Figure 4.

Impact of antenatal glucocorticoid treatment (AGT) on unconditioned and conditioned behaviors. Male and female rats exposed to AGT (dexamethasone, 0.5 μg/ml, in drinking water on gestational days 16–19; closed symbols in the line plots and solid bars in the bar plots) and controls (dams received normal drinking water; open symbols in the line plots and open bars in the bar plots) were tested in adulthood. Top panel (a, b): Spontaneous locomotor activity is suppressed in adult female, but not in male, progeny. Test-naive adult offspring were tested at 12 weeks of age for spontaneous locomotor activity in a novel, open-field environment (Day 1). Line plots (a) represent photobeam interruptions in 5 min time bins over a 90-min period, and histograms (b) represent the total number of beam breaks over the whole of the 90-min period for males and females. Activity was significantly attenuated by AGT in females, but not in males. Data are mean±SEM, n=6. ^#main effect of sex, p=0.001; *p<0.05 for AGT vs relative control group. Middle panel (c, d and e): Sensorimotor gating is significantly modulated after exposure to AGT in adult male, not female, progeny. The paradigm of prepulse inhibition (PPI) of the startle response was used to investigate sensorimotor gating in young adult offspring. For male (c) and female (d) groups, the line plots represent %PPI at each of the four prepulse intensities (3, 6, 12, and 16 dB above background white noise of 65 dB for 20 ms preceding the startle pulse of 120 dB for 40 ms); the adjacent histograms depict the mean %PPI across all four prepulse intensities. %PPI was calculated as 100% × (1−(mean reactivity in prepulse–pulse trials/mean reactivity in pulse-alone trials)). Data in e confirms that in both males and females, the startle response to the startle pulse alone (120 dB) was not significantly affected by AGT compared with controls. AGT significantly enhanced %PPI in adult males, but not in females. Data are mean±SEM, n=8; *p<0.05 for AGT vs vehicle. Bottom panel (f, g): Acquisition of discriminated approach behavior in adult male and female progeny is not affected by AGT. Autoshaping was conducted over 7 consecutive days with each daily session consisting of 50 trials (25 CS− and 25 CS+). (f) Approach responses to either reward-paired stimulus (CS+ square symbols) or unpaired stimulus (CS− circle symbols) in adult rats were measured, and (g) as an index of discriminative approach learning, the average difference score between approaches to CS+ and CS− were analyzed. Data are mean±s.e.m, n=14 (control males, control and AGT females), or n=12 (AGT males).