A chemistry of mammalian pheromones

Many mammalian social odors do not elicit an observable specific response in the recipient and therefore strictly cannot be considered to be pheromones. The pheromones now known in mammals are mostly transferred by contact and detected by accessory olfaction, which further indicates that pheromones in mammals should not be considered to be even a subclass of social odors. Aphrodisin, a female hamster pheromone that elicits sexual behavior in male hamsters, is a member of the lipocalycin family of 20 kDa extracellular proteins, and it is most closely related to rat odorant binding protein. Homologous proteins occur in the urine and scent glands of mice, rats and possibly voles, where they may serve as pheromone binding proteins. A 20 kDa protein, pheromaxein, binds the known pheromones androstenol and related steroids in boar saliva, and uncharacterized small proteins have been found in monkey and human skin gland secretions. Thus it appears that proteins may generally be associated with mammalian pheromones.