Effect of carnosine on rats under experimental brain ischemia.

The effect of dietary carnosine on the behavioral and biochemical characteristics of rats under experimental ischemia was studied. Carnosine was shown to improve the animals orientation and learning in "Open Field" and "T-Maze" tests, and this effect was accompanied with an increase in glutamate binding to N-methyl-D-aspartate (NMDA) receptors in brain synaptosomes. Long-term brain ischemia induced by both sides' occlusion of common carotid arteries 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 decreased (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 (compared to that of ischemic untreated rats) but NMDA binding to brain synaptosomal membranes being increased by ischemic attack was significantly suppressed 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 capacity to bind NMDA after ischemic attack.