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)

Clinical and basic research studies have linked cannabinoid consumption to the onset of psychosis, specially schizophrenia. In the present study we have evaluated the effects of the natural psychoactive constituent of Cannabis (-)-delta9-tetrahydrocannabinol on the acute actions of the psychostimulant, D-amphetamine, on behaviour displayed by male rats on a hole-board, a proposed animal model of amphetamine-induced psychosis. Cannabinoid-amphetamine interactions were studied (1) 30 min after acute injection of (-)-delta9-tetrahydrocannabinol (0.1 or 6.4 mg/kg, i.p.); (2) 30 min after the last injection of 14-daily treatment with (-)-delta9-tetrahydrocannabinol (0.1 or 6.4 mg/kg) and 3) 24 h after the last injection of 14-daily treatment with (-)-delta9-tetrahydrocannabinol (6.4 mg/kg). Acute cannabinoid exposure antagonized the amphetamine-induced dose-dependent increase in locomotion, exploration and the decrease in inactivity. Chronic treatment with (-)-delta9-tetrahydrocannabinol resulted in tolerance to this antagonistic effect on locomotion and inactivity but not on exploration, and potentiated amphetamine-induced stereotypies. Lastly, 24 h of withdrawal after 14 days of cannabinoid treatment resulted in sensitization to the effects of D-amphetamine on locomotion, exploration and stereotypies. Since (-)-delta9-tetrahydrocannabinol is a cannabinoid CB1 receptor agonist, densely present in limbic and basal ganglia circuits, and since amphetamine enhances monoaminergic inputs (i.e., dopamine, serotonin) in these brain areas, the present data support the hypothesis of a role for the cannabinoid CB1 receptor as a regulatory mechanism of monoaminergic neuron-mediated psychomotor activation. These findings may be relevant for the understanding of both cannabinoid-monoamines interactions and Cannabis-associated psychosis.
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PMID:Chronic (-)-delta9-tetrahydrocannabinol treatment induces sensitization to the psychomotor effects of amphetamine in rats. 998 95

Recent brain imaging studies suggest that schizophrenia may be related to abnormally high amphetamine-induced dopamine release. It is known that repeated use of amphetamine may cause paranoid psychosis and persisting stereotypies. The biochemical background for these signs and symptoms has not been clarified. In this study, positron emission tomography and [11C]raclopride were used to determine central D2-dopamine receptor density (Bmax) and apparent affinity (K(D)app) in Cynomolgus monkeys before and after 14 days of treatment with d-amphetamine sulphate (2 mg/kg/day; s.c.). One day after withdrawal from amphetamine, K(D)app was increased, suggesting [11C]raclopride competition with elevated concentration of dopamine. At 7 and 14 days after withdrawal, there was a 19-26% decrease in Bmax but no change in K(D)app as compared to baseline. Although this study was performed on two monkeys only, there was thus no support for the view that chronic intermittent hyperactivity of the dopamine system may be related to an upregulation of striatal D2-dopamine receptors. Repeated administration of amphetamine may, rather, cause a long-lasting downregulation of the D2-receptor density, which may be a neurochemical correlate to the abnormal movements, anhedonia, anxiety, and depression seen in psychostimulant abusers.
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PMID:Changes in striatal D2-receptor density following chronic treatment with amphetamine as assessed with PET in nonhuman primates. 1002 13

The present study reviews the long-term effects of neonatal hippocampal damage in monkeys on the development of memory functions and socioemotional behavior. The results showed that neonatal damage to the hippocampal formation impairs specific memory processes, such as those subserving automatic (as opposed to effortful) recognition memory and relational learning, while sparing the abilities to acquire skills, such as object discriminations. Furthermore, the neonatal hippocampectomy led to a progressive loss of social affiliation and a protracted emergence of locomotor stereotypies. While the memory losses following neonatal hippocampal lesions resemble those found after similar lesions acquired in adulthood, only the neonatal lesions resulted in a protracted emergence of abnormal behaviors. These later findings suggested that, presumably, the neonatal lesions impacted on neural systems remote from the site of damage. This was confirmed by our more recent neurobiological studies, demonstrating that neonatal, but not late, lesions of the medial temporal lobe region, disrupt the normal behavioral and cognitive processes subserved by the prefrontal cortex and the caudate nucleus. All together the data support the neurodevelopmental hypothesis viewing early insult to the medial temporal region as the origin of developmental psychosis in humans, such as schizophrenia.
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PMID:Memory and socioemotional behavior in monkeys after hippocampal damage incurred in infancy or in adulthood. 1043 98

