Experimental studies of remarkable monoamine releases and neural resistance to the transient ischemia and reperfusion

Abstract

IntroductionThe literature described that neural damage caused by ischemia definitely occurs in brain areas. However, few studies have shown real-time changes of extracellular monoamine levels at the time of transient ischemia. MethodsWe examined changes in the responses of dopamine (DA) and serotonin (5-HT) release in the nucleus accumbens (ACC) of rats treated with four-vessel occlusion (4VO) in experiment 1. In the second experiment, we investigated the selective neural vulnerabilities among the ACC, lateral hypothalamus (LH), and frontal cortex (FC) of rats treated with 4VO and four days of reperfusion. ResultsThe extracellular levels of DA and 5-HT were remarkably increased 200- and 20-fold upon the 10-min clipping of both common carotid arteries in transient cerebral ischemia, respectively. Each increased monoamine release returned to the baseline levels immediately. The release of DA in the ACC and FC was significantly decreased in the rats treated with the coagulation of bilateral vertebral arteries (2VO), compared with that of sham-operated rats. K+-induced DA release in the ACC and FC of 4VO-treated rats was increased without alteration of DA content. DiscussionSurviving dopaminergic neurons in the ACC and FC showed neural hyperfunction associated with the monoamine release, serotonergic neurons in particular these areas exhibiting functional resistance to the transient ischemic change. ConclusionIt is suggested that the remarkable extracellular release of DA and 5-HT was not the cause of the ischemic delayed neural degeneration in each brain area, and that the functions of neurotransmitter release involved remarkable resistance to the transient ischemia.