Ontogeny of behavioral development, arousal and stereotypes in two strains of mice.

A number of reflexes and amphetamine-induced locomotor and stereotyped behavior were assesses in 8, 16, 32, 90 and 360 day old C57BL/6J and SEC/1ReJ inbred mice. The data indicate that C57 mice are more precocious for a number of neuronal and behavioral mechanisms while SEC mice are less mature at birth. In addition, there are appreciable fluctuations of these behavioral patterns throughout life. A rise in arousal levels was evident in both strains between 8 and 16 days and between 32 and 90 days of age. Three-hundred-sixty days old mice presented a general decrease in the levels of arousal. These findings are discussed in terms of neuronal and behavioral plasticity and in relation to the ontogeny of the different catecholaminergic systems which modulate excitory and inhibitory different behavioral patterns at different ages.