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)

Family, twin, and adoption studies suggest that genetic factors play an important role in the etiology of schizophrenia. Detection of single gene(s) involved in a higher susceptibility to a hereditary disease is possible with linkage analysis. The effects of serotonin2-receptor antagonists on symptoms of schizophrenia suggest that a mutation in the gene coding for this receptor subtype might be involved in the pathophysiology of this disease. Recently a copy DNA encoding the serotonin 5-HT2 receptor has been isolated and with a human 5-HT2 receptor copy DNA probe the HTR2 locus has been mapped to chromosome 13. Using multipoint linkage analysis between schizophrenia and genetic markers spanning the region of the HTR2 locus, we were able to exclude linkage between this candidate gene and schizophrenia in a Swedish kindred. Given this result, we conclude that the serotonin 5-HT2 receptor gene itself is not a major susceptibility gene for schizophrenia in this family.
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PMID:Exclusion of linkage between the serotonin2 receptor and schizophrenia in a large Swedish kindred. 134 24

It has been suggested that sigma receptor antagonists may be useful as antipsychotic drugs and that 5-hydroxytryptamine (5-HT2) receptor antagonists produce improvements of the negative symptoms of schizophrenia. [1-(Cyclopropylmethyl)-4-(2'-(4''-fluorophenyl)-2'- oxoethyl)-piperidine HBr] (DuP 734) is a novel compound with high affinity for the sigma (Ki = 10 nM) and 5-HT2 (Ki = 15 nM) receptors, but low affinity for dopamine receptors (Ki > 1000 nM) as well as 33 other receptors, ion channels and second messenger systems in vitro. DuP 734 did not inhibit the synaptosomal uptake of dopamine, 5-HT or norepinephrine. Oral administration of DuP 734 potently blocked 5-hydroxy-L-trytophan (5-HTP)-induced head twitch in the rat (ED50 = 6.5 mumol/kg), indicating 5-HT2 antagonist activity. Extracellular single-unit recording studies demonstrated that DuP 734 antagonized the effect of the selective sigma ligand (+)-3-(3-hydroxyphenyl-N-(1-propyl) piperidine [(+)-3-PPP] on dopamine neuronal activity in the substantia nigra of the rat with an ED90 of 3.6 mumol/kg i.v. The sigma receptor agonists (+)-SKF 10,047 and phencyclidine both elicited rotational behavior in rats with unilateral lesion of the substantia nigra. The rotational behavior induced by either (+)-SKF 10,047 or phencyclidine was dose-dependently antagonized by DuP 734 with oral ED50 of 8.7 and 19.6 mumol/kg, respectively. The 5-HT2 receptor antagonist ICI 169,369, even at high doses (up to 33 mumol/kg, s.c.), did not antagonize the rotational behavior induced by (+)-SKF 10,047.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:DuP 734 [1-(cyclopropylmethyl)-4-(2'(4''-fluorophenyl)-2'-oxoethyl)- piperidine HBr], a sigma and 5-hydroxytryptamine2 receptor antagonist: receptor-binding, electrophysiological and neuropharmacological profiles. 136 72

The neurochemical properties of three novel benzazepine derivatives NNC-112, NNC-687 and NNC-756 were assessed. These compounds inhibited dopamine D1 receptor binding in vitro with low nanomolar to picomolar dissociation constants whereas those for the D2 receptor were in the micromolar range. Contrary to classical neuroleptics, but similar to the atypical neuroleptics, clozapine and fluperlapine, NNC-112, NNC-687 and NNC-756 were relatively more potent in inhibiting dopamine-stimulated adenylyl cyclase than [3H]SCH 23390 binding. Both NNC-112 and NNC-756 had high affinity for the 5-HT2 receptor whereas NNC-687 had low affinity for this receptor. The affinity for other receptors or neurotransmitter transporters was very low. In vivo, the dopamine D1 receptor selective profile of NNC-112, NNC-687 and NNC-756 was evident from the potent inhibition of D1 receptor binding whereas no effect on D2 receptor binding was apparent. In addition, the compounds blocked D1 receptor-mediated rotation in unilaterally 6-hydroxydopamine-lesioned rats, but had no effect on D2-induced rotation. Thus, NNC-112, NNC-687 and NNC-756 are potent and selective dopamine D1 receptor antagonists that may be useful in the treatment of schizophrenia.
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PMID:NNC-112, NNC-687 and NNC-756, new selective and highly potent dopamine D1 receptor antagonists. 139 49

The effects of 6-chloro-2-(1-piperaziny)pyrazine (MK-212), a centrally acting 5-HT1C/5-HT2 agonist, on body temperature and behavior were assessed using a single-blind cross-over design in 23 schizophrenic patients and 22 normal controls. Body temperature was assessed before drug administration and at 30-min intervals for 3 hr. Each subject was administered placebo or MK-212. MK-212 significantly elevated temperature in normal controls. There was no overall MK-212-induced increase in temperature compared to placebo in the schizophrenic patients; however, 13 of 23 (56.5%) patients had a larger increase in temperature after MK-212 than placebo, 3 of 23 (13.1%) had no change, whereas the temperature change after placebo was greater than after MK-212 in 7 of 23 (30.4%) patients. MK-212 produced significant increases in nausea, feeling strange, and arousal but these effects did not differ between groups. These results are consistent with decreased 5-HT2 receptor responsivity in some patients with schizophrenia.
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PMID:Effect of the serotonin agonist, MK-212, on body temperature in schizophrenia. 158 24

