[Spreading depression in the cortex and subcortical structures of the brain of the rat induced by exposure to focused ultrasound]

Abstract

Steady potential shifts produced by focused ultrasound were recorded in the cerebral cortex, hippocampus, thalamus and caudate nucleus of the rat. Impulses of 50-100 ms duration were presented with frequency 5 and 10 Hz. Negative slow potential shifts gradually increased up to 3-7 mV during 10-30 s and were often followed by the spreading depression (SD) waves. In every analyzed structure the SD amplitude reached 20-30 mV; the SD duration in the cortex, caudate nucleus and thalamus was 30-40 s while in the hippocampus it was 80-120 s. Seizures initiated by the ultrasound influence proceded in some cases the SD. Threshold ultrasound doses were not effective for 5-7 min after every the SD wave but at the end of the refractory period they became effective again. So, local influence of the focused ultrasound may result in functional blockade of the brain structures due to the cortical and subcortical spreading depression.