Effects of temperature on interictal discharge at penicillin epileptogenic foci

The effects of local brain temperature on acute focal penicillin epilepsy in the exposed hippocampus of cat were studied. Results from anesthetized and from immobilized, unanesthetized animals were compared. Over the temperature range 26 to 43 degrees C (at the alveus), the interictal spike interval and duration of the spike discharge varied inversely with temperature. The former showed a Q10 of 2.4 and the latter a Q10 of 1.5, with no difference due to type of preparation. A significant trans-hippocampal thermal gradient may imply that these values are underestimates by 20% or more. The low Q10 of duration of the paroxysmal discharge was consistent with the known temperature dependence of impulse conduction velocity of intracortical neural networks. The high Q10 of the interictal interval, on the other hand, was consistent with the view that some slow endogenous, perhaps metabolic factor such as a NA,K-ATPase modulated excitability at the focus of penicillin spikes.