CHRONIC EFFECTS OF TRANSIENT FOREBRAIN ISCHEMIA ON MONOAMINES IN THE SPONTANEOUSLY HYPERTENSIVE RAT-BRAIN

Using the 3-hr common carotid occlusion model in spontaneously hyperte nsive rats (SHRs), we investigated the changes in monoamines and their metabolites up to the chronic phase, 6 mouths after the transient for ebrain ischemia, in various brain regions. In the striatum, the levels of dopamine (DA) at the 3rd week and serotonin (5-HT) at the 2nd week were 1.6-fold and 2.4-fold higher than the levels in the respective s ham-operated controls coinciding with increases in their metabolites, homovanillic acid and 5-hydroxyindoleacetic acid. However, these marke d increases in both transmitters were transient aid their levels recov ered to the sham-operated levels. This transient increase in DA releas e in the striatum may be caused by ischemia-induced disruption of nerv e endings, and may aggravate tissue damage in the striatum at the chro nic phase after ischemia. Transient or lasting changes in noradrenalin e, DA, 5-HT and their metabolites were also observed in other brain re gions, the thalamus+midbrain and the hippocampus of SHRs after transie nt ischemia. These ischemia-induced alterations in monoamines at the c hronic phase may be partly involved in the late-onset sequelae seen in the cerebrovascular disorders.