Rapid induction of Arc is observed in the granule cell dendrites in the accessory olfactory bulb after mating

The activity-regulated cytoskeleton-associated protein (Arc), encoded by the immediate early gene arc, is enriched in the brain and is hypothesized to play a role in the activity-dependent neuronal plasticity in the hippocampus. In the present study, the time course of Arc expression during the post-mating period was determined immunocytochemically, and the localization of Arc in the neurons in the accessory olfactory bulb (AOB) of female mice after mating was analyzed using immunocytochemical electron microscopy. Transient increases in the number of Arc-immunoreactive cells were observed in the glomerular, mitral/tufted cell and granule cell layers of the AOB after mating. In particular, the increase in the granule cell layer was remarkable, and larger than the increases in the other layers. In addition, electron microscopic observation revealed that Arc immunoreactivity was in the dendrites of the granule cells 1.5 h after mating. These results indicate that expression of Arc protein is induced rapidly and transiently in granule cell dendrites after mating. It is postulated that Arc protein has a role in the neuronal plasticity of the AOB after mating.