Date of this Version
Behav Pharmacol. 2016 June ; 27(4): 321–330. doi:10.1097/FBP.0000000000000199.
Patients with schizophrenia smoke cigarettes at a higher rate than the general population. We hypothesized that a factor in this comorbidity is sensitivity to the reinforcing and reinforcement- enhancement effects of nicotine.
Phencyclidine (PCP) was used to model behavioral changes resembling negative symptoms of schizophrenia in rats. USVs in rats have been used to measure emotional states, with 50 kHz USVs indicating positive states and 22 kHz indicating negative. Total and categorized numbers of 22 and 50 kHz ultrasonic vocalizations (USVs) and USVs during a visual stimulus (e.g. a potential measure of reinforcement-enhancement) were examined in rats following .injection ofh PCP (2.0 mg/kg), and/or nicotine (0.2 or 0.4 mg/kg) daily for 7 days. PCP was then discontinued and all rats received nicotine (0.2 mg/kg and 0.4 mg/kg) and PCP (2.0 mg/kg) on 3 challenge days.
PCP acutely decreased 50 kHz vocalizations while repeated nicotine potentiated rates of vocalizations, with similar patterns during light presentations. Rats in the PCP and nicotine combination groups made more 50 kHz vocalizations compared to control groups on challenge days.
We conclude that PCP may produce a reward deficit that is shown by decreased 50 kHz USVs, and behaviors post-PCP exposure may best model the comorbidity between schizophrenia and nicotine.