Repeated subchronic exposure to phencyclidine elicits excessive atypical grooming in rats

Self-grooming in rodents is stereotypically sequenced and naturally occurs after arousal, novelty, or stress. Grooming expression and syntax resulting from stressful and appetitive conditions were assessed in male Long Evans rats treated daily with 10 mg/kg of phencyclidine (PCP) for 15 days. Approximately 20 h after the 1st, the 8th, and/or the 15th injection, grooming was induced with water sprays, a loud sound, or smearing food. Behaviors expressed during the seconds or minutes that followed induction were videotaped and codified. Results showed that subchronic treatment with PCP amplified the grooming response in all stressful and appetitive conditions, but provoked a disorganization of grooming sequences only under the stressful, water condition. Thus, PCP enhanced grooming expression indiscriminately. However, this behavior had to serve both hygienic and stress managing purposes in order for chain sequencing to become disorganized as a consequence of drug treatment. These results suggest that the detailed examination of grooming expression and organization is an appropriate tool to measure stress-induced behavioral sensitization and motor functions in animal models of neuropsychiatric disorders such as schizophrenia.