Cold enhances neuroprotection in hippocampal slices from hibernating Syrian hamsters

Hippocampal CA1 neurons may experience transient hypoxic periods during arousal from hibernation when oxygen consumption increases dramatically to support shivering and nonshivering thermogenesis. Previous studies showed that, following anoxic insult, hippocampal CA1 pyramidal neurons of euthermic Syrian hamsters ( Mesocricetus auratus ) are more highly neuroprotected than those of the rat, a nonhibernating species. Moreover, this augmented neuroprotection is greater at 30°C than at 35°C in slices from euthermic hamsters. We tested the hypothesis that in slices from hibernating hamsters the response to anoxic exposure on population spike amplitude (PSA) is attenuated with decreased temperature. CA1 pyramidal cell PSA was measured every minute throughout the experiment. Following a 15 min control period in oxygenated artificial cerebrospinal fluid (aCSF), oxygen was replaced with nitrogen for 15 min. Slices were then returned to oxygenated aCSF for a 30 min recovery period. Six minutes after nitrogen exposure at 35°C, PSA had an 81 ± 4.7% (mean ± standard error) drop from control values while a smaller drop (56.3 ± 9.2%) occurred at 30°C. Differences are significant (p<0.05) and consistent with our hypothesis that hypoxic tolerance (i.e., neuroprotection) is enhanced when temperature declines in hibernating hamsters. (Supported by a President's Undergraduate Fellowship to CL.)