An analysis of nicotine conditioned place conditioning in early postweanling and adolescent rats neonatally treated with quinpirole

Abstract

This study investigated nicotine place conditioning in early postweanling and adolescent male and female rats neonatally treated with quinpirole, a dopamine D 2/D 3 agonist. Previous research has shown that neonatal quinpirole treatment results in an increase of dopamine D 2-like receptor sensitivity that persists throughout the animal's lifetime, relevant to psychosis. Rats were neonatally treated with quinpirole or saline from postnatal day (P)1-21, and animals were conditioned with nicotine or saline daily from P23-30 as early postweanlings or P32-39 as adolescents in a two- or three-chambered place conditioning apparatus. A drug free test was given on P31 for early postweanlings, and P40 for adolescents. Results on the two chamber apparatus revealed that nicotine increased time spent in the drug-paired context at both ages tested. Neonatal quinpirole treatment resulted in less time spent in the drug-paired context in early postweanling males and increased time spent in the drug-paired context in adolescent females conditioned with nicotine. Adolescent females neonatally treated with saline and conditioned with nicotine on the two chamber apparatus did not differ from controls. On the three-chambered apparatus, nicotine increased time spent in the drug-paired context in both ages tested, which was blocked by neonatal quinpirole in early postweanling males, but enhanced by neonatal quinpirole treatment in adolescents. These results demonstrate both age and sex differences in the effects of nicotine and point to significant differences in performance depending on the apparatus used. Additionally, neonatal quinpirole enhanced the effects of nicotine, but this is true only in adolescents and task-dependent.