Dissociation of acute and chronic intermittent phencyclidine-induced performance deficits in the 5-choice serial reaction time task: influence of clozapine.
BACKGROUND
Cognitive deficits are a core feature of schizophrenia that respond minimally to existing drugs. PCP is commonly used to model schizophrenia-like deficits preclinically although different dosing protocols may affect different domains. Here we characterise the acute, and chronic intermittent effects of PCP in the 5-choice serial reaction time task (5-CSRTT) in rats, and assess the effects of clozapine. In a novel approach, we also assess the effects of increased inhibitory load and conduct clinically relevant signal detection analysis (SDA).


METHODS
The effects of acute and repeated PCP (2.58 mg/kg) treatment on attentional processes and inhibitory control were assessed during and following the chronic treatment regime in the presence or absence of chronic clozapine (20 mg/kg/day).


RESULTS
Thirty minutes post-PCP injection, there was an increase in anticipatory responding which disappeared after 24 h. Although, acute PCP did not change accuracy of responding or processing speed, repeated PCP revealed delayed deficits in cognitive processing speed which were partly ameliorated by clozapine. Extended inter-trial intervals increased premature responding, while SDA revealed that clozapine modified persistent PCP-induced deficits in lnBeta (a composite measure of risk taking versus caution).


CONCLUSIONS
Acute NMDA receptor antagonism impairs inhibitory control, whereas repeated treatment produces delayed deficits in cognitive processing speed. The ability of clozapine partially to restore persistent PCP-induced deficits in processing speed and in lnBeta is consistent with clinical findings. This suggests that the enduring effects of repeated PCP treatment, combined with SDA, offers a useful, translational, approach to evaluate novel cognitive enhancers in the 5-CSRTT.
Thomson
David M
DM
Psychiatric Research Institute of Neuroscience in Glasgow (PsyRING), Universities of Glasgow and Strathclyde, Glasgow, UK.
McVie
Allan
A
Morris
Brian J
BJ
Pratt
Judith A
JA
D000818:Animals; D014150:Antipsychotic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001288:Attention / Q000187:drug effects; D002755:Choice Behavior / Q000187:drug effects; D003024:Clozapine / Q000008:administration & dosage / Q000494:pharmacology*; D003072:Cognition Disorders / Q000139:chemically induced / Q000188:drug therapy*; D004195:Disease Models, Animal; D004334:Drug Administration Schedule; D018756:GABA Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D010622:Phencyclidine / Q000008:administration & dosage / Q000633:toxicity*; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time / Q000187:drug effects; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D017603:Signal Detection, Psychological; D013997:Time Factors
D014150:Antipsychotic Agents; D018756:GABA Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D010622:Phencyclidine; D003024:Clozapine