Figure 2. Decreased despair-like behavior and occlusion of ketamine's actions in 2BΔCtx animals.
(A) Experimental timeline: male animals between P50 and P70 were subjected to i.p. ketamine injection (ket) or saline control injection (sal). 30 min following injection, animals were analyzed in the tail suspension test (TST). At 25–30 hr post-injection, animals were subjected to electrophysiological analysis (see Figure 3). (B) A significant decrease in immobility scores was measured in 2BΔCtx animals in the TST and this was mimicked by treatment with the GluN2B-containing NMDAR selective antagonist Ro 25–6981. The decrease in immobility scores in the 2BΔCtx animals occluded effect of ketamine injection seen in littermate control animals. 2BΔCtx animals were also insensitive to chronic corticosterone treatment (Cort), while this same treatment increased immobility times in TST in control, corticosterone-treated animals. (C) 2BΔCtx exhibited a strong anxiolytic behavioral phenotype compared to control animals as measured in the elevated plus maze (EPM). (D) Measuring total distance traveled in the open field test (OFT) showed a strong and significant effect of ketamine in both genotypes, suggesting that the decreased immobility time in 2BΔCtx animals was not simply due to hyperlocomotion. (E) Food restriction was also used in control animals to demonstrate that the decreased immobility times in 2BΔCtx animals was not a consequence of decreased body mass. Data values are means ± sem. *p < 0.05; **p < 0.01; ***p < 0.001 t test with respect to control; n.c. = no significant change.