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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 45 (1985), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cholecystokinin octapeptide (CCK26–33) is metabolized by neural membranes with an initial cleavage to CCK29–33 and subsequent breakdown to CCK31–33 and CCK32–33; this pattern of proteolysis occurs on incubation with either P2 or purified lysed synaptosomal membranes. To determine whether the pattern of CCK26–33 proteolysis is unique to the brain and whether regional brain differences in its pathway or rate exist, we analyzed the proteolysis of CCK by synaptic membranes of various brain areas and cellular membranes of peripheral tissue. The pattern of degradation in brain did not differ among the regions studied. The overall proteolysis rate, as measured by the formation of tryptophan, was higher in the striatum than in the cortex, although CCK29–33 was formed at the same rate in both areas. In nonneural tissue, the rate of degradation was highest in liver membranes and lowest in pancreatic acinar cell preparations. Thus, it appears that degradative peptidases are not necessarily colocalized with CCK receptors. The pattern of product formation is the same in peripheral compared with CNS membranes; thus, the degradative pathway does not appear to be unique to brain tissue. The enzyme present in synaptic membranes that is responsible for CCK29–33 formation requires a metal ion and sulfydryl groups for the catalysis and thus is a metalloendopeptidase. Furthermore, its activity is inhibited by Ac-Gly-Phe-Nle-al, a peptide aldehyde whose sequence bears some homology to the amino acid sequence in the region of CCK26–33 that is cleaved by this enzyme.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The extracellular regulated kinases (ERK) 1 and ERK2 are members of mitogen-activated protein (MAP) kinase family that play an important role in transducing extracellular signals to the nucleus and have been implicated in a broad spectrum of biological responses. To test the hypothesis that MAP kinases may be involved in depression, we examined the activation of p44/42 MAP kinase and expression of ERK1 and ERK2 in the post-mortem brain tissue obtained from non-psychiatric control subjects (n = 11) and age- and the post-mortem interval-matched depressed suicide subjects (n = 11). We observed that p44/42 MAP kinase activity was significantly decreased in the prefrontal cortical areas (Brodmann's areas 8, 9 and 10) and the hippocampus of depressed suicide subjects without any change in the cerebellum. This decrease was associated with a decrease in mRNA and protein levels of ERK1 and ERK2. In addition, the expression of MAP kinase phosphatase (MKP)2, a ‘dual function’ ERK1/2 phosphatase, was increased in the prefrontal cortex and hippocampus. These studies suggest that p44/42 MAP kinases are less activated in the post-mortem brain of depressed suicide subjects and this may be because of reduced expression of ERK1/2 and increased expression of MKP2. Given the role of MAP kinases in various physiological functions and gene expression, alterations in p44/42 MAP kinase activation and expression of ERK1/2 may contribute significantly to the pathophysiology of depressive disorders.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 448 (1985), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 448 (1985), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 105 (1998), S. 719-734 
    ISSN: 1435-1463
    Keywords: Keywords: D3 antagonist ; schizophrenia ; UH232 ; antipsychotic ; dopamine.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. The aminotetralin derivative (+)-UH232 is a dopamine-receptor antagonist with complex pharmacological properties, including a 4 : 1 selectivity for the D3 vs. D2 receptor and a preference for the autoreceptors. Its behavioral profile differs markedly from that of other dopamine antagonists in exhibiting both stimulant and inhibitory features. In an effort to elucidate the role of different dopamine receptor subtypes in psychosis, we administered (+)-UH232 to drug-free schizophrenic patients. Six patients received single doses of (+)-UH232 over a dose range of 80 to 180 mg in a rising-dose, double-blind placebo-controlled design. Efficacy and safety were assessed over 8 hours after a single dose. In none of the patients at any of the doses was there an indication of a symptomatic psychosis improvement in response to (+)-UH232. On the contrary, an examination of individual cases revealed symptomatic worsening, such as increases in unusual thought content, anxiety, activation and hostility in four patients. No extrapyramidal movements were noted. Safety assessments were benign. These preliminary data suggest that putative dopamine D3 antagonism, in combination with preferential autoreceptor antagonism, does not alleviate but rather tends to worsen psychosis, at least following a single-dose regimen. However, the possibility cannot be excluded that a 5-HT2- receptor agonistic action of (+)-UH232, suggested by some animal data, has played a role in this treatment outcome. Replication with more selective agents and multiple dose regimens is necessary.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 101 (1995), S. 41-49 
    ISSN: 1435-1463
    Keywords: Tardive dyskinesia ; antipsychotic medications ; atypical neuroleptics ; haloperidol ; clozapine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Tardive dyskinesia (TD) is a serious human side effect of neuroleptic treatment in psychotic disorders. Although the etiology is clear (ie. chronic neuroleptic drugs), its pathophysiology has not yet been satisfactorily explained. This is important not only theoretically but also to inform drug development, allowing the introduction of antipsychotic compounds without TD liability. The development of an animal condition which putatively models these delayed onset dyskinesias, has provided a technique to differentiate between neuroleptic drug effect and dyskinesia correlates. We report here the development of oral dyskinesias in rats in response to a number of different neuroleptics, which have a range of neurochemical and clinical characteristics. Traditional neuroleptics (e.g. haloperidol) produced rat oral dyskinesias, in an open-cage environment. Clozapine, while it produced an increased rate of oral movements, showed a significantly decreased potency in this model. SCH23390 (D1 antagonist) neither produced the oral movements nor modified their onset by coadministration with raclopride. These data replicate and extend other similar studies in the literature. They suggest that clozapine differs from traditional neuroleptics with respect to motor side effects.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 101 (1995), S. 105-113 
