Neuronal plasticity and neurogenesis occur in the adult hippocampus and ă in other brain structures such as the olfactory bulb and often involve ă the neural cell adhesion molecule NCAM. During an olfactory associative ă discrimination learning task, NCAM polysialylation triggers neuronal ă plasticity in the adult hippocampus. The PST enzyme likely modulates ă this polysialylation, but not STX, a second sialyltransferase. How the ă two polysialyltransferases are involved in the adult olfactory bulb ă remains unknown. We addressed this question by investigating the effect ă of olfactory associative learning on plasticity and neurogenesis. After ă a hippocampo-dependent olfactory associative task learning, we measured ă the expression of both PST and STX polysialyltransferases in the ă olfactory bulbs of adult rats using quantitative PCR. In parallel, ă immunohistochemistry was used to evaluate both NCAM polysialylation ă level and newly-born cells, with or without learning. After learning, no ă changes were observed neither in the expression level of PST and NCAM ă polysialylation, nor in STX gene expression level and newly-born cells ă number in the olfactory bulb. (C) 2016 Elsevier Inc. All rights ă reserved.