Decrease of pre-synaptic noradrenergic fiber density in rat hippocampus after transient ischemia.

The selective loss of hippocampal CA-1 pyramidal neurons has been reported not to be accompanied by damage to presynaptic terminals in the stratum radiatum as shown by electron microscopic observations. However, we examined changes in the tyrosine hydroxylase (TH) immunoreactive fibers following transient ischemia in rats using an immunohistochemical method 1, 3, 7 and 30 days after ischemia. The present study indicates that ischemic neuronal injury spreads to pre-synaptic fibers after the disappearance of the post-synaptic CA-1 pyramidal neurons.