Effects of prenatal cocaine exposure on latent inhibition in 1-year-old female rats

Abstract

Prenatal cocaine exposure has been shown to produce attentional changes in human infants and children, as well as in preweanling and young adult animals. The aim of the current study was to determine whether attentional effects of in utero cocaine exposure persist into middle adulthood. Sprague-Dawley dams received twice-daily subcutaneous (sc) administration of either 20 mg/kg cocaine HCl or 0.9% saline vehicle from Gestational Day 8 to 20. Saline-injected dams were pair-fed to cocaine-injected subjects during prenatal treatment. A second control group received no treatment and had ad lib access to food. One-year-old female offspring were tested for latent inhibition (LI) of a context conditioning task, using freezing and vertical nose crossing (VNC) as behavioral measures of fear. Although freezing did not reveal any differences between prenatal treatment groups, a cocaine-dependent reduction in baseline VNC indicated that cocaine-exposed adult offspring were less explorative than controls. In addition, cocaine-exposed animals showed enhanced LI as measured by greater levels of VNC than controls in the context preexposed condition of the task. These results provide insight into the nature of attentional contributions to prenatal cocaine effects on learning and indicate that such effects persist well into adulthood.