Effect of carnosine on rats under experimental brain ischemia

The effect of dietary carnosine on the behavioral and biochemical character istics of rats under experimental ischemia was studied. Carnosine was shown to improve the animals orientation and learning in "Open Field" and "T-Maz e" tests, and this effect was accompanied with an increase in glutamate bin ding to N-methyl-D-aspartate (NMDA) receptors in brain synaptosomes. Long-t erm brain ischemia induced by both sides' occlusion of common carotid arter ies resulted in 55% mortality of experimental rats, and those who survived were characterized by partial suppression of orientation in T-maze. In the group of rats treated with carnosine, mortality after ischemic attack was d ecreased (from 55% to 17%) and most of the learning parameters were kept at the pre.-ischemic level. Monoamine oxidase B (MAO B) activity in brain of the carnosine treated rats was not changed by ischemia significantly (compa red to that of ischemic untreated rats) but NMDA binding to brain synaptoso mal membranes being increased by ischemic attack was significantly suppress ed and reached the level characteristic of normal brain. The suggestion was made that carnosine possesses a dual effect on NMDA receptors resulting in increase in their amount after long-term treatment but decrease the capaci ty to bind NMDA after ischemic attack. (C) 2000 Tohoku University Medical P ress.