Selective and long-term learning impairment following neonatal hypoxic-ischemic brain insult in rats.
We examined four different learning and memory tasks in rats which had been subjected to left carotid artery ligation followed by 2 h hypoxia (8% oxygen) when they were 7 days old. The examination began on the 4th week after insult and continued to 18 weeks post-insult. Compared with the control group, the hypoxic-ischemic group showed significant learning impairments in choice reaction time tasks relating to the attention process, and in plus-maze tasks and water maze tasks which examine long-term reference memory. In eight-arm radial maze tasks representing both short-term working memory and long-term reference memory, inferiority of the hypoxic-ischemic group was transient. Results of the sensorimotor test were normal in the hypoxic-ischemic group although slight flexion and twisting in the right forelimb was observed in 30% of the hypoxic-ischemic group when suspended by the tail. These abnormalities did not affect the results of learning tests. Findings of the study indicate that left-side brain damage produced by hypoxia-ischemia at 7 days of age resulted in selective and long-lasting learning and memory impairment.
Ikeda
T
T
Department of Obstetrics and Gynecology, Miyazaki Medical College, 5200 Kihara, Kiyotake-Cho, 889-16, Miyazaki, Japan. tikeda@post1.miyazaki-med.ac.jp
Mishima
K
K
Yoshikawa
T
T
Iwasaki
K
K
Fujiwara
M
M
Xia
Y X
YX
Ikenoue
T
T
D000818:Animals; D002755:Choice Behavior; D005260:Female; D020925:Hypoxia-Ischemia, Brain / Q000523:psychology*; D007859:Learning Disabilities / Q000503:physiopathology*; D008297:Male; D018782:Maze Learning; D008568:Memory; D008959:Models, Neurological; D051381:Rats; D017208:Rats, Wistar