With microinjection of 6-hydroxydopamine (6-OHDA) into the ventral hippocampus (VHIP) of rats, the effect of 6-OHDA lesion of hippocampal noradrenergic system on the plasma corticosterone (CS) response to acute hypoxia was investigated. It was found that the plasma CS response to inhalation of 10.4% O2 (30 min) was increased markedly; while the plasma CS level and the noradrenaline (NA) contents in hippocampus were decreased (-33.2% and -38.5%, respectively) 2 weeks after microinfusion of 6-OHDA (8 micrograms/2 microliters) into VHIP; however, the CS response to acute hypoxia was unaffected by 6-OHDA lesion of VHIP. The results above suggest that NA in hippocampus may participate in the regulation of the hypoxia-induced increase of plasma CS concentration in rats.