Changes in CNS responses to high pressure during maturation of newborn mice.

From birth to maturity CD-2 mice were exposed to progressively increasing pressures of helium-oxygen. In all age groups a regular progression of changes in locomotor behavior was observed including, in sequence, increased locomotor activity and two types of convulsions designated as types I and II. The effects of altering compression rate and of reserpine pretreatment were recorded for all age groups. Maturation in these mice is associated with increased resistance to high-pressure neurological syndrome convulsions of either type, in contrast to what might have been expected from previous phylogenetic studies. The patterns in development of the two seizure types differ greatly in detail, further supporting the previously advanced inference that they represent neurological events that differ in kind rather than merely quantitatively. The effect of the results on theories that concern the mechanism of action of pressure on the vertebrate central nervous system is discussed.