Exploratory behavior and locomotor activity: a failure to find effects in animals prenatally exposed to cocaine

Pregnant Long-Evans rats were administered cocaine orally (60 mg/kg) on gestational days 14-21, or subcutaneously (40 mg/kg) on gestational days 8-21. The oral dosage of cocaine produced some maternal lethality and reduced maternal weight gain throughout the pregnancy by approximately 12%. The subcutaneous dosage regimen reduced the lethality but still caused a decrease in maternal weight gain. Neither dosing regimen affected the number of pups in the litter, their weight, or growth. The offspring of dams that received the oral dosage were examined as adults in an automated holeboard apparatus and were also tested at postnatal day 21 and as adults in an open field. Adult animals exposed prenatally to cocaine did not differ from untreated controls in any of the automated measures of the holeboard apparatus or in the various behaviors, including nosepokes, recorded in the open field. Animals in the vehicle control group did make fewer nosepokes in the open field than the cocaine group, which did not differ from untreated animals. The offspring of dams given the subcutaneous dosage regimen were observed in the open field at day 21. In this case, the prenatal cocaine group had a tendency to make fewer crosses into adjacent quadrants, to rear less often, and to make fewer nosepokes than the control groups. Based on these and other data from our lab, it does not appear that in the rat, prenatal cocaine exposure has pronounced effects on subsequent exploratory behavior and activity in weanling or adult animals.