Relationship between the peculiarities of elaboration and retention of brightness discrimination and the serotonin content in the rat brain.

The role of serotonin in memory consolidation was investigated by comparing the serotonin content in the brain of young and old animals which differed in the duration of consolidation process and by comparing the serotonin content in the brain with the efficiency of retrieval of memory traces in animals of the same age. Old rats had the serotonin content higher in the hippocampus and lower in the hemispheres, diencephalon, midbrain and medulla as compared with young ones. Elaboration of brightness discrimination increased the brain serotonin content in old animals and decreased it in young ones. Inverse correlation occurred between the serotonin content in the hippocampus, midbrain and the medulla and retention of conditioned reflexes in rats of the same age. No correlation occurred between the serotonin content in the cerebral structures and the rate of conditioning.