A STUDY OF SINGLE CORTICAL NEURONS DURING SPREADING DEPRESSION

Abstract

In cats, microelectrodes were used to record simultaneously the slow potential changes and alterations in "spontaneous" or antidromically driven units during spreading depression (S.D. As S.D. passed through the recording area "spontaneous" units initially ceased firing, then 5-20 seconds later, discharged tonically for a short period. The units subsequently remained silent for 2-4 minutes, following which gradual recovery of firing occurred. During the burst the spike amplitude decreased until no longer detectable. Antidromic units with intermittent B invasion reverted to full invasion with the initial phase of S.D., after which continuous attenuation of the A and B spikes occurred reaching a point where only a small A or axon spike remained. Attenuation of "spontaneous" and antidromic spikes is thought to indicate extensive A and B membrane depolarization. Reversion to full invasion in the antidromic units, indicating soma depolarization, occurred at the same times as the initial cessation of firing in the "spontaneous" units. Depolarization of pre-synaptic structures producing "anomalous" presynaptic inhibition could explain absence of firing in face of post-synaptic depolarization. It is concluded from the above that all neural elements of cortex are depolarized during S.D.