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  • 1
    ISSN: 1432-2072
    Keywords: Key words Nicotine ; Prepulse inhibition ; Schizophrenia ; Sensorimotor gating ; Startle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rationale: A recent report described sex differences in the effects of nicotine use and withdrawal on prepulse inhibition of acoustic startle (PPI), but no sex differences in PPI in non-smokers. Objective: To determine whether previously reported male〉female acoustic PPI reflect sex differences in smoking effects on PPI, rather than simple sex differences in the regulation of PPI. A retrospective analyses of 〉600 carefully screened normals tested over the past 12 years was completed. Results: Male〉female acoustic PPI was detected in analyses that included: 1) all subjects; or 2) self-declared non-smokers. Conclusions: Sex differences in PPI cannot be accounted for by smoking history, because they are present across a large sample of non-smoking normal controls.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 84 (1984), S. 163-166 
    ISSN: 1432-2072
    Keywords: Place-preference ; Amphetamine ; Locomotor behavior ; Conditioned locomotion ; Hyperactivity ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The relationship between the motor-activating and positive-reinforcing properties of d-amphetamine was examined in the place-preference paradigm. Two groups of animals were trained to associate one environment with amphetamine, and another environment with saline. Annimals that were allowed to locomote in both environments during training later demonstrated a preference for the amphetamine-paired environment; animals in which hyperactivity was limited in both environments later failed to show any preference. However, both groups of animals demonstrated a conditioned locomotor activation to the amphetamine-associated environments. Our results suggest that a place-preference demonstrated for an amphetamine-paired environment depends on the ability of the drug to increase locomotor behavior.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 120 (1995), S. 433-441 
    ISSN: 1432-2072
    Keywords: Accumbens ; Dopamine ; Glutamate ; Prepulse ; Schizophrenia ; Sensorimotor ; Startle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prepulse inhibition (PPI) is the normal reduction in startle reflex that occurs when a startling stimulus is preceded by a weak prepulse. PPI is reduced in patients with schizophrenia and in rats after central dopamine (DA) activation. The DA agonist-induced disruption of PPI in rats may thus model some features of impaired sensorimotor gating in schizophrenia. Ascending DAergic and descending glutamatergic fibers converge within the nucleus accumbens (NAC), and interactions at this DA-glutamate interface have been implicated in the pathophysiology of schizophrenia. In this study, we examined the role of NAC DA-glutamate interactions in the regulation of PPI in rats. Intra-NAC infusion of the non-NMDA antagonist, CNQX, attenuated the PPI-disruptive effects ofd-amphetamine (AMPH), but CNQX did not affect PPI when injected alone, nor did it reverse the PPI-disruptive effects of the direct D2/D3 agonist quinpirole. Intra-NAC infusion of the non-NMDA agonist AMPA significantly reduced PPI. The PPI-disruptive effects of AMPA were blocked by haloperidol and by 6-hydroxydopamine (6OHDA) lesions of the NAC. These data suggest that the PPI-disruptive effects of AMPH are dependent on tonic non-NMDA receptor activation in the NAC, and that non-NMDA receptor activation in the NAC results in a DA-dependent reduction in PPI. The parsimonious interpretation of these data is that non-NMDA glutamate receptors in the NAC facilitate presynaptic DA function, and that this DA-glutamate interaction is a critical regulatory substrate of sensorimotor gating.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2072
    Keywords: Prepulse inhibition of startle ; Sensorimotor gating ; Neonatal lesion ; Hippocampus ; Ibotenic acid ; Apomorphine ; Startle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Neonatal excitotoxic hippocampal damage in the rat results in postpubertal onset of a variety of abnormal behaviors related to excessive dopaminergic transmission in the mesolimbic/nigrostriatal system, and thus may be considered an animal model of some aspects of schizophrenia. Because sensorimotor gating is impaired in adult patients with schizophrenia and in rats with experimentally induced mesolimbic dopamine hyperactivity, the present experiments investigated the effects of neonatal (postnatal day 7, PD7) ibotenic acid (3 µg) lesions of the ventral hippocampus (VH) on the amplitude and prepulse inhibition (PPI) of acoustic startle in prepubertal (PD35) and postpubertal (PD56) rats. Startle was elicited using 105 and 118-dB pulses alone or preceded by 4, 8, or 16 dB above-background prepulses in rats treated