Fig. 2. Ketamine increases cyclin D1 and cyclin-dependent kinase 4 (cdk4) expression. (A ) Western blot of the brain extracts from postnatal day 7 rats treated with repeated injections of saline or ketamine show a dose-dependent increase in both cyclin D1 and cdk4 (n = 3, *P < 0.05). (B ) Western blot of protein lysates from primary neurons exposed to ketamine at different concentrations demonstrate a similar pattern (n = 4, *P < 0.05). Data are presented as mean ± standard error.