The protective effect of hypothermia on hippocampal slices from guinea pig during deprivation of oxygen and glucose.

Using guinea pig hippocampal slice preparations, the effect of temperature on the electrical activity and the protective effect of hypothermia against deprivation of both oxygen and glucose were studied by recording field potentials of pyramidal cell layer (CA3-4 area) and by measuring the content of adenosine triphosphate (ATP), phosphocreatine (PCr) and lactate of each slice. Cooling the perfusion medium from 37 to 21 degrees C caused a decrease in the amplitude of field potentials, although the amplitude increased (120%) transiently at around 33 degrees C. The electrical activity ceased at around 22 degrees C. When the temperature was raised from 21 to 37 degrees C, the activity recovered reversibly. However, when the temperature was raised to above 38 degrees C, the amplitude decreased and disappeared irreversibly at 42 degrees C. During deprivation, energy consumption (total approximately P used; 2 X delta ATP + delta PCr + 1.3 X delta lactate) was suppressed by lowering the tissue temperature and the initial (0-2.5 min deprivation) energy use rate was calculated to be 42.2 at 37 degrees C, 22.8 at 28 degrees C and 7.0 at 21 degrees C (approximately P m mol/kg protein/min), respectively. From these values, Q10 was estimated to be 2.05. With regard to the protective effect of hypothermia, the critical survival time (period of deprivation of oxygen and glucose for the complete recovery in neural activity and the level of high energy phosphates) was 10 min at 37 degrees C, 15 min at 28 degrees C, and 45 min at 21 degrees C, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)