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  • 1
    Electronic Resource
    Electronic Resource
    Abolition of the expression but not the acquisition of latent inhibition by chronic amphetamine in rats (1984)
    Springer
    Psychopharmacology 83 (1984), S. 194-199 
    Details
    ISSN: 1432-2072
    Keywords: Chronic amphetamine ; Latent inhibition ; Conditioned suppression ; Schizophrenia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The animal amphetamine model of schizophrenia has been based primarily on stereotyped behavior. The present study sought to demonstrate an amphetamine-induced deficit in attentional processes. To this end, the effects of acute and chronic (14 days) 1.5 mg/kg dl-amphetamine administration on the ability of rats to ignore irrelevant stimuli were examined using the paradigm of latent inhibition (LI) in a conditioned emotional response (CER) procedure. The procedure consisted of three stages: pre-exposure, in which the to-be-conditoned stimulus, tone, was presented without being followed by reinforcement; acquisition, in which the pre-exposed tone was paired with shock; and test, in which LI was indexed by animals' suppression of licking during tone presentation. Experiment 1 showed that chronic but not acute treatment abolished LI. Experiment 2 showed that animals receiving chronic amphetamine pretreatment but pre-exposed and conditioned without the drug, exhibited normal LI. In Experiment 3, animals which received chronic amphetamine pretreatment and were pre-exposed under the drug but conditioned without it, also showed normal LI. The implications of these results for the animal amphetamine model of schizophrenia are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00429734
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  • 2
    Electronic Resource
    Electronic Resource
    The abolition of the partial reinforcement extinction effect (PREE) by amphetamine (1985)
    Springer
    Psychopharmacology 86 (1985), S. 318-323 
    Details
    ISSN: 1432-2072
    Keywords: dl-Amphetamine ; Continuous reinforcement ; Partial reinforcement ; Resistance to extinction ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of amphetamine administration on the partial reinforcement extinction effect (PREE) at one trial a day, were examined. Two groups of rats were trained to run in a straight alley. The continuously reinforced (CRF) group received food reward on every trial. The partially reinforced (PRF) group was rewarded on a quasirandom 50% schedule. All animals were then tested inextinction. dl-Amphetamine 1.5 mg/kg was administered in a 2×2 design, i.e., drug-no drug in acquisition and drug-no drug in extinction. The PREE, i.e., increased resistance to extinction exhibited by PRF animals as compared to CRF animals, was obtained in animals that received saline in acquisition, independently of drug treatment in extinction. In contrast, amphetamine administered in acquisition abolished the PREE irrespective of drug treatment in extinction. In addition, amphetamine administered in extinction alone increased resistance to extinction in PRF animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00432221
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  • 3
    Electronic Resource
    Electronic Resource
    The effects of clonidine on the partial reinforcement extinction effect (PREE) (1986)
    Springer
    Psychopharmacology 90 (1986), S. 95-100 
    Details
    ISSN: 1432-2072
    Keywords: Clonidine ; Continuous reinforcement ; Partial reinforcement ; Resistance to extinction ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Clonidine has been reported to exert anti-anxiety effects in animals and man similar to those of benzodiazepines. The present experiment examined the effects of clonidine administration on the partial reinforcement extinction effect (PREE) which is known to be sensitive to benzodiazepine action. Two groups of rats were trained to run in a straight alley. The continuously reinforced (CRF) group received food reward on every trial. The partially reinforced (PRF) group was rewarded on a quasi-random 50% schedule. All animals were then tested in extinction. Clonidine 50 μg/kg was administered in a 2×2 design, i.e., drug-no drug in acquisition and drug-no drug in extinction. The PREE, i.e., increased resistance to extinction exhibited by PRF animals as compared to CRF animals, was obtained in animals that received saline in acquisition, independently of drug treatment in extinction, as well as in animals that received clonidine in both acquisition and extinction, but not in animals that received clonidine in acquisition alone. The administration of clonidine in extinction alone increased resistance to extinction in both the CRF and PRF animals. The increase in resistance to extinction, typically obtained with benzodiazepine treatment, indicates that clonidine exerts anxiolytic effects, supporting the involvement of the noradrenergic system in anxiety. However, clonidine did not fully reproduce the effects of benzodiazepines on the PREE, suggesting that the two classes of drugs may act via different noradrenergic mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172878
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  • 4
    Electronic Resource
    Electronic Resource
    Facilitation of latent inhibition by haloperidol in rats (1987)
    Springer
    Psychopharmacology 91 (1987), S. 248-253 
    Details
    ISSN: 1432-2072
    Keywords: Haloperidol ; Latent inhibition ; Conditioned ; suppression ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Latent inhibition (LI) is a behavioral paradigm in which prior exposure to a stimulus not followed by reinforcement retards subsequent conditioning to that stimulus when it is paired with reinforcement. Two experiments investigated the effects of 0.1 mg/kg haloperidol administration on LI as a function of number of CS pre-exposures. The investigation was carried out using a conditioned emotional response (CER) procedure consisting of three stages: pre-exposure, in which the to-be-conditioned stimulus, tone, was repeatedly presented without reinforcement; conditioning, in which the pre-exposed stimulus was paired with shock; and test, where LI was indexed by animals' suppression of licking during tone presentation. The three stages were conducted 24 h apart. In Experiment 1, 40 CS pre-exposures were given. LI was obtained in both the placebo and haloperidol conditions, but the effect was much more pronounced under the drug. Experiment 2 used ten CS pre-exposures. LI was not obtained in the placebo animals but was clearly evident in animals injected with haloperidol. The implications of these findings for the effects of neuroleptics on learning are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00217073
