The effects of prenatal cocaine exposure and genotype on the ultrasonic calls of infant mice

Estimates are that as many as 44,000 humans are exposed to cocaine in utero per year. In this study we examined the effects of prenatal cocaine exposu re on one aspect of the mother-infant relationship in mice, infant ultrason ic calls. We mated C57BL/10J female mice with males of three different inbr ed strains (producing pups of three different Fl genotypes). We injected th ose females, subcutaneously, with saline or 20 mg/kg of cocaine hydrochlori de on days 7 - 17 of gestation. That dosage did not compromise mother or pu p viability, weight, or gestation length. On postnatal days 2 - 4, we recor ded and measured the calls of pups while they were separated from their nes t and slightly chilled. The results indicate changes in the ultrasonic call s as a function of cocaine and genotype. Overall, cocaine reduced the numbe r of calls and increased the beginning pitch of calls. Pups of one genotype , a C57BL/10J x SJL/J hybrid were unaffected by cocaine exposure. The effec ts of cocaine, though reliable, were small, explaining only 1 - 2% of the t otal sum of squares. The size of the effect is in part due to the different ial effect of cocaine on different genotypes. (C) 2001 Elsevier Science Inc . All rights reserved.