Cerebral ischaemia in the rat: increased permeability of post-synaptic membranes to horseradish peroxidase in the early post-ischaemic period.

An earlier study of the rat hippocampal stratum radiatum after transient cerebral ischaemia has shown cell membrane breaks, mainly post-synaptically, occurring as early as 20 min after an ischaemic episode. In the present study HRP was injected into the lateral ventricle 10-15 min after ischaemia and allowed to diffuse until 60 min post-ischaemia. Ultrastructural examination in the control animals, showed that HRP was localized exclusively in the extracellular space. After 10 min of transient ischaemia, HRP was not confined to the extracellular space, but was also seen in about 10% of apical dendrites. Only a very few pre-synaptic terminals showed the presence of HRP. Thus, there is evidence of early post-ischaemic membrane damage occurring in vivo in the apical dendrites of the CA-1 pyramidal cells.