Phencyclidine (PCP) and other N-methyl-D-aspartate (NMDA) antagonists induce schizophrenia-like symptoms in humans. In rodents, PCP induces a syndrome of stereotypies and hyperactivity that is accompanied by stimulation of striatal dopamine release. Glycine and other NMDA agonists reverse PCP-induced behaviors in rodents and ameliorate PCP psychosis-like symptoms of schizophrenia in clinical trials. Glycine levels in vivo are regulated by the actions of glycine (GLYT1) transporters. The present study investigates effects of glycine and the prototypic glycine transport inhibitor glycyldodecylamide (GDA) on striatal dopamine release in vitro using a mouse striatal assay. Glycine and GDA significantly inhibit NMDA-induced striatal dopamine release, consistent with their ability to enhance local striatal inhibitory neurotransmission in vitro and to reverse PCP-induced hyperactivity in vivo.
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PMID:Inhibition of striatal dopamine release by glycine and glycyldodecylamide. 1082 63

Neonatal lesions of the ventral hippocampus in rats produce changes in spontaneous and pharmacologically induced dopamine-dependent behaviors that emerge in early adulthood. Neural mechanisms underlying these changes may have implications for understanding the neurobiology of schizophrenia, putatively a neurodevelopmental disorder. In this study, we evaluated the effects of MK-801 (dizocilpine), on automated measures of distance traveled and stereotypies in adult rats with neonatal (postnatal day 7) lesions, and tested the effects of haloperidol, clozapine and an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA) antagonist LY293558 on the MK-801-induced behaviors. The lesioned rats showed significantly greater increases in motor activity after 0.05 and O.1 mg/kg of MK-801 than did controls. Both haloperidol (0.1 and 0.4 mg/kg) and clozapine (4 and 10 mg/kg) reduced hyperlocomotion elicited by 0.2 mg/kg MK-801 in the ventral hippocampus (VH)-lesioned and sham rats. Haloperidol was more potent than clozapine in decreasing MK-801-induced stereotypy, especially in the lesioned rats. Moreover, an AMPA antagonist normalized exaggerated MK-801-induced hyperolocomotion in the lesioned rats at doses that had no effect in controls. These results demonstrate that the lesioned rats are more sensitive to MK-801 during adulthood than control rats, and that antidopaminergic drugs as well as AMPA antagonists antagonize the MK-801-induced behaviors. The neonatal lesion rat model may be useful to further our understanding of the interactions between dopamine and glutamate and their role in the pathophysiology of schizophrenia.
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PMID:Exaggerated MK-801-induced motor hyperactivity in rats with the neonatal lesion of the ventral hippocampus. 1110 81

Repeated amphetamine treatment results in sensitisation both of its behavioural effects, and of its dopamine (DA)-releasing effects on which the former largely depend. Understanding the nature of the sensitised response may help to explain behaviours which emerge only with repeated treatment, such as particular stereotypies and effects on social behaviour in animals, and links between these effects and the emergence of dependence and psychotic symptoms in humans. We show here that a single pretreatment with amphetamine (1mg/kg) is sufficient to sensitise the locomotor response to amphetamine challenge (1mg/kg) 24h later. We have used in vivo microdialysis in the nucleus accumbens in unrestrained rats to demonstrate a corresponding potentiation in the DA response; the marked increase in accumbens dialysate DA following amphetamine (to 427% of basal) was significantly potentiated (to 675% of basal) by the pretreatment, without any alteration in the basal DA. There was also no change in the expected reduction in DA metabolites. Replacement of perfusate calcium by magnesium left the response to acute amphetamine challenge substantially unaffected, as expected from previous reports; however, the potentiation of the DA response by amphetamine pretreatment was prevented. Similarly the potentiated response was attenuated by administration of ondansetron, a 5HT-3 antagonist, (0.01mg/kg) before each amphetamine treatment. The ability of amphetamine to disrupt latent inhibition (L1), which is also disrupted in acute schizophrenia, has been suggested to provide a model of schizophrenia linking underlying cognitive deficits with the DA theory of the disorder. Since LI is disrupted by two systemic administrations of amphetamine 24h apart, but not by one, the present results are consistent with the concept that it is the calcium, and hence impulse, dependence of increased accumbal DA release, rather than its magnitude, which is critical for the disruption of LI.
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PMID:Calcium dependence of sensitised dopamine release in rat nucleus accumbens following amphetamine challenge: implications for the disruption of latent inhibition. 1122 3

