Influence of glutamate on the content and metabolism of dopamine in the nigrostriatal system of rats distinguished by capacity for learning

Abstract

The effect of repeated (over the course of nine days) intrastriatal microinjections of glutamate (5 or 0.5 micrograms in 0.75 microliters of physiological solution daily) were investigated in 42 male Sprague-Dawley rats. Twenty-nine rats were preliminarily trained in a Skinner box using food reinforcement. It was demonstrated that the administration of glutamate to rats not subjected to training increases the content of homovanillic acid in the striatum. A similar influence in rats that are capable of learning leads to an increase in the content of dopamine and a decrease in the level of homovanillic acid in this nucleus, while it does not induce changes in the biochemical indicators under investigation in those rats that are incapable of learning. Microinjections of glutamate also do not alter the capacity for learning in any of the groups of animals. The possible causes for the different influence of intrastriatal microinjections of glutamate on the activity of the nigrostriatal system of rats differing by capacity for learning are discussed.

The effects of development of a food-related operant reflex on the receptor binding of glutamate in the rat brain

“…Thus, high levels of glutamate receptor binding in the striatum cannot be regarded as a specific correlate of the ability of rats to form food-procuring behavior. This partially explains the fact that our previous attempts to influence learning ability by repeated intrastriatal microinjections of glutamate led to negative results [4].…”