Access of urinary nonvolatiles to the mammalian vomeronasal organ.

Guinea pigs were allowed to investigate urine that contained rhodamine, a nonvolatile fluorescent dye. Guinea pigs given free access to dyed urine exhibited fluorescence in their vomeronasal and septal organs but not on their olfactory epithelium. Fluorescence was not seen when unadulterated urine was presented. Thus compounds of low volatility, which do not reach the olfactory epithelium, may stimulate the vomeronasal system and provide information that is normally not provided by gustation or olfaction.