pharmacological action of substituted benzamide drugs. 614 87

The glutamate antagonist glutamic acid diethyl ester is found to produce catalepsy in rats, when administered into the lateral ventricle. Since the cerebrospinal fluid content of glutamate is reduced in patients with schizophrenia, the central effects of glutamate antagonists are a possible experimental model for schizophrenia.
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PMID:Glutamic acid diethyl ester induces catalepsy in rats. A new model for schizophrenia? 689 56

Iloperidone (1-[4-[3-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-1- piperidinyl]propoxy]-3-methoxyphenyl]ethanone) demonstrated a potent antipsychotic profile in several in vitro and in vivo animal models. Iloperidone displaced ligand binding at D2 dopamine receptors (IC50 = 0.11 microM) and displayed a high affinity for serotonin (5-HT2) receptors (IC50 = 0.011 microM) and alpha-1 receptors (IC50 = 0.00037 microM). In vivo, iloperidone antagonized apomorphine-induced climbing behavior in mice at low doses with good oral bioavailability, prevented 5-HT-induced head twitch in rats at low doses, and inhibited self-stimulation behavior in rats, pole climb avoidance in rats and continuous Sidman avoidance responding in monkeys. The latter assay also demonstrated a good duration of action. Iloperidone was substantially less active in models of extrapyramidal side effect (EPS) liability, such as preventing apomorphine-induced stereotypy and causing catalepsy in rats. In single dopamine neuron sampling studies, iloperidone demonstrated clozapine-like effects on the number of active midbrain dopamine neurons. Based on the significant increase in the open arm time seen after iloperidone treatment in the elevated plus maze assay and increased interaction score in social interaction, iloperidone may also have favorable effects in the clinic on anxiety and, possibly, negative symptoms. Clinical trials are under way of the use of iloperidone for the treatment of schizophrenia.
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PMID:The pharmacological profile of iloperidone, a novel atypical antipsychotic agent. 756 15

Ziprasidone (CP-88,059) is a combined 5-HT (serotonin) and dopamine receptor antagonist which exhibits potent effects in preclinical assays predictive of antipsychotic activity. Whereas the compound is a dopamine antagonist in vitro and in vivo, its most potent action is antagonism of 5-HT2A receptors, where its affinity is an order of magnitude greater than that observed for dopamine D2 sites. Laboratory and clinical findings have led to a hypothesis that antagonism of 5-HT2A receptors in the brain limits the undesirable motor side effects associated with dopamine receptor blockade and improves efficacy against the negative symptoms of schizophrenia. Ziprasidone possesses an in vitro 5-HT2A/dopamine D2 receptor affinity ratio higher than any clinically available antipsychotic agent. In vivo, ziprasidone antagonizes 5-HT2A receptor-induced head twitch with 6-fold higher potency than for blockade of d-amphetamine-induced hyperactivity, a measure of central dopamine D2 receptor antagonism. Ziprasidone also has high affinity for the 5-HT1A, 5-HT1D and 5-HT2C receptor subtypes, which may further enhance its therapeutic potential. The prediction of antipsychotic efficacy without severe motor side effects is supported by the relatively weak potency of ziprasidone to produce catalepsy in animals, contrasted with its potent antagonism of conditioned avoidance responding and dopamine agonist-induced locomotor activation and stereotypy. The compound is well tolerated in animals at doses producing effective dopamine antagonism in the brain. Ziprasidone should be a valuable addition to the treatment of psychotic disorders.
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PMID:Ziprasidone (CP-88,059): a new antipsychotic with combined dopamine and serotonin receptor antagonist activity. 756 37


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