| Abstract: | Electrical stimulation (ES) at the surface of the rat brain (10–200 Hz; brief trains of 10 pulses) was found to be most effective for evoking waves of spreading depression (SD) in the cortex. Repeated stimuli spaced at 10–15 min intervals did not produce convulsive activity and nor did mechanisms of SD inhibition set in under these conditions. A 5–6-fold reduction in SD threshold occurred when the intra-burst rate was increased from 10 to 200 Hz. Temporal summation of residual processes occurring with suprathreshold ES applied at the rate of 50 and 200 Hz resulted in significant broadening of the SD focus in the ES area and regular occurrence of additional SD foci on the side ipsilateral to stimulation and in the contralateral cortex. The protracted changes in cortical excitation lingering after ES by high-frequency currents brought about a decline in SD threshold and pointed to the active part played by synaptic processes in triggering this reaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 6, pp. 789–796, November–December, 1989. |