Ten male inpatients (aged 29 +/- 6 years) with a DSM-III diagnosis of schizophrenia participated in a 4-week open dose escalation study of amperozide, a novel 5-HT2 receptor antagonist. The maximum daily dose of amperozide was 20 mg. A close dose-plasma concentration relationship showed considerable interindividual variation in the steady-state plasma levels at a given dose. Approximately equal concentrations of amperozide and its metabolite, N-deethylated amperozide, were seen in plasma. The prolactin levels were not increased during amperozide treatment. No changes occurred in hematological or other laboratory parameters. ECG showed changes in T-wave morphology and a prolongation of the QTc time. One patient was withdrawn from the trial due to aggravation of psychotic symptoms, and two patients had a brief, temporary discontinuation of the drug due to somatic illness. Six patients were improved during amperozide treatment, as assessed by the Clinical Global Improvement Scale. Among the responders the total CPRS was reduced by a mean of 64% and total BPRS score by a mean of 46%. Mild tremor was a frequent side effect, but other extrapyramidal symptoms were rare. Nausea was seen in six patients and of a more pronounced character in one patient. In general, the severity of the side effects increased with increasing doses of amperozide.
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PMID:Effects of amperozide in schizophrenia. An open study of a potent 5-HT2 receptor antagonist. 192 36

Stimulation of 5-HT2 receptors in mammals by agonists causes detrimental neurological, psychological, and circulatory effects. 5-HT2 antagonists block the elicited effects, but by themselves, they do not cause any apparent behavioral, neurological or subjective effects. However, 5-HT2 antagonists increase slow wave sleep and have a therapeutic action on impaired circulation, dysthymia, and negative symptoms in schizophrenia. Chronic treatment of rodents with various 5-HT2 antagonists was reported to cause an anomalous desensitization and 5-HT2 receptor down regulation. In this study we further investigated the 5-HT2 receptor regulation in vivo and in vitro by agonist and antagonist treatment. Treatment of rats with the 5-HT2 agonist, 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) (2.5 mg/kg s.c., every 8 h), rapidly caused desensitization of the head twitch response (-20% and -80% after 2 and 4 injections) and a decrease in the number of frontal cortical 5-HT2 receptors labeled with [3H]ketanserin (-24% and -41%, 24 h after 2 and 4 injections). The receptor resynthesis/degradation revealed half-times of 5 days initially to 3 days in the later drug-free period. Administration of the antagonist ketanserin (2.5 mg/kg, s.c., every 8 h) 15 min before the agonist, antagonized the acute behavioral effect but did not prevent the 5-HT2 receptor down regulation after 4 treatments. In contrast, ketanserin by itself, given 4 times, caused a reduction in the Bmax-value of [3H]ketanserin binding by 19% and given 10 times it caused a reduction in the Bmax-values by 28% and 31% of [3H]ketanserin and [3H]DOB binding in the frontal cortex. Hence 5-HT2 receptors labeled by an antagonist and an agonist ligand were similarly decreased. In vascular smooth muscle cells in culture kept for at least 24 h in a serotonin-free medium before treatment, the 5-HT2 receptor mediated 5-HT-induced inositol phosphate formation, was rapidly desensitized by agonist treatment: -20% after 15 min and -80% after 1 h incubation of the cells with 10(-5) M 5-HT or DOM. After 2 h and 24 h treatment resensitization occurred with half-times of 5 h and 12 h, respectively. Pretreatment of the cells for 15 min or 24 h with 10(-7) M of the antagonists setoperone or ketanserin, followed by extensive washing, caused a reduction in the 5-HT-induced inositol phosphate formation by about 50% with setoperone and by 30% with ketanserin. Effects of 15 min and 24 h drug pretreatment were similar.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:5-HT2 receptors, roles and regulation. 225 9

The effect of the putative antipsychotic compound amperozide on the electrical activity of single identified midbrain dopamine (DA) neurons was investigated in the chloral hydrate anesthetized male rat. While the activity of DA cells in the substantia nigra was unaffected, DA neurons of the ventral tegmental area (VTA), the origin of the mesolimbocortical DA system, were affected in either of two ways: 1) increased firing rate and burst firing, i.e. an excitation, or 2) regularization of the firing pattern. Reversible cold inactivation of the medical prefrontal cortex (PFC) induced a pacemaker-like firing of VTA-DA cells, an effect blocked by amperozide in the cells excited by the drug. Cells responding with a regularization were not protected against the effect of PFC inactivation. These different effects of amperozide, which may in part be mediated by 5-HT2 receptor blockade, suggest an antipsychotic activity of amperozide, particularly in schizophrenia with negative symptoms.
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PMID:Effects of amperozide, a putative antipsychotic drug, on rat midbrain dopamine neurons recorded in vivo. 230 93