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  • 5
    Electronic Resource
    Electronic Resource
    Latent inhibition is not affected by acute or chronic administration of 6 mg/kg dl-amphetamine (1987)
    Springer
    Psychopharmacology 91 (1987), S. 345-351 
    Details
    ISSN: 1432-2072
    Keywords: Amphetamine ; Latent inhibition ; Conditioned suppression ; Animal model of schizophrenia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Latent inhibition (LI) is a behavioral paradigm in which animals learn to ignore a repeatedly presented stimulus not followed by meaningful consequences. We previously reported that LI was disrupted following the administration of 1.5 mg/kg dl-amphetamine. The present experiments investigated the effects of 6 mg/kg dl-amphetamine administration on LI in a conditioned emotional response (CER) procedure consisting of three stages: pre-exposure, in which the to-be-conditioned stimulus, tone, was repeatedly presented without reinforcement; conditioning, in which the pre-exposed stimulus was paired with shock; and test, where LI was indexed by animals' suppression of licking during tone presentation. The three stages were conducted 24 h apart. In Experiment 1, the drug was administered in a 2×2 design, i.e. drug-no drug in pre-exposure and drug-no drug in conditioning. LI was obtained in all conditions. In Experiment 2, animals were given either 5 days of 6 mg/kg amphetamine pretreatment and amphetamine in pre-exposure and conditioning or 7 days of saline. LI was not obtained under amphetamine, but this outcome reflected a state-dependency effect. In Experiment 3, animals received either 5 days of amphetamine pretreatment and amphetamine in pre-exposure, conditioning and test or 8 days of saline. LI was obtained in both the placebo and amphetamine conditions. Experiments 4a and 4b compared the effects of two drug doses, 1.5 (4a) and 6 mg/kg (4b), administered in pre-exposure and conditioning. LI was abolished with the 1.5 mg/kg dose but not with the 6 mg/kg dose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00518189
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  • 6
    Electronic Resource
    Electronic Resource
    The effects of haloperidol on the partial reinforcement extinction effect (PREE): implications for neuroleptic drug action on reinforcement and nonreinforcement (1988)
    Springer
    Psychopharmacology 95 (1988), S. 528-533 
    Details
    ISSN: 1432-2072
    Keywords: Haloperidol ; Partial reinforcement ; Continuous reinforcement ; Extinction ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of haloperidol 0.1 mg/kg on the partial reinforcement extinction effect (PREE) paradigm at one trial a day, were examined. Two groups of rats were trained to run in a straight alley. The continuously reinforced (CRF) group received food reward on every trial. The partially reinforced (PRF) group was rewarded on a quasirandom 50% schedule. All animals were then tested in extinction. Haloperidol 0.1 mg/kg was administered in a 2 × 2 design, i.e., drug-no drug in acquisition and drug-no drug in extinction. The PREE, i.e., increased resistance to extinction of partially reinforced as compared to continuously reinforced animals, was obtained in all four drug conditions. The administration of haloperidol in acquisition increased markedly resistance to extinction in CRF animals. The administration of the drug in extinction decreased resistance to extinction in both CRF and PRF animals. The results are explained in terms of two independent actions of haloperidol: the well-known effect of reduction in the effectiveness of reinforcement as well as enhancement of the effectiveness of nonreinforcement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172968
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  • 7
    Electronic Resource
    Electronic Resource
    Long-term attentional deficit in nonhandled males: possible involvement of the dopaminergic system (1988)
    Springer
    Psychopharmacology 95 (1988), S. 231-236 
    Details
    ISSN: 1432-2072
    Keywords: Latent inhibition ; Early handling ; Haloperidol ; Amphetamine ; Male ; Female ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Latent inhibition (LI) is a behavioral paradigm in which nonreinforced pre-exposure to a stimulus retards subsequent conditioning to that stimulus. The development of LI is considered to reflect learning not to attend to, or ignore, irrelevant stimuli. In our previous studies investigating the effects of early handling on LI, we have shown that normal LI was obtained in handled males and females, as well as in nonhandled females. In contrast, nonhandled males failed to show LI. This finding pointed to a long-term attentional deficit in nonhandled males. Since there is evidence that the development of LI is mediated by the dopaminergic system, the present experiments tested the possibility that the attentional deficit of nonhandled males may be related to a dopaminergic dysfunction. Experiment 1 tested whether the administration of haloperidol, which was shown to enhance LI in normal animals, would reinstate the LI effect in nonhandled males. Infantile handled (Days 1–22) and nonhandled male and female rats were tested in maturity in the LI paradigm, using a conditioned emotional response procedure. Experiment 2 tested the locomotor response of handled and nonhandled males to 0.3, 1 and 2.5 mg/kg d-amphetamine. Experiment 1 showed that handled males, handled females and nonhandled females showed a normal LI effect, whereas nonhandled males failed to develop LI. Haloperidol enhanced LI in all the groups, but this effect was most dramatic in nonhandled males, in which the drug reinstated LI. Experiment 2 showed that nonhandled males exhibited a reduced locomotor response to d-amphetamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174515
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