Age effects on pheromone induced Fos expression in olfactory bulbs of a primate.

In the gray mouse lemur, a prosimian primate, aging is associated with a reduction of olfactory behaviors and sexual stimulation. To assess the effect of aging on the central response to pheromone stimulation in this primate, we measured the c-fos expression in the main and accessory olfactory bulbs of adult and aged male mouse lemurs, following exposure to the volatile phase of urine from proestrous females. In adults, pheromone exposure increased the number of Fos-positive neurons in the main olfactory bulb without changes in the accessory olfactory bulb. Fos expression was not increased by the odorant stimulation in aged mouse lemurs. Our results may explain the age-related decrease in behaviors associated with olfactory stimulation in this primate.