Rate factors in development of the high-pressure neurological syndrome.

The effect of varying the pressure/time profile upon development of tremors and convulsions of the high-pressure neurological syndrome was studied in adult mice and squirrel monkeys and in baby mice. Two distinct response patterns were observed. In the adults rapid compression produces early onset of convulsions; convulsions subside rapidly when animals are held at constant pressure just above the convulsion point; and interrupted compression schedules show that total compression time rather than instantaneous compression rate at the moment seizures develop is the controlling parameter. Baby mice up to 12 days of age, by contrast, fail to show any perceptible relation between compression rate and convulsion threshold pressure (Pc); their seizures continue for a considerable period of time after a constant pressure level just above the convulsion threshold has been reached; and interrupted compressions of type a fail to change their convulsion threshold. Together with supplementary data regarding tremor thresholds and the transient increase of convulsion thresholds by prior seizures these results lead to a proposed schema describing these phenomena in terms of a pressure-dependent primary event predisposing to tremors and convulsions; a time-dependent event counteracting the convulsions (absent in baby mice); and a transient effect of prior convulsions, raising subsequent Pc.