[Interstrain differences in the maturation of congenital reflexes in 101/HY and CBA mice in early postnatal ontogeny]

We have identified interstrain differences in the rate of formation of certain reflexes and parameters of physical development in CBA/LacSto and 101/HY mice. We have shown that in young 101/HY mice, the maturation of reflexes reflecting the development of the vestibular, neurosensory, and neuromuscular systems, such as surface righting, bar holding, negative geotaxis, and auditory startle response, takes place later during postnatal life. Opening of eyes and auditory canals in mice of all studied groups takes place at the same time. In CBA females, maturation of cliff avoidance reflex occurs later than in 101/HY females; hair also appeared later. Body weight of young 101/HY mice of both sexes is significantly higher during the period of postnatal development from day 2 to day 20 than in the CBA strain. However, the relative brain weight was lower in the 101/HY strain. CBA males had a higher brain weight and also showed a faster rate of formation of inborn reflexes. We discuss possible factors underlying the observed difficulties in the rate of formation of reflexes in 101/HY and CBA young mice in relation to general background information about their genetic and neurobehavioral features. The results provide evidence that these differences are genetically determined; the rate of reflex formation does not depend on the overall physical development of mice and is rather due to a delay and/or abnormalities in nervous system development.