Fig. 1.

Behavioral phenotype of prenatally exposed VPA animals. Frequencies on the nest, arch-back nursing (ABN), passive nursing (PN), and licking and grooming (LG) were largely unaltered between saline- and VPA-treated dams, with the exception of P1 frequencies on the nest (t test with Bonferroni correction, n = 4–6/grp (a–d). No differences in eye openings were detected at P14 (Fisher’s exact test, females, p = 0.088; n = 19–25/grp; (e)). Histograms of ultrasonic vocalization lengths display qualitative differences in calls of various lengths over time and between treatment groups of each sex (n = 10/grp; (f–i)), with females having significantly reduced mean call lengths at P7 (not displayed, t test with Holm-Bonferroni correction, p < 0.01). VPA-treated males and females called significantly less than saline animals at P11 (j) and had higher frequency calls ((k); t tests with Holm-Bonferroni correction). VPA-treated males were less willing to approach maternal bedding at P9 (Fisher’s exact test; n = 14–16/grp; (l)). After fear conditioning to light at P8–10, VPA treated animals of both sexes displayed heightened fear-potentiated startle responses (t tests; n = 20–23/grp; (m)). Prenatal VPA treatment also enhanced startle amplitudes in the presence of maternal, but not neutral, odor (t tests with Bonferroni corrections; n = 14–17/grp, only males (n)). Juvenile VPA-treated females spent less time in the center of the open field (t test; n = 22–26/grp; (o)). Female and male VPA juveniles approached a social stimulus less than did saline males in the social preference test (post-hoc t tests with Bonferroni corrections; n = 21–26/grp; (p)). Males also displayed lower approaches to and less time in proximity to a novel conspecific, as well as more time in an empty arena during the social novelty component (p, q). Juvenile VPA males displayed enhanced baseline startle amplitudes (post-hoc t test with Bonferroni correction; n = 22–25/grp; (r)). FS female saline, FV female VPA, MS male saline, MV male VPA. Group (grp) indicates each of the four drug/sex combinations. Asterisks indicate significant comparisons between VPA and saline groups *p < 0.05; **p < 0.01; ***p ≤ 0.001