with vehicle or apomorphine (APO; 0.025 or 0.1 mg/kg SC). At PD35, PPI in VH-lesioned rats did not differ significantly from these measures in sham operated rats. Apomorphine significantly increased startle amplitude and reduced PPI in both sham operated and VH-lesioned rats at PD35. At PD56, startle amplitude in VH-lesioned rats was not significantly different from controls, but PPI was reduced significantly compared to controls. Ventral hippocampus lesioned rats also exhibited an exaggerated reduction in PPI after treatment with APO. These findings provide further evidence of postpubertal impairments that may be related to increased mesolimbic dopamine transmission and receptor sensitivity in rats with neonatal hippocampal damage, and provide further support for the fidelity of this animal model of schizophrenia.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2072
    Keywords: Key words Cocaine ; Neurotoxicity ; Prepulse inhibition ; Schizophrenia ; Startle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Deficient sensorimotor gating, as measured by a relative loss of prepulse inhibition (PPI) of the startle reflex, has been reported in schizophrenia patients and in rats treated acutely with dopamine (DA) agonists or other psychotomimetic agents. For this reason, PPI has been used as a cross-species measure for studying the neurochemistry of specific information processing deficits in schizophrenia. Cocaine is a DA reuptake inhibitor which can precipitate psychosis after sustained use in humans. In rats, sustained exposure to cocaine results in neuropathological and neurochemical changes in several brain regions, and is also associated with specific prolonged behavioral abnormalities. In the present study, we examined the effects of both acute and sustained cocaine administration on PPI and other measures of the startle reflex in rats. Cocaine produced a significant, dose-dependent reduction in PPI, both after acute administration, and after 3 days of sustained administration via implanted subcutaneous pellets. PPI returned to control levels when rats were tested 10 days after sustained (5 day) cocaine administration. The effects of acute cocaine administration on PPI are consistent with those of other DA agonists and psychotomimetics, but PPI does not appear to be sensitive to lasting effects of a method of prolonged cocaine administration associated with neuropathological and neurochemical changes in several brain regions.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2072
    Keywords: Acoustic startle response ; Dopamine ; Nucleus accumbens ; Prepulse inhibition ; Schizophrenia ; Sensorimotor gating
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies have demonstrated that several dopamine agonists disrupt sensorimotor gating as measured by prepulse inhibition (PPI) of the acoustic startle response (ASR) in rats. Schizophrenic patients also exhibit deficits in PPI when the prepulse preceeds the startle stimulus by less than 500 ms. In experiment 1, dopamine (0–40 µg) infused directly into the nucleus accumbens in rats caused a dose-dependent decrease in PPI at prepulse intervals shorter than 500 ms. In experiment 2, this effect of accumbens dopamine infusions on sensorimotor gating was found to vary with changes in prepulse intensity. These findings strongly suggest that increased mesolimbic dopamine activity is one substrate of the sensorimotor gating deficits in rats that are caused by treatment with dopamine agonists; similar substrates might mediate deficits in PPI exhibited by schizophrenic patients.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 105 (1991), S. 347-354 
    ISSN: 1432-2072
    Keywords: Prepulse inhibition ; Sensorimotor gating ; Startle ; Hippocampus ; Dopamine ; Schizophrenia ; Carbachol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Prepulse inhibition (PPI) is the decrease in a startle response that occurs when the startling stimulus is preceded by a weaker stimulus or “prepulse”. Schizophrenic patients exhibit abnormally low levels of PPI when the prepulse precedes the startle stimulus by less than 500 ms. A similar deficit in sensorimotor gating can be demonstrated in rats after stimulation of D2 dopamine (DA) receptors by systemic administration of DA agonists or by infusion of DA directly into the nucleus accumbens. We now demonstrate that carbachol infusion into the dentate gyrus of the hippocampal formation disrupts PPI in the rat. This disruption of sensorimotor gating occurs when the startling stimulus is either acoustic or tactile. Carbachol infusion into the neocortex has no effect on PPI. While pretreatment with the D2 DA receptor antagonist spiperone reverses the disruption of PPI caused by systemic administration of apomorphine, this pretreatment fails to reverse the disruption of PPI induced by carbachol infusion into the hippocampus. These results demonstrate that pharmacologic stimulation of the hippocampus disrupts sensorimotor gating in the rat by a mechanism distinct from that of DA agonists. Prepulse inhibition of the startle reflex is an animal model in which pharmacologic stimulation of the hippocampus mimics the deficits in sensorimotor gating observed in schizophrenic patients.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2072
