Vomeronasal/accessory olfactory system and pheromonal recognition

Pregnancy block in mice requires exposure of recently mated females tourinary pheromones of a strange male, and when working with inbred strainsthis invariably requires urine from an outbred line. The pheromones whichinduce oestrus and early puberty in mice have been identified as thebrevicomins and dihydrothiazoles. Since the same vomeronasal, neural andneuroendocrine pathways are also activated in pregnancy block, thesecompounds are likely candidates for pregnancy blocking pheromones. However,these relatively simple chemicals lack the capacity to code for differingmouse strains. Since large quantities of the polymorphic major urinaryproteins from the lipocalin family found in urine serve as transporters forthe dihydrothiazoles and brevicomins, and differ across strains, then theseproteins must participate in pheromone recognition in the context ofpregnancy block.