Mise en evidence d'effects grand-maternels sur les conduites maternelles de la souris

Continuous recording of locomotor activity and time spent in the nest were performed on mice during the five first days postpartum. We compared mice of the C57BL/6 inbred strain to mice of the two reciprocal F2's derived from the C57BL/6 and BALB/c parental strains. All animals reared foster pups of the C57BL/6 strain. The results did not show any difference between the three groups for the total amount of time spent in the nest ; this parameter decreases with days. No difference appeared between the C57BL/6 group and the F2 B6CxCB6 group (having a grandmother of the C57BL/6 strain), whereas each of these groups differed significantly from F2 CB6xB6C group (having a grandmother of the BALB/c strain) for the following indices : locomotor activity, mean duration of a stay in the nest, mean duration of an absence from the nest and percentage of nocturnal activity. These results are discussed in terms of grandmaternal effects as far as the variation in the strain of the grandmother is the only factor which can account for these differences in behavior.