Time-dependent changes of vasoactive substances in rat cerebral ischemia

Time-dependent changes in the tissue concentration of tyrosine hydroxylase (TH), adrenaline (A), noradrenaline (NA), and neuropeptide Y (NPY) in the early stages of cerebral ischemia were studied immunohistochemically in the amygdaloid complex of rats subjected to 1 h cerebral ischemia. Immunoreactivity to TH on the lesioned side reached a nadir at 12 h after cerebral ischemia, then gradually increased over 24 h to normal reactivity, but TH immunoreactivity between the ischemic side and the contralateral side was no different for up to 12 h after ischemia. The blood concentrations of NA and A were elevated to about twice the control concentration 12 h after ischemia, then gradually decreased back to normal. NPY immunoreactivity of both sides did not change for up to 6 h after ischemia, but NPY immunoreactivity on the lesioned side decreased over 12 h and maintained a plateau. These findings suggest that responses to cerebral ischemia between catecholamines and peptides are varied.