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Published on: September 27, 2019
Analysis of licking microstructure provides no evidence for a reduction in reward value following acute or
Emma S Lydall1, Gary Gilmour, Dominic M Dwyer
1School of Psychology, Cardiff University, Tower Building, Park Place, Cardiff, CF10 3AT, UK. LydallES@Cardiff.ac.uk
Rationale:
The N-methyl D-aspartate antagonist phencyclidine (PCP) is purported to mimic the negative, cognitive and positive symptoms of schizophrenia. Thus, acute and sub-chronic PCP treatment in rodents might produce anhedonia, a decrease in the pleasure produced by rewards.
Objectives:
Experiment 1 investigated whether acute PCP treatment changes the value of sucrose. A comparison was made to (+)MK-801, a drug often used interchangeably with PCP in preclinical studies. Experiment 2 assessed the effects of withdrawal from sub-chronic PCP treatment on the value of sucrose.
Methods:
Experiment 1 examined the dose-response effects of PCP and (+)MK-801 on licking microstructure during sucrose consumption. Experiment 2 assessed the effects of withdrawal from sub-chronic PCP treatment (5 mg/kg twice daily for 7 days), on licking microstructure during sucrose consumption. Locomotor activity testing was carried out in experiment 2 to confirm the sensitisation effect of the PCP regimen on amphetamine-induced hyperlocomotion.
Results:
Low to moderate acute doses of PCP and (+)MK-801 increased the amount of sucrose consumed. Higher doses decreased consumption and the number of licks per cluster (cluster size) but also increased the average inter-lick interval, which may indicate motor impairment. There was no evidence that withdrawal from sub-chronic PCP treatment produced decreases in consumption or lick cluster size.
Conclusions:
Following acute PCP treatment, we found no evidence of reduced reward value without the presence of confounding motor deficits. Sub-chronic PCP withdrawal also produced no decrease in reward value. Therefore, the current results indicate that neither acute PCP treatment nor sub-chronic PCP withdrawal produce consummatory anhedonia.
