During pregnancy, baby mice are surrounded by fluids such as amniotic fluid that have a characteristic odor. After birth, the young are able to recognize in their mother thisunique combination of smells, and this is the signal for them to start sucking milk and feeding. These are the results of a work published in the magazineCurrent Biologywhich shows that, contrary to what was thought, pheromones are not responsible for awakening this instinct in all mammals.
Previous studies have shown that female rabbits use a pheromone that triggers an automatic response in the young to start sucking. Therefore, many scientists thought that this would be the mechanism used by all mammals. However, the new research shows that in mice, which have a similar rearing style to humans, the process is different. “We were hoping to find a pheromone that would control sucking in mice, but we discovered a totally different mechanism,” explained Darren Logan, one of the authors, from the Wellcome Trust Sanger Institute (UK). “We have shown, for the first time, thatmice do not respond to a pheromoneRather, they react to a learned response, based on a mixture of smells: the unique smell of the mother. “
The researchers held the newborn babies by cesarean section to breasts that had been washed and then immersed in different fluids: amniotic fluid, breast saliva, breast milk and urine. Only the pups that smelled amniotic fluid began to suck.
Furthermore, in another experiment, the researchers used mice genetically modified to lack agene affecting the pheromone detection regionin the nose. If the signal to feed depended on some pheromone included in the amniotic fluid, the modified mice would not detect it and, therefore, would not begin to suckle. However, these individuals began to feed without problem. The authors believe that this study will open doors to investigate the neural pathways involved in instinctual behavior in humans.