    ISSN: 1435-1463
    Keywords: MK801 ; phencyclidine ; NMDA receptor ; hippocampus ; psychosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have previously shown that a single dose of PCP produces a dose-related increase in NMDA-sensitive3H-glutamate binding in CA1 of hippocampus 24 hours later, and some regional changes in kainate binding. Here we report that dizocilpine (MK 801) (O.1 mg/kg and 1 mg/kg), a selective agonist at the PCP receptor and a noncompetitive antagonist of NMDA, produces a similar increase in NMDA-sensitive glutamate and kainate receptor binding in hippocampus 24 hours after a dose. These observations support the conclusion that blockade of glutamate-mediated transmission at the NMDA receptor selectively increases NMDA-sensitive glutamate receptor binding in CA1 of hippocampus and kainate binding in CA3 and dentate gyrus at putatively delayed time points. Several additional areas outside of hippocampus also showed receptor changes at 24 hours after MK801.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of neural transmission 88 (1992), S. 165-175 
    ISSN: 1435-1463
    Keywords: Partial dopamine agonist ; schizophrenia ; (−)-3PPP ; antipsychotic ; autoreceptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The dopamine (DA) autoreceptor agonist (−)-3PPP (preclamol) was tested in male schizophrenic volunteers for safety. The drug was administered intramuscularly in a single rising dose design, crossed with a similar “rising dose” placebo period; all evaluations and raters were blind to drug or placebo administration. Pharmacokinetic, endocrine, safety, and mental status outcome measures were completed before and after each single dose of drug or placebo. Pharmacokinetic analysis showed blood levels between 200–500 pmoles/ml after the intramuscular drug doses of 30–40 mg. Drug half life is 2–2.5 hrs. Growth hormone (GH) levels were elevated in a linear fashion to the 30 mg dose; whereafter, the drug failed to affect GH at all. All safety evaluations were negative, including any untoward effects on the major organ systems. After single dose drug administration, evidence of antipsychotic action occurred in two of the four subjects. This study suggests that (−)-3PPP/preclamol is a safe drug for study in the treatment of schizophrenia and may have antipsychotic efficacy.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1435-1463
    Keywords: Chronic haloperidol ; chronic clozapine ; dose-response ; oral dyskinesias ; tardive dyskinesia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Whether the pathophysiology and treatment of neurolepticinduced oral dyskinesias in rats parallel that for tardive dyskinesia in humans remains a question. To address the issue further, Sprague Dawley rats were treated for 6 months with multiple oral doses of haloperidol (1.5 and 3.0 mg/ kg/day) or clozapine (10, 20, and 30 mg/kg/day) and compared with water treated animals. The rate of oral dyskinesias was monitored at study start and monthly by trained raters who were blind to treatment group. All haloperidoltreated rats developed oral dyskinesias at a significantly higher rate than rats treated with water (p=0.0007) or those treated with clozapine (p=0.0017). Each dose of haloperidol produced significantly higher rates of oral dyskinesias than did any dose of clozapine and did so in an apparent dose-sensitive manner. Clozapine lacked a dose-sensitive relationship with the oral dyskinesias, and failed to show a significant difference in rate from control rats at any dose. Plasma levels of haloperidol with these doses were in the human therapeutic range; with clozapine only the highest dose produced plasma levels in the human therapeutic range. These data show little association between rat oral dyskinesias and clozapine treatment, whereas a strong association is present with haloperidol. The data are, thereby, consistent with the clinical association of tardive dyskinesia with typical neuroleptics like haloperidol but not with the atypical neuroleptic clozapine.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1435-1463
    Keywords: Keywords: Neurotensin ; schizophrenia ; receptor ; human ; postmortem ; autoradiography.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary. [3H]Neurotensin binding and autoradiographic techniques were used to determine the distribution and density of neurotensin receptors in normal and schizophrenic postmortem brain tissue. Coronal hemi-brain blocks of tissue were cut at the level of the caudate and hippocampus from frozen brain tissue obtained from normal individuals with no known psychiatric or neurologic illnesses and from schizophrenic subjects off- or on-antipsychotic drugs at the time of death. Each hemi-block was further divided, sectioned, thaw mounted on to slides, incubated with [3H]neurotensin and apposed to film. Digitized images were analyzed for binding densities. Areas of intense binding include the substantia nigra, the entorhinal cortex, superficial layers of the cingulate, middle frontal, and insular cortices; and with moderate binding in nucleus accumbens, and caudate. Schizophrenic patients off- (3 months or more) or on-antipsychotic drugs at the time of death were tested; all patients showed a reduced level of neurotensin receptors in the caudate (68% of normals), cingulate (34%) and prefrontal cortices (25%).
    Type of Medium: Electronic Resource
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