    Keywords: Corticotropin-releasing factor ; Startle ; Chlordiazepoxide ; Anxiety ; Strychnine ; Amphetamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A series of experiments was performed to investigate the effects of corticotropin-releasing factor (CRF) on the amplitude of the acoustic startle response (ASR) in rats. Intracerebroventricular (ICV) administration of 1 μg rat CRF significantly potentiated acoustic startle amplitude; these effects were reversed in a dose-dependent manner by pretreatment with the benzodiazepine chlordiazepoxide (CDP). Doses of CDP that anatgonized CRF-potentiated ASR did not lower startle baseline or antagonize amphetamine-or strychnine-potentiated ASR. These results suggest that CRF has “anxiogenic” properties and may serve as a neuroendocrine modulator of stress-enhanced behaviors.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2072
    Keywords: Apomorphine ; Dopamine ; Frontal cortex ; Hippocampus ; Schizophrenia ; Startle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Sensorimotor gating of the startle reflex is impaired in humans with schizophrenia and in rats after mesolimbic D2 dopamine receptor activation. The loss of startle gating after D2 activation in rats has been used as an animal model of impaired sensorimotor gating in schizophrenia, because the ability of antipsychotics to restore startle gating in D2-activated rats correlates significantly with antipsychotic clinical potency. Substantial evidence indicates that the pathophysiology of schizophrenia includes structural and functional deficits in prefrontal and temporal regions, particularly the dorsolateral prefrontal cortex and the hippocampus and parahippocampal gyrus. The present study assessed startle gating in adult rats after ibotenic acid lesions of the medial prefrontal cortex or ventral hippocampus. Medial prefrontal cortex lesioned rats exhibited normal startle amplitude and normal sensorimotor gating, as reflected by prepulse inhibition (PPI) of the startle reflex. Hippocampus lesioned rats exhibited elevated startle amplitude, and similar to rats with medial prefrontal cortex lesions, did not show significant changes in basal PPI. Low doses of the mixed dopamine agonist apomorphine did not significantly reduce PPI in sham lesioned rats, but significantly disrupted PPI in both medial prefrontal cortex- and ventral hippo-campus lesioned rats. These data are consistent with the hypothesis that cell damage in frontal and temporal cortex increases the sensitivity to the sensorimotor gating-disruptive effects of dopamine receptor activation.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2072
    Keywords: Key words Antipsychotics ; Chlorpromazine ; Clozapine ; Haloperidol ; Ketamine ; Prepulse inhibition ; Schizophrenia ; Seroquel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Sensorimotor gating of the startle reflex – measured by prepulse inhibition (PPI) – is impaired in schizophrenia patients and in rats treated with either dopamine (DA) agonists or with N-methyl-D-aspartate (NMDA) antagonists. While both typical and atypical antipsychotics restore PPI in DA agonist-treated rats, studies thus far have demonstrated that only atypical antipsychotics restore PPI in rats treated with NMDA antagonists. This model for predicting atypical antipsychotic properties has been studied extensively in rats, and there is interest in moving these studies into humans, where the NMDA antagonist ketamine is also reported to significantly reduce PPI. In anticipation of such studies, and to facilitate the use of this model in humans, we examined the effects of high and low potency typical antipsychotics (haloperidol and chlorpromazine), the atypical antipsychotic clozapine, and the putative atypical antipsychotic, Seroquel, on ketamine-disrupted PPI in rats, across a range of ketamine that produced submaximal, as well as maximal disruptions of PPI. Ketamine dose-dependently reduced PPI, and this effect was significantly opposed by Seroquel, clozapine and chlorpromazine, but not haloperidol. The effects of chlorpromazine on ketamine-disrupted PPI demonstrate that the ability of antipsychotics to restore PPI in NMDA antagonist-treated rats is not specific to clinically atypical antipsychotics. Receptor properties shared by Seroquel, clozapine and chlorpromazine, but not haloperidol, may implicate critical substrates in the NMDA antagonist-induced disruption of PPI.
    Type of Medium: Electronic Resource
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