Spreading depression in the thalamus, hippocampus and caudate nucleus of the rat during electrical stimulation of the parietal area of the cortex

Parameters of electrical stimulation (ES) of the rats cerebral cortex which synaptically induced spreading depression (SD) in deep structures were found. The thalamic SD was regularly triggered by short (0.02-0.05 s) high-frequency (200-500 Hz) ES of the parietal cortical surface. In this case the EEG control showed the absence of any seizure activity in the cortical and subcortical structures. Nembutal (20-40 mg/kg) raised the SD thresholds, but did not prevent the short-latency thalamic SD. The ES of the parietal cortex was not sufficiently effective for SD synaptic excitation in the hippocampus and caudate nucleus. In contrast to the thalamic SD, the hippocampal one was accompanied by the episodes of epileptiform activity at certain SD phases. Thus, the low subseizure threshold of the synaptically triggered cortical and subcortical SD should be taken into account when biological purpose of the SD is discussed.