Clozapine can produce greater clinical improvement in both positive and negative symptoms than typical antipsychotic drugs in neuroleptic-resistant schizophrenic patients. The clinical response may occur rapidly in some patients but is delayed in others. Clozapine has also been reported to produce fewer parkinsonian symptoms, to involve a lower risk of producing tardive dyskinesia, and to produce no serum prolactin elevations in man. It seems likely that these effects are the result of a common biological mechanism or related mechanisms, rather than unrelated effects. Other atypical antipsychotic drugs, such as melperone and fluperlapine, share at least some of these properties. A relatively low affinity for the D-2 dopamine (DA) receptor and high affinity for the 5-HT2 receptor, producing a high 5-HT2/D-2 ratio, best distinguishes atypical antipsychotics like clozapine from typical antipsychotic drugs. Through its weak antagonist action on D-2DA receptors and a potent inhibitory effect on 5-HT2 receptors, as well as its ability to increase DA and 5-HT2 release, clozapine may be able to permit more normal dopaminergic function in the anterior pituitary, the mesostriatal, mesolimbic and mesocortical regions. The numerous advantages of clozapine over typical neuroleptics are consistent with the primary importance of DA to the pathophysiology of schizophrenia. The secondary but still significant role of 5-HT in the action of clozapine may either be direct or via the effect of 5-HT on dopaminergic mechanisms. Some aspects of schizophrenia could be due to a dysregulation of the interaction between serotonergic and dopaminergic neurotransmission.
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PMID:Clozapine: new research on efficacy and mechanism of action. 256 75

It has been suggested that a combined blockade of 5-HT2 and D2 dopamine receptors may be superior to D2 dopamine antagonists alone in the treatment of schizophrenia. Risperidone, which has a high affinity for 5-HT2 and D2 dopamine receptors in vitro, is a new antipsychotic drug that has been developed according to this hypothesis. The aim of this study was to examine if risperidone indeed induces 5-HT2 and D2 dopamine receptor occupancy in vivo in humans. Central receptor occupancy was examined by positron emission tomography (PET) in three healthy men after oral administration of 1 mg risperidone. [11C]N-methylspiperone ([11C]NMSP) was used as a radioligand for determination of 5-HT2 receptor occupancy in the neocortex. Both an equilibrium ratio analysis and a kinetic three-compartmental analysis indicated a 5-HT2 receptor occupancy about 60%. [11C]raclopride was used as a radioligand for determination of D2 dopamine receptor occupancy in the striatum and the calculated occupancy was about 50%. This is the first quantitative determination of 5-HT2 receptor occupancy induced by an antipsychotic drug in the living human brain. The results indicate that 5-HT2 receptor occupancy should be very high at the dose level of 4-10 mg risperidone daily, as suggested for clinical use. Risperidone is thus an appropriate compound for clinical evaluation of the benefit of combined 5-HT2 and D2 dopamine receptor blockade in the treatment of schizophrenia.
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PMID:5-HT2 and D2 dopamine receptor occupancy in the living human brain. A PET study with risperidone. 753 Mar 76

In vivo occupation of dopamine D1 and D2 and serotonin (5-HT)2 receptors by typical and atypical antipsychotic drugs (APD) was examined using N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline, which nonselectively and irreversibly inactivates these receptor sites. APD were classified as typical or atypical based on their capacity to induce extrapyramidal side effect in humans and/or catalepsy in laboratory rodents. Pretreatment of rats with typical APD (haloperidol, 0.25-3 mg/kg; chlorpromazine, 5-10 mg/kg; cis-flupenthixol, 1 mg/kg; zotepine, 5 mg/kg; nemonapride, 0.5-2 mg/kg) potently reversed the N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline-induced D2 receptor inactivation in rat striatum. In contrast, some atypical APD or its candidates (clozapine, 5-30 mg/kg; fluperlapine, 10 mg/kg; risperidone, 0.25-3 mg/kg; setoperone, 0.025-0.25 mg/kg; ORG 5222, 0.25 mg/kg) showed considerable occupation of 5-HT2 receptors in cerebral cortex with smaller or negligible occupation of D2 and D1 receptors. Pretreatment with the other atypical APD (sulpiride, 30 mg/kg; amperozide, 1 mg/kg) had no effect on these three receptors, although at higher doses, sulpiride (60 mg/kg) and amperozide (5 mg/kg) slightly but significantly reversed D2 and 5-HT2 receptor inactivation, respectively. It was concluded that a certain group of atypical APD is characterized by high occupancy of 5-HT2 receptor with lower or minimal occupancy of D2 and D1 receptors in vivo. The relevance of these characteristics of atypical APD was discussed in relation to extrapyramidal side effects and the therapeutic effects on schizophrenia.
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PMID:Dopamine D1, D2 and serotonin2 receptor occupation by typical and atypical antipsychotic drugs in vivo. 768 43


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