Alteration of high pressure nervous syndrome in rats by alteration of colonic temperature.

The components of the high pressure nervous syndrome (HPNS) have been clearly described previously. Animal studies of HPNS, however, have been characterized by nonstandardized definitions of the various HPNS parameters, based on visual observations. Where EEG's have been used in HPNS studies, the frequent occurrence of movement-induced artifact has made much of the data difficult to interpret. Because of these limitations, efforts to clarify the influence of environmental variables on the syndrome have led to varying results, especially with respect to the influence of temperature. The technique used in this study consistently yielded artifact-free EEGs from unanesthetized, moving rats during simulated heliox dives. Typical seizure patterns in the EEG recordings were combined with clinical seizure activity to define HPNS convulsion-threshold pressure (Pc). By manipulating body temperature artificially, three groups of rats were investigated--hypothermic, euthermic, and hyperthermic animals. An inverse relationship between body temperature and HPNS convulsion-threshold pressure was demonstrated.