Repeated Exposure to Ketamine in Adolescent Rats Results in Persistent Anxiety in the Adulthood

Background. Adolescent development of the prefrontal cortex (PFC) is accompanied by important changes in glutamatergic, GABAergic and dopaminergic circuitries, susceptible to modulation by N-methyl-D-aspartate receptors (NMDAR) antagonists. Repeated ketamine was associated with social and memory deficits, but other relevant factors, such as anxiety, were not sufficiently addressed. The present study aimed to examine the behavioral and molecular consequences of repeated exposure to ketamine with a particular focus in anxiety. Methods. We treated male adolescent Wistar rats, starting postnatal day (PND) 35, with ketamine (30 mg/kg, i.p, 7 days). Behavioral evaluation was conducted in the adulthood (PND 60). The elevated plus maze (EPM) and open field tests were used to evaluate anxiety and locomotion, while sociability and novelty recognition were assessed through the novel object recognition (NOR) and the sociability and social novelty tests. At the end of the behavioral evaluation, brains were dissected and the prefrontal cortex used for biochemical evaluation. Results. Analysis of the elevated plus maze (EPM) data revealed a ketamine-induced anxiety-like profile, corroborated by the open field data. Ketaminetreated rats also failed to increase contact time with a conspecific in the social affiliation test and with an unknown rat in the novelty preference test. At the molecular level, frontal expression levels of tyrosine hydroxylase were found decreased. Conclusion. Altogether, these results show that repeated ketamine-exposure in the adolescent may result in long-term anxiety