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Latent inhibition (LI) refers to retarded conditioning to a stimulus that has been
repeatedly presented without reinforcement. LI is impaired in schizophrenic patients
and in rats treated with amphetamine. Neuroleptic drugs produce two effects in this
test paradigm: antagonism of amphetamine-induced disruption of LI, and enhancement
of LI when administered on their own. The present experiments tested the effects of
the atypical neuroleptic, clozapine, on LI. The experiments used a conditioned emotional
response procedure in rats licking for water, consisting of three stages: preexposure,
in which the to-be-conditioned stimulus (tone) was repeatedly presented without reinforcement;
conditioning, in which the preexposed stimulus was paired with reinforcement (foot
shock); and test, in which LI was indexed by animals' degree of suppression of licking
during tone presentation. In experiments 1 and 2, the effects of 5.0 and 10.0 mg/kg
clozapine on LI were assessed following 20 or 10 tone preexposures, respectively.
Experiments 3 and 4 used 40 preexposures and investigated antagonism of amphetamine-induced
disruption of LI by 5.0 and 10.0 mg/kg clozapine, respectively. The results demonstrated
that clozapine possesses a neuroleptic profile in the LI model, namely, it facilitates
the development of LI and antagonizes amphetamine-induced disruption of LI.
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Article info
Publication history
Received in revised form:
October 3,
1995
Received:
October 19,
1994
Footnotes
This research was supported by a grant from the Ministry of Science and The Arts—Israel, and the Commission of the European Community.
Identification
Copyright
© 1996 Society of Biological Psychiatry. Published by Elsevier Inc.
