Role of locus coeruleus in cerebral circulation and catecholamine metabolism

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(1)Neuronal activities in locus ceruleus respond to cerebral homodynamic changes induced by hypercapnia.When CO2 inhalation was applied, the significant increase in blood flow of the cerebral cortical tissue ipsilateral to the locus ceruleus was observed. The frequency of action potentials showed a gradual increase following the start of CO2 inhalation and reached a significant level by 40 seconds with maximum of 147 (〕SY.+-.〔) 22 % of the control value at 50 seconds. The cessation of CO2 inhalation induced a gradual recovery in the frequency of the action potential to the control level.(2)Cerebral intraparenchymal vasoconstriction induced by locus ceruleus stimulation.Cerebral blood volume(CBV) on the stimulated side gradually decreased following the start of 20Hz stimulation and reached a significant level by 80 seconds with a maximum of -0.15 (〕SY.+-.〔) 0.05vol% of the control value(p<0.05) at 140 seconds. CBV on the contralateral side was also reduced significantly. 50 Hz stimulation also resulted in a reduction in CBV bilaterally.(3)Locus ceruleus alters intraparenchymal vasoconrtrictive activities following subarachnoid hemorrhage.The CBV deresased significantly during the stimulation of locus ceruleus ; the decrease from the control value(6.3 vol%) was 0.14 (〕SY.+-.〔) 0.04 vol% at 80 seconds(p<0.05), 0.15 (〕SY.+-.〔) 0.03 vol% at 120 seconds. After the cessation of the stimulation, CBV showed a gradual recovery.(4)Catecholamine analysis by microdialysis technique.Perfusate from the cerebral cortex using microdialysis was analyzed by using high pressure liquid chromatography. We succeed in detectig norepinephrine, dopamine, DOPAC, HVA, serotonin, and 5-HIAA in same sample.