Learning-induced plasticity of N-methyl-D-aspartate receptors is task and region specific

Changes in binding of [3H]dizocilpine maleate to N-methyl-D-aspartate-sensitive ion channel receptors were evaluated after learning in order to specify brain regions which might be involved in memory formation. Rats were trained in a five-trial session of 40 min, to discriminate among three odours to obtain food reinforcement. Another group was trained in an eight-arm maze to choose always the same three arms to obtain food reinforcement (nine trials over 150 min). In rats killed 30 min after odour discrimination learning, dizocilpine maleate binding was significantly reduced in hippocampal sub-regions CA3, CA1 and fascia dentata and in frontal cortex. After spatial learning, changes in binding were limited to the amygdala, where a decrease was also observed. These results indicate that functional changes occur in specific brain regions after learning and suggest anatomical loci for further study of synaptic changes at a morphological level, after spatial learning or odour discrimination.