Cellular swelling during cerebral ischaemia demonstrated by microdialysis in vivo: preliminary data indicating the role of excitatory amino acids.

When rapid cellular swelling occurs, water moves from the extracellular space (ECS) into the cells and the concentration of ECS markers which do not move into the cells increases. Cellular swelling during cerebral ischaemia has therefore been demonstrated in vivo as an increase in ECS markers which is measurable with intracerebral electrodes. We attempted to detect the cellular swelling by brain microdialysis employing a similar principle. Dialysis probes were placed in the hippocampus, and perfused for 20 min with 14C-sucrose as an ECS marker. The probes were subsequently perfused without 14C-sucrose and the dialysate concentration of 14C-sucrose was determined at 1-min intervals. The dialysate concentrations of 14C-sucrose suddenly became elevated 1-3 min after the onset of cerebral ischaemia, indicating the occurrence of cellular swelling. The present technique is useful because it enables the mechanism of cellular swelling to be analyzed by observing the effects of pharmacological agents administered through a dialysis probe. Preliminary data indicating the role of excitatory amino acids in producing cellular swelling during cerebral ischaemia are presented as an example.