Time interval after ischaemic preconditioning affects neuroprotection and gliosis in the gerbil hippocampal CA1 region induced by transient cerebral ischaemia.

OBJECTIVES

Ischaemic preconditioning (IPC) can increase ischaemic tolerance of the central nervous system (CNS) to a subsequent longer or lethal period of transient ischaemia. In this study, we examined neuroprotective effects of time intervals after IPC against ischaemic insult in the hippocampus.

METHODS

Animals were randomly assigned to six groups; sham-operated-group, ischaemia-operated-group, and three IPC (12 hours, 1- and 2-day intervals after IPC) plus ischaemia-groups (IPC-12 hour, 1 and 2-day interval-ischaemia-operated-groups). For neuroprotection, we carried out cresyl violet (CV) staining neuronal nuclei (NeuN) immunohistochemistry and Fluoro-Jade B histofluorescence staining. In addition, we examined gliosis using immunohistochemistry for GFAP (a marker for astrocytes) and Iba-1 (a marker for microglia).

RESULTS

A significant loss of neurons was observed in the stratum pyramidale (SP) of the hippocampal CA1 region (CA1) in the ischaemia-operated-group and IPC-12 hours interval-ischaemia-operated-groups. In the IPC-1 day interval-ischaemia-operated-group, CA1 pyramidal neurons were well protected from ischaemic insult; the neuroprotective effect in the IPC-2 day interval-ischaemia-operated-group was less than that in the IPC-1 day interval-ischaemia-operated-group. On the other hand, we observed changes in glial cells (astrocytes and microglia) in the CA1 of all groups. The distribution pattern of glial cells only in the IPC-1 day interval-ischaemia-operated-group was similar to that in the sham-group.

CONCLUSION

In brief, our findings indicate that 1 day after IPC displays a mighty neuroprotection and shows an inhibition of glial activation in the CA1 induced by transient ischaemic insult.