Protease-sensitive urinary pheromones induce region-specific Fos-expression in rat accessory olfactory bulb

Vomeronasal organs of female Wistar rats were exposed with sprayed urine pr eparations of male Wistar rats prior to sacrifice. Exposure to crude urine and ultrafiltrated urine preparation (<5000 Da) induced significant Fos exp ression, which is correlated with cellular activity, in the mitral/tufted c ell layer of the accessory olfactory bulb (AOB), while exposure to the rema ining substances after ultrafiltration (>5000 Da) and control salt solution did not. Exposure to urine preparation treated with papain induced express ion of Fos-immunoreactive cells in the rostral region of the AOB, but did n ot induce such expression in the caudal region. Exposure to urine preparati on treated with pronase induced urine-specific Fos immunoreactivity neither in the rostral nor in the caudal region These results suggest that at leas t two different peptides carrying pheromonal activities are contained in ma le Wistar rat urine. (C) 1999 Academic Press.