Relationship between neuronal activity and extracellular potassium during seizure in the ventrobasal thalamus of the cat

M. J. Gutnick, U. Heinemann

Research output: Contribution to journalArticlepeer-review

Abstract

Extracellular potassium concentration ((K+)0) and neuronal activities were simultaneously recorded in the specific thalamic nucleus Ventralis Posterolateralis (VPL) using double-barrelled, ion-sensitive microelectrodes. Resting levels of thalamic (K+)0 were between 2.7 and 3.2 in mM/1. During repetitive stimulation of the contralateral cuneate nucleus, (K+)0 never increased by more than 0.7 mM/l. However, repetitive stimulation of the ipsilateral primary sensorimotor cortex, or underlying white matter caused thalamic (K+)0 to increase to levels as high as 12 mM/l. Similar increases were observed during transition from interictal to ictal activity in penicillin-induced cortical epileptogenic foci. These large changes in (K+)0 were closely related to generation of high-frequency bursts of action potentials in thalamocortical relay (TCR) neurons. During the course of a propagated seizure, (K+)0 gradually fell from the peak level. At the conclusion of the seizure, neuronal bursting abruptly ceased, and (K+)0 rapidly decayed to below the baseline level. During the decay in (K+)0, negative thalamic field potentials evoked by afferent stimuli were increased in amplitude, and the safety factor for antidromic invasion of TCR neurons by cortically-evoked action potentials was markedly reduced. These results suggest that seizure termination is associated with hyperpolarization of thalamic neurons, which may be due to activation of an electrogenic pump mechanism.

Original languageEnglish
Pages (from-to)No. E 323
JournalElectroencephalography and Clinical Neurophysiology
Volume43
Issue number4
StatePublished - 1977

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