SUSTAINED INCREASE IN ADRENERGIC ACTIVITY IN GERBIL STRIATUM FOLLOWING TRANSIENT ISCHEMIA

We investigated the changes in striatal monoaminergic functions, focus ing on the release and metabolism, in a cerebral ischemic model induce d by a 5-min bilateral occlusion of the carotid arteries (BOCA) and re perfusion in anesthetized gerbils. In the microdialysis study, the str iatal extracellular level of dopamine (DA) markedly increased (144-fol d) immediately after BOCA. Although norepinephrine (NE) and 5-hydroxyt ryptamine (5-HT) could not be detected in the dialysates throughout th e baseline period, they increased to detectable levels after BOCA. On the contrary, the tissue contents of NE and 5-HT decreased or tended t o decrease up to 4 hr following reperfusion. Striatal DA contents did not show any changes in the early period after ischemia-reperfusion an d slightly increased at 4 hr or later. Tissue contents of 3-methoxytyr amine (3-MT), a metabolite of DA by catechol-O-methyltransferase (COMT ), increased 0 and 5 min after reperfusion. Normethanephrine (NMN), wh ich is a metabolite of NE by COMT, also increased not only 5 min after but also up to 4 hr after ischemia-reperfusion, indicating a sustaine d increase in NE release. These results suggested that the neuronal ac tivity of NE, which is supposed to exert a protective effect on ischem ic damage, was enhanced for a longer period than that of DA after tran sient ischemia.