Effects of heating on electrical activities of guinea pig olfactory cortical slices

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Abstract
We examined the effect of heating on electrical activity of neurons in the guinea pig olfactory cortex slice. At the control temperature (37° C) the potential evoked by stimulation of the lateral olfactory tract consisted of an initial spike (IS) potential and a negative (N) potential. The IS potential is considered to be presynaptic and the other transsynaptic. The IS potential decreased in amplitude on heating and completely disappeared at 49° C. However, it recovered when the temperature was lowered to 37° C after five minutes of incubation at 49° C. In contrast, the N potential increased in amplitude at 39° C, was completely suppressed at 47° C and did not recover when the temperature was dropped to the control temperature. The maximum temperature from which the N potential recovered was 43° C. Unit activity was extracellularly recorded from neurons in the slice. On heating the brain slice some neurons showed an increase in activity, others a decrease, and the rest were unaffected. We conclude that neurons in the olfactory cortex have different thermal sensitivities.