Amphetamine-induced social isolation in monkeys has often been considered a valid animal model for certain negative symptoms of schizophrenia. However, there appear to be many ambiguities in relation to the exact nature of the isolation. Therefore, the effect of orally administered amphetamine (AMP) on the occurrence of social isolation in Java monkeys was studied. In part I the rank dependency of the effects of AMP (0.5mg/kg) was investigated in four alpha-males and three beta-males. AMP increased 'proximity' and 'passive groom', and decreased 'active allogroom' in alpha-males. In contrast, AMP decreased all three behavioural elements to a certain extent in beta-males. It is concluded that AMP induces social isolation in beta-males, but not in alpha-males. In part II of this study the AMP-induced behaviour of the treated monkey and the simultaneously occurring changes in the non-treated monkeys were investigated in a detailed study of a single social group. AMP significantly reduced the frequency of 'exploration', 'locomotion', 'self-groom', 'swing', 'active groom', 'inspect', 'approach' and originally-present stereotypies. Thus AMP apparently reduces the ability to initiate behaviour which is characteristic for the adult animal. AMP did not affect the frequency of 'present' and 'play' and enhanced that of 'aggression' and 'fear' in the beta-male; it also elicited various juvenile-like behaviours in both alpha- and beta-males, suggesting that AMP induces a behavioural regression. Furthermore, the behaviour of the non-treated monkeys of the group was decisive for the occurrence of social isolation of the treated monkey. Thus, the effects of AMP on the social behaviour of Java monkeys depend on the individual sensitivity, the social position which the subject occupies in its group, and the behaviour of the partners of the treated subject.
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PMID:The influence of social structure on social isolation in amphetamine-treated Java monkeys (Macaca fascicularis). 1122 37

To study whether an early lesion of prefrontal cortex (PFC) would influence mesolimbic dopaminergic sensitization induced by intermittent electrical stimulation (IES) of the ventral tegmental area (VTA) or change social interactions in animals exposed to both electrical sensitization and prefrontal lesions, we examined the behaviour of rats with or without early prefrontal lesions following repeated electrical stimulation of the VTA. Additionally, we wanted to study the influence of immobilization stress on rats exposed to a combination of prefrontal lesion and daily restraint in Plexiglas tubes prior to IES. Neither early lesion of PFC nor repeated restraint influenced development of sensitization. However, the combination of early prefrontal lesion and IES resulted in changes in social interactions neither seen following IES nor in lesioned rats. The changes were most pronounced in the group exposed to both IES, prefrontal lesions and restraint. Furthermore, repeated restraint caused a significant increase in the threshold current for provocation of the behavioural response related to VTA stimulation (head stereotypies/sniffing). The implications of the findings for sensitization of the mesolimbic dopaminergic system as a model for development of schizophrenia are discussed.
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PMID:Dopaminergic sensitization of rats with and without early prefrontal lesions: implications for the pathogenesis of schizophrenia. 1128 43

