Cocaine alters cyclic motor activity in the fetal rat.

Individual rat fetuses were exposed to cocaine by injection into the cisterna magna on E20 or E21 of gestation. On E20, cocaine elevated motor activity throughout the 20-min session, with activity increasing to double SAL-injected levels by the end of the session. On E21, overall activity also was elevated after cocaine, increasing four- to fivefold in the first 5 min of the session, and decreasing to twice the levels of SAL controls thereafter. Movement time series were subjected to spectral analysis to characterize cyclic motor organization. Cyclicity was evident in 67% of control and 97% of cocaine-injected fetuses. Cocaine increased the number of peaks in the movement spectrum and resulted in greater spectral density at the primary frequency of cyclic movement. Prenatal exposure to cocaine may alter patterns of cyclicity in the fetus, with consequences for the normal development of attention and behavioral state in the neonate.