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

We examined the effect of heating on electrical activity of neurons in the guinea pig olfactory cortex slice. At the control temperature (37 degree 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 degree C. However, it recovered when the temperature was lowered to 37 degree C after five minutes of incubation at 49 degree C. In contrast, the N potential increased in amplitude at 39 degree C, was completely suppressed at 47 degree 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 degree 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.