Antipsychotic drugs are used to treat a wide variety of child psychiatric disorders characterized by psychotic symptoms, aggression, excitement, tics, stereotypies and hyperactivity nonresponsive to other therapies. Unfortunately, typical antipsychotics have many adverse effects limiting their long-term use. Novel antipsychotics with combined dopaminergic and serotonergic action, such as risperidone, appear to offer better safety and efficacy profiles in controlled studies of adult patients, and therefore appeared as promising pharmacotherapeutic agents in child psychiatry. The purpose of this retrospective chart review was to obtain data on the potential effectiveness and tolerability of risperidone in children and adolescents presenting with a variety of chronic and severe psychiatric disorders who had been unresponsive to previous pharmacological treatments. Charts for 106 children and adolescents (males n = 81 or 76.4%; females n = 25 or 23.6%), presenting with attention deficit and/or hyperactivity disorder (n = 49 or 46.2%), conduct disorder (n = 13 or 12.3%), oppositional-defiant disorder (n = 5 or 4.7%), behavioural problems not otherwise specified (n = 2 or 1.9%), autism (n = 8 or 7.5%), Asperger's syndrome (n = 8 or 7.5%), pervasive developmental disorder (PDD) not otherwise specified (n = 4 or 3.8%), anxiety (n = 6 or 5.7%), depression (n = 2 or 1.9%), dysthymia (n = 2 or 1.9%), schizophrenia (n = 4 or 3.8%), adjustment disorder (n = 1 or 0.9%) and obsessive-compulsive disorder (n = 2 or 1.9%) were reviewed retrospectively to determine the tolerability and potential efficacy of risperidone treatment for a variety of psychiatric disorders. Six subjects also presented with mental retardation. The average length of illness prior to risperidone treatment was 5 years and the average age of risperidone treatment onset was 11 years. The mean daily dose of risperidone was 1.2 mg (range = 0.25 to 8.0 mg). Very few adverse effects were reported. The average length of risperidone treatment was 11 months with the majority (n = 75 or 76%) of patients maintained on risperidone following study termination. Seven cases (6.6%) were missing follow-up data. The majority (n = 78 or 74%) of patients were taking concurrent psychiatric medications, most commonly stimulants for the treatment of ADHD. Clinical global improvements for children and adolescents at the final study visit were marked (n = .37 or 34.9%), moderate (n = .40 or 37.7%), mild (n = 13 or 12.4%), none (n = 12 or 11.3%), or worse (n = 1 or 1%). Three cases (2.9%) were missing clinical improvement data. Results suggest that risperidone may be useful for managing behavioural disturbances and psychotic symptoms associated with a wide variety of childhood psychiatric disorders. For most patients in the study, a combination of risperidone and adjunctive pharmacotherapy was beneficial. Controlled and discontinuation studies of risperidone treatment in children and adolescents with behavioural and psychotic disorders are recommended.
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PMID:A retrospective chart review of risperidone use in treatment-resistant children and adolescents with psychiatric disorders. 1181 3

Schizophrenic psychosis is rare in patients below 15 years of age. Early diagnosis is crucial as the illness is likely to have a poor outcome: indeed, duration of untreated psychosis may exert a negative influence on the prognosis. Thus, it may be highly relevant to recognise premorbid changes of character traits, behaviour and cognitive problems which are reflected in worsening school performance. For example, some 40 to 50% of the children who later develop a psychosis will show social withdrawal, loss of interest in age-appropriate activities, peculiar or immature responsiveness, increasingly suspicious, fearful or depressive states, baseless despair, unusual somatic complaints, concentration problems, cognitive and linguistic disabilities, and peculiar motor movement disorders such as bizarre, ritualistic behaviour, mannerisms, stereotypies, echopraxia. These features are non-specific: they can but need not represent the early signs indicating later development of schizophrenia. They should be evaluated in terms of potential psychosocial, genetic and somatic pre-, peri- and postnatal risk categories. During the child's development these features may build up to constitute vulnerability and stress factors that may lead to psychotic breakdown. Early age of onset correlates with high social disability scores. Complete remission is an extremely rare event in patients with gradual-insidious onset of psychosis.
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PMID:[Schizophrenia in childhood and adolescence. Symptomatology, clinical course, etiological and therapeutic aspects]. 1247 7


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